藤井 義明 (フジイ ヨシアキ)
工学研究院 環境循環システム部門 地圏循環工学分野 | 特任教授 |
Last Updated :2025/02/13
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- 2021年07月, 7th Moratuwa Engineering Research Conference (MERCon 2021), Best Paper Award
Effective Stress Coefficient Through MFEM and Confining Pressure Dependency of Bibai Sandstone
Dassanayake, A;Fujii, Y - 2021年05月, 岩の力学連合会, 論文賞
Development of a 3D Numerical Simulator for Complex Rock Fracturing and Fragmentation Considering Elastic Anisotropy, and Development of a Numerical Simulator for 3-D Dynamic Fracture Process Analysis of Rocks Based on Hybrid FEM-DEM Using Extrinsic Cohesive Zone Model
Fukuda, D;Mohammadnejad, M;Liu, H;Zhang, Q;Zhai, J;Dehkhoda, S;Chan, A;Kodama, J;Fujii, Y;Fukuda, D;Nihei, E;Cho, S.-H;Oh, S;Nara, Y;Kodama, J;Fujii, Y - 2021年05月, 日本材料学会, 論文賞
Extrinsic Cohesive Zone Modelに基づくハイブリッドFEM-DEMを用いた岩石の3次元動的破壊過程解析法の開発に関する基礎的検討
福田大祐;二瓶恵理菜;趙祥鎬;呉世旭;奈良禎太;児玉淳一;藤井義明 - 2020年07月, 6th Moratuwa Engineering Research Conference (MERCon 2020), Best Paper Award
Stability Analysis of Slopes in Aruwakkalu Limestone Mine: A Finite Element Approach
Thirukumaran, A;Dananjaya, L;Dilshan, T;Dassanayake, A;Jayawardane, C;Wickrama, M;Fujii, Y;Boeut, S - 2019年12月, YSRM2019 & REIF2019, The 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future, Excellent Paper Award
Fukuda, D;Mohammadneja, M;Liu, H;Han, H;Kodama, J.-I;Fujii, Y - 2017年05月, 日本材料学会, 優秀講演発表賞
Smeared Crack Model及び有限要素法を用いた岩石の動的亀裂進展解析に関する基礎的研究
福田大祐;二瓶恵理菜;児玉淳一;藤井義明;Sang-Ho CHO;Se-Wook OH - 2017年01月, 第14回岩の力学国内シンポジウム, 最優秀ポスター賞
3次元動的破壊プロセス解析法を用いた岩石の動的引張試験に関する基礎的検討
二瓶恵理菜;福田大祐;Sang-Ho CHO;Se-Wook OH;児玉淳一;藤井義明 - 2015年12月, Elsevier, Recognized Reviewer
Yoshiaki FUJII - 2014年11月, Int. J. Rock Mech. Min. Sci., Outstanding Contribution in Reviewing
藤井 義明 - 2014年05月, EUROCK 2014, Outstanding Paper Award for Young Scientists and Engineers
Temperature-Confining Pressure Coupling Effects on the Permeability of Three Rock types under Triaxial Compression
Alam, A. K. M. B;Fujii, Y;Fukuda, D;Niioka, M - 2010年06月, 日本応用地質学会北海道支部・北海道応用地質研究会合同研究発表会, 優秀発表者賞
珪質泥岩を対象にした孔壁変形法による初期地圧測定-幌延深地層研究センター,深度250m連絡坑道での測定事例-
熊倉聡;杉田裕;真田祐幸;中村隆浩;小原勇一;菅原隆之;藤井義明 - 2010年06月, EUROCK 2010, Best PaperAward for Young Scientists and Engineer
Prediction of Rock Mass Failure-time of Geo-hazards
Mufundirwa A;Fujii, Y;Kodama, J - 2006年01月, 第35回岩盤力学に関するシンポジウム, 優秀講演論文賞
数種の岩石の凍結融解および凍上に伴う変形挙動
小玉齊明;赤川敏;藤井義明;石島洋二 - 2002年05月, 地盤工学会, 事業企画推進賞
岩盤崩落の機構解明と計測技術に関する研究委員会 - 1999年06月, 資源・素材学会北海道支部, 支部長賞佳作
岩盤力学の新たなる展開、-軸差応力・軸差ひずみ・せん断破壊・摩擦角からの脱却-
藤井 義明 - 1997年03月, 資源・素材学会, 奨励賞
深部炭鉱における地圧現象に関する一連の研究
藤井 義明
論文
- Effect of the Connectivity of Weak Rock Zones on the Mining-Induced Deformation of Rock Slopes in an Open-Pit Mine
Cheng Zhang, Amagu amagu Clement, Jun-ichi Kodama, Atsushi Sainoki, Yoshiaki Fujii, Daisuke Fukuda, Shuren Wang
Sustainability, 16, 14, 5974, 5974, MDPI AG, 2024年07月12日
研究論文(学術雑誌), Geological structures significantly influence mining-induced deformations in open-pit mines, with their variations and interactions adding complexity to the excavation process and introducing uncertainties in deformation outcomes. This study utilized numerical simulations to analyze the impact of weak rock zones in a specific open-pit limestone quarry in Japan on mining-induced deformation. The simulation results were both qualitatively and quantitatively validated against field measurements, enhancing the reliability of the findings. Subsequently, four conceptual models were developed based on the characteristics of the quarry to investigate the mechanisms by which weak rock zones affect rock slope deformations. Our analyses demonstrated that slip deformation occurred exclusively when two weak rock zones were connected. This deformation was associated not only with shear failure in the upper weak rock zone but also with the contraction and bending of the lower weak rock zone. Furthermore, the simulation results were consistent with field data and supported by the conceptual models, confirming that the proposed sliding mechanisms can effectively explain the observed deformation behaviors. The insights gained from these models provide valuable references for managing similar geological challenges in other open-pit mines. - Integrating the effect of abutments in estimating the average vertical stress of elastic hard rock pillars by combining numerical modelling and artificial neural networks
