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Tatsuya Ishikawa
Faculty of Engineering　Civil Engineering　Natural Disasters and Adaptation
Professor
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Last Updated :2024/05/09

Researcher Profile and Settings

Affiliation

  • Faculty of Engineering　Civil Engineering　Natural Disasters and Adaptation

Job Title

  • Professor

Degree

  • Dr. Eng.

URL

Research funding number

  • 60359479

J-Global ID

Research Interests

  • 地盤工学   数値解析   土砂災害   防災   舗装工学   積雪寒冷地   礫質土   交通荷重   主応力軸回転   繰返しせん断   凍結融解   路盤   環境技術   凍上   地球温暖化ガス排出削減   粒状構造物   繰返し塑性   主応力回転   路盤・路床   気候変動   鉄道   礫材   天然ガス   維持管理工学   不飽和土   せん断試験   自然災害   水工水理学   移動荷重   斜面崩壊   粒子破砕   火山灰質土   凍結・融解作用   地盤防災   室内要素試験   寒冷地地盤防災工学   Geotechnical Engineering(5203)   

Research Areas

  • Social infrastructure (civil Engineering, architecture, disaster prevention) / Disaster prevention engineering
  • Social infrastructure (civil Engineering, architecture, disaster prevention) / Geotechnical engineering

Educational Organization

Academic & Professional Experience

  • 2019/04 - Today Hokkaido University Faculty of Engineering
  • 2017/04 - 2019/03 Hokkaido University Faculty of Public Policy
  • 2013/10 - 2017/03 Hokkaido University Faculty of Engineering
  • 2010/04 - 2013/09 Hokkaido University Faculty of Engineering
  • 2007/04 - 2010/03 Hokkaido University Graduate School of Engineering
  • 2002/10 - 2007/03 Hokkaido University Graduate School of Engineering

Association Memberships

  • JAPAN SOCIETY FOR NATURAL DISASTER SCIENCE   （社）地盤工学会   岩の力学連合会   ISSMGE   （社）土木学会   ISRM   日本地すべり学会   IACM   

Research Activities

Published Papers

  • Junling Si, Tatsuya Ishikawa, Daoju Ren, Kimio Maruyama, Chigusa Ueno
    Sustainability (Switzerland) 15 (18) 2023/09 [Refereed]
     
    Although the theoretical pavement structure design method (TPSDM) is widely used for designing asphalt pavements in Japan, it still exhibits certain limitations, such as not considering the variation in moduli of the base and subgrade layers due to water contents, freeze–thaw action, and stress states. This study aims to enhance Japanese TPSDM’s accuracy by considering variations in the resilient modulus of environmental impacts, pavement materials, pavement structure, and traffic load actions to accurately calculate the mechanical responses and predict pavement fatigue life. Firstly, the study develops a 3D Thermo-Hydro-Mechanical (THM) model using the finite element method (FEM) to investigate temperature and moisture distributions of the pavement with time. Then, based on the numerical results of the moisture, temperature, and stress state obtained from the THM analysis, the constant resilient modulus of the base and subgrade layers in the Japanese TPSDM is replaced with a resilient modulus that considers the stress state and the combined effects of water content fluctuations and freeze–thaw action. Finally, the fatigue life of the pavement is calculated based on the obtained mechanical response in THM analysis. The reliability and validity of the proposed fatigue life prediction method are well verified by comparing the calculated with the actual pavement fatigue life. Results indicate that the modifications improve the Japanese TPSDM by considering the environmental impacts, traffic load actions, pavement materials, and pavement structure, thereby improving the accuracy of predicting the fatigue life of asphalt pavements, particularly in cold regions.
  • Wentao He, Tatsuya Ishikawa, Yulong ZHU
    Soils and Foundations 63 (1) 0038-0806 2023/02 [Refereed]
     
    Runoff generated by heavy rainfall in natural catchment area and caused by ditch clogging in artificial structure increases the instability of the slope. The effects of runoff are usually neglected in traditional rainfall-induced slope failure analysis. In order to consider the effects of runoff on the slope instability, this study attempts to simulate the runoff, infiltration and slope instabilities simultaneously on both wide/narrow area. For this purpose, this study firstly proposes a coupled model of surface flow, subsurface flow, and soil mechanics based on Diffusion wave equations, Richards's equation, Green-Ampt infiltration capacity model, and local factor of safety approach in wide area simulation. Next, snowmelt and surface grass layer are additionally considered in narrow area simulation. Finally, the proposed coupled model is applied to two slopes at Nissho Pass and Kuromatsunai in Hokkaido, Japan. The slope instabilities assessment approach provides an effective method for simulating runoff and slope instabilities. In wide area, the distribution map of the factor of safety has significant implications for precisely determining the dangerous spots and accurately releasing the warning information. In narrow area, the slope disaster points caused by the ditch clogging are extracted and effect of grass layer on slope stability assessment is demonstrated. The construction and maintenance of the drainage system can be re-designed to ensure all the surface flow caused by the precipitation drain out smoothly.
  • Junping Ren, Shoulong Zhang, Tatsuya Ishikawa, Shuangyang Li, Chong Wang
    Geoderma 430 0016-7061 2023/02 [Refereed]
     
    The increasing use of the seasonally frozen and permafrost regions for civil engineering constructions and the effects of global warming on these regions have stimulated research on the behaviors of frozen soils. In the present study, the frost heave characteristics of a coarse-grained soil with volcanic nature was experimentally investigated. A large soil tank model was established in laboratory for this purpose. The effects of temperature boundary, external water supply, and water transfer type on the frost heave characteristics of the volcanic soil were studied, through a series of frost heave tests. The particle image velocimetry (PIV) technique was used to quantify the full field deformation of the soil specimen. The results suggest that temperature gradient inside the soil specimen is the driving force for the migration of pore water and vapor. The largest increment in water content generally agrees well with the frost penetration depth. The contribution of vapor to the frost heave of the soil specimen is typically small. The applied seeding method, selected subset size, image-object space calibration, and calculation processes ensured accurate PIV results. Discussions regarding the presented experimental investigation and the employment of PIV technique for quantifying frozen soil deformation are summarized. These findings and discussions can provide valuable insights into the frost heave behavior of the studied soil in particular, as well as promote the application of PIV for frozen soil engineering.
  • J. Si, T. Ishikawa
    Smart Geotechnics for Smart Societies 2537 - 2540 2023/01/01 
    To understand the actual response of asphalt pavement in cold regions, this study establishes a coupled thermo-hydro-mechanical (THM) Finite Element analysis of asphalt pavement incorporating a Mr-prediction model, which can adequately evaluate the influences of stress state, freeze-thaw, and water content on the resilient modulus (Mr). The FE analysis can not only obtain the changes in water content and temperature of the pavement, but also quantitatively reflect the synergistic effects on the resilient modulus. For this reason, the FE analysis can reproduce a typical Sandwich-Structure in the thawing season. This is of great significance to predict the mechanical properties and fatigue life of asphalt pavements in cold regions.
  • Wentao He, Tatsuya Ishikawa, Binh T. Nguyen
    Transportation Geotechnics 38 2023/01 [Refereed]
     
    The utilization of vegetation to prevent shallow slope failure and erosion has received significant attention in recent years, since it is recognized that vegetation has the mechanical and hydrological strengthening effect on soils. To accurately evaluate the mechanical properties of grassed soil and effect of grass age, grassed soils with grass ages of 2, 4, 6 and 8 months as well as bare soil are cultivated and prepared. Then, considering that grass layer in nature is usually situated above ground water table in the non-saturation state, a sequence of unsaturated triaxial tests are performed for soil specimens with different grass ages and matric suctions. Experimental results reveal that both grass root and matric suction enhance soil shear strength. The peak shear strength and cohesion of grassed soils tend to increase with increasing grass ages or matric suctions. Moreover, it is recognized that compared with grass root, the matric suction causes a more significant reinforcement effect for increasing total cohesion of soil sample. On the other hand, grassed soil has a higher water retention capacity, and under the same matric suction conditions, the soil specimen with older grass age have higher volumetric water content. Furthermore, the measured total cohesion for unsaturated soil is validated by the proposed calculation equation based on Vanapalli model, and the calculated results fit the measured results well. Calculated and experimental results have good agreement showing the proposed equation can properly reflect the increase in the unsaturated mechanical properties of grassed soil.
  • Shoulong Zhang, Tatsuya Ishikawa
    Lecture Notes in Civil Engineering 288 LNCE 375 - 384 2366-2557 2023 [Refereed]
     
    In the seasonally frozen regions, railway subgrades are subjected to freeze-thaw cycles due to environmental temperature change. The railway track is likely to be deformed during the freezing and thawing processes of subgrades. The wheel-rail force will increase due to the frost heave induced track deformation. As a result, the increased wheel-rail force will affect the settlement of ballast layer. In this study, firstly, the track deformation induced by the frost heave of railway subgrade was investigated. In the freeze-thaw analysis, the buried structure of box culvert embedded in the subgrade was selected as an analytical example. The track surface deformation above the transition zone was calculated through finite element analysis, considering the influences of groundwater levels and temperature boundary conditions. Secondly, the calculated absolute value of track deformation was inputted into the vehicle-track model as excitation. Then the calculated result was outputted for the calculation of ballast layer settlement.
  • Yu Wei Wu, Tatsuya Ishikawa
    Research in Cold and Arid Regions 14 (4) 223 - 234 2097-1583 2022/08 [Refereed]
     
    Damage caused by frost heave leads to costly maintenance in cold regions, like Hokkaido, Japan. Therefore, the study of the frost mechanism with experimental and numerical methods has been of great interest. Numerous models have been developed to describe the freezing process of saturated soil, which differs from the partially saturated conditions in the field. In fact, most subsurface soils are unsaturated. The freezing process of partially saturated soils is more complex than saturated soils, as the governing equations show strongly nonlinear characteristics. This study proposes a thermo-hydro-mechanical coupled model considering the heat transfer, water infiltration, and deformation of partially saturated soil to reproduce the freezing process of partially saturated frost susceptible soils distributed in Hokkaido. This model better considers the water-ice phase change and soil freezing characteristic curve (SFCC) during freezing under field conditions. The results from the multiphysics simulations agree well with the frost heave and water migration data from frost heave tests of Touryo soil and Fujinomori soil. In addition, this study discussed the influence of the various factors on frost heave amount, including temperature gradients, overburden pressures, water supply conditions, cooling rates, and initial saturation. The simulation results indicate that the frost heave ratio is proportional to the initial degree of saturation and is inversely proportional to the cooling rate and overburden pressure. Moreover, simulation under the open system generates much more frost heave than under the closed system. Finally, the main features of the proposed model are revealed by simulating a closed-system frost heave test. The simulation results indicate that the proposed model adequately captures the coupling characteristics of water and ice redistribution, temperature development, hydraulic conductivity, and suction in the freezing process. Together with the decreased hydraulic conductivity, the increased suction controls the water flow in the freezing zone. The inflow water driven by cryogenic suction gradient feeds the ice formation, leads to a rapid increase in total water content, expanding the voids that exceed the initial porosity and contributing to the frost heave.
  • Shoulong Zhang, Tatsuya Ishikawa, Bin Luo
    Transportation Engineering 8 2666-691X 2022/06 [Refereed]
     
    In the seasonally frozen regions, railway subgrades are subjected to freeze-thaw cycles due to environmental temperature change. The railway track is likely to be deformed during the freezing and thawing processes of subgrades. As a result, the train operations will be severely affected. In the present study, the track deformation induced by the freeze-thaw of railway subgrade was investigated. In the freeze-thaw analysis, different types of the buried structure (for example, box culvert, pipe culvert) embedded in the subgrade were selected as an analytical example, as the transition section of buried structure owning complex boundary conditions is likely to experience significant frost heave and thaw settlement. The track surface deformation above the transition section was calculated through finite element analysis, considering the influences of groundwater levels and temperature boundary conditions. Two indices, namely, wavelength and amplitude, were used to quantify the surface deformation. The influence of variation of groundwater level and different seasonal temperatures on the deformation was investigated from the aspects of absolute value. Subsequently, to evaluate the influence of subgrade freeze-thaw induced track deformation on train vibration, the vehicle dynamic analysis was conducted using a vehicle-track model. The calculated absolute value of track deformation was inputted into the vehicle-track model as excitation. Finally, the car body vibration was evaluated from the aspect of safety (minimum vertical wheel-rail force and maximum vertical wheel-rail force) and stability (car body acceleration and Sperling index). This study can facilitate understanding the influence of subgrade freeze-thaw on vehicle vibration.
  • Yuwei Wu, Tatsuya Ishikawa, Kimio Maruyama, Chigusa Ueno, Tomohisa Yasuoka, Sho Okuda
    Applied Sciences (Switzerland) 12 (9) 2076-3417 2022/05/01 [Refereed]
     
    The deterioration of roads in cold regions can result in unsafe driving conditions and high maintenance costs. Frost heaving is regarded as one of the main reasons for road degradation. Generally, frost heave is caused by water migrating from the unfrozen zone to the freezing front, where it is then transformed into an ice lens. Frost heave can be reduced by removing frost-susceptible soil, raising the temperature, or removing water from the soil. Among these methods, the most economical and practical approach is to reduce the water content. Recently, an innovative geotextile known as wicking fabric (WF) has been used to drain water from unsaturated conditions and minimize frost heaving. The objective of this study was to evaluate the inhibition effects of WF on frost heave under different experimental conditions in the freezing process. In this study, a thermo-hydro-mechanical (THM) coupled numerical model is proposed to simulate the freezing process of subgrade soil with WF. The evaporation model is used to simply describe the water absorption characteristics of WF. The numerical model was validated by comparing the simulation results with the experimental results of the wicking fabric model (WWF) and the non-wicking fabric model (NWF). Additionally, parametric analysis was conducted to examine the effectiveness of WF in reducing frost heave under various experimental conditions. As a result, the freezing process of soil installed with WF was accurately simulated by the proposed model. WF showed inhibition effects on frost heave under various experimental conditions. The results indicate the following: (1) Compared to Touryo soil (a high frost-susceptible clay-sand soil), WF inhibited frost heave more effectively in Toma-komai soil (a medium frost-susceptible lean clay), while the inhibition effect of WF in Fujinomori soil (a medium frost-susceptible lean clay) was limited. (2) WF has a more significant frost heave inhibition effect at a slower cooling rate in the freezing process. (3) The further the WF is installed from the groundwater level (GWL), the greater its impact on inhibiting frost heave.
  • Binh T. Nguyen, Tatsuya Ishikawa, Yulong Zhu, Srikrishnan Siva Subramanian, Thanh Truong Nguyen
    Engineering Geology 300 0013-7952 2022/04 [Refereed]
     
    The instantaneous profile (IP) method is widely used for determining the coefficient of permeability of unsaturated soils. IP method requires the measurement or control (i.e., zero flux) of flux at any one end of a soil profile. Besides, there are requirements of variations in volumetric water contents (VWCs) and pore-water pressures (PWPs) at various points from the above-mentioned one end of the soil profile to a particular point in which the unsaturated coefficient of permeability is derived. The measurement or control of flux at one end of the soil profile requires high accuracy which causes difficulty while performing tests in the laboratory and field. To overcome the difficulty of the IP method, this study proposes a new simplified transient method for determining the coefficient of permeability of the unsaturated soil. Variations in volumetric water contents and corresponding pore-water pressures at three points are required in the new simplified transient method. The intellectual advantage of this method as compared to the IP method is that there is no need to measure or control the flux at one end of the soil profile. Therefore, this new method is more practical and is expected to be widely used in both laboratory tests and field tests. The validity of the new simplified transient method is verified through numerical simulations considering a one-dimensional seepage for four different types of soils including coarse-grained soil, sand, clay, and silty sand with gravel. The applicability of the new simplified transient method is demonstrated by comparing the unsaturated coefficients of permeability of soils computed by the new simplified transient method and the IP method. Good agreements in comparisons prove that the new simplified transient method is effective for determining the unsaturated coefficient of permeability of soil regardless of soil types and hydraulic functions features.
  • Tianshu Lin, Tatsuya Ishikawa, Jiaqiang Yang, Tetsuya Tokoro
    Cold Regions Science and Technology 194 0165-232X 2022/02 [Refereed]
     
    This study examines the effects of freeze-thaw actions and the concurrent seasonal fluctuations in water content, named as climate effect in this study, on the resilient modulus of subgrade materials to evaluate their mechanical behavior in cold regions. A series of suction-controlled resilient modulus tests on subgrade materials with variant freeze-thaw, wheel loads, and water contents conditions were conducted using a newly developed test apparatus. Test results were used to construct a simple model to estimate the climate effect on the resilient modulus by considering the synergistic effects between water content and freeze-thaw. Besides, this study calculated the fatigue life of eight local flexible pavement projects with variant subgrade layer moduli considering climate effect by combining the newly proposed model and long-term in-situ measured data. Results proved that climate-related degradation of the subgrade materials decreases the fatigue life of asphalt pavements in cold regions.
  • 片寄陸, 中津川誠, 石川達也
    土木学会論文集 B1(水工学)(Web) 78 (2) 2185-467X 2022 [Refereed]
  • 小原悠佑, 石川達也, 所哲也
    地盤工学シンポジウム論文集(Web) 63rd 2022 [Refereed]
  • Yulong Zhu, Tatsuya Ishikawa, Yafen Zhang, Binh T. Nguyen, Srikrishnan Siva Subramanian
    Landslides 19 (8) 2021 - 2032 1612-510X 2022 [Refereed]
     
    Limited by the independence and its defects of each general software package, simultaneous analysis of runoff, seepage, and large-deformation analysis is still an inevitable challenge. Generally, one of seepage, landslide-related large-deformation, and runoff is ignored or indirectly assessed during unsaturated soil landslide runout simulation. To provide a brand new solution, this paper declares a local shear strength (LSS) method to evaluate rainfall/runoff-induced reduction of the unsaturated soil shear strength. After that, a hybrid coupled hydro-mechanical framework is proposed to simulate rainfall/runoff-induced landslide runout within an unsaturated soil slope. The decrease in local shear strength corresponding to the decrease in matric suction is defined by shifting the Mohr–Coulomb (M-C) failure envelope towards compressive stress space during rainfall/runoff infiltration. Based on the proposed local shear strength method, the variable matric suction obtained from the bidirectionally coupled runoff and seepage analysis in FEM is unidirectionally transferred to the variable local shear strength for each soil material point in MPM (i.e., this is a FEM-MPM hybrid coupled model). Then, the correctness of the proposed hybrid coupled hydro-mechanical framework is effectively verified by a hypothetical homogeneous slope model. The results show that the slope stable/unstable state simulated by the proposed hybrid coupled hydro-mechanical framework has a good consistency with that simulated by the shear strength reduction technique (SSRT) and limit-equilibrium method (LEM). Afterward, combined with a case study of a natural landslide in Hokkaido, Japan, it is proved to be effective for simulating landslide runout subjected to rainfall/runoff infiltration by using the proposed hybrid coupled hydro-mechanical framework in an unsaturated soil slope.
  • Tomohisa Yasuoka, Tatsuya Ishikawa, Bin Luo, Yuwei Wu, Kimio Maruyama, Chigusa Ueno
    Lecture Notes in Civil Engineering 165 509 - 520 2366-2557 2022 [Refereed]
     
    The frost heave of subgrade soil causes cracking and unevenness of pavement structure in cold region, which leads to uncomfortable driving and high maintenance cost. As one of the measures against frost heave damage, it has been considered to mitigate frost heave by draining water from the subgrade soil in road structure since soil moisture plays a critical role in ground heaving. The wicking fabric, a new type of geosynthetics drainage material, has been recently developed to drain water out of pavement and reduce the water content. Previous studies indicated that the wicking fabric has great promise as n effective means to solve the frost-heave-related problems on road systems. The purpose of this study is to verify the effectiveness of the wicking fabric for frost-heaving mitigation under local weather and soil conditions in Hokkaido by conducting the coupled thermo-hydro-mechanical (THM) analysis. The result of analysis indicates that wicking fabric has an excellent ability to drain water in road structure and that wicking fabric is an effective approach to mitigate frost heave.
  • Tianshu Lin, Tatsuya Ishikawa, Tetsuya Tokoro, Kimio Maruyama, Chigusa Ueno
    Lecture Notes in Civil Engineering 164 29 - 39 2366-2557 2022 [Refereed]
     
    In Japanese pavement design method, fatigue life criteria for cracking and rutting come from the US Asphalt Institute model, which relates failure loading number to the tensile strain on the lower surface of the asphalt mixture layer and the compressive strain on the top layer of the subgrade, respectively. These strains closely relate to the moduli of each layer. Japanese pavement design method assumes the moduli of base and subgrade layers are constant throughout the whole year. However, as proven by numerous past studies, these moduli are strongly affected by variation of water content and freeze-thaw cycle. To be precise, rising water content, as a result of the inflow of water or the thawing of ice lenses, causes a temporary decrease in the stiffness of subgrade and base course material. Besides, ice formation tends to break some of the particle contacts and interlocking of soil particles, which also leads to a degradation of base course material. Basically, climatic effects (variation of water content and freeze-thaw cycle) on base and subgrade layers material are not fully captured in Japanese pavement design method now. This study calculates the fatigue life of eight local flexible pavement projects with variation of base layer moduli considering freeze-thaw action and seasonal fluctuation in water content to capture the effects of climate on the fatigue life of the pavement. Long-term measured performance data are used to calibrate the rutting model. Results proved that climate-related degradation of the granular base decreases the fatigue life against rutting of asphalt pavements in cold regions.
  • T. Ishikawa, B. Dareeju, C. Gallage, L. Tianshu
    Geotechnical Engineering 52 (4) 23 - 32 0046-5828 2021/12 [Refereed]
     
    Water content of rail track subgrade materials fluctuates throughout the year due to the number of wetting and drying cycles, introducing unsaturated properties into the subgrade. Conservative rail track design guidelines are, however, mainly based on two extreme saturation conditions: fully dried or fully saturated. Current knowledge on the effects of subgrade water content on residual and resilient behaviour of the track foundation under the effects of Principal Stress Axis Rotation (PSAR) is limited and the potential of expansibility of foundation materials further upsurge the complexities towards the designing of the rail tracks. This study demonstrates the contributions of the PSAR on the resilient behaviour of foundation materials. Three different materials, including an expansive soil type have been subjected to drained cyclic vertical and torsional shear tests in a Modified Multi-Ring Shear (MMRS) apparatus and it is concluded that the resilient behaviour of the foundation materials is functions of the PSAR, material type, water content, and potential of expansibility.
  • Yulong Zhu, Tatsuya Ishikawa, Tomohito J. Yamada, Srikrishnan Siva Subramanian
    Journal of Infrastructure Preservation and Resilience 2 (1) 2021/12 [Refereed]
     
    AbstractTo semi-quantitatively assess the effects of climate change on the slope failures, this paper proposes an effective approach for evaluating the influences of climate change on slope stability in seasonally cold regions. To discuss climate change, this study firstly analyzes the trend of the two main climate factors (precipitation and air temperature) based on the regression analysis results of the meteorological monitoring data during the past 120 years in different scales (e.g., world, country (Japan), and city (Sapporo)), and the downscaled outputs of three different regional atmospheric models (RAMs) with lateral boundary conditions from three different general circulation models (GCMs). Next, to discuss the effects of different climate factors (air temperature, precipitation, etc.) and to determine the key climate factors on the slope instability, a slope stability assessment approach for evaluating the effects of climate changes on slope instability is proposed through the water content simulation and slope stability analysis with considering freeze-thaw action. Finally, to check the effectiveness of the above assessment approach, assessment of instability of an actual highway embankment slope with the local layer geometry is done by applying the past and predicted future climate data. The results indicate that affected by global warming, the air temperature rise in some cold cities is more serious. The climate changes (especially the increase in precipitation) in the future will increase the infiltration during the Spring season. It will lengthen the time that the highway slope is in an unstable state due to high volumetric water content, causing the occurrence of slope failures will be more concentrated in April. While during the Ssummer-Autumn period, the time domain of its occurrence will become wider.
  • Jiaqiang Yang, Tatsuya Ishikawa, Tetsuya Tokoro, Takahisa Nakamura, Ippei Kijiya, Takashi Okayasu
    Transportation Geotechnics 30 2214-3912 2021/09 [Refereed]
     