Nevaid Dzimunya, Yoshiaki Fujii, Youhei Kawamura
Underground Space, 13, 121, 135, Elsevier BV, 2023年12月, [査読有り]
英語, 研究論文(学術雑誌) - Importance of Stress and Temperature-Dependent Permeability of Rocks and its Application in Underground Nuclear Waste Disposal
Alam, A. K. M. B, Fujii, Y, Dipu, N. H, Boeurt, S, Rahim, B. A
MIST International Journal of Science and Technology, 11, 39, 49, 2023年, [査読有り]
英語 - Creep Damage Model for Rockburst at Mufulira Mine in Zambia
P. Sinkala, M. Nishihara, Y. Nakayama, Y. Fujii, J. Kodama, D. Fukuda, E. Chanda
Mining, Metallurgy & Exploration, 39, 5, 1983, 2000, Springer Science and Business Media LLC, 2022年10月, [査読有り]
研究論文(学術雑誌) - A Three-Dimensional Constitutive Model for Rocks Based on a Strain-Dependent Elastic Modulus
Z. Li, Y. Fujii, J. Kodama, D. Fukuda, A. B. N. Dassanayake, P. Sinkala
Lithosphere, 2021, Special 7, GeoScienceWorld, 2022年09月05日, [査読有り]
研究論文(学術雑誌), Abstract
Our research group previously proposed a simple two-dimensional (2D) constitutive model for rocks to simulate not only the axial stress–axial strain relationship, but also the axial stress–lateral strain relationship, with few complicated equations. However, the failure envelope that it predicted was linear, and it did not consider the effect of the intermediate principal stress (σ2). In the present study, the authors modify this simple 2D model to have a convex failure criterion. Then, the model is extended to a simple three-dimensional (3D) model that well approximates true triaxial stress–strain curves for real rocks under specific values of σ2 and σ3 and uses only four parameters. However, the predicted peak stress–σ2 relationship is linear. Finally, a modified 3D model was developed, which exhibited the true triaxial convex failure criterion. The equations in this model are simpler than the conventional true triaxial failure criteria. The proposed models can be implemented with a finite element method to improve the design of rock structures. - Prediction of mining-induced subsidence at Barapukuria longwall coal mine, Bangladesh
A. K. M. Badrul Alam, Yoshiaki Fujii, Shaolin Jahan Eidee, Sophea Boeut, Afikah Binti Rahim
Scientific Reports, 12, 1, Springer Science and Business Media LLC, 2022年08月30日, [査読有り]
研究論文(学術雑誌), Abstract
It is essential to predict the mining-induced subsidence for sustainable mine management. The maximum observed subsidence having a noticeable areal extent due to Northern Upper Panels (NUP) and Southern Lower Panels (SLP) at the Barapukuria longwall coal mine is 5.8 m and 4.2 m, respectively, after the extraction of a 10 m thick coal seam. The mining-induced subsidence was simulated by the Displacement Discontinuity Method. The numerical model considered the effects of the ground surface, mining panels, faults, and the dyke. The predicted and the observed subsidence due to the mining of NUP and SLP were compared by varying Young's modulus, and the 0.10 GPa Young's modulus was found to be the best match in the geo-environmental condition. The effects of the faults and the dyke in the calculation were negligible. Future subsidence was predicted by considering 30 m extraction of the thick coal seam as 15.7–17.5 m in NUP and 8.7–10.5 m in SLP. The vulnerable areas demarcated considering the tilt angle and extensile strain might extend up to the coal mine office area and some villages. - An Experimental Investigation on the Creep Behavior of Deep Brittle Rock Materials
Haozhe Chen, Zhushan Shao, Yoshiaki Fujii
Materials, 15, 5, 1877, 1877, MDPI AG, 2022年03月02日, [査読有り]
研究論文(学術雑誌), The stability of deep rock engineering, especially during the excavation, is inextricably linked to the time-dependent mechanical properties of brittle rock. Therefore, the uniaxial creep test in a multilevel loading path is carried out, accompanying the real-time DIC (digital image correlation) and AE (acoustic emission) technologies. For the quartz sandstone, the lateral strain is more sensitive to increasing stress levels, and the lateral ductility is more significant during the creep process. The saturated quartz sandstone shows a certain bearing capacity before the volumetric dilation predominance. The softening effect of moisture causes a nearly invariable Poisson’s ratio during the middle stress stages, as well as the more notable increasing trend of a steady creep rate with an increasing stress level, reflected by the larger slope and the intercept in the fitting relations. The main shear pattern and the combination of the shear and splitting failures are separately shown by the dry and saturated quartz sandstone. For the granite, both compression and extension exist in the creep deformation, and the failure may first occur in the prominent deformation area with a cracking noise. The AE hits present a similar time-dependent behavior to the strain of rock, and the attenuation trend happens in both the AE amplitude and energy before the rock enters the unsteady phase. The incomplete specimen of granite exhibits a lower strength and a larger deformation, owing to the more remarkable damage accumulation reflected by the spatial distribution of the AE event points. - 樹木が侵入する岩盤割れ目の変位挙動
小玉齊明, 藤井義明, 菅原隆之, 宮下尚志
土木学会論文集C(地圏工学), 78, 4, 277, 286, 2022年, [査読有り]
日本語, 研究論文(学術雑誌) - A case study on severe damage at a tunnel in serpentinite rock mass
Y. Fujii, N. Ikeda, Y. Onoe, Y. Kanai, T. Hayakawa, D. Awaji, J. Kodama, D. Fukuda, A. K.M.B. Alam, A. B.N. Dassanayake
SN Applied Sciences, 4, 1, 2022年01月, [査読有り]
研究論文(学術雑誌), Abstract: Face squeezing, floor heave, and buckling of invert were found after a 10-day holiday in 2014 around the serpentinite face of a tunnel in Hokkaido, Japan. The damage continued for over 2 months, extending 400 m toward the entrance causing a massive roof fall. The tunnel was excavated again with a circular section and extra-thick shotcrete, and the face had crossed the damaged part 6 years after the damage occurred. Uniaxial and triaxial compression tests were carried out to obtain the mechanical properties of the serpentinite to clarify the severe damage mechanism at the tunnel. The main experimental findings are as follows. The uniaxial compressive strength of the serpentinite samples was very low, and the ratio of the strength to the estimated overburden pressure was extremely low. The parameter n indicated that the time-dependent deformation of the serpentinite was not large but the same as ordinary rocks. All specimens showed strain-hardening in the triaxial compression test, and the friction angle was very low by the brucite content. Only primary creep was observed in the multistage triaxial creep test. The pressure on the shotcrete from rock mass for the damaged tunnel was enough to cause creep deformation and failure of shotcrete. From the above findings, designing the concrete lining that can support the earth and water pressure is recommended for tunnel excavation in such a weak serpentinite rock mass, particularly with a very low friction angle by brucite. Highlights: Face squeezing, floor heave, and buckling of invert were found after a 10-day holiday around the serpentinite face in Hokkaido, Japan.The time-dependent deformation of the serpentinite was not large but the same as ordinary rocks.All specimens showed strain-hardening in the triaxial compression test, and the friction angle was very low by the brucite content.Only primary creep was observed in the multistage triaxial creep test.The severe damage to the tunnel was not a brittle creep failure of the serpentinite rock mass itself but the shotcrete lining. - Numerical analysis of impact of fault and weak rock formation on mining-induced deformation of rock slope