    With the ballast aging, the changes in the size and shape of the ballast particle reduce the drainage capacity, as well as cause a greater permanent deformation of the railroad ballast. Therefore, it is meaningful to investigate the effect of aging on the mechanical behavior of unsaturated ballast, and to estimate the cyclic plastic deformation by considering the aging effects. Here, “aging effect” means the increase in fine fraction content and the particle shape becomes rounded and smooth as compared with fresh ballast. In this study, the influence of aging on the cyclic plastic deformation of unsaturated ballast was evaluated through a series of cyclic loading triaxial compression tests. Test results indicate that the cyclic plastic deformation of ballast is seriously affected by water content, fine fraction content and drainage condition, and the increasing trend becomes more remarkable at the water-rich aged ballast under the fully undrained condition since the effective confining pressure decreases due to the generation of excess pore water pressure. Furthermore, the applicability of two types of estimation models (i.e., a semi-empirical model named University of Illinois at Urbana-Champaign (UIUC) model, and an elasto-plastic model named subloading surface extension (SSE) model) to the prediction for cyclic plastic deformation of unsaturated ballast is also verified in this study by comparing with results of cyclic loading triaxial compression tests. As the result, it is revealed that the UIUC model is suitable for predicting the cyclic plastic deformation of fresh ballast (or slightly aged ballast) with different water contents under the fully drained condition, and the SSE model shows good potential to estimate the cyclic plastic deformation of fresh and aged ballasts by considering the effects of water content and drainage condition. The findings of this study indicate that drainage conditions have a significant effect on predicting the cyclic plastic deformation of aged ballast, and appropriate test conditions for triaxial compression tests (i.e., CD and CU tests) should be selected according to hydraulic properties (i.e., permeability and water retentivity) of the aged ballast.
  • Junping Ren, Shoulong Zhang, Chong Wang, Tatsuya Ishikawa, Sai K. Vanapalli
    Journal of Testing and Evaluation 51 (1) 0090-3973 2021/08/01 [Refereed]
     
    In frozen soils, a portion of pore water remains unfrozen due to the effects of capillarity, adsorption, and possibly solute. The variation of the amount of unfrozen water and ice in a frozen soil, which is primarily influenced by subzero temperature, has great impacts on the physical and mechanical behavior of the soil and is critical for broad applications ranging from engineering to climate change. In the present study, the various methods that have been used for determining unfrozen water (and ice) content are comprehensively reviewed. Their principles, assumptions, advantages, and limitations are discussed. It is noted that there is yet no perfect way to accurately quantify unfrozen water content in frozen soils. In addition, the soil-freezing characteristic curve (SFCC) of a typical volcanic soil sampled in the Hokkaido prefecture of Japan is investigated. The unfrozen water content of the prepared soil specimens was measured using a cheap moisture sensor, which is based on the frequency domain reflectometry technique. The temperature of the specimens was determined by a rugged temperature sensor. Different numbers of freeze-thaw (F-T) cycles and different freezing/thawing methods (i.e., one- and three-dimensional) were considered, and their effects on the SFCC were investigated. The experimental results suggest that neither the F-T cycles nor the freezing/thawing methods had significant influence on the measured SFCC. The presented comprehensive review and experimental investigations are of importance for both the scientific and engineering communities.
  • Tatsuya Ishikawa, Masayuki Yoshimi, Koichi Isobe, Shoji Yokohama
    Soils and Foundations 61 (4) 1151 - 1171 0038-0806 2021/08 [Refereed]
     
    The 2018 Hokkaido Eastern Iburi earthquake with the JMA seismic intensity of 7 occurred at a central south part of Hokkaido, Japan at 3:08 a.m. on September 6, 2018. Considering the social importance of this historical earthquake-induced geo-disaster, the Japanese Geotechnical Society (JGS) organized a “JGS Survey Team for Geotechnical Disasters in Hokkaido, Japan Induced by the 2018 Hokkaido Eastern Iburi earthquake,” mainly comprised of experts from the industry and academia of the Hokkaido branch of JGS. The aim of the survey team was to investigate the phenomena and factors which contributed to disaster recovery and disaster prevention/mitigation from both short- and mid- to long-term perspectives, and to provide academic advice to related government organizations. Based on the results of the site investigations conducted by the JGS survey team (JGS, 2019), this report provides a summary of the geotechnical damage caused by 2018 Hokkaido Eastern Iburi earthquake by presenting the detail of strong seismic motion and a various types of geo-disasters which occurred due to the earthquake. Furthermore, this report highlights future research issues on disaster prevention/mitigation in Hokkaido considering the features of the geo-disasters attributed to the earthquake.
  • Tianshu Lin, Tatsuya Ishikawa, Kimio Maruyama, Tetsuya Tokoro
    Transportation Geotechnics 28 2214-3912 2021/05 [Refereed]
     
    Current Japanese design guide uses mechanical-empirical criteria to predict the failure loading number against fatigue cracking and rutting. However, these criteria have some limitations that the variation in moduli of base and subgrade layer due to the fluctuation in water contents, freeze–thaw history, and stress states are not considered. As well known, these factors greatly affect the soil mechanical properties like resilient modulus. Besides, present rutting failure criterion provides no indication of the behavior of rutting over time, and the effect of principal stress axis rotation on rutting development is also not captured. To overcome such limitations, this study modified the present Japanese pavement design method through the following two main aspects: (1) Replacing constant elastic modulus of base and subgrade layer to resilient modulus related to stress states and complex climate conditions, which are defined as the combination of fluctuating water content and freeze–thaw action; (2) Modifying rutting failure criterion by considering generally used MEPDG model and also the effect of principal stress axis rotation. All modifications are performed based on laboratory element test like suction-controlled freeze–thaw triaxial test, which could simulate complex climate conditions, and multi-ring shear test, which could simulate principal stress axis rotation. Besides, modified criteria are examined by comparing to long-term measured performance of test pavements built in Hokkaido, the north island of Japan. Modified Japanese pavement design method shows high applicability and accuracy on the pavement life prediction, especially for the flexible pavement in cold regions like Hokkaido.
  • Jiaqiang Yang, Tatsuya Ishikawa, Tianshu Lin, Tetsuya Tokoro, Takahisa Nakamura, Yoshitsugu Momoya
    Transportation Geotechnics 27 2214-3912 2021/03 [Refereed]
     
    To better understand adverse impacts of aging on track maintenance, the hydro-mechanical behavior of unsaturated fresh and aged ballasts was investigated by means of saturated permeability tests, water retention tests, and monotonic loading triaxial compression tests. Firstly, the aged ballast was prepared through the Los Angeles abrasion (LAA) test to reproduce the gradation and particle shape for in-situ aged ballast extracted from actual railway tracks in Japan. Moreover, the results of saturated permeability tests and water retention tests prove that aging induces a remarkable decrease in the saturated coefficient of permeability and a significant increase in water retentivity compared with fresh ballast, due to the presence of fine fraction content. For the shear strength, the effective shear strength parameters of fresh ballast under fully drained conditions (CD test) are close to those under fully undrained conditions (CU test), regardless of water content. However, for the aged ballast, due to the low permeability, it is difficult to simulate fully drained conditions with laboratory tests, even at a very low axial strain rate (0.01%/min). In this case, the effective shear strength parameters of aged ballast are more suitable to be determined by the CU test. Besides, the results of triaxial compression tests prove that aging reduces the effective internal friction angle of ballast, while it increases the total cohesion compared with fresh ballast, especially under the high saturation condition. Lastly, the shear strength of both materials has a decreasing tendency with increasing water content, and the declining trend of shear strength is more noticeable for aged ballast. Therefore, the effects of aging and moisture content on the hydro-mechanical behavior of the railroad ballast should be synergistically considered in the railway track design.
  • Yulong Zhu, Tatsuya Ishikawa, Srikrishnan Siva Subramanian, Bin Luo
    Soils and Foundations 61 (1) 198 - 217 0038-0806 2021/02 [Refereed]
     
    In 2005, the Japanese government launched a new nationwide early warning system for predicting debris flow and slope failure disasters based on rainfall intensity and the Soil Water Index (SWI). However, the Japanese government has not set early warning criteria in many mountain areas. In addition, the existing early warning criteria in some areas are much higher than realistic ones, and snowmelt water is not considered in the calculation of the SWI. These two factors have been the cause of many slope failures in seasonally cold regions, induced by rainfall and/or snowmelt, which were not predicted. Therefore, this study attempts to propose a new determination method for setting early warning criteria for rainfall- and/or snowmelt-induced slope failures in seasonally cold regions. For this purpose, the study firstly proposes a combination model for estimating snow density that incorporates the hourly snowmelt water into the Japanese early warning system more accurately by using meteorological monitoring data and modeled snow density. Next, based on case studies and parametric analyses for slope stability assessment, new early warning criteria are proposed for predicting three different patterns of slope failures under two typical types of precipitation (rainfall and snowmelt) conditions. Finally, a new determination method for setting early warning criteria in seasonally cold regions is proposed by referring to the existing early warning criteria near the target area, in accordance with the precipitation types and the local ground conditions of the slopes. Since the existing early warning criteria near the target area already take the effects of the variations in local geology and geography into account, the new determination method for early warning criteria can be applied to arbitrary areas in seasonally cold regions, without directly considering the local soil properties, in the actual design and maintenance works.
  • Junping Ren, Shoulong Zhang, Tatsuya Ishikawa, Sai K. Vanapalli
    Sustainable Civil Infrastructures 80 - 96 2366-3405 2021 [Refereed]
     
    Volcanic soils are widely distributed in the Hokkaido prefecture of Japan, where seasonal freezing and thawing occur. In frozen soils, a portion of pore water remains unfrozen, due to the effects of capillarity, adsorption, and possibly solute. The variation of the amount of unfrozen water in a frozen soil, which is primarily influenced by subzero temperature, has great impacts on the physical and mechanical behavior of the soil. In the present study, the soil-freezing characteristic curve (SFCC) of a typical volcanic soil sampled in Hokkaido, namely, the Komaoka soil, was investigated. The unfrozen water content of the prepared Komaoka soil specimens was measured using a cheap and convenient moisture sensor. The temperature of the specimens was determined by a rugged temperature sensor. Different number of freeze-thaw (F-T) cycles, and different freezing/thawing methods (i.e. one- and three-dimensional) were considered, and their effects on the SFCC were investigated. The experimental results suggest that neither of the F-T cycles nor the freezing/thawing methods had significant influence on the measured SFCC. The present study can contribute to understanding the freezing characteristic of the investigated soil in specific and that of other cold region soils in general.
  • Takumi Murakami, Tatsuya Ishikawa, Nguyen Thanh Binh, Akira Mori, Seiya Yokota
    Lecture Notes in Civil Engineering 126 457 - 465 2366-2557 2021 [Refereed]
     
    In cold regions, soil slope failures frequently occur due to an increase in the degree of saturation of soil by snowmelt and rainfall infiltration. However, studies related to the coupled effects of snowmelt and rainfall infiltration in cold region are very limited. This paper studies a soil slope failure occured on snowmelt period at a natural cut slope of the expressway in Hokkaido, Japan. According to the disaster investigation report, the slope failure was occured by inflitration of snowmelt, rainfall and overflow water from the drainage ditch. To investigate the cause of the slope failure, reproduction analysis which includes the three-dimensional unsaturated/saturated seepage analysis and slope stability analysis was performed. The numerical simulation considers the effects of snowmelt, rainfall, overflow from drainage ditch and surface grass. It is concluded that the overflow from the drainage ditch had serious effects on this slope failure. Moreover, the numerical simulation approach can reproduce the slope failure caused by infiltration of snowmelt, rainfall and overflow from drainage ditch.
  • Yulong Zhu, Tatsuya Ishikawa, Srikrishnan Siva Subramanian
    Lecture Notes in Civil Engineering 125 680 - 687 2366-2557 2021 [Refereed]
     
    An integrated model of fully coupled two-phase surface and subsurface flow was built by using GETFLOWS (GEneral purpose Terrestrial fluid-FLOW Simulator), a finite difference fluid-flow numerical simulator, to perform quantitative evaluation of exchange of overland water and groundwater, subsurface seepage and surface water runoff on the hillside slope surface. Surface water on hillside slope was modeled as open-channel flows and coupled with air-water two phase Darcy flow for underground permeation by using a generalized flow formula. In this study, a simple verification model was firstly built and validated by the extensively used Abdul and Gillham example with simulating the coupled surface and subsurface flow. Then a three-dimensional integrated model of surface and subsurface flow was built by using the DEM (Digital Elevation Model) of a natural mountain slope in Hokkaido, Japan, where runoff induced several debris flows and slope failures occurred during Typhoon 10 hit Hokkaido in 2016. Finally the results of integrated simulation was compared with the results from two-dimensional (2D) impermeable plane flow simulation using Nays2D Flood solver of the iRIC software in the same region. The results suggest that on the hillside slope upstream of embankment, the infiltration rate is equals to the rainfall intensity at the beginning of the rainfall event. After the rainfall intensity is greater than the soil infiltration capacity, runoff is generated. The runoff from upstream allows more water to infiltrate into the embankment causing the possibility of slope failure at the exit of the valley to be much greater than other locations along the highway.
  • Binh T. Nguyen, Tatsuya Ishikawa, Takumi Murakami
    Transportation Geotechnics 25 2214-3912 2020/12 [Refereed]
     
    This study investigates the effects of grass age on hydraulic properties of coarse-grained volcanic soil, namely: Komaoka soil. The soil-water characteristic curve (SWCC), unsaturated coefficient of permeability, outflow, runoff, and the variations in volumetric water content/matric suction under different rainfall intensities varying from 15, 30, 60, to 120 mm/h are measured by carrying out column tests. In addition, permeability tests are performed to determine the saturated coefficients of permeability of bare soil and grassed soils. In these tests, grassed soils with grass ages varying from 1 to 6 months are used to study the influence of root volume ratio on the hydraulic properties. The experimental results reveal that the grass age has an influence on the hydraulic properties of Komaoka soil. At the same volumetric water content, grassed soil with higher grass age has higher matric suction. Both saturated and unsaturated coefficient of permeability are significantly reduced with the increase in the grass age. Moreover, there is a decrease in the outflow and an increase in the runoff for grassed soil with higher grass age. Matric suction decreases later in grassed soil than that of bare soil under rainfall events. The higher the grass age, the longer time is taken to observe the change in matric suction. However, the matric suction of grassed soil is dramatically reduced while there is a gradual decrease in matric suction of bare soil. Furthermore, even though the matric suctions remain constant at somewhere in the vicinity of 2 kPa under long and intense rainfall events, higher volumetric water contents are recorded for grassed soil with higher age. The new model is proposed to estimate the unsaturated coefficient of permeability of coarse-grained soil due to the effects of grass roots. The good agreement between estimations and experimental results shows that the proposed model is useful to capture the decrease in unsaturated coefficient of permeability of grassed soil.
  • Yulong Zhu, Tatsuya Ishikawa, Srikrishnan Siva Subramanian, Bin Luo
    Engineering Geology 275 0013-7952 2020/09/20 [Refereed]
     
    High-velocity runoff generated in hillslopes during heavy rainfall caused by typhoon increases chances of instability of the embankment slopes at the exit of the gully. Such effects of high-velocity runoff are usually neglected in conventional rainfall-induced slope failure analysis. In order to consider the effects of runoff on the slope instability, this study attempts to simulate the runoff, infiltration, seepage, and slope instabilities on a small catchment-scale simultaneously. For this purpose, this study firstly proposes a coupled model of surface flow, subsurface flow, and soil mechanics based on shallow water equations, Richards's equation, Green-Ampt infiltration capacity model, and local factor of safety (LFS) approach. Next, to make the proposed coupled model effective in the practical analysis of runoff, a diffusion wave approximation of shallow water equations is validated by numerical simulations, and then it is used to replace shallow water equations in the proposed coupled model. Finally, the proposed coupled model is verified by Abdul and Gillham system and applied to a natural slope in Hokkaido, Japan inside a small catchment with an area of 0.4675 km2. The numerical results highlight the influences of runoff from upstream on the embankment slope failure at the exit of the gully. Furthermore, the small catchment-scale slope instabilities assessment approach proposed in this study provides an effective approach for simulating heavy rainfall induced runoff and slope instabilities. The distribution map of the factor of safety (FOS) has significant implications for precisely determining the dangerous spots (instead of areas) on a small catchment-scale and accurately releasing early warning information to these dangerous spots.
  • S. Siva Subramanian, X. Fan, A. P. Yunus, T. Asch, G. Scaringi, Q. Xu, L. Dai, T. Ishikawa, R. Huang
    Journal of Geophysical Research: Earth Surface 125 (5) 2169-9003 2020/05/15 [Refereed]
     
    The frequency of snowmelt-induced soil slope instabilities is increasing in some seasonally cold regions because of climate change. Reliable hazard assessment and risk mitigation of snowmelt-induced landslides require physically-based prediction models. However, existing models either apply only at the slope scale or assume precipitation as the sole landslide trigger. In doing so, they neglect the complexity and coupled nature of the thermo-hydro-mechanical processes leading to slope instability in seasonally cold regions (such as snow accumulation and melting, infiltration and surface runoff, soil saturation, pore water pressure buildup and dissipation). Here, we present a spatially distributed and sequentially coupled numerical model to simulate snowmelt-induced slope instabilities at the catchment scale. The model accounts for temperature-dependent changes in the soil hydraulic behavior related to changes in water state by means of a routine implemented in a geographic information system. We verified the performance of the model using a case study of spring snowmelt-induced soil slope failures that occurred after the 2004 Mid-Niigata earthquake in Japan. Considering limitations and simplifications, the model was able to predict the triggering condition, magnitude, and spatial distribution of the snowmelt-induced landslides with a satisfactory degree of accuracy. We believe that the robustness and simplicity of our numerical approach make it suitable for implementation in early warning systems.
  • Yulong Zhu, Tatsuya Ishikawa, Srikrishnan Siva Subramanian
    8th Japan-China Geotechnical Symposium: Challenges to Breakthrough in Geotechnic 41 - 46 2020 [Refereed]
     
    An iterative cross-coupled surface and subsurface flows model is proposed to simulate the runoff generation and infiltration of a wide area hillside slope. Surface water on hillside slope was modeled as 2D shallow water equations and subsurface flow was modeled as 3D Richards's equation. The infiltration capacity was estimated by Green-Ampt infiltration model. The water depth calculated by 2D shallow water equations was applied to 3D Richards's equation as the water head boundary condition and the infiltration or exfiltration calculated by Richards's equation was applied to the runoff simulation as source item. In this study, first, an approximation of shallow water equations that simplifies the equations of motion by considering only the main contributions was used. Then, the simplified runoff model was validated by the extensively used tilted impermeable V-catchment example with only simulating surface runoff flows. The iterative cross-coupled surface and subsurface flows model was verified by a simple 2D unsaturated-saturated model. The simulation results show that the iterative cross-coupled surface and subsurface flows model can reproduce rainfall generated runoff and infiltration. Finally, the runoff generation and infiltration of a natural mountain slope in Hokkaido were simulated, as the runoff caused several slope failures in this area during Typhoon 10 in 2016.
  • Satoshi Nishimura, Keisuke Sasahara, Tatsuya Ishikawa
    8th Japan-China Geotechnical Symposium: Challenges to Breakthrough in Geotechnic 288 - 293 2020 [Refereed]
     
    Snow cover melting leads to a release of stored winter-time precipitation over a relatively short period of time and thus affects the stability of embankment and cut slopes. Capturing the patterns of pore water pressure responses against the snow melt water infiltration and reflecting them into seepage flow analysis and mechanical stability analysis may lead to more precise assessment of the spring-time instability peculiar to snowy cold regions. This paper describes lessons from the authors' experience in monitoring snow and ground conditions in three sites in Hokkaido, which were with limited access during winter. From long-term observation spanning up to 5 years, patterns and features in the snow cover evolution and ground responses are summarised. A correlation was found between the peak snow cover depth and the delay in slope surface pore water pressure responses, which represents the significant time required for melted snow to travel through the snow beneath. Reflecting this delay could lead to more precise spring-time pore water pressure assessment in slopes.
  • Jiaqiang Yang, T. Ishikawa, S. Matsutani, T. Tokoro, T. Nakamura, Y. Momoya
    16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 2020 [Refereed]
     
    In this paper, the effects of water content and fine fraction content on permanent stains of ballasts were studied by the laboratory element tests. The experimental results show that the increasing trend of permanent strain becomes more remarkable in such a case where both water content and fine fraction content increase. Besides, the UIUC rutting model was evaluated to estimate the effects of water content and fine fraction content on permanent deformation of ballasts by comparing the experimental results. The results show that the UIUC rutting model can well estimate the permanent deformation of ballast with various water contents and fine fraction contents.
  • Tianshu Lin, T. Ishikawa, R. Aoki, T. Tokoro
    16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 2020 [Refereed]
     
    This paper describes the result from resilient modulus tests of unfrozen, freeze-thawed, unfrozen-wheel loaded, freeze-thawed-wheel loaded, and frozen-wheel loaded-thawed soil, aiming to qualitatively and quantitatively estimate the effect of freeze-thaw and wheel loads on resilient properties. Freeze-thaw process not only reduces resilient modulus greatly, but also weaken the influence of bulk stress and deviator stress on resilient modulus. For unfrozen soil, wheel loads decrease the resilient modulus. For freeze-thawed soil, the wheel loads increase the influence of deviator stress on resilient modulus. Regression analysis with universal model displays good performance for all tests. However, the modified universal model used in enhanced integrated climatic model (EICM) does not show good applicability for freeze-thawed soil and the reason still need further investigation.
  • Tetsuya Tokoro, Tatsuya Ishikawa
    Lecture Notes in Civil Engineering 49 71 - 78 2366-2557 2020 [Refereed]
     
    In this study, permeability coefficient of frozen soil has been measured by transient pulse method for specimens in which ice lenses did not exist by applying axis stress more than ice pressure calculated by generalized Clausius–Clapeyron equation. The applicability of the transient pulse method for frozen soil was examined by comparing the previous study conducted by authors. It is found that the permeability coefficient has a dependency on temperature and changes drastically over the tested temperature range. These tendencies of the permeability coefficient under negative temperature were similar to the permeability coefficient obtained by the constant head permeability test. Therefore, it is concluded that transient pulse method can be available to measure the permeability coefficient of frozen soil.
  • Tatsuya Ishikawa
    16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 2020 [Refereed]
     
    This paper examines the effects of freeze-thaw and water content on the deformation-strength properties of subbase course materials to evaluate the mechanical behavior of granular base in cold regions. Water retention tests of freeze-thawed subbase course materials, CBR tests of freeze-thawed subbase course materials under various water contents, and resilient modulus tests in unsaturated condition were conducted using three newly developed test apparatuses. Moreover, these results were compared with long-term field measurement at a model pavement structure, including FWD tests. As the results, it was revealed that the deformation-strength characteristics of unbound subbase course materials degrade due to freeze-thaw and increment of the water content in thawing season. This indicates that the freeze-thaw of granular base has a strong influence on the fatigue life of pavement structures.
  • Tatsuya Ishikawa, Tianshu Lin, Shinichiro Kawabata, Shuichi Kameyama, Tetsuya Tokoro
    Transportation Geotechnics 21 2214-3912 2019/12 [Refereed]
     
    This study examines the effects of freeze-thaw and water content on the resilient deformation characteristics of subbase course materials to evaluate the mechanical behavior of granular base in cold regions. A series of resilient modulus tests on subbase course materials under various water contents were conducted using a newly developed test apparatus. Besides, the test results were compared with the results of freeze-thaw CBR tests and the long-term field measurement at a model pavement structure including FWD tests. As the results, it was revealed that the resilient deformation characteristics of unbound granular base materials (UGBMs) deteriorate due to freeze-thaw and increment of the water content in thawing season. This indicates that the freeze-thaw of granular base has a strong influence on the fatigue life of pavement structures.
  • Tianshu Lin, Tatsuya Ishikawa, Bin Luo
    Transportation Research Record 2673 (3) 439 - 449 0361-1981 2019/03/01 [Refereed][Not invited]
     
    This paper proposes a modified University of Illinois at Urbana–Champaign (UIUC) model to predict permanent deformation behavior of unbound aggregate materials. Most existing models relate permanent deformation to resilient properties, whereas the UIUC model treats shear strength as a critical factor in permanent deformation behavior. Three types of test, monotonic shearing test, cyclic axial loading test, and cyclic axial and shear loading test, were conducted by multi-ring shear apparatus on two kinds of parallel grading aggregate materials, natural crusher-run and recycled crusher-run obtained from demolished concrete structure. Test results demonstrate that shear strength is the core factor in permanent deformation behavior, compared with resilient properties, and principal stress axis rotation (PSAR) greatly increases the permanent deformation. By considering the effect of PSAR on permanent deformation, a new parameter, (Rs)ave, is added to the conventional UIUC model to modify it. Regression analysis results verify that the modified UIUC model has good applicability for predicting permanent deformation of aggregates with different water contents and stress states, and with and without PSAR. The modified UIUC model builds a relation between test results with and without PSAR. A simple framework is also proposed for predicting permanent deformation in flexible pavement structures based on the modified UIUC model.
  • Tatsuya Ishikawa, Tianshu Lin, Jiaqiang Yang, Tetsuya Tokoro, Erol Tutumluer
    Transportation Geotechnics 18 149 - 162 2214-3912 2019/03 [Refereed][Not invited]
     
    The main objective of this study is to evaluate the practicality of the UIUC model to the Japanese design standard for ballasted tracks of aged lines as well as of new lines by considering some uncertain effects which are not verified and incorporated in the UIUC model, like the effects of ballast fouling, fluctuation in moisture content, and principal stress axis rotation. For this reason, in this study, first the trends in the permanent deformation accumulation of ballasts with various moisture contents and fine fraction contents under moving wheel loads were examined based on the results of advanced laboratory element tests such as triaxial compression tests on unsaturated ballasts and multi-ring shear tests on ballasts under moving wheel loads. Next, the applicability of the UIUC models to the estimation of the permanent deformation accumulation of ballasts were verified by considering the influences of fine fraction content, moisture content, and principal stress axis rotation, and a modification method of the UIUC model necessary for improving the prediction precision and extending the applicability was proposed.
  • Tatsuya Ishikawa, Tianshu Lin, Srikrishnan Siva Subramanian, Tetsuya Tokoro
    7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019 2019 [Refereed][Invited]
     
    This paper reviews and summarizes previous researches related to the unsaturated soil mechanics for the disaster prevention and maintenance of traffic infrastructures in snowy cold region from the viewpoints of experimental and analytical studies. In this paper, two case studies, namely "slope stability problem" and "pavement rutting problem" in thawing periods, are presented. This paper mainly discusses the contributions of unsaturated soil mechanics to the disaster prevention and maintenance of traffic infrastructures in snowy cold region in terms of the mechanism of the slope failures and pavement rutting, and its influencing factors by comparing the phenomena in temperate regions with those in snowy cold regions.
  • Tianshu Lin, Tatsuya Ishikawa, Tetsuya Tokoro
    7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019 576 - 581 2019 [Refereed]
     
    Resilient modulus (Mr), the ratio of the amplitude of cyclic axial stress to the amplitude of the resultant recoverable axial strain, is especially important in mechanistic pavement design procedure and it usually decreases in thaw season. This loss of stiffness was attributed to the change of moisture and the effect of freeze-thaw has not been considered completely. This paper proposed a new test method for resilient modulus of unsaturated unbound granular materials subjected to freeze-thaw action. By controlling the matric suction stable during freeze-thaw process, the water content before and after freeze-thaw is constant. As a result, the effect of freeze-thaw on resilient modulus could be studied. Test results illustrate that freeze-thaw process not only reduces resilient modulus greatly, but also weakens the influence of bulk stress, deviator stress, and matric suction on resilient modulus, even with same water content before and after freeze-thaw. Besides, a freeze-thaw process also leads to a smaller Secant Young's modulus and a larger permanent axial strain under repeated axial loads.
  • Binh T. Nguyen, Tatsuya Ishikawa, Takumi Murakami
    7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019 660 - 668 2019 [Refereed]
     
    Vegetation has been recognized as an environmentally friendly method for stabilizing soil slope. Whereas hydrological effects of vegetation are experimentally investigated by several researchers, the field studies are rarely conducted and gain less attention. In this research, a field study was carried out on unsaturated soil slopes. The field measurement consisted of two neighboring cut slopes, namely bare soil slope and grassed soil slope. Field measurement results reveal that grass has influences on reducing and stabilizing the soil water content, increasing matric suction, and lowering soil temperature in warm seasons. The approach of coupled nonisothermal-seepage numerical analysis for unsaturated soil slope considering impacts of grass is suggested. The good agreement in comparisons between simulation and field measurement indicates that the proposed approach is useful to consider the influences of grass on the soil behaviors against climate variations.
  • T. Tokoro, T. Ishikawa
    7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019 582 - 586 2019 [Refereed]
     
    This study aims to reveal the effect of suction on the ice formation in unsaturated soil. Unfrozen water content was measured by a pulse NMR for the saturated and unsaturated silt prepared by vapor pressure technique. Based on the data, for the unsaturated frozen soil with the initial high water content, the unfrozen water content of the unsaturated soil has the same tendency as that of saturated soil. While, water rarely freezes in case of low water content. Water cannot freeze less than the water content corresponding to the beginning of residual water saturation for all conditions. Furthermore, the unfrozen water ratio of the unsaturated soil is higher than that of the saturated soil. Therefore, these results revealed that suction has strong influence on the ice formation in unsaturated soil.
  • KIJIYA Ippei, ITOH Kazuki, NAKAMURA Takahisa, ISHIKAWA Tatsuya, OKAYASU Takashi
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 75 (2) I_105 - I_113 2185-6559 2019 [Refereed]
     

     Ballasted track has the structure to lay the ballast under the sleeper. The ballast shows the plastic deformation behavior by cyclic train load gradually and we keep soundness of ballast to repair when its plastic deformation gets greater. It seems difficult to predict the deformation behavior of ballast subjected to cyclic train loading because its shape is granular, and then we can not predict the temporal change of deformation and select the weak point, needed to be repaired which has the vertical track regularity inspected by the track inspection.

     In this study, we aim to resolve and reproduce the deformation behavior of ballast subjected to cyclic loading, and considered to use the finite numerical analysis with subloading surface model as unconventional plasticity. We simulated the element test of ballast and the full scale model test of ballasted track on straight roads and considered the validity of the numerical analysis method.

  • NAKAMURA Takahisa, MOMOYA Yoshitsugu, ISHIKAWA Tatsuya, HAYANO Kimitoshi
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 75 (1) 41 - 52 2185-6559 2019 [Refereed][Not invited]
     

     Development of the seismic design and the seismic countermeasures of the structures supporting railroad ballasted tracks are progressing; development of them for ballasted tracks is also required. In this study, we conducted small-scale model tests to evaluate the mechanism of reduction of the lateral ballast resistance during shaking. The deformation behavior inside the ballast during shaking was photographed and image analysis by PIV was performed; then it was found out that a shear plane was generated in the loading direction from the depth of the bottom of the sleeper. Large shaking table tests were also conducted using a full-scale model to investigate the effect of the seismic countermeasures for ballasted tracks. It was confirmed that both the buckling prevention plates and the ballast retaining wall had high seismic countermeasure effect.

  • Tatsuya Ishikawa, Srikrishnan Siva Subramanian, Tetsuya Tokoro
    Lecture Notes in Civil Engineering 28 467 - 498 2366-2557 2019 [Refereed][Invited]
     
    Climate change-induced large-scale natural hazards are problematic for confrontation. Many of the snowy cold regions of Japan, i.e. Hokkaido, experience multifaceted types of natural disasters, i.e. slope failures and debris flows due to abnormal weather and rainfall patterns which were never encountered in the past. In consideration of the change of extreme weather patterns in future, this study has attempted to develop a wide-area disaster risk assessment at first with introducing an early warning criterion for snowy cold regions and then by proposing and analysing the applicability of a wide-area slope failure analysis method. To this end, we have performed early warning and wide-area numerical modelling studies for various cases of soil slope failures in Hokkaido which shows new paths for the disaster mitigation.
  • Tomoyuki Aoyagi, Jiaqiang Yang, Shingo Matsutani, Tatsuya Ishikawa, Takahisa Nakamura, Yoshitsugu Momoya
    Lecture Notes in Civil Engineering 29 409 - 422 2366-2557 2019 [Refereed][Not invited]
     
    With time passing, the performance of railway ballasted track and road pavement gradually degrades along with the degradation in railroad ballast and base course layer. However, the Japanese design standard does not consider the age-related deterioration of ballasted track and asphalt pavement. To establish a rational maintenance method of aged ballasted track and road pavement, this study focused on the water retentivity. In this paper, a water retention test apparatus was newly developed to carry out water retention test for coarse granular materials subjected to freeze-thaw. The test samples are Toyoura sand, clean and fouled ballast, and new and aged crusher runs. First, the performance of the newly developed test apparatus was examined by comparing the test results of water retention tests of this paper with the past researches. Second, the influence of age-related degradation for coarse granular materials on the water retentivity was discussed by comparing the test results for aged test samples with the new ones. As a result, the following findings were obtained: (a) The developed test apparatus can carry out highly accurate water retention tests in a wide suction range and greatly shorten the testing time. (b) SWCC is seriously affected by the intrusion of fouling materials, regardless of the sample.
  • Srikrishnan Siva Subramanian, Tatsuya Ishikawa, Tetsuya Tokoro
    Soils and Foundations 58 (3) 582 - 601 0038-0806 2018/06 [Refereed][Not invited]
     
    In Hokkaido, Japan, soil slope failures occur frequently during the snow melting season. These slope failures are triggered by the excess amount of water derived from snowmelt and rainfall. For the prediction of snowmelt-induced soil slope failures in seasonally cold regions, an early warning criterion is required. The existing Japanese early warning criteria for sediment disasters, i.e., the relationship between the 60-min cumulative rainfall and the Soil Water Index (SWI), the effective rainfall index etc., consider the influence of rainfall and the time-dependent random moisture of the soil. However, these criteria do not consider the soil moisture contributed by the snowmelt water. In this study, therefore, the applicability of the existing early warning criteria to predict snowmelt-induced soil slope failures is examined. An empirical method to quantify the amount of snowmelt water is presented. Various scenarios of conceptual soil slope failures are studied using numerical simulations under different magnitudes of rainfall and snowmelt water. As a result, a revision is introduced for the SWI and the effective rainfall index, adding the amount of snowmelt water to that of rainfall, and slope failure scenarios are studied. Based on the results, a new early warning criterion, the Effective Precipitation (EP) index, is introduced. It is found that the new failure criterion performs well for the prediction of snowmelt-induced soil slope failures.
  • Thanh Binh Nguyen, Ishikawa Tatsuya, Siva Subramanian Srikrishnan
    PANAM UNSATURATED SOILS 2017: FUNDAMENTALS 2017-November (301) 135 - 145 0895-0563 2018 [Refereed][Not invited]
     
    Vegetation is increasingly used in geotechnical practice in order to reduce the amount of infiltration on the soil. However, elaborate studies and numerical methods considering the influence of vegetation on rainfall infiltration and soil slope stability have been very limited. In order to understand the mechanism of seepage behaviour and investigate differences in the amount of infiltration and runoff water between bare soil and grassed soil, a series of column tests and numerical analyses were performed. Experimental test results reveal that the grass cover plays an important role in minimizing the infiltration. Furthermore, soil-water retention and seepage behavior under unsaturated condition of grassed soil differ from those of bare soil. In this study, a numerical simulation approach was proposed and it was found to be useful by reproducing the experimental test results with good agreement.
  • Bin Luo, Tatsuya Ishikawa, Tetsuya Tokoro
    PROCEEDINGS OF GEOSHANGHAI 2018 INTERNATIONAL CONFERENCE: MULTI-PHYSICS PROCESSES IN SOIL MECHANICS AND ADVANCES IN GEOTECHNICAL TESTING 315 - 324 2018 [Refereed][Not invited]
     
    The prediction of stress change in pavement structure is quite essential for the design, construction, and maintenance of pavement in the seasonal cold region. Much attention is concentrated on the change of elastic modulus of soils due to freezing and thawing. To overcome the limitation of conventional design method, in which the elastic modulus of materials needs to be assigned manually to various thermal state layer by layer, a comprehensive analysis method is proposed in this study. This analysis can specify temperature-dependent modulus, and a typical pavement in the cold region was selected and simulated. It is revealed that snow cover on footpath can affect the thermal pattern in the pavement, which leads to differential frost penetration along the cross-section of the pavement. The stress change induced by frost action of soil shows the reverse trend between frozen and unfrozen (thawed) layers. The stress increment in subgrade during spring season should be accounted properly.
  • Go Hirose, Yuzuru Ito, Tatsuya Ishikawa, Satoshi Akagawa
    Journal of Japan Society of Civil Engineers 6 (1) 156 - 166 2187-5103 2018 [Refereed]
     
    In this study, freeze-thaw experiments were conducted on saturated fine-grained soils using different pre-consolidation pressures and overburden loads in order to predict the permeability of freeze-thawed soil. Two types of freeze-thawed experiments were carried out with the artificial ground freezing on-site construction condition considered: (1) one-dimensional freeze-thaw test, and (2) a horizontal displacement restrained freeze-thaw and vertical permeability test, which enables horizontal freezing under restricted horizontal displacement. The results show that the permeability of freeze-thawed soil is obviously influenced by overburden pressure rather than pre-consolidation pressure, overconsolidation ratio, and frost heave ratio. The results also suggest that the permeability of freeze-thawed soil can be predicted by the freeze-thaw test in which the effective overburden pressure is considered, rather than strength or over consolidation ratio of the ground materials and other freezing conditions.
  • Toshihiro Morii, Tatsuya Ishikawa, Kaoru Kobayashi, Yoshinori Hanada, Kenta Muto
    Proceedings of the 7th China-Japan Geotechnical Symposium: New Advances in Geotechnical Engineering, CJGS 2018 2018-March 220 - 226 2018 [Refereed][Not invited]
     
    Capillary barrier (CB) is a tilting soil layer system which is composed of a finer soil layer underlain by a coarser soil layer. Water infiltrating into soil is suspended just above an interface between the soil layers and diverted downward along the interface. Because of this diversion of infiltration water, the CB has been employed in a top cover of waste landfills and mining wastes to reduce water infiltration into the protected waste materials. Water flow downward along the interface accumulates gradually its mass of flow due to continuous infiltration from the soil surface, and, at some length along the interface, water percolates into the coarser soil layer. A horizontal distance from the beginning of water flow to this point of percolation is called a diversion length of the CB, and is one of important parameters in designing structural dimensions and configuration of the CB system and in selecting a suitable combination of the finer and coarser soils. Shallow land waste repository, in which the top CB and bottom CB are placed to reduce infiltration due to rainfall and to divert percolating water through the protected waste material respectively, is proposed to isolate effectively a hazardous waste material or a very low level radioactive waste. A laboratory soil box test was conducted to investigate and estimate the diversion length, and a trial embankment was constructed in the field to investigate performance of the CB in the shallow land waste repository. The diversion length can be estimated with a practical accuracy based on saturated and unsaturated hydraulic properties of soils employed in the CB, inclination of the interface and infiltration rate expected in the field. Field observation of soil water movement in the test embankment shows excellent and stable diversion of infiltration water in the CB system.
  • Biyanvilage Dareeju, Chaminda Gallage, Tatsuya Ishikawa, Manika Dhanasekar, Les Dawes
    Journal of GeoEngineering 13 (4) 161 - 170 1990-8326 2018 [Refereed][Not invited]
     
    Cumulative plastic deformation characteristics of rail tracks under moving wheel loads are complex problems. Globally the rail industry is challenged by effective maintenance strategies to ensure safety of the rail track structures. Influence of particle size distributions (PSDs) on the cyclic cumulative plastic deformation of coarse materials in the rail track substructure layers under moving wheel load is not well understood. Conventional test approaches, namely the direct shear test, the cyclic single point load test, and the California bearing ratio test, cannot replicate the actual stress-strain state of coarse materials under moving wheel loads. The multi-ring shear apparatus, an improved torsional simple shear apparatus to replicate moving train wheel loading conditions, was used in this study. The PSDs of coarse materials were experimentally simulated through modifications to the mass portions of different glass beads. The moving wheel loads introduce higher plastic deformation and lower resilient modulus irrespective of the PSDs compared to cyclic single point load tests. Further study with three natural coarse materials (Toyoura sand and two ballast types) indicates that the cumulative plastic deformation has nonlinear relationships between the principal stress axis rotation and PSDs of the materials.
  • Bin Luo, Hao Lai, Tatsuya Ishikawa, Tetsuya Tokoro
    SCIENCES IN COLD AND ARID REGIONS 9 (3) 229 - 235 1674-3822 2017/06 [Refereed][Not invited]
     
    The uneven frost heave of frost-susceptible subgrade soil causes track irregularity, which highly enhances train vibration and affects the comfort and safety of railway transportation. This paper presents a coupled thermo-hydro-mechanical (THM) analysis for the freezing behavior of railway located above a box culvert. The vertical acceleration of the vehicle, an indicator of riding comfort, is predicted through a vehicle dynamic model. The results reveal that the existence of a box culvert changes the subgrade thermal pattern, leading to a deeper frost penetration depth. The frost heave amount above the box culvert is larger than the adjacent section, resulting in uneven track structure upheave and track irregularity. This frost-induced track irregularity highly affects train vibration.
  • Biyanvilage Dareeju, Chaminda Gallage, Tatsuya Ishikawa, Manicka Dhanasekar
    Soils and Foundations 57 (3) 423 - 438 0038-0806 2017/06 [Refereed][Not invited]
     
    The cumulative plastic deformation of rail track subgrade materials under moving wheel loads is a complex problem. The plastic deformation and resilient modulus of subgrade materials subjected to moving wheel loads are a function of Principal Stress Axis Rotation (PSAR). Difficulties associated with the control of PSAR in conservative experimental methods lead to inaccurate estimations of the actual plastic deformation characteristics of rail track subgrade. Therefore, this study modifies a torsional multi-ring shear apparatus to evaluate the deformation characteristics of subgrade materials under moving wheel loads. The performance of this modified apparatus is evaluated by comparing the experimental results with those of small-scale model tests on an asphalt roadbed rail track with sandy subgrade. The evaluation suggests that the modified multi-ring shear apparatus has an excellent capability to estimate the deformation characteristics of rail track subgrade under moving wheel loads. A series of modified multi-ring shear tests is then conducted to investigate the effects of the loading conditions, the subgrade density, and the loading frequency on the deformation of subgrade materials under moving wheel loads. The results of these tests show that cyclic single-point load tests underestimate the actual deformation characteristics of subgrade materials irrespective of the subgrade density and the loading frequency. Furthermore, the ratio between the plastic cumulative deformations obtained from the moving wheel loading and from the cyclic single-point loading, referred to as the “ratio of axial strain” (Rs), is introduced to evaluate the plastic deformation characteristics of rail track subgrade materials under moving wheel loads only, using the results of cyclic single-point loading tests. Finally, an empirical formula is proposed to predict the cyclic plastic deformation of rail track subgrade materials as a function of the number of loading cycles.
  • Subramanian Srikrishnan Siva, Ishikawa Tatsuya, Tokoro Tetsuya
    Engineering geology Elsevier 221 (221) 154 - 169 0013-7952 2017/04/20 [Refereed][Not invited]
     
    In Hokkaido Japan, soil slope failures along some of the national highways are reported frequently in recent years. A stability assessment method which can consider the impact of seasonal changes like freeze-thaw action, snowmelt water infiltration etc. is of utmost importance and considered to be an immediate requirement for geotechnical practitioners, in order to properly predict the slope stability. In this study, a slope stability assessment approach based on two-dimensional numerical modelling is recommended which considers the water content changes of the soil induced by the seasonal climatic effects i.e. freeze-thaw action, snowmelt water infiltration etc. Two case studies of slope failures in Hokkaido have been studied using the recommended approach. In order to visualise the climatic parameters of most influence on slope stability, parametric studies have been performed through which many useful results in view of the soil slope stability in seasonal cold regions have been obtained. It is found that the freeze-thaw action has a considerable impact on the soil water content and slope stability. On the other hand, the snowmelt water infiltration has a very significant impact on soil slope stability. The recommended numerical modelling approach is found to be very useful in analysing the soil slope stability in seasonal cold regions.
  • Siva Subramanian Srikrishnan, Ishikawa Tatsuya, Tokoro Tetsuya, Kusunoki Fumiya
    Japanese Geotechnical Society Special Publication 公益社団法人 地盤工学会 5 (2) 135 - 140 2188-8027 2017 [Refereed][Not invited]
     

    In seasonal cold regions like Hokkaido, the soil surface up to a shallow depth is frozen during the winter. An earthquake during the freezing period and thawing period may cause severe disasters i.e. slope failures induced by the combined effects of seismicity and snow melt water. The influences of freezing conditions on the seismic behaviour of soil need to be studied elaborately. In this study, a series of shaking table tests were performed with frozen surface layer and numerical analysis has been performed to simulate the seismic behaviour of soil under the frozen surface state. The numerical analysis has been done based on the series of shaking table tests performed under two different conditions i.e. without a frozen soil surface layer and with 10 cm frozen soil at the surface. Loose density (Dr=30~35 %) and high density (Dr=75~80 %) Toyoura sand have been used to study the liquefaction behaviour. Different liquefaction behaviour is observed when considering surface frozen conditions under both loose and high relative densities of soil. Through the shaking table tests and numerical simulations performed, it is clear that the frozen surface layer severely affects the seismic response of the soil and if these conditions prevail on a soil slope during an earthquake, a sliding slope failure causing the movement of frozen soil layer may occur conceivably.

  • Akira Mori, Srikrishna Siva Subramanian, Tatsuya Ishikawa, Masahiro Komatsu
    Procedia Engineering 189 533 - 538 1877-7058 2017 [Refereed][Not invited]
     
    In cold regions, frequent incidents of soil slope failures occur due to snowmelt and rainfall. These failures are triggered by an increase in the degree of saturation of soil due to infiltration of water derived from rainfall and snowmelt. This study investigates a soil slope failure occurred on November 27, 2015 at a cut slope of an expressway in Hokkaido, Japan. The soil slope failure is investigated using a recommended stability assessment approach considering non-isothermal coupled seepage flow simulation followed by a limit equilibrium slope stability analysis. It is concluded that at the thawing period, the slope stability is affected by rainfall and snowmelt water infiltration and later in November the failure happened due to overflow of water from a drainage ditch.
  • Bin Luo, Tatsuya Ishikawa, Tetsuya Tokoro, Hao Lai
    Transportation Research Record 2656 (1) 12 - 22 0361-1981 2017 [Refereed][Not invited]
     
    Evaluation of frost heave is essential for good design of a geotechnical structure in cold regions. Frost heave often causes severe roughness and cracking of structures like pavements. To model frost heave around a box culvert, a practical coupled thermo-hydro-mechanical (THM) model is presented. The performance of the proposed THM model, which can predict the freeze–thaw behavior of unsaturated soil, is demonstrated through frost heave tests under different conditions. A pavement structure located above a box culvert was simulated, and the analysis could reproduce phenomena observed in the field, including uneven upheave of the pavement and frost-heaving force induced by frost-susceptible backfill. To mitigate such damages, the mechanism and countermeasure of uneven frost heave were investigated. It was revealed that the freeze–thaw action considerably affects smoothness and failure of the pavement structure. In addition, the use of insulation may reduce roughness and extend the fatigue life of the pavement structure. The findings of this study are useful for minimizing frost heave in geotechnical structures.
  • 廣瀬剛, 伊藤譲, 石川達也, 赤川敏
    土木学会論文集 C(地圏工学)(Web) 公益社団法人 土木学会 73 (2) 131 - 140 2185-6516 2017 [Refereed][Not invited]
     
     Prediction of the permeability of freeze-thawed soils is significantly important in the case that a final disposal site is being constructed in a cold region or a large-scale frozen earth wall is operating for a long period. Although a large number of knowledge has been obtained, it still is difficult to predict the permeability of freeze-thawed soils in a practical level. This study proposes a permeability prediction method of freeze-thawed soils based on the experimental findings.
     In this study, freeze-thaw experiments were conducted with saturated fine-grained soils with different pre-consolidation pressures and overburden loads in order to predict the permeability of freeze-thawed soil. Two types of freeze-thawed experiments were carried out with the artificial ground freezing on-site construction condition considered, one is one-dimensional freeze-thaw test, and the other is horizontal displacement restrained freeze-thaw and vertical permeability test, which enables horizontal freezing under restricted horizontal displacement.
     The result has revealed that the permeability of freeze-thawed soil is obviously influenced by overburden test pressure rather than pre-consolidation pressure, over-consolidation ratio and frost heave ratio. The result suggests that the permeability of freeze-thawed soil can be predicted by the freeze-thaw test for which the effective overburden pressure is considered, rather than strength or hardness of the ground materials and other freezing conditions are. Moreover, void ratio and permeability after freeze-thaw tended to approach the value of unfrozen soils with an increases of pressure. Furthermore, it has been suggested that the permeability of freeze-thawed soils in an actual artificial ground freezing method might be increased by non uniformity in distribution of void ratio due to frost heave.
  • Hosoda Mitsuru, Tanaka Hirofumi, Ishikawa Tatsuya
    Kozo Kogaku Ronbunshu. A (Journal of Structural Engineering. A) 公益社団法人 土木学会 63 (0) 171 - 181 1881-6614 2017 [Refereed][Not invited]
     
    The rail corrugation on high rail often generates on ballast-less track, however its mechanism has been not known in detail yet. In this paper, first of all, we assumed that the track supporting stiffness under sleeper influenced the generation situation of high rail corrugation based on the results of the various field investigations. Then, we developed vehicle dynamic simulation models by means of multibody dynamics for verifying the influence of the track supporting stiffness. In addition, we simulated on-board measurement for verifying adequacy of analysis method. Finally, we examined influence of the track stiffness on the dynamic interaction between vehicle and track.
  • Tetsuya Tokoro, Tatsuya Ishikawa, Srikrishnan Siva Subramanian
    ICSMGE 2017 - 19th International Conference on Soil Mechanics and Geotechnical Engineering 2017-September 1597 - 1600 2017 [Refereed][Not invited]
     
    The objective of this study is to clarify the mechanism of geotechnical disasters due to the earthquake during winter. Shaking table tests were conducted for the soil model with the frozen surface layer to reveal the dynamic behavior. Temperature-controlled direct shear tests were also conducted using bilayer specimen composed of unfrozen and frozen soil to evaluate the strength characteristics of the boundary layer between unfrozen and frozen soil. Based on the test results, under the frozen surface condition, different dynamic behaviors from unfrozen condition were observed. The excess pore water pressure distribution was uniform in unfrozen soil because of the high permeability of sand and the existence of the surface frozen layer. Furthermore, liquefaction occurs only in the superficial layer of unfrozen layer and liquefaction strength under surface frozen condition rises in comparison with the unfrozen condition. It is assumed that increment in the surface friction between frozen and unfrozen soil, obtained by the direct shear test, reduces the movement of soil particles.
  • Erol Tutumluer, Tatsuya Ishikawa
    ICSMGE 2017 - 19th International Conference on Soil Mechanics and Geotechnical Engineering 2017-September 1325 - 1332 2017 [Not refereed][Invited]
     
    Today's needs of urban transportation including roads, railways, airports and harbours demand significant resources for infrastructure development in view of rapid and efficient public and commercial (freight) services. In most cases, authorities have had difficulties in meeting these service demands due to the rapidly growing public, industrial, mining and agricultural sectors in many parts of the world. In order to maximise efficiency and to reduce the costs of maintenance, sound technical knowledge is required. This general report presents major technical advancements around the globe encompassing 31 articles from 19 countries and it is classified into 3 sessions, namely: "Rail session", "Pavement session" and others.
  • Srikrishnan Siva Subramanian, Tatsuya Ishikawa, Tetsuya Tokoro
    ICSMGE 2017 - 19th International Conference on Soil Mechanics and Geotechnical Engineering 2017-September 2203 - 2206 2017 [Refereed][Not invited]
     
    Soil slope failures are often triggered by snowmelt water infiltration and rainfall infiltration in seasonal cold regions like Hokkaido, Japan. The water content fluctuation of a soil slope in seasonal cold regions is governed by the freeze-thaw action and infiltration resulting from snowmelt water and rainfall. In this study, to scrutinise the climatic influence which has a profound effect on unsaturated soil slope stability in seasonal cold regions, a series of parametric numerical simulation studies have been performed for an embankment slope failure case example based on a slope stability assessment approach. As a result, it is found that the snowmelt water infiltration and freeze-thaw action have very significant impacts on soil slope stability and for the assessment of the long-term stability of unsaturated soil slopes these phenomena should be considered. In addition, to predict the snowmelt induced soil slope failures, an early warning/prediction criterion is recommended which considers the short-term and long-term snowmelt/rainfall infiltration effects. The new early warning criterion applied and tested using the case example performs well under different climatic influences and can be used for the prediction and early warning of snowmelt induced soil slope failures in seasonal cold regions.
  • T. Ishikawa, S. Matsutani, T. Tokoro, T. Nakamura, Y. Momoya
    Bearing Capacity of Roads, Railways and Airfields - Proceedings of the 10th International Conference on the Bearing Capacity of Roads, Railways and Airfields, BCRRA 2017 1817 - 1825 2017 [Refereed][Not invited]
     
    This paper examines the influence of parallel grading on the hydro-mechanical characteristics of unsaturated fouled ballast by conducting a series of triaxial compression tests and water retentivety tests on various fresh and fouled ballasts with parallel grading in unsaturated conditions. As the results, it was revealed that soil-water characteristic curves and relationships between degree of saturation and peak shear strength were seriously affected by intrusion of fouling materials into fresh ballast, and that the hydro-mechanical characteristics of unsaturated fouled ballast was influenced by the average grain size even if employing the parallel gradation of grain size distribution. These results indicate that for the precise evaluation of the mechanical property of unsaturated fouled ballast, it is important to carefully interpret the test results using the parallel grading geomaterials.
  • Tetsuya Tokoro, Tatsuya Ishikawa, Shoya Shirai, Tsutomu Nakamura
    Soils and Foundations 56 (5) 927 - 936 0038-0806 2016/10/01 [Refereed][Not invited]
     
    This study estimates the water dependence of the thermal conductivity of soils and proposes a new thermal conductivity model and empirical equation for soil. Thermal conductivity tests for three different soil types were conducted under different moisture contents using the thermal probe method. Electrical conductivity tests were also performed to obtain the electrical resistibilities of the soils, and the influence of the moisture content on thermal conductivity was examined using the electrical conductivity data. The results show that the water dependence of thermal conductivity strongly correlates to the electrical resistibility. The relationships between the moisture contents and the thermal conductivities of the three soil types are found to be nonlinear, with an inflection point in each relationship. The moisture contents corresponding to these inflection points approximately agree with each other. The provision of a current flow largely along the pore water indicates that the thermal conductivity of a soil depends on whether or not the pore water, which significantly contributes to heat conduction, is continuous. The presence of pore water in soils can explain the water dependence of thermal conductivity. This study further proposes a model to estimate the thermal conductivity of soil and an empirical equation based on electrical conductivity test results.
  • Tatsuya Ishikawa, Tetsuya Tokoro, Seiichi Miura
    Soils and Foundations 56 (5) 790 - 804 0038-0806 2016/10/01 [Refereed][Not invited]
     
    The aim of this study is to evaluate the effects of freeze–thaw action on the water retention–permeability characteristics of volcanic coarse-grained soils under unsaturated conditions in order to examine the hydraulic behavior of volcanic soil during the snow-melting season. In this study, a series of water retention, permeability, and slaking tests on three types of crushable volcanic coarse-grained soils, differing in their degrees of particle crushability, were performed under various degrees of saturation and freeze–thaw histories, while comparing the test results with those of non-crushable sand. Based on the experimental results, the effects of freeze–thaw action on the water retentivity, permeability, and particle breakage were examined. The test results indicated that freeze–thaw action has a strong influence on the hydraulic behavior of crushable volcanic coarse-grained soils under unsaturated conditions, even if the soil is a non-frost-susceptible geomaterial.
  • Dareeju Biyanvilage, Gallage Chaminda, Dhanasekar Manika, Ishikawa Tatsuya
    Japanese Geotechnical Society Special Publication 公益社団法人 地盤工学会 2 (46) 1619 - 1622 2188-8027 2016 [Refereed][Not invited]
     
    Cyclic plastic deformation of subgrade and other engineered layers is generally not taken into account in the design of railway bridge transition zones, although the plastic deformation is the governing factor of frequent track deterioration. Actual stress behavior of fine grained subgrade/embankment layers under train traffic is, however, difficult to replicate using the conventional laboratory test apparatus and techniques. A new type of torsional simple shear apparatus, known as multi-ring shear apparatus, was therefore developed to evaluate the actual stress state and the corresponding cyclic plastic deformation characteristics of subgrade materials under moving wheel load conditions. Multi-ring shear test results has been validated using a theoretical model test results; the capability of the multi-ring shear apparatus for replicating the cyclic plastic deformation characteristics of subgrade under moving train wheel load conditions is thus established. This paper describes the effects of principal stress rotation (PSR) of the subgrade materials to the cyclic plastic deformation in a railroad and impacts of testing methods in evaluating the influence of principal stress rotation to the track deterioration of rail track.
  • Ishikawa Tatsuya, Kijiya Ippei, Tokoro Tetsuya, Sato Masaru
    Japanese Geotechnical Society Special Publication 公益社団法人 地盤工学会 2 (13) 531 - 536 2188-8027 2016 [Refereed][Not invited]
     
    This paper presents numerical simulations on frost heave phenomenon observed at the earth structures and pavement structures using a coupled thermo-hydro-mechanical (THM) FE analysis, which can consider the change in deformation-strength characteristics and water retention-permeability characteristics due to freeze-thaw actions, and can reproduce frost-heave of soils under unsaturated conditions based on the results of frost heave tests. In order to evaluate the influences of freeze-thaw action on the interaction between frost-susceptible soil ground and structures quantitatively, a series of numerical simulations for cut slope and pavement structure subjected to freeze-thaw actions were performed. As the results, it was revealed that the coupled FE analysis employed in this study has a sufficient applicability to the precise prediction for the frost-heave behavior of soil ground, and that the frost-heave behavior has a considerable influence on the deformation and failure of earth structures in terms of the deformation and stress state of structures by examining the relation between frost heave and frost penetration depth.
  • 廣瀬剛, 伊藤譲, 石川達也, 赤川敏, 所哲也, 大西有三, 上田保司
    地盤改良シンポジウム論文集(CD-ROM) 12th ROMBUNNO.3‐3  2016 [Refereed][Not invited]
  • X. Y. Zheng, T. Ishikawa, T. Tokoro
    Unsaturated Soil Mechanics from Theory to Practice - Proceedings of the 6th Asia-Pacific Conference on Unsaturated Soils 275 - 280 2016 [Refereed][Not invited]
     
    Slope failures or landslides on soil ground formed by volcanic soils occur frequently in Hokkaido, Japan.The objective of this paper is to examine the effect of fine particles run off on the shear strength of volcanic coarse-grained soils under unsaturated condition. An unsaturated triaxial apparatus was used and a series of monotonic triaxial compression tests for a crushable volcanic coarse-grained soil from which fine particles have been partially removed previously were performed under various degree of saturation. By comparing test results to the previous research, it has been known that the shortage in fine particles have a strong effect on the shear strength of volcanic coarse-grained soil in both saturated and unsaturated conditions.With fine particles run off, the shear strength decreased sharply as if it has suffered a deterioration process.
  • Chaminda Gallage, Biyanvilage Dareeju, Manika Dhanasekar, Tatsuya Ishikawa
    Procedia Engineering 143 252 - 259 1877-7058 2016 [Refereed][Not invited]
     
    Precise assessment of cyclic plastic deformation of rail track subgrade is essential in designing cost effective rail tracks. Plastic deformation of rail tracks is often underestimated due to the omission of effects of principal stress axis rotation and water content on subgrade deformation. Moisture content of rail track subgrade is influenced by infiltration, seasonal ground water table variation and climate changes. To understand the influence of principal stress axis rotation and moisture content on the plastic deformation of soil, a series of cyclic moving wheel loading tests and cyclic triaxial compression tests were performed on unsaturated Toyoura sand, using a modified multi-ring shear apparatus. Results show that the presence of water in sand affects the cyclic plastic deformation of subgrade of rail tracks, significantly. The subgrade water content variation combined with the principal stress axis rotation further increases the accumulation of the cyclic plastic deformation of subgrade under moving wheel loads. Experimental results further conclude that the conventional experimental methods are unable to accurately assess the rail track deterioration process introduced by water content of rail track subgrade under repeated moving wheel load and highlight the requirements of realistic test methods such as the cyclic moving load multi-ring shear test, the cyclic hollow cylindrical test, or the model test in predicting rail track deterioration process of unsaturated subgrade under moving wheel loads.
  • S. Seto, T. Ishikawa, B. Dareeju, C. Gallage, B. Luo
    Civil-Comp Proceedings 110 1759-3433 2016 [Refereed][Not invited]
     
    The research presented in this paper includes an experimental study to evaluate the synergistic effects of principal stress axis rotation and change in water content on the mechanical behavior of a railway roadbed. This is in order to examine the mechanism of cyclic plastic deformation of railway roadbed subjected to cyclic moving wheel loads at a ballasted track. Three types of tests, namely a static torsional shear test, a single-point loading method and a moving-wheel loading method, were mainly performed with mixed soil which was composed of silicabentonite sand (silica 74.7%, bentonite 25.3%) and Toyoura sand subject to an air-dried condition and an unsaturated condition. Based on the test results, the influence of water content and moving-wheel loads on the deformation-strength characteristics of geomaterials were examined. The results revealed that the difference in the loading method and water content has a considerable influence on the cyclic plastic deformation of the railway roadbed. This leads to the conclusion that for the precise prediction of the long-term performance of substructures for a ballasted track under cyclic moving-wheel loads, it is important to take into account the synergistic effects of principal stress axis rotation and water content change on the cyclic plastic deformation characteristics of the railway roadbed.
  • Tatsuya Ishikawa, Shinichiro Kawabata
    Geotechnical Special Publication 2016-January (262 GSP) 77 - 85 0895-0563 2016 [Refereed][Not invited]
     
    This paper examines the effects of freeze-thaw and water content on the mechanical behavior of granular base by performing model tests of granular roadbed and CBR tests of base course materials. We also evaluate the influences of the change in the performance of granular base on the fatigue life of pavement structures in cold regions by applying the theoretical design method for asphalt pavement in consideration of the effects found in the above-mentioned experiments. As the results, it was revealed that the bearing capacity of granular base increases in freezing season and decreases in thawing season. This indicates that the freeze-thaw of granular base has a strong influence on the fatigue life of pavement structures in cold regions because it varies the deformation-strength characteristics of base course materials.
  • Tatsuya Ishikawa, Shinji Fuku, Takahisa Nakamura, Yoshitsugu Momoya, Tetsuya Tokoro
    Procedia Engineering 143 268 - 275 1877-7058 2016 [Refereed][Not invited]
     
    This paper evaluates the synergistic effects of water content and fine fraction on shear behavior of unsaturated fouled ballast by performing a series of triaxial compression tests and water retention tests on fresh and fouled ballasts in unsaturated conditions. As the results, it was revealed that soil-water characteristic curves and relationships between degree of saturation and peak shear strength were seriously affected by intrusion of fouling materials into fresh ballast, and that the decreasing trend of peak strength becomes more remarkable in such a case where both water content and fine fraction increase. These results indicate that for the precise prediction of the long-term performance of transportation infrastructures and the evaluation for mechanical property of railroad ballast under repeated train passages, it is important to take into account the synergistic effects of water content and fine fraction on the deformation-strength characteristics of ballast in accordance with the degree of ballast fouling.
  • Shinichiro Kawabata, Tatsuya Ishikawa, Shuichi Kameyama
    Procedia Engineering 143 828 - 835 1877-7058 2016 [Refereed][Not invited]
     
    We used a newly developed freeze-thaw California bearing ratio (CBR) test apparatus to investigate the effects of freeze-thaw history on the bearing capacity characteristics of granular base course material. It was found that CBR was reduced by freeze-thaw under all water content conditions. Taking the example of C-40, which is frequently used as a base course material, freeze-thaw cycles reduced CBR to about 0.6 times its initial value. We found volume expansion in even non-frost susceptible C-40, and therefore investigated changes in particle pore water due to freeze-thaw cycles. We found that freezing causes particle pore water to be dislocated to particle surfaces, thereby causing interparticle friction and altering the void structure.
  • ISHIKAWA Tatsuya, MATSUTANI Shingo, TOKORO Tetsuya, NAKAMURA Takahisa, MOMOYA Yoshitsugu
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 72 (3) I_151 - I_158 2185-6559 2016 [Refereed][Not invited]
     
     This paper evaluates the synergistic effects of water content and fine fraction on shear behavior of unsaturated fouled ballast by performing a series of monotonic loading and repeated loading triaxial compression tests and water retention tests on fresh and fouled ballasts with different water contents. As the results, it was revealed that the soil-water characteristic curves and relationships between degree of saturation and peak shear strength were seriously affected by intrusion of fouling materials into fresh ballast, and that the decreasing trend of peak strength becomes more remarkable in such a case where both water content and fine fraction increase. These indicate that for the precise prediction of the long-term performance of ballasted track and the mechanical behavior of railroad ballast under repeated loads, it is important to take into account the synergistic effects of water content and fine fraction on the deformation-strength characteristics of fouled ballast.
  • Tatsuya Ishikawa, Seiichi Miura
    Soils and Foundations 55 (2) 242 - 257 0038-0806 2015/04 [Refereed][Not invited]
     
    This paper presents an experimental study to evaluate the synergistic effects of principal stress axis rotation and change in water content on the mechanical behavior of granular roadbed subjected to cyclic moving wheel loads. Two types of small scale model tests and laboratory element tests, in which a single-point loading method and a moving-wheel loading method were adopted, were mainly performed with a base course material under air-dried condition and saturated condition. Based on the test results, the applicability of a multi-ring shear test, which is a torsional simple shear test, to an element test of granular base course materials subjected to moving wheel loads, and the influence of water content and moving-wheel loads on the deformation-strength characteristics of granular roadbed were examined. The results indicate that the multi-ring shear test has excellent applicability to the estimation of deformation behavior of granular base course materials subjected to repeated moving-wheel loads. Besides, it was revealed that residual settlement of submerged granular roadbed is more likely to increase with the repetition of moving-wheel loads than that of air-dried one and under single-point loading, showing that the difference in the loading method and water content has a considerable influence on the cyclic plastic deformation of granular roadbed. These lead to the conclusion that for the precise prediction of the long-term performance of granular roadbed under cyclic moving-wheel loads, it is important to take into account the synergistic effects of principal stress axis rotation and change in water content on the cyclic plastic deformation characteristics of granular base course materials.
  • Ishikawa Tatsuya, Tokoro Tetsuya, Seiichi Miura
    Japanese Geotechnical Society Special Publication 公益社団法人 地盤工学会 1 (1) 1 - 20 2188-8027 2015 [Refereed][Invited]
     
    This study examines the mechanism of the geohazards occurred at a volcanic soil slope in cold regions and its influencing factors in consideration of the effects of freeze-thaw actions on the physical properties, the water retention-permeability characteristics, and the deformation-strength characteristics of volcanic soils from the viewpoint of both experimental study and analytical study. To this end, we performed the long-term field measurement, model tests, laboratory element tests, and numerical simulations by taking volcanic soil slope subjected to freeze-thaw actions. As the results, this study revealed that there is a difference in the slope failure mechanism between cold region and warm-temperate region, and that freeze-thaw actions seriously influence thermo-hydro-mechanical behaviour of crushable volcanic coarse-grained soil slope under unsaturated condition even if the soil is a non-frost-susceptible geomaterial. Furthermore, this study clarified the mechanism, the endogenous factors, and the exogenous factors of the slope failure for volcanic soil ground in Hokkaido in comparison with the slope failure in warm-temperate regions.
  • Zheng Xiaoyi, Ishikawa Tatsuya, Tokoro Tetsuya
    Japanese Geotechnical Society Special Publication 公益社団法人 地盤工学会 1 (7) 11 - 16 2188-8027 2015 [Refereed][Not invited]
     
    In Hokkaido, Japan, over 40% area has been covered by volcanic coarse-grained soils. Due to the extreme weather in Hokkaido, snowfall always reaches several meters. After winter, a large amount of snow melts into water simultaneously, and at the same time permeated into ground rapidly and continuously. Fine particles contained in soil, therefore, will be carried out of soil structure by water. Changes in soil structure should be expected. The main purpose of this paper is to examine influences of fine particles run off on the shear behavior and Soil-Water Characteristic Curve, SWCC, which plays a very important role in the determination of unsaturated soil property function, of the volcanic coarse-grained soil under unsaturated condition. A series of triaxial compression tests and soil-water characteristic test were performed for volcanic coarse-grained soil from which fine particles were removed by water flow previously. The experimental results show that the shear strength of volcanic coarse-grained soil decreases a lot under both saturated condition and unsaturated condition when fine content was removed. Fine particles run off also gives a strong influence to soil-water characteristic curve. It causes a right shift in soil-water characteristic curve.
  • Siva Subramanian Srikrishnan, Ishikawa Tatsuya, Yokohama Shoji, Tokoro Tetsuya
    Japanese Geotechnical Society Special Publication 公益社団法人 地盤工学会 1 (7) 5 - 10 2188-8027 2015 [Refereed][Not invited]
     
    Slope instability issues due to freeze-thaw action, rainfall and seismicity are common in cold regions like Hokkaido. It is essential to study the varied impacts of temperature difference and infiltration due to rainfall on soil slope stability. The main objective of this study is to find a suitable slope stability assessment method considering the effects of freeze-thaw and rainfall. An embankment slope failure study performed by previous researchers has been numerically simulated. A modelling methodology to perform freeze-thaw, seepage and limit equilibrium slope stability analysis has been adopted and followed. Crucial parameters for slope stability i.e. initial moisture content, moisture content distribution during failure were obtained from the simulation and then compared with the measurement data. The numerical results compared with the measured data provide rational satisfaction and demonstrate the applicability of the software code in order to predict the stability of slope. The numerical modelling approach used in this study is found useful in analysing the rational stability of soil slopes and to simulate the moisture content distribution of slopes subjected to freeze-thaw and rainfall infiltration.
  • ISHIKAWA Tatsuya, KIJIYA Ippei, TOKORO Tetsuya
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 71 (3) I_185 - I_192 2185-6559 2015 [Refereed][Not invited]
     
     This paper develops a coupled thermo-hydro-mechanical (THM) FE analysis, which can reproduce frost-heave phenomenon of soils observed in snowy cold regions, and examines the applicability of the proposed coupled THM analysis in terms of the validity of its governing equations and the setting method of input parameters by performing numerical simulations for frost heave tests. In addition, by conducting a series of numerical simulations for pavement structures subjected to freeze-thaw action, the influence of frost heave-thaw on the interaction between soil ground and structures was evaluated. As the result, it was revealed that the frost heave-thaw behavior has a considerable influence on the fatigue life of pavement structure.
  • T. Ishikawa, I. Kijiya, T. Tokoro, M. Sato
    Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014 415 - 420 2015 [Refereed][Not invited]
     
    This study proposes a new numerical model to simulate the Thermo-Hydro-Mechanical (THM) behavior of saturated and unsaturated soils suffered from one-dimensional freeze-thawing. First, a coupledTHM FE analysis, which can consider the change in deformation-strength and water retention-permeability characteristics due to freeze-thaw actions, was newly developed. It also can reproduce frost heave phenomenon of soils under saturated and unsaturated conditions based on the results of frost susceptibility tests. Subsequently, a series of numerical simulations on frost heave tests of a soil specimen was conducted by the proposed FE analysis, and the analytical results were compared with experimental results to examine the applicability of the coupled FE analysis. As the result, it was revealed that the coupled FE analysis proposed in this study has valuable advantages of excellent applicability to the precise prediction method for the thermal-hydro-mechanical behavior of frost-susceptible soils during freeze-thaw. © 2015 Taylor & Francis Group, London.
  • T. Ishikawa, S. Miura, T. Tokoro
    Geomechanics from Micro to Macro - Proceedings of the TC105 ISSMGE International Symposium on Geomechanics from Micro to Macro, IS-Cambridge 2014 2 1415 - 1420 2015 [Refereed][Not invited]
     
    This study examines the effect of freeze-thaw actions and wet-dry cycles on the particle crushability and water retentivity of volcanic coarse-grained soils. A series of slaking tests for a cylindrical specimen made of two volcanic coarse-grained soils, which had different degree of particle crushability from each other, was performed under various freeze-thaw sequences. The dependency of the degree of particle breakage on freeze-thaw actions, the influences of the change in particle shape and the increase in fines content on the water retentivity were examined by performing slaking tests, sieve analysis and particle image analysis. Test results showed that particle breakage of non-frost susceptible volcanic coarse-grained soils increases by freeze-thaw actions and wet-dry cycles, and that shape change with the grain refining of volcanic soil particles due to freeze-thaw actions and wet-dry cycles causes a gradual fluctuation in the water retentivity. © 2015 Taylor & Francis Group.
  • ISHIKAWA Tatsuya, KIJIYA Ippei, TOKORO Tetsuya, AKAGAWA Satoshi
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 70 (3) I_65 - I_70 2185-6559 2015 [Refereed][Not invited]
     
     This study proposes two kinds of estimation methods for the frost heave ratio of unsaturated frost-susceptible soils under low overburden pressure such as subgrade soils at the pavement structure in cold regions. One is the modified Takashi's equation in contemplation of matric suction of soils under low overburden pressure. The other is the simple frost heave model which evaluates the effects of initial water content, Bishop's effective stress and water absorption during freezing on the frost heave ratio. In addition, the applicability and the usefulness of both methods were discussed based on the results of frost susceptibility tests. As the results, it was revealed that the estimation methods proposed in this study have an excellent applicability to the precise prediction for the frost-heave phenomenon of unsaturated subsurface ground in cold regions.
  • Tatsuya Ishikawa, Seiichi Miura, Etsuo Sekine
    Transportation Geotechnics 1 (4) 157 - 170 2214-3912 2014/12/01 [Refereed][Not invited]
     
    This study examines a simplified and practical prediction method for the cumulative residual settlement of ballasted track under repeated train passages, and the applicability and usefulness of the proposed method are discussed by comparing the experimental results of cyclic loading tests of model ballasted track structures with the analytical results. As the results, this study proposed a new analytical procedure with iterative calculation by linear elastic Finite Element (FE) analysis, which can evaluate the effects of continuous rotation of principal stress axis due to moving-wheel loads by taking into consideration the cumulative strain characteristics of ballast obtained from laboratory element tests such as multi-ring shear tests adopting the moving-wheel loading method in terms of the practical use. In addition, it was revealed that when laboratory element tests with high accuracy was conducted under experimental conditions similar to the actual phenomena in order to grasp the cumulative strain characteristics of ballast and then plastic deformation analysis was performed based on the findings above, the proposed analytical procedure could roughly estimate the cyclic plastic deformation of railroad ballast under repeated moving-wheel loads even with a simple linear elastic FE analysis. These findings confirm sufficient applicability of the proposed analytical procedure to the estimation of the cumulative residual settlement observed at ballasted track structures subjected to repeated train passages.
  • Yuan Zhang, Tatsuya Ishikawa, Tetsuya Tokoro, Tomoyoshi Nishimura
    Transportation Geotechnics 1 (2) 74 - 89 2214-3912 2014/06 [Refereed][Not invited]
     
    The aim of this study is to clarify strength characteristics of a subbase course material changed due to the degree of saturation and the strain rate. A series of monotonic triaxial compression tests was carried out under desired unsaturated and strain rate conditions using a medium-size triaxial compression apparatus. The test results indicate that the degree of saturation can significantly affect shear behaviors of the subbase course material in terms of the shear strength and deformability. On the other hand, the triaxial compression tests with the strain rate of 0.5%/min were conducted as well as those with 0.05%/min, which has been usually employed. The experimental results show that the mechanical behavior of the subbase course material is susceptible to the strain rate, and such relations can vary depending on the degree of saturation in shear. Furthermore, change in the strength parameters such as the total internal friction angle and the total cohesion resulting from the degree of saturation and the strain rate effects will be discussed. The calculation results show that the effects of degree of saturation and strain rate on the total internal friction angle appear to be negligible, while the total cohesion can be affected by the degree of saturation and the strain rate. More specifically, the failure envelope for the subbase course material is nonlinear under the low suction ranges. Therefore, the failure surface drawn through the failure envelope with respect to the matric suction is curved surface. The failure surface for unsaturated specimens with higher strain rate is located above that with lower strain rate. © 2014 Elsevier Ltd.
  • T. Ishikawa, S. Miura, E. Sekine
    Geotechnical Engineering 45 (1) 56 - 66 0046-5828 2014/03 [Refereed][Not invited]
     
    This study presents an experimental, analytical and numerical studies to elucidate the dynamic response of ballasted track structures subjected to horizontal seismic motions. First, a series of shaking table tests for one-third small-scale model ballasted tracks was performed. As the results, it was revealed that the existence of grouted layer had a serious influence on the seismic performance of ballasted track structures. Next, numerical simulations of the shaking table tests were conducted with a newly proposed analytical procedure which utilizes FE analysis considering the cumulative strain characteristics of ballast. As the results, it was revealed that as the analytical procedure could roughly estimate the residual displacement of railroad ballast after seismic motions, it was effective to evaluate the seismic performance of ballasted track structures for practical use. Copyright © 2014 Southeast Asian Geotechnical Society (SEAGS). All Rights Reserved.
  • A. Inam, T. Ishikawa, S. Miura
    Geotechnical Engineering 45 (1) 74 - 84 0046-5828 2014/03 [Refereed][Not invited]
     
    Nowadays, in order to economize the cost of pavements, recycled crusher-run (recycled concrete) that is recycled material is employed as base course material instead of natural crusher-run (andesite). Therefore, mechanical response of recycled crusher-run is required to evaluate in order to construct quality roads with minimum cost. In this research paper, an attempt is made to determine strengthdeformation characteristics of unsaturated recycled crusher-run material, under various loading conditions and saturation degrees. In addition, cyclic plastic deformation behaviour of two types of materials that are natural crusher-run (andesite) and recycled crusher-run (recycled concrete) is compared and analysed. A series of laboratory element test were carried out by using multi-ring shear apparatus, which can take in to account the rotation of principal stress axis. The experimental results show that, cyclic plastic deformation considerably enhances due to the rotation of principal stress axis under repeated axial and shear loading tests. Moreover, cyclic plastic deformation of recycled crusher-run material increases to some extent when compared with natural crusher-run material under same experimental conditions. Copyright © 2014 Southeast Asian Geotechnical Society (SEAGS). All Rights Reserved.
  • Tatsuya Ishikawa, Yuan Zhang, Tetsuya Tokoro, Seiichi Miura
    Soils and Foundations 54 (1) 67 - 80 0038-0806 2014/02 [Refereed][Not invited]
     
    This paper proposes a testing method for evaluating the effect of water content on the deformation-strength characteristics of unsaturated subbase course materials. A medium-size triaxial apparatus for unsaturated soils is newly developed in order to examine the mechanical behavior of unsaturated subbase course materials subjected to fluctuations in water content and to shorten the testing time. It adopts the pressure membrane method with hydrophilic microporous membrane filters, instead of the pressure plate method with ceramic disks, and controls both pore air pressure and pore water pressure at the cap and the pedestal separately. The results of the proposed testing method, carried out by this apparatus, are shown to conform well to the results of previous researches. This indicates that the medium-size triaxial apparatus for unsaturated soils is highly useful for triaxial compression tests and water retentivity tests on unsaturated granular base course materials and for shortening the total testing time. © 2014 The Japanese Geotechnical Society.
  • 石川達也, 桃谷尚嗣
    地盤工学シンポジウム論文集(CD-ROM) 地盤工学会 59 615 - 622 2014 [Refereed][Not invited]
  • T. Tokoro, S. Shirai, T. Nakamura, T. Ishikawa
    Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 2 1709 - 1714 2014 [Refereed][Not invited]
     
    The purpose of this study is to clarify the soils thermal conductivity dependency on water content. In this study, thermal conductivity tests were conducted for three types of soils under different moisture content using a thermal probe method. Water retention tests were also carried out in order to examine the effect of moisture content in the thermal conductivity of soils. Based on experimental results, it was revealed that soils thermal conductivity dependency on water content differed depending on the water retentivity characteristic of soils. The relationships between moisture content and thermal conductivity in the three types of soils are not linear, and it was observed an inflection point in each relationship. This indicates that thermal conductivity of soils depends on whether pore water, which contributes to conduct heat, is structurally continuous. Therefore, soils thermal conductivity dependency in water content can be explained by the structural configuration of pore water in the soils. © 2014 Taylor & Francis Group.
  • T. Ishikawa, T. Tokoro, D. Nakamura, S. Yamashita
    Unsaturated Soils: Research and Applications - Proceedings of the 6th International Conference on Unsaturated Soils, UNSAT 2014 2 1189 - 1195 2014 [Refereed][Not invited]
     
    The objective of this study is to propose a laboratory element test for evaluating the air-permeability of unsaturated soils subjected to freeze-thaw action and to examine the effects of freezethawing and moisture content on air-permeability of unsaturated soils. This study develops a new test apparatus and perform a series of air-permeability tests for unsaturated soils under various freeze-thaw histories and moisture contents. As the results, it was revealed that the test device could evaluate airpermeability of geomaterials. Besides, it was recognized that though the difference in coefficient of air permeability before and after freeze-thaw were not observed in non-frost susceptible sand, the airpermeability of frost susceptible volcanic cohesive soil differs according to the moisture content and freezing rate. This indicates that the freeze-thaw action has strong influences on the air-permeability of frost susceptible geomaterials in unsaturated condition. © 2014 Taylor & Francis Group.
  • KAWABATA Shinichiro, ISHIKAWA Tatsuya, KAMEYAMA Shuichi
    Japanese Geotechnical Journal 公益社団法人 地盤工学会 9 (1) 1 - 13 1880-6341 2014 [Refereed][Not invited]
     
    This research examined the effect of freeze-thaw actions on the bearing capacity of base course material C-40 by using our newly developed freeze-thaw CBR test apparatus. It was found that freeze-thaw history caused a decrease in the CBR of C-40 under various water content conditions. This is because the freeze action promotes to drain water absorbed into crushed stones. The increase in water on the surface of soil particles causes the decrease in interparticle friction and the change in soil skeleton structure, which resulted in the deterioration of bearing capacity. It was also found that while the decrease in CBR brought from the decrease of interparticle friction recovers over time, while that brought from the change of soil skeleton structure does not recover.
  • T. Ishikawa, Y. Zhang, S. Kawabata, S. Kameyama, T. Tokoro, T. Ono
    18th International Conference on Soil Mechanics and Geotechnical Engineering: Challenges and Innovations in Geotechnics, ICSMGE 2013 2 1287 - 1290 2013 [Refereed][Not invited]
     
    This paper examines the effects of freeze-Thaw and water content on the deformation-strength properties of subbase course materials to evaluate the mechanical behavior of granular base in cold regions. CBR tests of freeze-Thawed subbase course materials under various water contents, and the resilient modulus tests in unsaturated condition were conducted using two newly developed test apparatuses. Moreover, these results were compared with long-Term field measurement at a model pavement structure, including FWD tests. As the results, it was revealed that the deformation-strength characteristics of unbound granular base course materials deteriorate due to freeze-Thaw and increment of the water content in thawing season. This indicates that the freeze-Thaw of granular base has a strong influence on the fatigue life of pavement structures.
  • Yuan Zhang, Tatsuya Ishikawa, Tetsuya Tokoro, Satoru Shibuya
    Springer Series in Geomechanics and Geoengineering 501 - 506 1866-8755 2013 [Refereed][Not invited]
     
    The objective of this paper is to examine the influences of moisture content, loading speed, and degree of compaction on the shear behavior of compacted sandy soil under unsaturated conditions. A series of triaxial compression tests with various experimental conditions were carried out by using triaxial apparatus for unsaturated soil. The test results show that the shear strength of unsaturated soil decreases with the increase in moisture content and increases due to increment of loading speed. The effect of degree of compaction is also discussed. The results reveal that moisture content, loading speed, and degree of compaction have strong influences on the shear behavior of unsaturated sandy soil. © Springer-Verlag Berlin Heidelberg 2013.
  • Tatsuya Ishikawa, Tetsuya Tokoro
    Springer Series in Geomechanics and Geoengineering 3 143 - 148 1866-8755 2013 [Refereed][Not invited]
     
    The objective of this study is to evaluate the effect of freeze-thaw action on the strength and water retention-permeability characteristics of crushable volcanic coarse-grained soils in unsaturated conditions. A series of triaxial compression tests, water retention tests and permeability tests were performed for volcanic coarse-grained soils under different freeze-thaw histories. Test results showed that the particle breakage caused by the freeze-thaw action made the shear strength in unsaturated conditions decrease and the water retentivity increase, while not affecting the permeability. These indicate that the freeze-thaw action has strong influences on the hydro-mechanical characteristics of a crushable volcanic coarse-grained soil in unsaturated conditions even if the soil lacks in frostsusceptibility. © Springer-Verlag Berlin Heidelberg 2013.
  • T. Kawaguchi, D. Nakamura, S. Yamashita, S. Yamasaki, T. Ishikawa
    18th International Conference on Soil Mechanics and Geotechnical Engineering: Challenges and Innovations in Geotechnics, ICSMGE 2013 1 357 - 360 2013 [Refereed][Not invited]
     
    In cold and snowy areas, surface soils on slopes often move downward especially in early spring. Its moving caused by repeated freeze-thaw cycles. If we properly evaluate slope stabilities and carry out effective slope protection works, we should understand variations of strengths, stiffnesses, permeabilities, and so on in the cycles. By the way, it is known that repeated freeze-thaw cycles make ice lenses within surface soil. They spread parallel to ground surface so they are arranged parallel to shear stress on the slope. In this study we carried out frost heave tests that obtained changes of the void ratio and permeability in the cycle of freezing and thawing, direct box shear tests that obtained strength-deformation characteristics in the cycles, and the bender element tests that also obtained velocities of shear waves with vertical and horizontal propagation in the cycles. Then we conclude that the formation of ice lenses made parallel to shear stress is important for mechanical properties of surface soils.
  • ISHIKAWA Tatsuya, ZHANG Yuan, KAWABATA Shinichiro, KAMEYAMA Shuichi, TOKORO Tetsuya
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 69 (3) I_207 - I_214 2185-6559 2013 [Refereed][Not invited]
     
     This paper examines the effects of freeze-thaw and water content on the resilient deformation characteristics of subbase course materials to evaluate the mechanical behavior of granular base in cold regions. A series of resilient modulus tests on subbase course materials under various water contents were conducted using a newly developed test apparatus. Besides, the test results were compared with the results of freeze-thaw CBR tests and the long-term field measurement at a model pavement structure including FWD tests. As the results, it was revealed that the resilient deformation characteristics of unbound granular base course materials deteriorate due to freeze-thaw and increment of the water content in thawing season. This indicates that the freeze-thaw of granular base has a strong influence on the fatigue life of pavement structures.
  • KAWABATA Shinichiro, ISHIKAWA Tatsuya, TOYOTA Kunio, YAMAUCHI Satoru, KAMEYAMA Shuichi
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 69 (3) I_191 - I_198 2185-6559 2013 [Refereed][Not invited]
     
     The freezing condition of the NEXCO standard frost heave test (NEXCO method) was improved with the objective of reducing the variation in the results. Also, a large diameter testing apparatus was produced with a diameter up to Φ150 mm to enable the JGS standard frost heave test (JGS method) to be applied to subgrade soil and base course material, and the effect of the difference in the test method and the specimen size on the frost heave test results was investigated. Stable results could be obtained by changing the freezing condition of the NEXCO method from an air cooled type to a refrigerant circulation type. No difference was seen between the results of the Φ150-JGS method and the Φ100-JGS method, which indicates that the effect of the increase in diameter is small.
  • Influence of moisture content, loading speed and degree of compaction on the shear behavior of sandy soil
    Zhang, Y, Ishikawa, T, Tokoro, T, Shibuya S
    Proceedings of the 2nd International Symposium on Constitutive Modeling of Geomaterials - Advances and New Applications - 501 - 506 2012/10 [Refereed][Not invited]
  • Aasim Inam, Tatsuya Ishikawa, Seiichi Miura
    Soils and Foundations 52 (3) 465 - 480 0038-0806 2012/06 [Refereed][Not invited]
     
    It is generally observed that the stress state induced through traffic loads inside the substructure of pavements cannot be exactly reproduced in laboratory element tests. Moreover, there are not sufficient studies that examine the behavior of granular material under unsaturated conditions, although such conditions are very prevalent in pavement structures. In this research, an attempt is made to determine the cyclic plastic deformation characteristics of unsaturated granular base course material, and to examine the effect of the rotation of the principal stress axis (experienced by pavement elements under traffic loads) on the mechanical behavior of unsaturated granular base course material by applying various loading methods. A series of laboratory element tests using a multi-ring shear apparatus, which can take into account the rotation of the principal stress axis, were carried out on granular base course material under different moisture contents. The experimental results show that the moisture content has an obvious effect on both the shear behavior and the cyclic plastic deformation of granular base course material. However, the moisture content for the maximum deformation of granular base course material varies according to the loading method. It is also explained that cyclic plastic deformation considerably increases due to the rotation of the principal stress axis under repeated axial and shear loading tests. Therefore, the principal stress axis rotation has a significant influence on the cyclic plastic deformation of unsaturated granular base course material. © 2012 The Japanese Geotechnical Society.
  • KAWABATA Shinichiro, ISHIKAWA Tatsuya, MURAYAMA Takumi, KAMEYAMA Shuichi
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 68 (3) I_115 - I_122 2185-6559 2012 [Refereed][Not invited]
     
     In this research we used our newly made freeze-thaw CBR test apparatus to examine the effect of freeze-thaw action on the bearing capacity of base course material C-40. It was found that freeze-thaw history caused a decrease in the CBR in all water content conditions. Because the freeze action promotes to drain of particle pore water, it caused the decrease in interparticle friction and the change in void structure, which resulted in the deterioration of CBR. It was also found that while the CBR deterioration brought from the decrease of interparticle friction recovers over time, which brought from the change of void structure does not recover.
  • ISHIKAWA Tatsuya, ZHANG Yuan, TOKORO Tetsuya
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 68 (3) I_105 - I_113 2185-6559 2012 [Refereed][Not invited]
     
     This paper proposes a testing method for evaluating the effect of water content on the deformation-strength characteristics of unsaturated base course materials. A medium-size triaxial apparatus for unsaturated soils was newly developed in order to examine the mechanical behavior of unsaturated base course materials subjected to fluctuation in water content and to shorten the testing time. Results show that the proposed testing method carried out on this apparatus conform well to the results of previous researches. This indicates that the medium-size triaxial apparatus is highly useful at triaxial compression tests and water retention tests of unsaturated granular base course materials and in shorten the total testing time.
  • 石川達也, 木次谷一平, 所哲也
    地盤工学シンポジウム論文集 57th 159‐166  2012 [Refereed][Not invited]
  • T. Ishikawa, S. Kawabata, S. Kameyama, R. Abe, T. Ono
    ADVANCES IN TRANSPORTATION GEOTECHNICS II 118 - 124 2012 [Refereed][Not invited]
     
    This paper examines the effects of freezing and thawing on the mechanical behavior of granular base under unsaturated conditions through the long-term field measurement and FWD tests for pavement structure subjected to freeze-thaw actions, and by performing CBR tests for freeze-thawed base course material using a newly developed test apparatus. We also evaluate the influences of the change in the bearing capacity of granular base due to freeze-thawing on the fatigue life of pavement structures by applying the theoretical design method for pavement structures in consideration of the effects found in the above-mentioned experiments. As the results, it was revealed that the bearing capacity of granular base increases in freezing season and decreases due to increment of the water content in thawing season. This indicates that the freeze-thaw of granular base has a strong influence on the fatigue life of pavement structure in cold regions.
  • T. Ishikawa, Y. Zhang, H. Segawa, S. Miura, T. Tokoro
    ADVANCES IN TRANSPORTATION GEOTECHNICS II 534 - 540 2012 [Refereed][Not invited]
     
    This paper proposes a testing method for evaluating the effect of water content on the deformation-strength characteristics of unsaturated base course materials. A medium-size triaxial apparatus for unsaturated soils was newly developed in order to examine the mechanical behavior of unsaturated base course materials subjected to fluctuation in water content and to shorten the testing time. It adopts the pressure membrane method with hydrophilic microporous membrane filters instead of the pressure plate method with ceramic disks, and controls both pore air pressure and pore water pressure at cap and pedestal separately. Results show that the proposed testing method carried out on this apparatus conform well to the results of previous researches. This indicates that the medium-size triaxial apparatus is highly useful at triaxial compression tests and water retention tests of unsaturated granular base course materials and in shorten the total testing time.
  • A. Inam, T. Ishikawa, S. Miura
    ADVANCES IN TRANSPORTATION GEOTECHNICS II 213 - 218 2012 [Refereed][Not invited]
     
    This research paper proposes a testing method to determine cyclic plastic deformation characteristics of unsaturated recycled crusher-run material, and accordingly examines the effect of moisture content under single-point loading and moving-wheel loading. In Japan, natural crusher-run material is employed in pavements for base course layer. Nowadays, in order to economize the cost of pavements, recycled crusher-run material made from construction waste is also used as base course material for low volume roads. A series of laboratory element test using multi-ring shear apparatus were carried out on recycled crusher-run material under different degrees of saturation. The experimental results show that, moisture content has obvious effect on cyclic plastic deformation of recycled crusher-run material. It is also explained that cyclic plastic deformation significantly increases under moving-wheel loading tests. Moreover, cyclic plastic deformation of recycled crusher-run material increases to some extent when compared with natural crusher-run material under same experimental conditions.
  • A. Inam, T. Ishikawa, S. Miura
    5th Asia-Pacific Conference on Unsaturated Soils 2012 2 611 - 616 2011/11 [Refereed][Not invited]
     
    This research paper proposes a new testing method to determine cyclic deformation characteristics of unsaturated granular material, and accordingly examines the effect of moisture content under moving wheel loads. A series of laboratory element test using multi-ring shear apparatus, which can consider change in direction of principal stress axis like traffic loads in real condition, were carried out on granular material under different moisture contents. Results show that, moisture content has obvious effect on shear behavior of granular material and also explain that cyclic deformation increases due to rotation of principal stress axis. Results further show that, water content has a great influence on the cyclic plastic deformation of granular material.
  • Tatsuya Ishikawa, Seiichi Miura
    Soils and Foundations 公益社団法人 地盤工学会 51 (5) 785 - 799 0038-0806 2011/10 [Refereed][Not invited]
     
    The objective of this study is to evaluate the effect of freeze-thaw action on the deformation-strength characteristics of crushable volcanic coarse-grained soils, wherein significant particle breakage occurs even under relatively low stress levels and saturated conditions. A series of monotonic triaxial compression tests was performed for volcanic coarsegrained soils under various freeze-thaw histories. On the basis of the test results, we examined the above-mentioned effect and the relationship between the degree of particle breakage and the freeze-thaw history. The results indicate that the degree of particle breakage under consolidation and shear increased with freeze-thaw action; and consequently, the strength and the stiffness of the soils decreased with an increase in the number of freeze-thaw cycles. Moreover, to examine the influence of freeze-thaw action on the single-particle hardness of volcanic coarse-grained soils, single-particle crushing tests were conducted. The test results revealed that volcanic soil particles become more fragile after being exposed to freeze-thaw action, and as a result, the degree of particle breakage increases. These results indicate that the freeze-thaw action has a strong influence on the deformation-strength characteristics of crushable volcanic soils in terms of an increase in particle breakage, even if the soils lack frost-heave characteristics.
  • Dependency of shear behavior of recycled crusher-run material on moisture content evaluation by multi-ring shear testing
    Inam, A, Ishikawa, T, Miura, S
    Proceedings of the 2nd Japan-Korea Joint Workshop on Unsaturated Soils and Ground 189 - 198 2011/09 [Refereed][Not invited]
  • Tatsuya Ishikawa, Etsuo Sekine, Seiichi Miura
    Canadian Geotechnical Journal 48 (5) 691 - 703 0008-3674 2011/05 [Refereed][Not invited]
     
    This paper describes a new testing method to examine the mechanical behavior of railroad ballast subjected to repeated train passages on ballasted track. Two types of cyclic loading tests, namely a single-point loading test and a movingwheel loading test, were performed with small-scale models of ballasted track. Next, a "multi-ring shear apparatus" was developed as a type of torsional simple shear apparatus, and the applicability of a newly proposed multi-ring shear test to an element test of railroad ballast subjected to moving-wheel loads was examined by comparing the results of multi-ring shear tests with those of small-scale model tests. As a result, it was recognized that cumulative strain obtained from multi-ring shear tests is almost equivalent to the one derived from small-scale model tests. Moreover, it was revealed that the difference between loading methods has a considerable influence on the cyclic plastic deformation of railroad ballast because settlement in a moving-wheel loading test was much larger than the one in a single-point loading test. These results lead to the conclusion that a multi-ring shear test has an excellent applicability to the estimation of deformation behavior of granular materials subjected to moving-wheel loads.
  • 石川達也, 川端伸一郎, 亀山修一, 安倍隆二, 小野丘
    Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 公益社団法人 土木学会 67 (3) I_109 - I_116 2185-6559 2011 [Refereed][Not invited]
     
     This paper examines the effects of freezing and thawing on the mechanical behavior of granular base under unsaturated condition through the long-term field measurement of ground temperature, water content and deformation inside pavement, by performing FWD tests before and after freeze-thawing and by developing a new CBR test of freeze-thawed base course materials. We also evaluate the influences of the change in the stiffness of granular base due to freeze-thawing on the fatigue breaking of pavements in cold regions by applying the theoretical design method for asphalt pavement in consideration of the effects found in this paper. As the result, it was revealed that the freeze-thawing of granular base has a strong influence on the fatigue life of pavement structure in cold regions because it varies the deformation-strength characteristics of base course materials.
  • T. Ishikawa, S. Miura, K. Itou
    Unsaturated Soils - Proceedings of the 5th International Conference on Unsaturated Soils 1 549 - 554 2011 [Refereed][Not invited]
     
    This paper examines the effect of freeze-thaw action on the deformation-strength characteristics of crushable volcanic coarse-grained soil in unsaturated condition. An unsaturated triaxial apparatus, which can simulate freeze-thaw sequence in real foundations, was developed and a series of monotonic triaxial compression tests for a crushable volcanic coarse-grained soil exposed to freeze-thaw action were performed under various degrees of saturation. Test results showed that the freeze-thaw action made the amount of particle breakage under consolidation and shear increase for crushable volcanic coarse-grained soils, and its shear strength and deformation modulus under unsaturated conditions decreased by being exposed to freeze-thaw action. These indicate that the freeze-thaw action has strong influences on the deformation-strength characteristics of a crushable volcanic soil in unsaturated conditions even if the soil lacks in frost heave characteristics. © 2011 Taylor & Francis Group, London.
  • 粒状路盤の力学挙動に及ぼす凍結融解作用の影響評価
    石川 達也, 安倍 隆二, 吉田 有喜, 三浦 清一
    土木学会舗装工学論文集 15 201 - 209 2010/12 [Refereed][Not invited]
  • Alexander Camarena Capriles, Tatsuya Ishikawa, Seiichi Miura
    Geomechanics and Geotechnics: From Micro to Macro - Proceedings of the International Symposium on Geomechanics and Geotechnics: From Micro to Macro, IS-Shanghai 2010 1 689 - 693 2010/10 [Refereed][Not invited]
     
    Failures due to rainfall, In slopes formed from volcanic soils are frequent in Hokkaido, Japan. In this study an analytical procedure to simulate rainfall-induced slope failure is proposed. The slope failure is simulated by combining two different methods, namely discontinuous analysis based on Distinct Element Method (DEM), and seepage analysis based on Finite Element Method (FEM). In order to simulate and analyze the behavior of the soil due to changes in water content accurately, the Contact-Bond model approach is used in the discontinuous simulations. To begin with, discontinuous analysis was performed for triaxial compression tests of saturated and unsaturated soils, and seepage analysis was also performed, In order to determine appropriate input parameters for the DEM simulations. The results obtained from the two numerical simulations were combined in a DEM model of the slope where the failure dynamics were examined. With this method, the efficacy of using the Contact-Bond model approach for the failure dynamics can be analyzed. The validity of this analytical procedure was evaluated by comparing experimental results of test models with the numerical simulation. © 2011 Taylor & Francis Group.
  • Effect of freeze-thaw action on strength characteristics of unsaturated coarse-grained soil
    Ishikawa, T, Ito, K, Miura, S
    Proceedings of 5th International Conference on Unsaturated Soils (UNSAT10) 549 - 554 2010/09 [Refereed][Not invited]
  • Tatsuya Ishikawa, Tetsuya Tokoro, Kohei Ito, Seiichi Miura
    Soils and Foundations 50 (3) 431 - 440 0038-0806 2010/06 [Refereed][Not invited]
     
    This paper proposes new testing methods for evaluating the effects of freeze-thaw action on the deformation-strength characteristics and the water retention-permeability characteristics of granular materials under unsaturated conditions. A triaxial apparatus and a permeability apparatus for unsaturated soils, with cooling systems to control the temperature of soil specimens and use the pressure membrane method instead of the pressure plate method, were newly developed in order to examine the hydro-mechanical behavior of unsaturated soils subjected to the freeze-thaw sequence, as experienced by in-situ soils in cold regions. Results indicate that the proposed testing methods with these newly developed test apparatuses are highly useful in the evaluation of the effect of freeze-thaw action on the hydro-mechanical behavior of unsaturated granular materials and in the reduction of total testing time.
  • KAWAMURA Shima, MIURA Seiichi, ISHIKAWA Tatsuya, YOKOHAMA Shoji
    Doboku Gakkai Ronbunshuu C 公益社団法人 土木学会 66 (3) 577 - 594 1880-604X 2010 [Refereed][Not invited]
     
      Collapse of slope formed from volcanic soils has been frequently caused in Hokkaido, Japan. This study aims at clarifying failure mechanism of volcanic slope caused by both rainfall and freeze-thaw action. In particular, the effects of freeze-thaw action, slope angle, density and friction of impermeable layer in the slope on mechanical behavior were detailedly investigated on volcanic slopes having several shapes. The results showed that; surface slope failure depends strongly on slope angle, the friction characteristics of impermeable layer and rainfall intensity, and the formation of frozen layer in spring season and the softening of slope by freeze-thaw action in summer season are important for evaluating the stability of volcanic slope.
  • 石川達也, 関根悦夫
    応用力学論文集(CD-ROM) 13 1031 - 1039 2010 [Refereed][Not invited]
  • TOKORO Tetsuya, ISHIKAWA Tatsuya, AKAGAWA Satoshi
    Japanese Geotechnical Journal 公益社団法人 地盤工学会 5 (4) 603 - 613 1880-6341 2010 [Refereed][Not invited]
     
    A method for measuring the permeability coefficient of frozen soils in which generalized Clausius-Clapeyron equation is applicable has been proposed. In this method, in order to acquire continuous water flow, soil’s ice segregation phenomena have been prevented by applying axial stress. The top and bottom of the specimen were kept at normal temperature and the center of the specimen was controlled at minus temperature. Flow rate have been measured by applying differential head and the permeability coefficients were calculated by water flow in steady state. In this study, a test apparatus was newly developed using this measurement method and permeability coefficients at various temperatures were measured. As a result, the permeability coefficient of frozen soil has been shown to have a temperature dependency and the coefficient decreased rapidly around 0 °C.
  • S. Kawamura, S. Miura, T. Ishikawa
    Geotechnical Special Publication (202 GSP) 152 - 158 0895-0563 2010 [Refereed][Not invited]
     
    Collapse of volcanic slopes induced by rainfall has been frequently induced in Hokkaido, Japan, especially the middle southern area. It has been known that volcanic slopes in Hokkaido have a strong potential to cause such failure. The objective of this study is to reveal failure mechanism of volcanic slopes caused by both rainfall and freeze-thaw actions. A series of model tests was performed on volcanic slopes having several moisture contents. In particular, the effect of freeze-thaw actions on mechanical behavior at failure was investigated detailedly. © 2010 ASCE.
  • 移動輪荷重作用下の粒状路盤の力学挙動に及ぼす含水状態の影響評価
    石川 達也, 細田 充, 三浦 清一, 関根 悦夫
    土木学会舗装工学論文集 14 9 - 17 2009/12 [Refereed][Not invited]
  • Tetsuya Tokoro, Tatsuya Ishikawa, Seiichi Miura
    Unsaturated Soils: Theoretical and Numerical Advances in Unsaturated Soil Mechanics - Proceedings of the 4th Asia Pacific Conference on Unsaturated Soils 179 - 184 2009/11 [Refereed][Not invited]
     
    Many steady-state methods for measurement of the permeability coefficient have been proposed. However, an extensive amount of time is required to complete a series of permeability tests. The purpose of this paper is to shorten the testing time of the steady-state pressure method by using a membrane filter. In order to measure the unsaturated permeability, a triaxial apparatus capable of performing the steady-state membrane method was developed. The permeability test was conducted by applying matric suction and a differential water head to both ends of the specimen at the same time. A water retention test can be simultaneously conducted by measuring inflow and outflow of water. As a result, soil-water characteristic curves and relationships between degree of saturation and permeability coefficientwere in good agreement with previously published experimental data. The newly developed pressure membrane method takes a shorter time than the pressure plate method. © 2010 Taylor & Francis Group London.
  • T. Ishikawa, K. Ito, S. Miura
    Unsaturated Soils: Theoretical and Numerical Advances in Unsaturated Soil Mechanics - Proceedings of the 4th Asia Pacific Conference on Unsaturated Soils 159 - 164 2009/11 [Refereed][Not invited]
     
    The objective of this study is to evaluate the effect of freeze-thaw action on the soil water characteristics of crushable granular materials. An unsaturated triaxial apparatus, which could apply freeze-thaw sequence to a test specimen, was newly developed, and a series of water retention tests for a crushable volcanic coarse-grained soil and non-crushable sand exposed to various freeze-thaw histories were performed. The change in the shape of water retention curves due to freeze-thawing and the relationship between degree of particle breakage and freeze-thaw history are examined. Results revealed that since particle breakage for crushable volcanic coarse-grained soil increased with an increase in freeze-thawing cycles, the freeze-thaw action has strong influences on the soil water characteristics even if the soil lacks in frost heave characteristics. © 2010 Taylor & Francis Group, London.
  • T. Ishikawa, S. Miura, T. Tokoro
    Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering 1 833 - 836 2009/10 [Refereed][Not invited]
     
    This paper proposes new testing methods for evaluating the effects of freeze-thaw action on the deformation-strength characteristics and water retention-permeability characteristics of granular materials in unsaturated conditions. A triaxial and a permeability apparatus, which have a cooling system to control the temperature of the soil specimen, were developed in order to examine the hydro-mechanical behavior of unsaturated soils subjected to freeze-thaw sequence similar to that experienced by in-site soil in cold regions. Results indicate that the proposed testing methods with the newly developed test apparatuses are highly useful in the evaluation of the effects of the freeze-thaw action on the hydro-mechanical behavior of unsaturated soils. © 2009 IOS Press.
  • Application of coupled thermo-mechanical analysis to slope behavior during freezing and thawing in cold regions
    Ishikawa, T, Sato, M, Miura, S. Akagawa, S, Kawamura, S
    Proceedings of IS Kyoto09 409 - 415 2009/05 [Refereed][Not invited]
  • Tatsuya Ishikawa, Etsuo Sekine, Seiichi Miura
    CJWPT 2009: PROCEEDINGS OF THE 5TH CHINA-JAPAN WORKSHOP ON PAVEMENT TECHNOLOGIES 113 - + 2009 [Refereed][Not invited]
     
    This paper presents a simple method to estimate the cyclic plastic deformation of ballasted track subjected to repeated train passages in terms of the strength and deformation characteristics of coarse granular materials. A new analytical procedure with linear elastic FE analysis considering the cumulative strain characteristics of poorly-graded crushed stone, that is ballast, which were derived from two types of multi-ring shear tests, namely a fixed-place loading test and a moving wheel loading test, was proposed. As the results, it was revealed that the newly proposed analytical procedure could roughly estimate the residual settlement of railroad ballast under cyclic moving wheel loads, by comparing test results of cyclic loading tests for small scale model of ballasted track with the results of FE analysis.
  • T. Ishikawa, T. Kamei, E. Sekine, Y. Ohnishi
    BEARING CAPACITY OF ROADS, RAILWAYS AND AIRFIELDS, VOLS 1 AND 2 2 1207 - + 2009 [Refereed][Not invited]
     
    The paper proposes a new analytical procedure that involves discontinuous analysis to estimate the bearing capacity of granular roadbed used in ballasted track, namely "railroad ballast." To examine the applicability of the procedure, a series of numerical simulation bearing capacity tests for a 1/5 scale model of a real ballasted track were performed by employing discontinuous deformation analysis (DDA) that regards a particle of crushed stone as an irregular polygon. By comparing the analytical results and experimental results, the effect of roadbed stiffness on the bearing capacity of railroad ballast was examined. As the result, it was revealed that the roadbed stiffness has significant influence on the bearing capacity of railroad ballast, and that discontinuous analysis is an effective method to simulate the mechanical behavior of railroad ballast if the roadbed, which has been often modeled as a continuum, can be approximated with discontinuous modeling well.
  • S. Kawamura, S. Miura, T. Ishikawa, H. Ino
    PREDICTION AND SIMULATION METHODS FOR GEOHAZARD MITIGATION 25 - + 2009 [Refereed][Not invited]
     
    Collapse of slope formed from volcanic soils has been frequently caused in Hokkaido, Japan. This study aims at clarifying failure mechanism of volcanic slope caused by both rainfall and freeze-thaw action. In particular, the effects of freeze-thaw action, slope angle, density and friction of impermeable layer in the slope on mechanical behavior at failure were detailedly investigated on volcanic slopes having several shapes.
  • T. Ishikawa, S. Miura, S. Akagawa, M. Sato, S. Kawamura
    Prediction and Simulation Methods for Geohazard Mitigation 409 - 416 2009/01/01 [Refereed][Not invited]
     
    This paper presents a new analytical procedure with a coupled thermo-mechanical FE analysis to simulate the mechanical behavior of frost heaved soil slope during freezing and thawing. First, a coupled thermo-mechanical FE analysis, which can consider the change in deformation-strength characteristics due to freeze-thaw action, was newly developed. Next, to examine the applicability of the coupled analysis and to analyze the mechanical behavior of frost heaved soil slopes during freezing and thawing, a numerical simulation of a freeze-thawing test for model slope was conducted. As the results, it is revealed that the coupled analysis proposed in this paper is an effective method to simulate the slope behavior during freezing and thawing, and that freeze-thaw action has a profound influence on the slope failure at a subsurface layer in cold regions.
  • Application of DDA to mechanical behavior of granular base-subgrade system
    Ishikawa, T, Sekine, E, Ohnishi, Y
    Proceedings of International Mini-Symposium for Numereical Discontinuous Analysis 41 - 52 2008/11 [Refereed][Not invited]
  • T. Ishikawa, S. Miura
    12th International Conference on Computer Methods and Advances in Geomechanics 2008 1 1219 - 1226 1345-9139 2008/10 [Refereed][Not invited]
     
    This paper proposes a new analytical procedure to simulate the frost heave of granular materials. The objective of the research is to examine the applicability of discontinuous analysis to numerical simulation for the mechanical behaviour of granular materials subjected to freeze-thaw action. In this paper, numerical simulations of freeze-thawing triaxial compression tests for glass beads were performed with three-dimensional DEM coupled with a thermal analysis, and the applicability of the DEM to the freezing-thawing behaviour of granular materials was discussed. As the results, it was shown that the proposed DEM model that puts many small elements between soil particles, which expand with dropping the temperature, can simulate the freezingthawing behaviour of granular materials to some extent though there is room for further investigation as to numerical modelling and setting analytical parameters.
  • T. Ishikawa, M. Hosoda, S. Miura, E. Sekine
    Advances in Transportation Geotechnics - Proceedings of the 1st International Conference on Transportation Geotechnics 185 - 191 2008/08 [Refereed][Not invited]
     
    This paper presents an experimental study to evaluate the effects of water content on the mechanical behavior of gravel subjected to moving wheel loads. First, two types of small scale model tests which adopted a fixed-place loading method and a moving loading method were performed with a base course material under air-dried condition and saturated condition. Next, two types of multi-ring shear tests which could consider a change in direction of principal stresses like traffic loads were performed likewise. Based on test results, the relationships between the water content of test samples and the deformation-strength characteristics were examined. As the results, it was revealed that the shear strength of gravel decreased and the cumulative residual strain increased due to the saturation in both tests, regardless of loading methods. This indicates that the water content of gravel influences the mechanical behavior of granular roadbed strongly. © 2008 Taylor & Francis Group, London.
  • ISHIKAWA Tatsuya, KAMEI Takehiko, SEKINE Etsuo, OHNISHI Yuzo
    JOURNAL OF PAVEMENT ENGINEERING, JSCE 公益社団法人 土木学会 13 (13) 125 - 132 1884-8176 2008 [Refereed][Not invited]
     
    The paper proposes a new analytical procedure with discontinuous analysis to estimate the bearing capacity of granular roadbed used in ballasted track or road pavement. To examine the applicability, a series of numerical simulations bearing capacity tests for 1/5 scale model of real ballasted track were performed with DDA that regards a particle of crushed stone as an irregular polygon. Based on the comparison of analytical results with experimental results, the effect of subgrade stiffness on the bearing capacity of granular roadbed was examined. As the result, it is revealed that the subgrade stiffness has a great influence on the bearing capacity of granular roadbed, and that discontinuous analysis is an effective method to simulate the mechanical behavior of granular roadbed if the subgrade which behaves as a continuum can be approximated with discontinuous modeling well.
  • ISHIKAWA Tatsuya, OZAKI Yuta, MIURA Seiichi
    Doboku Gakkai Ronbunshuu C 公益社団法人 土木学会 64 (3) 712 - 717 1880-604X 2008 [Refereed][Not invited]
     
    The objective of this study is to evaluate the effect of freeze-thaw sequence on the mechanical behavior of crushable volcanic coarse-grained soils. A new test apparatus, which can simulate freeze-thaw sequence in real foundations, was developed and a series of triaxial compression tests and water retention tests were performed. Test results showed that the freeze-thaw sequence made the amount of particle breakage increase, and as the result its strength decreases and water retention capacity increases by being exposed to freeze-thaw action. This indicates that the freeze-thaw action has strong influences on the mechanical behavior of crushable volcanic soils even if the soil lacks in frost heave characteristics.
  • 石川達也, 里優, 三浦清一, 赤川敏, 川村志麻
    岩の力学国内シンポジウム講演論文集 12th(CD-ROM) ROMBUNNO.98 - 36 1883-1486 2008 [Refereed][Not invited]
  • T. Ishikawa, S. Miura, K. Ito, Y. Ozaki
    DEFORMATION CHARACTERISTICS OF GEOMATERIALS, VOLS 1 AND 2 2 557 - + 2008 [Refereed][Not invited]
     
    The objective of this study is to evaluate the effect of freeze-thaw action on the deformation-strength characteristics of crushable volcanic coarse-mined soil in saturated condition, wherein particle breakage significantly takes place even under relatively low stress levels. A new test apparatus, which can simulate freeze-thaw sequence in real foundations, was developed and a series of monotonic triaxial compression tests for a volcanic coarse-grained soil were performed under various freeze-thaw histories. Test results showed that the freeze-thaw action made the amount of particle breakage under consolidation and shearing increase, and as the result its strength and shear modulus decrease with the increase in freeze-thawing cycles. This indicates that the freeze-thaw action has strong influences on the deformation-strength characteristics of crushable volcanic soil even if the soil lacks in frost heave characteristics. Moreover, to examine the influence of freeze-thaw action on the single particle hardness of volcanic coarse-grained soils, single particle crushing tests were performed. Test results revealed that a constituent particle of volcanic soils became more fragile by being exposed to freeze-thaw action, and as a result, the amount of particle breakage increased.
  • Effect evaluation of moving load on cyclic deformation of crushed stone
    Ishikawa, T, Sekine, E
    Proceedings of the 13th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering 1 435 - 438 2007/12 [Refereed][Not invited]
  • Fundamental study for slope failure of volcanic soil ground by DDA
    Ishikawa, T, Kawamura, S, Miura, S, Ohnishi, Y
    Proceedings of 8th International Conference on the Analysis of Discontinuous Deformation 61 - 66 2007/08 [Refereed][Not invited]
  • Effect of moving wheel load on cyclic deformation of granular material
    Ishikawa, T, Sekine, E, Miura, S
    Proceedings of the 4th JAPAN/CHINA Workshop on Pavement Technologies 41 - 50 2007/07 [Refereed][Not invited]
  • Influence of degree of saturation on strength characteristics of crushable volcanic coarse-grained soils
    Ishikawa, T, Ozaki, Y, Miura, S
    Proceedings of the 3rd Asian Conference on Unsaturated Soils 223 - 229 2007/04 [Refereed][Not invited]
  • SEKINE Etsuo, ISHIKAWA Tatsuya, MIURA Seiichi
    JOURNAL OF PAVEMENT ENGINEERING, JSCE 公益社団法人 土木学会 12 (12) 47 - 55 1884-8176 2007 [Refereed][Not invited]
     
    This paper presents a simple method to estimate cyclic plastic deformation of ballasted track subjected to repeated train pas-sages in terms of the strength and deformation characteristics of coarse granular materials. A new analytical procedure with linear elastic FE analysis considering the cumulative strain derived from multi-ring shear test results of poorly-graded crushed stone, namely ballast, was proposed, and it was revealed that the analytical procedure could roughly estimate the residual settlement of railroad ballast under cyclic moving wheel loads, by comparing test results of small scale model tests of ballasted track with the analytical results.
  • ISHIKAWA Tatsuya, SEKINE Etsuo, IZUMI Go
    Doboku Gakkai Ronbunshuu F 公益社団法人 土木学会 63 (4) 517 - 529 1880-6074 2007 [Refereed][Not invited]
     
    This study presents an experimental study to elucidate the dynamic response of railway track structures subjected to horizontal seismic loads. A series of shaking table tests for one-third scale models of ballast track and grouted ballast track was performed. Based on test results, the seismic stability and ductility beyond failure of railroad ballast were quantitatively evaluated associated with the observed movement of ballast particles inside railroad ballast. As the results, an evaluation method of seismic performance of railway track was proposed correspondent to magnitude of earthquake motions, and it was revealed that the difference in track structure had a serious influence on the seismic performance of railway track.
  • ISHIKAWA Tatsuya, SEKINE Etsuo
    Doboku Gakkai Ronbunshuu F 公益社団法人 土木学会 63 (4) 506 - 516 1880-6074 2007 [Refereed][Not invited]
     
    This study presents an experimental study to elucidate the dynamic response of railroad ballast subjected to seismic loads. A series of shaking table tests for ballast and gravel was performed. In these tests, a one-third scale model of railroad ballast as well as a full scale model was used. Based on test results, the seismic stability and ductility beyond failure of railroad ballast are quantitatively evaluated. Moreover, effects of the scale factor between prototypes and the models on the dynamic response of granular materials are discussed. This study proposes an evaluation method of seismic performance of railroad ballast by small scale model tests.
  • T. Ishikawa, S. Miura, E. Sekine
    Design and Construction of Pavements and Rail Tracks: Geotechnical Aspects and Processed Materials 53 - 64 2007/01/01 
    This paper introduces a new testing method to examine the effects of the rotation of principal stress axes on cyclic plastic deformation ofrailroad ballast. “Multi-ring shear apparatus” was newly developed as a kind of torsional simple shear test apparatus, and the applicability of the multi-ring shear test to an element test ofrailroad ballast subjected to moving wheel loads was examined by comparing test results of the multi-ring shear tests with those of model tests. As the results, it was revealed that the multi-ring shear test is appropriate for simulating the actual stress states inside substructures under train loads.
  • Ishikawa Tatsuya, Sekine Etsuo, Miwa Masashi, Ohnishi Yuzo
    Journal of applied mechanics 公益社団法人 土木学会 10 (10) 513 - 522 1345-9139 2007 [Refereed][Not invited]
     
    This paper examines the effects of particle properties such as particle shape and grain size distribution of particle assemblage on the bearing capacity of railroad ballast in numerical simulations with discontinuous analysis. Here, two evaluation indexes of particle shape, namely “angularity” and “sphericity”, were employed. To evaluate the effect quantitatively, a series of numerical simulations that regard a ballast particle as a regular or an irregular polygon were performed. As the result, it can be observed that the particle shape of numerical models, especially the angularity has a greater effect on the bearing capacity of railroad ballast than the grain size distribution, and that the imitation of the shape of real ballast particles makes numerical results similar to experimental results.
  • Ishikawa Tatsuya, Tamaki Kazumi, Miura Seiichi
    Journal of applied mechanics 土木学会 9 (9) 641 - 648 1345-9139 2006/09 [Refereed][Not invited]
     
    This paper presentsa numerical experiment to reveal the effect of freeze-thaw action on the mechanical behavior of granular materials in tams of micmmechanics. The odjective is to propose a new analytical procedure to simulate the mechanical behavior of granular materials subjected to freeze-thaw sequence. Numerical simulations of freezing-thawing triaxial compression tests were performed with 3D DEM coupled with a thermal analysis, and the applicability of the DEM to the freezing-thawing behavior of granular materials was discussed As the results, it was showed that the proposed DEM model that puts many small elements which expand with dropping the temperature between soil particles can simulate the freezing-thawing behavior of granular materials to some extent though there is room for further investigation as to numerical modeling and setting analytical parameters.
  • ISHIKAWA Tatsuya, SEKINE Etsuo, MIURA Seiichi
    JOURNAL OF PAVEMENT ENGINEERING, JSCE 公益社団法人 土木学会 11 (11) 23 - 31 1884-8176 2006 [Refereed][Not invited]
     
    The objective of this paper is to propose a new testing method to examine the effects of moving wheel load on cyclic plastic deformation of railroad ballast in terms of the strength and deformation characteristics. Applicability of a newly developed multi-ring shear test, which can make the principal stress axes rotate, to an element test of granular materials subjected to moving wheel load was examined by comparing the laboratory element test results with the moving wheel loading test results of small scale model track. As the results, it was revealed that the mechanical behavior of railroad ballast under moving wheel loads is very similar to that of granular material subjected to the principal stress axis rotation during shear. Accordingly, it was confirmed that the multi-ring shear test is appropriate for simulating the actual stress states inside substructures under moving wheel loads.
  • T. Ishikawa, S. Miura, S. Yokohama, R. G. Mijares
    Geomechanics and Geotechnics of Particulate Media 121 - 126 2006 [Refereed][Not invited]
     
    The objective of this study is to evaluate the effect of degree of saturation on the strength characteristics of volcanic coarse-grained soils, wherein particle breakage significantly takes place during loading and deformation processes, under various degrees of saturation conditions. In this paper, a series of monotonic triaxial compression tests for two kinds of volcanic coarse-grained soils are performed under various degrees of saturation conditions, and the relationships between degree of saturation, degree of particle breakage and strength are examined based on experimental results. As the result, the following conclusions are obtained: The shear strength of crushable coarse-grained volcanic soils decreases with an increase in the amount of particle breakage. Particle breakage is strongly influenced by the degree of saturation of the soil matrix. Accordingly, as the crushable volcanic coarse-grained soil becomes saturated, particle breakage becomes more dominant, thereby decreasing the shear strength of the soil.
  • T. Ishikawa, K. Kobayashi, E. Sekine, Y. Ohnishi
    Geomechanics and Geotechnics of Particulate Media 389 - 395 2006 [Refereed][Not invited]
     
    This paper examines the effects of particle shape on the bearing capacity of railroad ballast in numerical simulations with discontinuous analysis. A series of numerical simulations that regard a ballast particle as a regular or an irregular polygon were performed. Here, the particle shape of railroad ballast in numerical models was evaluated by two kinds of analytical methods, namely "argument function" and "radius function." Next, the correlations of the evaluation indexes of particle shape with the strength-deformation characteristics of granular materials in numerical models were examined. As the result, it can be observed that the particle shape of numerical models, especially the angularity has greater effect on the bearing capacity of railroad ballast than the sphericity, and that the imitation of the shape of real ballast particles makes analytical results similar to experimental results.
  • Influence of input parameters on energy loss in free fall tests with DDA
    Ishikawa, T, Miura, S, Ohnishi, Y
    Proceedings of 7th International Conference on the Analysis of Discontinuous Deformation 147 - 158 2005/12 [Refereed][Not invited]
  • Development and performance evaluation of multi-ring shear apparatus
    Ishikawa, T, Miura, S, Sekine, E
    Proceedings of Geotechnical Aspects and Processed Material in Design and Construction of Pavement and Rail Track 53 - 64 2005/09 [Refereed][Not invited]
  • ISHIKAWA T.
    Proc. of the 7th International Conference on the Bearing Capacity of Roads, Railways and Airfields, Trondheim, 2005 1/1(CD-ROM)52  2005/06 [Refereed][Not invited]
  • Numerical Simulation of Shear Tests for Granular Materials with 3D DEM
    Ishikawa, T, Tamaki, K, Miura, S
    Proceedings of the 11th International Conference on Computer Methods and Advances in Geomechanics 2 65 - 72 2005/06 [Refereed][Not invited]
  • SEKINE Etsuo, ISHIKAWA Tatsuya
    JOURNAL OF PAVEMENT ENGINEERING, JSCE 公益社団法人 土木学会 10 (10) 53 - 60 1884-8176 2005 [Refereed][Not invited]
     
    This paper presents a simple method to estimate cyclic plastic deformation of ballasted track subjected to repeated train passages in terms of the strength and deformation characteristics of coarse granular materials. A new analytical procedure with linear elastic FEM analysis considering the cumulative strain derived from element test results of ballast was proposed, and it was revealed that the analytical procedure could roughly estimate the residual settlement of railroad ballast, which is an assemblage of poorly-graded crushed stone, by simulating small scale model tests of ballasted track.
  • T Ishikawa, K Tamaki, Y Ohnishi, S Miki
    Contribution of Rock Mechanics to the New Century, Vols 1 and 2 1227 - 1232 2004 [Refereed][Not invited]
     
    This paper shows an analytical study to evaluate the effects of pore pressure on the strength and deformation characteristics of saturated granular materials. Six simulations of triaxial compression tests were performed regarding a constituent particle as an element of discontinuous analysis (DDA). The method to build pore pressure such as pore water pressure and frost heaving pressure into DDA and the applicability of the improved DDA to the shearing behavior of saturated granular materials at undrained condition were discussed. As the results, the numerical algorithm for detecting voids and outer circumference of granular assemblage and loading pore and lateral pressure was proposed, it was showed that the improved DDA can examine the action of pore pressure though there is room for further investigation.
  • T Ishikawa, E Sekine, A Khono, S Miura
    CYCLIC BEHAVIOUR OF SOILS AND LIQUEFACTION PHENOMENA 633 - 640 2004 [Refereed][Not invited]
     
    This paper presents a method to estimate cyclic plastic deformation of railroad ballast, which is an assemblage of poorly-graded crushed stone, subjected to repeated train passages. First, to understand the behavior of railroad ballast under train loads, small scale model tests which adopt moving loads as the loading method were performed. Second, to examine their strength and deformation characteristics, cyclic loading and monotonic loading triaxial compression tests were performed. Finally, to develop a simple prediction method of residual settlement in ballasted track under repeated loads, the application method of Finite Element Method was discussed by simulating small scale model tests of ballasted track with linear elastic FE analysis. This paper proposes an estimation method to predict residual settlement of railroad ballast under repeated moving loads in terms of the strength and deformation characteristics of coarse granular materials.
  • Modeling for Energy Dissipation in Free Fall Tests of Spherical Stone with Discontinuous Analysis
    Ishikawa, T, Ohnishi, Y, Jian Hong Wu, Nishiyama, S
    Proceedings of SRA03 1105 - 1110 2003/06 [Refereed][Not invited]
  • T Ishikawa, E Sekine
    DEFORMATION CHARACTERISTICS OF GEOMATERIALS 841 - 848 2003 [Refereed][Not invited]
     
    This study presents an experimental study to elucidate the dynamic response of railroad ballast subjected to seismic loads. A series of shaking table tests for the uniformly graded crushed stone was performed. In these tests, a full scale model of railroad ballast as well as a one-third scale model with uniformly graded crushed stone whose mean grain size was different from ballast despite similar grain size distribution was used. Based on test results, the seismic stability and ductility beyond failure of railroad ballast are quantitatively evaluated associated with the observed movement of ballast particles inside railroad ballast. Moreover, effects of the scale factor between prototypes and the models on the dynamic response of granular materials are discussed associated with the strength and deformation characteristics of ballast and gravel obtained by triaxial compression tests. This study proposes an evaluation method of seismic stability and ductility correspondent to magnitude of earthquake motions.
  • Shaking table tests of coarse granular materials with discontinuous analysis
    Ishikawa, T, Ohnishi, Y, Sekine, E
    Proceedings of 5th International Conference on the Analysis of Discontinuous Deformation 181 - 188 2002/10 [Refereed][Not invited]
  • 「MTT作業計画支援システム」の試行について
    奥村 陽一, 沼倉 明夫, 小野 重亮, 蔭山 朝昭, 石川 達也, 三和 雅史, 藤森 寿雄, 森 忠夫, 都築 達彦
    土木学会鉄道力学論文集 (6) 55 - 59 2002/07 [Refereed][Not invited]
  • 横圧載荷による木まくらぎ状態判定試験
    小林 潤, 石川 達也, 小野 重亮, 峰岸 大介
    土木学会鉄道力学論文集 (6) 49 - 54 2002/07 [Refereed][Not invited]
  • Effects of Moving Wheel Load on Cyclic Deformation of Railroad Ballast
    Ishikawa, T, Sekine, E
    Proceedings of Railway Engineering-2002 2002/07 [Refereed][Not invited]
  • MIWA M.
    Railway Engineering 2002, London 2002/07 [Refereed][Not invited]
  • MIWA M.
    WCRR2001, Koeln 2001/11 [Refereed][Not invited]
  • MIWA Masashi, ISHIKAWA Tatsuya, OYAMA Tatsuo
    Doboku Gakkai Ronbunshu 公益社団法人 土木学会 681 (681) 51 - 65 0289-7806 2001/07/20 [Refereed][Not invited]
     
    In this paper we investigate the transition process of surface irregularity to determine maintenance strategies effectively. From the statistical data analysis, we develop a degradation model and restoration model. Next, in order to obtain an optimal maintenance policy based upon both maintenance costs and level of irregularity for riding quality and safety we propose an all integer mathematical programming model for making optimal multiple tie tamper (MTT) operation scheduling. This scheduling model allows us to decide when a MTT should be allocated to each depot, and which lot should be executed maintenance with the MTT.
  • A Study on the Time Dependency of Granular Materials with DDA
    Ishikawa, T, Ohnishi, Y
    Proceedings of 4th International Conference on the Analysis of Discontinuous Deformation 271 - 280 2001/06 [Refereed][Not invited]
  • Application of discontinuum analysis to cyclic plastic deformation of coarse granular materials
    Ishikawa, T, Ohnishi, Y
    Proceedings of the 10th International Conference on Computer Methods and Advances in Geomechanics 321 - 324 2001/01 [Refereed][Not invited]
  • Application of discontinuum analysis to track deterioration in ballasted track
    Ishikawa, T, Ohnishi, Y, Namura, A
    Proceedings of Railway Engineering-2000 2000/07 [Refereed][Not invited]
  • MIWA M.
    Railway Engineering 2000, London 2000/07 [Refereed][Not invited]
  • ISHIKAWA Tatsuya, OHNISHI Yuzo, HORIIKE Takahiro
    Doboku Gakkai Ronbunshu 公益社団法人 土木学会 2000 (645) 15 - 28 0289-7806 2000 [Refereed][Not invited]
     
    In order to understand the deformation of “railroad ballast”, which is a component of the ballasted track composed of crushed stone, the simulations of full-scale track tests regarding its part as an assemblage of coarse granular materials were performed in this paper. And the applicability of discontinuum analysis to the cyclic plastic deformation of railroad ballast was discussed in comparing analytical results with DDA (Discontinuous Deformation Analysis) and experimental results. As a result, some new guidelines for the application method of DDA were indicated, and the cyclic plastic deformation of railroad ballast was proved the fabric transformation of particle alignment accompanied by sliding between particles in terms of the mechanics of granular materials.
  • MIWA M.
    WCRR'99, Tokyo 1999/10 [Refereed][Not invited]
  • 鉄道構造物等設計標準［有道床軌道］に準じた構造解析手法に関する一考察
    石川 達也, 内田 雅夫
    土木学会鉄道力学論文集 (3) 31 - 36 1999/06 [Refereed][Not invited]
  • T Ishikawa, M Kamon, A Namura
    PRE-FAILURE DEFORMATION CHARACTERISTICS OF GEOMATERIALS, VOL 1 783 - 791 1999 [Refereed][Not invited]
     
    This paper presents experimental and analytical studies to elucidate such phenomenon observed in ballasted railway track that irregularity of rail level under train passage gets worse, that is "track deterioration", in terms of cyclic deformation of railroad ballast. Vertical cyclic loading tests were performed with full-scale track attaching special test facilities, and the application method of the discrete analysis to the cyclic deformation of railroad ballast was also discussed by simulating full-scale track tests with DDA and FEM. As the result, it was concluded that the cyclic deformation of railroad ballast occurred by the movement of ballast particles, accompanied by the fabric transformation of particle alignment.
  • T Ishikawa, Y Ohnishi
    ICADD-3: THIRD INTERNATIONAL CONFERENCE ON ANALYSIS OF DISCONTINUOUS DEFORMATION - FROM THEORY TO PRACTICE, PROCEEDINGS 107 - 116 1999 [Refereed][Not invited]
     
    This paper presents an analytical study to elucidate the cyclic plastic deformation of railroad ballast in ballasted railway track under train passage, that is "track deterioration". The simulations of full-scale vertical cyclic loading tests of railroad track regarding a ballast particle as a DDA block were performed, and the applicability of DDA to the cyclic plastic deformation of railroad ballast was discussed. It was found that the cyclic plastic deformation of railroad ballast could be defined as the fabric transformation of particle alignment accompanied by sliding between particles. DDA is useful to trace the movement of particles and to unveil the complex deformation mechanics of granular ballast materials.
  • Ishikawa Tatsuya, Ohnishi Yuzo
    Doboku Gakkai Ronbunshu 公益社団法人 土木学会 1998 (589) 205 - 217 0289-7806 1998 [Refereed][Not invited]
     
    In this paper, as the basic study to analyze the deformation of “ballast”, a track component of ballasted track which is composed of crushed stone, regarding its part as an assemblage of coarse granular materials, the application method of discrete analysis treating the problem including discontinuous boundaries to cyclic deformation of coarse granular materials was discussed by simulating triaxial tests of railroad ballast with DDA (Discontinuous Deformation Analysis). As a result, it was revealed that some new guidelines for the application method of DDA were indicated, and also quasi-static performance of railroad ballast is discussed in terms of fabric transformation of particle alignment.
  • DDA applied to deformation analysis of coarse granular materials (ballast)
    Ishikawa, T, Ohnishi, Y, Namura, A
    Proceedings of 2nd International Conference on the Analysis of Discontinuous Deformation 253 - 262 1997/07 [Refereed][Not invited]
  • Ishikawa Tatsuya, Sunaga Makoto, Dong Jun, Namura Akira
    Doboku Gakkai Ronbunshu 公益社団法人 土木学会 1997 (575) 169 - 178 0289-7806 1997 [Refereed][Not invited]
     
    To analyze the deformation of ballast regarding a part of ballasted track which is composed of crushed stone as an assemblage of coarse granular materials, cyclic loading and monotonic loading triaxial compression tests with stress condition of ballast under train passage were performed on samples of railroad ballast. As a result, the quasi-static characteristics of railroad ballast needed for numerical modeling were determined. It was revealed that the triaxial test results of railroad ballast basically provide useful data for elucidating plastic deformation of ballast in detail.
  • M Uchida, H Takai, T Ishikawa, E Yazawa, M Miwa
    INTERNATIONAL RAILWAY CONFERENCE ON BETTER JOURNEY TIME - BETTER BUSINESS 1996 (8) 189 - 198 1356-1448 1996 [Refereed][Not invited]
  • Ishikawa Tatsuya, Namura Akira
    Doboku Gakkai Ronbunshu 公益社団法人 土木学会 1995 (512) 47 - 59 0289-7806 1995 [Refereed][Not invited]
     
    In order to elucidate the phenomenon observed in ballasted track that irregularity of rail level accumulates in terms of the plastic deformation of railroad ballast, vertical and horizontal cyclic loading tests of constant load amplitude were performed with full-scale track. As a result, it was revealed that an effective estimation of the deformation of railroad ballast needs considering coarse granular materials as its material property. Besides, the deformation properties were quantified by test results, and a method to predict deformation quantity of railroad ballast was proposed, which has high utility value for design and maintenance of track structure.
  • 石川達也, 名村明
    土質工学会シンポジウム発表論文集 (Ryujotai no Rikigaku...) 51 - 52 1993 [Refereed][Not invited]

Books etc

  • 北海道の地盤と防災
    地盤工学会北海道支部 2022/09
  • 地震による地すべり災害－2018年北海道胆振東部地震
    北海道大学出版会 2020/09
  • 斜面の凍上対策の調査・設計マニュアル（案）
    地盤工学会北海道支部 2016/09
  • 2014年制定 舗装標準示方書
    土木学会 2015/10
  • Advances in Transportation Geotechnics II
    CRC Press 2012/08
  • 舗装工学ライブラリー6 積雪寒冷地の舗装
    土木学会 2011
  • 斜面の凍上被害と対策のガイドライン
    地盤工学会北海道支部 2010/03
  • 地盤材料試験の方法と解説 第8編 特殊土の試験
    地盤工学会 2009
  • 計算力学レクチャーシリーズ6不連続変形法（DDA）
    丸善 2005

MISC

Awards & Honors

  • 2022/06 土木学会技術賞
  • 2022/06 地盤工学会技術業績賞
  • 2019/06 地盤工学会事業企画賞
  • 2018/06 地盤工学会事業企画賞
  • 2018/04 地盤工学会功績賞
  • 2017/09 平成29年度科研費の審査委員表彰

Research Grants & Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2020/04 -2024/03 
    Author : 安福 規之, 村上 哲, 笠間 清伸, 酒匂 一成, 所 哲也, 石川 達也, 川尻 峻三, 川村 志麻, 石藏 良平
     
    本研究では、気候変動災害脆弱地域と想定される九州と北海道の自然・人工斜面を対象として、１）経年的に変化する地盤災害に対する免疫性（災害免疫力）の工学的評価、２）降雨・融雪形態の変化や地震動と関連付けた地盤災害危険個所の抽出と危険度判定手法の高度化、３）降雨形態の変化を反映した実用的な土砂移動量と移動距離の算定手法の確立、４）適応策整備順位とその効果の客観化、経年変化の時間軸を導入した地盤災害脆弱性マップの事例作成をめざしている。当該年度の研究実績を以下に示す。 １）については、災害免疫力を経年的に変化する災害抵抗力と社会的リスクの積として表現し、切土のり面の経年変化を反映した災害抵抗力の評価手法とその適用事例を示した。また、九州地域における降雨や地盤情報のデータベース化と過去の福岡県管理道路の豪雨災害事例の収集整理を行い、新たに導入した雨量超過比による豪雨履歴と被災の関係を明らかにした。 ２）と３）に関しては、短期雨量指標と土壌雨量指数を用いて土砂災害発生危険基準線（CL）について福岡県の情報を収集し、地盤・地形・地質特性および 降雨情報などとの関係について機械学習を使って分析を行い、影響指標を具体化した。同様の取り組みを北海道でも実施し、雨慣れの影響を精査し、地域性について分析した。また、河川堤防において、高浸透外力下でパイピング破壊リスクが高まる基礎地盤条件を精査し、平均動水勾配の時間変化に着目した破壊リスク算定モデルを提案した。さらに、北海道において降雨後に地震動を受ける火山灰盛土の斜面崩壊機構を調査・分析し、その履歴順番の違いが崩壊に及ぼす影響を考察した。加えて、地震後の道路盛土の耐津波抵抗性を精緻な大型模型実験を通して分析した。 ４）に関しては、地域性を反映した地盤災害脆弱性の定義と適応枠組みを新たに提示し、斜面崩壊事例に基づいた地域減災力評価指標を提案した。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
    Date (from‐to) : 2019/10 -2023/03 
    Author : 上北 恭史, 藤田 香織, マルティネス アレハンドロ, 石川 達也
     
    本研究は東欧に残る校倉造木造教会堂の保存のために、その主な損傷を引き起こしていると思われる凍土の凍結融解による斜面崩壊のメカニズムを明らかにし、不同沈下や地すべりがもたらす木造教会堂の損傷およびその対策について研究をすることを目的にしている。そのため木造教会堂の建つ地盤にボーリングによる土壌解析や観測井を用いたモニタリング計測を行い、凍結融解作用による斜面崩壊の過程を地盤工学的に明らかにし、木造教会堂の保存対策や修理方針の策定を検討していく。 モニタリングを行う木造教会堂は、ウクライナ西部のlviv県に位置するポテリッチの聖神降臨聖堂(Potelych-Tserkva of the Descent of the Holy Spirit)を候補とした。この教会堂は16世紀初頭に建設され、ハリキ(Halych)様式と呼ばれる東側のアプスと中央部礼拝室上に塔をもつ古い形式で、ポーランドとウクライナの世界遺産「ポーランドとウクライナのカルバティア地方の木造教会群」の構成資産のうちのひとつである。この教会堂は科学研究費基盤研究B「ウクライナ木造教会堂群保存手法の構築－日欧校倉造修理工法の比較議論を通して」(16H04483)で調査を行い、地すべりによる不同沈下のために躯体中央部に亀裂を発生させており、校倉構造全体に歪を生じさせていることを把握した。そして教会堂内部にフレームを新たに組んで補強していることを確認している。これらの応急修理を担当したリヴィウ工科大学および本研究の共同研究者のキエフ建設大学の助言により、本教会堂をモニタリング実施を行う候補とした。 モニタリングを2020年度から開始するためにリヴィウ工科大学にボーリング掘削と土壌解析を依頼することとした。この土壌解析の成果に基づいて多段傾斜計等のセンサーの設置およびデータ収集のためのデータロガーの設置を検討している。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2019/04 -2023/03 
    Author : 早野 公敏, 石川 達也, 桃谷 尚嗣, 中村 貴久
     
    鉄道・道路施設では道床材，路盤材として砕石を主体とする粗粒材を広く使用している．これまでの研究で敷設後20年以上のバラスト軌道，供用30年以上のアスファルト舗装において交通荷重の繰返しによる破砕・細粒化が生じている．細粒化が進行すると雨水浸透に伴う沈下が頻発しさらには脱線や陥没のリスクが高まる．近年では降雨特徴の変化により突発的に変状が生じるケースが増加し，これらの予防や維持管理コストの最小化のためには道床・路盤材の交換や改良のタイミングの適切な判断が重要となる．また，災害後の早期復旧に破砕・細粒化が生じた道床・路盤材の再利用を求める場合もある．しかし現状では細粒化後の供用性予測の不確実性は高く，降雨後に沈下が頻発する現象や災害発生などに基づいて事後に経験的に判断することが多い．そこで本研究では破砕・細粒化した道床・路盤材の雨水浸透に伴う沈下特性や支持力特性を解明し，交換や改良の適切なタイミング・効果を科学的に評価できる新たな維持管理体系を構築することを行った． 具体的に2019年度は，室内要素試験および室内模型実験を主として実施し，経年劣化による細粒分増加が道床材の締固め特性，透水特性，繰返し変形特性，支持力特性に及ぼす影響を調査した．まず，経年劣化により破砕・細粒化した道床材の締固め試験を行い，細粒化の程度による締固め曲線の違いを明らかにした．次に道床材の透水性・繰返し変形特性に与える道床材細粒化の影響を透水試験・三軸試験により評価した．続いて室内模型実験により道床の支持力特性に破砕・細粒化が及ぼす影響を調べ，室内要素試験結果による評価結果との整合性について検討を行った．
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2018/06 -2021/03 
    Author : Ishikawa Tatsuya
     
    In order to develop a highly versatile slope disaster risk assessment method that predicts through rainfall habituation, which is an index of geodisaster resistance, this study discussed (a) proposal of rainfall habituation index for soil ground, (b) establishment of a method for investigating the degree of rainfall habituation, and (c) construction of a method for evaluating the risk of heavy rain induced geodisasters by considering rainfall habituation. As a result, in order to examine the potential risk of a geodisaster which is expected to occur when high-latitude cold regions with little heavy rainfall, such as Hokkaido and Tohoku in Japan, experience torrential rains due to climate change based on case studies of geodisasters that have occurred in the past in warm regions, this study proposed a method that can examine predicting the occurrence of slope disasters and assessing risks in a unified manner for various regions with different rainfall histories.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2017/04 -2020/03 
    Author : Ito Yuzuru
     
    The frozen earth wall of the Fukushima Nuclear Power Plant prevents an inflow of the groundwater to the nuclear reactor building and prevents increase of the contaminated water.It is assumed that the earth wall is maintained for a long term. Then a horizontal shrinkage crack by de-hydration due to frost heave occurs in front of the ice lens, and it was assumed that the extremely great increase in hydraulic conductivity might generate in front of the frozen earth wall. To confirm this hypothesis and to propose the preventive measure to this phenomenon, we developed the experimental device which could freeze-thaw the specimen horizontally and conduct permeability test vertically. The test result shows that even if a frost front remained at the constant position, a change of the void structure continued with time regardless of the frost-susceptibility of the fine-grained soil, and it was considered that the possibility that water shield of the earth wall was spoiled may be increasing.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2016/04 -2020/03 
    Author : ISHIKAWA Tatsuya
     
    High-latitude zone like Hokkaido is an important region where it is expected to benefit and develop from global warming in future, while it is also expected that new types of geotechnical disasters, which never experienced before, will occur due to climate change. Therefore, in this study, we have constructed a theoretical system that reasonably explains the geotechnical disasters peculiar to snowy cold regions, which are different from the geotechnical disasters observed in warm regions, from the viewpoint of multiphysics (multiphase mechanics) and space-time multiscale by considering the interaction between thermal / hydraulic boundary condition changes and mechanical behavior in the normal to low temperature range. In addition, by using this theoretical system, we have proposed a hierarchical methodology that can evaluate the wide-area risk of geotechnical disasters in high-latitude cold regions occurred under near future weather conditions supposed by the climate change prediction.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2018/10 -2019/03 
    Author : Takahashi Hiroaki
     
    Comprehensive investigation on the 2018 Hokkaido Eastern Iburi earthquake and its disaster was conducted. Mainshock rupture initiated at deepest part and major slip was occurred in 20-30km deep. Multiple simultaneous landslides in Atsuma town was induced by combination of strong ground shaking and weak sliding layer between pyroclastic fall deposit layers. Halloysite cray minerals was discovered in all sliding layers. Simulation suggested landslides might attack residential houses within 6 seconds. Observed peak ground motions in nearby area were larger than common distance attenuation model. Severe wooden house damage in Mukawa town was due to amplified seismic waves due to site effects. Sounding and boring investigation revealed filled low-density volcanic ash and higher groundwater level in liquefaction area. Electricity blackout caused severe damage in social and economic activities of Hokkaido. These scientific outcomes were explained to residents at public briefing session.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2015/04 -2018/03 
    Author : Kawabata Shinichiro
     
    In this research, we compile data on frost heave and associated damage to roadways, consider additional parameters for roadway design, and examine new methods of assessment. Specifically, we investigate pavement surface conditions over a total of 800 km of roadway and use the data to find the relation among type of earthwork (cut or fill), freezing index, and damage from frost heave damage. Additionally, we examined 51 types of subgrade soil sampled at heaved locations. The results elucidate the regional characteristics of the freezing index at 323 points throughout Japan. For comparison, we reviewed more than 100 years of weather data, using it to reveal long-term fluctuations in the freezing index. Finally, we show that differences in how pavement is visually inspected affects the accuracy of the resulting assessments.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2015/04 -2018/03 
    Author : ISHIKAWA Tatsuya
     
    In Hokkaido, fluctuations in the water retention and infiltration characteristics of soil ground due to the seasonal variation of land use and weather condition are extremely large throughout the year, so there is a possibility that it may enhance the occurrence of sediment-related disasters at torrential downpours caused by climate change. This study proposed a quantification method of the infiltration rate of rainfall / snow melting water, which can be a criterion for the occurrence of sediment-related disasters, from the viewpoints of snow cover / vegetation, rainfall intensity / snow melting rate, soil property, water content of the ground and frozen state. In addition, this study developed a coupled slope stability analysis for snowy cold regions by incorporating a newly proposed mathematical model for the infiltration characteristics of surface flow in the case where snow cover and vegetation are considered as an element in numerical analysis.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/04 -2017/03 
    Author : ITO Yuzuru
     
    In Fukushima 1st Nuclear Power Plant, the ice wall was planned to build over the ground with sandy soil and mud stone layers, in which a large quantity of ground water was flowing toward the Pacific Ocean. Therefore, many questions arise whether the ice wall can be completed, whether the frozen ground has small enough permeability and what will happen when frozen soil melts due to power supply lost. As a result of the research, the following conclusion was obtained.(1) A prediction of limited ground water speed in the ice wall construction by the numerical computation accorded with the theoretical value, and, furthermore, they agreed with the result of the model experiment. (2) The experiment method that had high precision to measure a permeability of the frozen ground was developed. (3) A method to estimate the permeability of freeze-thawed soil was developed by the newly designed horizontal displacement restricted freeze-thaw test system.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/04 -2017/03 
    Author : KAWAGUCHI Takayuki
     
    This study measured detailed temperature distribution around buried pipes under the pavement and vertical stresses in the ground, as well as seasonal changes of incremental stress exerted by vehicle wheel loads for damage risk assessment of buried pipes beneath pavements in cold regions. Results revealed that these measured values change significantly as a result of the ground’s freeze-thaw process. In addition, we found that the incremental stress in the ground increases with the vehicle weight and that the rate of increase changes with freezing and thawing. The stress distribution (transmission) in the ground was also found to change with freezing and thawing.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2012/04 -2015/03 
    Author : ISHIKAWA Tatsuya, KIMURA Ichiro
     
    This research develops an analytical procedure using a phenomenalistic mathematical model for the phase change-dependent geotechnical hazards in snowy cold regions by performing experimental and analytical studies. First, we established a new testing method for model tests on soil grounds subjected to freeze-thaw actions and seepage flow, and revealed that seepage pressure and frost-susceptibility and water retention-permeability characteristics of geomaterials seriously influenced the seepage erosion behavior of freeze-thawed soil ground. Next, we developed a numerical model to simulate this seepage erosion phenomenon with the framework of hydraulic erosion and overhanging failure by a triple-grid approach. Since the numerical results showed a good agreement with the experimental results, we concluded that the newly proposed analytical procedure is applicable to a freeze-thaw and seepage-erosion complex geotechnical hazards, which may occur in the snowy cold regions.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011/04 -2015/03 
    Author : ISHIKAWA Tatsuya, MIURA Seiichi, YAMASHITA Satoshi, KAWABATA Shinichiro, KAWAGUCHI Takayuki, TOKORO Tetsuya, KITAMURA Ryosuke, KIMURA Ichiro, NISHIMOTO Satoshi
     
    This research mainly studies the systematization of new geotechnical hazards in snowy cold regions caused by climate change and its long-term hazard assessment by performing laboratory element tests, model tests, numerical simulations, and data analysis. As the results, this research clarified a failure mechanism of freeze-thawed slope subjected to a large amount of infiltration in a short time due to torrential rainfall and rapid snow melting, and its influential factors by establishing new laboratory element tests and model tests on unsaturated geomaterials subjected to freeze-thaw actions and seepage erosion, and developing a new analytical procedure using coupled thermo-hydro-mechanical FE analysis. Furthermore, we proposed an assessment method for a new type of freeze-thaw and seepage-erosion complex geotechnical hazards, which may occur in the snowy cold regions, by predicting climate change in the near future based on data analysis of temperature data for past some decades.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011/04 -2014/03 
    Author : MIURA SEIICHI, ISHIKAWA Tatsuya, KAWAMURA Shima, YOKOHAMA Shoji
     
    The aim of this study is to reveal the failure mechanism of volcanic slopes in cold regions and to propose a prediction method on failure. To achieve the purposes, full-scale embankments were constructed under several conditions in Sapporo, Japan. A typical volcanic soil in the field was adopted as a soil material. After construction of embankments, changes in soil moisture, temperature, pore water pressure were investigated using devices such as soil moisture meters, etc. Simultaneously, a series of model tests was performed on small size slopes formed by the same material as that in the field to compare with the mechanical behavior of embankments. A series of triaxial tests was also conducted on compacted volcanic soils subjected to freeze-thaw cycles using a new apparatus. As a result, a reasonable prediction method of failure was proposed based on changes in water content, and its validity was confirmed.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2010 -2012 
    Author : SHIBUYA Satoru, KAWAGUCHI Takayuki, TORII Nobuyuki
     
    In order to examine the applicability of L-shaped drainage method in in-situ in this study, the full-scale model test was performed. As a result, the excellent effect on the applicability to the reinforced soil retaining wall of L-shaped drainage using Geosynthetics in this research could be evaluated.
  • 凍結融解地盤の温度依存型透気係数推定方法の提案
    北海道ガス：平成２２年度北海道ガス大学助成制度
    Date (from‐to) : 2010/04 -2011/03 
    Author : 石川 達也
  • 凍結融解地盤の温度依存型透気試験方法の開発
    北海道ガス：平成２１年度北海道ガス大学助成制度
    Date (from‐to) : 2009/04 -2010/03 
    Author : 石川 達也
  • 凍結融解作用を受ける斜面の崩壊予知・災害危険度評価システムの確立
    国土交通省：道路政策の質の向上に資する技術研究開発
    Date (from‐to) : 2007/04 -2010/03 
    Author : 三浦 清一
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2009 -2010 
    Author : 石川 達也, 山下 聡
     
    1.凍結時および融解時の不飽和地盤の透気係数を計測・評価するため、凍上性・非凍上性地盤材料(火山灰質土と豊浦砂)の凍結融解不飽和透気試験を室内及び屋外で実施した。その結果、以下のような知見が得られた。(1)試験時の含水比が透気係数に及ぼす影響は土質によって異なり、火山灰質土では、飽和度60%以下では飽和度の上昇に伴い透気係数が高くなるというという豊浦砂と逆の傾向が得られた。これは、締固め時の含水比変化に伴う土の骨格構造の変化に起因すると考えられ、締固め含水比を土質に応じて変えることで、地盤材料の透気性を制御できる可能性がある。(2)凍上性火山灰質土においても、非凍上性の豊浦砂と同様、地温0℃付近で透気係数は大きく変化した。しかしながら、同一飽和度(空気間隙比)で透気係数を比較した場合、豊浦砂では凍土の透気係数は未凍土よりも若干低くなったが、火山灰質土では、地温の低下に伴い透気係数は上昇した。また、凍上時の火山灰質土の透気係数は非凍上時よりも高くなった。これらは、両者の含水比の違いによる未凍結時の土壌水分挙動、土の骨格構造及び間隙水の氷結様式の違いに起因すると考えられる。(3)凍上性火山灰質土では、凍結融解が繰り返され飽和度が一定値以上に増加すると間隙水の増加により空気は透り難くなり、加えた水分の凍結・凍上によりさらに透気係数は低下する傾向が確認された。 2.開発した透気試験方法によれば、不飽和状態で繰返し凍結融解作用を受ける凍上・非凍上性地盤材料の温度依存型透気係数の評価が可能であること、および不飽和地盤の透気係数は、温度依存性を示すとともに、地盤材料の凍上性、保水性・透水性、締固め特性の影響を多大に受けることが明らかになった。積雪寒冷地で地盤の透気性を検討する場合、これらの要因を考慮することが精確な挙動予測に重要となる。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2008 -2010 
    Author : ISHIKAWA Tatsuya, MIURA Seiichi, YOKOHAMA Shouji, KAMEYAMA Shuichi, YAMASHITA Satoshi, ONO Takashi, ABE Ryuji, SEKINE Etsuo, HACHIYA Yoshitaka
     
    In this study, we proposed new testing methods for the evaluation of the deformation-strength characteristics of base course materials subjected to freeze-thaw action, and examined the mechanical behavior of granular base before and after freeze-thawing and under freezing. We also evaluated the influences of the change in the performance of granular base due to freeze-thawing on the fatigue breaking of pavements in cold regions by applying the theoretical design method for asphalt pavement. As the result, it was revealed that the freeze-thawing of granular base has a strong influence on the fatigue life of pavement structure in cold regions because it varies the deformation-strength characteristics of base course materials.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2007 -2009 
    Author : MIURA Seiichi, AKAGAWA Satoshi, ISHIKAWA Tatsuya, YOKOHAMA Shoji, KAWAMURA Shima, IWAHANA Go, ITOU Yoshihiko, NISHIMOTO Satoshi
     
    We elucidated the interaction between various factors which caused subsurface failure of volcanic soil ground subjected to freeze-thaw action in cold regions in terms of soil mechanics, and we proposed a new simple prediction method for the rain-induced slope failure in snow-melting seasons in consideration of the degradation of deformation-strength characteristics of geomaterials due to freeze-thawing. We also developed a geo-information database which integrated the various different kinds of information such as weather reports, geotechnical information, and records for past geohazards. Based on these achievements, finally, we developed the system which could evaluate a risk of rain-induced slope failure at subsurface layers suffered from freeze-thaw by using both above-mentioned prediction method and geo-information database.
  • 寒冷地用舗装構造の路盤・路床の変形挙動評価試験法に関する研究
    北海道ガス：平成１９年度北海道ガス大学助成制度
    Date (from‐to) : 2007/04 -2008/03 
    Author : 石川 達也
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2006 -2007 
    Author : ISHIKAWA Tatsuya, MIURA Seiichi, YOKOHAMA Shoji, SEKINE Etsuo
     
    This study examines the mechanical behavior of granular materials under saturated and unsaturated conditions subjected to cyclic moving loads, for example gravel roadbed and railroad ballast, and both a new testing methods and new analytical procedure to examine the effects of the rotation of principal stress axes and water content on cyclic plastic deformation of granular base course materials are proposed. The following conclusions can be obtained; 1. Two types of small scale model tests which adopted a fixed-place loading method and a moving loading method were performed with a base course material under air-dried condition and saturated condition. As the results, it was revealed that the water content of the base course material influences the mechanical behavior of granular base strongly, and the effect on the development of residual settlement for granular base under cyclic loading remarkably comes to the surface in employing moving loads. 2. Two types of multi-ring shear tests, which can consider a change in direction of principal stresses like traffic loads, were performed in the same way as loading methods in small scale model tests. As the results, it was revealed that the shear strength decreased and the cumulative residual strain increased due to the saturation, and that the mechanical behavior in multi-ring shear tests is very similar to that in small scale model tests, regardless of loading methods and water contents. 3. A new method to estimate cyclic plastic deformation of granular base under repeated wheel traveling in terms of the strength and deformation characteristics of granular base course materials was proposed. The simple analytical procedure with linear elastic FE analysis considering the cumulative strain derived from multi-ring shear test results of base course materials can roughly estimate the residual settlement of granular base under saturated and unsaturated conditions subjected to cyclic moving loads.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2004 -2006 
    Author : MIURA Seiichi, AKAGAWA Satoshi, ISHIKAWA Tatsuya, YOKOHAMA Shoji, KAWAMURA Shima
     
    Based on the experimental and numerical studies of slope stability of crushable soils, the following conclusions are obtained: 1.Effect of freeze-thaw sequence on static mechanical behavior of volcanic soil (1)Particle breakage of volcanic coarse-grained soil significantly occurs due to the repetition of freeze-thaw sequence. The particle breakage affects strongly on static strength and rigidity of volcanic soil. (2)Volcanic soil subjected to freeze-thaw sequences may produce a remarkable crushability at low confining pressure level. This fact suggests that deterioration in the stability of slope near the surface is significant on snowy cold region. 2.Effect of freeze-thaw sequence on dynamic mechanical behavior of volcanic soil (1)Shear modulus of volcanic coarse-grained soil decreases due to freeze-thaw sequences. On the other hand, freeze-thaw action may less affect hysteresis damping ratio. (2)Liquefaction resistance of volcanic soil decreased due to freeze-thaw sequences. This fact may attribute the reduction of the liquefaction resistance to the increase in finer content induced by particle breakage during freeze-thaw sequences. 3.Rainfall-induced slope collapse for crushable volcanic soil and its evaluation (1)From the results of model tests, it is found that excess pore water pressure and saturation degree play a key role in the slope failure induced by rainfall. (2)Depth and shape of impermeable layer in the slope are critical to estimate the stability of slope. 4.Numerical analysis for rainfall-induced slope failure for crushable volcanic soil (1)A series of numerical analysis by DEM showed that proposed small void elements between soil particles, which are able to expand in accordance with temperature depression, can simulate the mechanical freeze-thaw performance of granular materials. (2)Discontinuous Deformation Analysis (DDA) could explain the slope failure mechanism if rainfall and dilatancy effects on volcanic soil are estimated appropriately into analysis algorithm.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2003 -2004 
    Author : ISHIKAWA Tatsuya, MIURA Seiichi, YOKOHAMA Shoji, SEKINE Etsuo
     
    This study examines the mechanical behavior of granular materials subjected to cyclic moving loads, for example gravel roadbed and railroad ballast, and both a new testing method and new analytical procedures to examine the effects of the rotation of principal stress axes on cyclic plastic deformation of granular materials are proposed. The following conclusions can be obtained ; 1.Cyclic plastic deformation obtained through moving loading tests is much larger than those obtained through fixed-place cyclic loading tests when other experimental conditions are the same. Accordingly, the difference in loading methods has a significant influence on the cyclic plastic deformation of granular materials. 2.Residual strain obtained through cyclic loading triaxial tests with constant amplitude of deviator stress while controlling confining pressure constant is very small compared with the macro residual strain calculated from force-displacement relationships in moving loading tests, while that of cyclic torsional simple shear tests using a newly developed "Multi-ring shear apparatus" is almost equivalent to moving loading tests. Therefore, the multi-ring shear test is appropriate for an element test to simulate the actual stress states inside substructures under traffic loads. Moreover, it was revealed that the rotation of principal stress axes has a significant effect on cyclic deformation characteristics of granular materials. 3.Two analytical procedures for simulating the mechanical behavior of granular materials subjected to cyclic moving loads were proposed. One is linear elastic FE analysis considering the material properties of cumulative strain derived from element test results of granular materials, which can roughly estimate the residual settlement of granular substructures due to cyclic loading. The other is discontinuous analysis which elements imitate the shape of real gram particles well because it was revealed that the element shape is one of the dominant factors to determine the mechanical behavior of granular assemblage in discontinuous analysis.
  • 凍結融解地盤の性能評価・挙動予測技術の開発
    Date (from‐to) : 2004
  • 粒状構造物の力学的安定性に関する研究
    Date (from‐to) : 2002
  • Study on dynamic stability characteristics of granular materials
    Date (from‐to) : 2002

Educational Activities

Teaching Experience

  • Geotechnical Analysis
    開講年度 : 2021
    課程区分 : 修士課程
    開講学部 : 工学院
  • Inter-Graduate School Classes(Educational Program):JICA Development Study Program
    開講年度 : 2021
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : Disaster prevention; Natural disaster; Flood; Heavy rainfall; Tsunami; Liquefaction; Earthquake; Japan’s ODA
  • Geotechnical Analysis
    開講年度 : 2021
    課程区分 : 博士後期課程
    開講学部 : 工学院
  • Mechanics of Soils I
    開講年度 : 2021
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 土の基本的性質，土の分類，透水，地盤内応力，圧密，締固め
  • Mechanics of Soils II
    開講年度 : 2021
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 地盤のせん断強さ，土圧，土留め構造物，斜面の安定，地盤の支持力，構造物基礎
  • Engineering Ethics
    開講年度 : 2021
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 技術者倫理，倫理規定，土木技術史，倫理問題事例研究
  • Highway Engineering
    開講年度 : 2021
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 幾何設計、 交通流、 交通制御、 ITS、 アスファルト、コンクリート、 舗装構造設計、舗装維持補修
  • Exercise in Mechanics of Soils
    開講年度 : 2021
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 土の基本的性質、土中水と浸透、地盤内応力と変形、土の圧縮と圧密、応力とテンソルの基礎、破壊基準、排水強度と非排水強度、土圧、斜面の安定、地盤の支持力

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