C. Zhang, C. A. Amagu, J. Kodama, A. Sainoki, S. Ogawa, C. Umeda, Y. Fujii, D. Fukuda
IOP Conference Series: Earth and Environmental Science, 861, 3, 032087, 032087, IOP Publishing, 2021年10月27日, [査読有り]
英語, 研究論文(国際会議プロシーディングス), Geological structures, such as fault, geological discontinuity, and weak rock formation are likely to play a critical role in the stability and behaviour of rock slopes. However, the impact of such geological structures on the mining-induced deformation of rock slopes in an open-pit mine remains unclear. This study takes an open-pit limestone quarry in Japan as an example to discuss the mechanical interaction between specific geological structures. In this quarry, below the mining area is a vertical fault intersecting with a weak rock formation almost parallel to the slope surface. Based on these unique geological structures, numerical simulations are conducted in the framework of discrete element method while considering different geological situations to elucidate the impact of each geological structure. The analysis results show that the vertical fault and weak rock formation significantly impact the deformation of the rock slope during mining progression. In the case of a fault-only model, no slip occurs. However, in the case of the fault and weak rock formation model, as the mining face is crossing the fault, apparent slip occurs along the weak rock formation. In this model, although the vertical fault constrains the sliding of the upper discontinuities at the early stage, the normal stress of the weak rock formation decreases gradually as the mining progresses, and local shear failure occurs at the intersection of the weak rock formation and fault, which leads to the slip. However, rock slope displacement due to the slip gradually decreases and eventually stabilizes as the working face gets away from the vertical fault. This study provides new insight into the deformation mechanism of the rock slope and serves as a reference for future mining and slope prevention work. - Displacement Measurements and Numerical Analysis of Long-Term Rock Slope Deformation at Higashi-Shikagoe Limestone Quarry, Japan
Clement A. Amagu, Cheng Zhang, Jun-ichi Kodama, Kazuyuki Shioya, Tomoyuki Yamaguchi, Atsushi Sainoki, Daisuke Fukuda, Yoshiaki Fujii, Mostafa Sharifzadeh
Advances in Civil Engineering, 2021, 1, 15, Hindawi Limited, 2021年10月11日, [査読有り]
研究論文(学術雑誌), The Higashi-Shikagoe limestone quarry is an open-pit mine situated in Hokkaido Prefecture, Japan, that has experienced four slope failure incidents since 1996. The rock slope behaviour has been monitored since the first failure event by measuring the rock slope surface displacement using an automated polar system. Recent measurements have revealed a gradual decrease of the distance between the beam generator and mirrors over time; however, the displacements and decrease rate differs between the centre and left- and right-hand sides of the quarry. This implies that the deformation characteristics of the rock slope and factors influencing the slope deformation differ at the centre and left- and right-hand sides of the quarry. In this study, the two-dimensional finite element method was used to identify the causes of slope deformation by investigating the effects of limestone excavation at the foot of the rock slope, the deterioration of a ∼70 m-thick clay layer at the rock slope foot wall, and shear failure owing to rainfall infiltration. The numerical results show that slope deformation on the left-hand side and centre of the quarry are induced by clay deterioration, whereas the right-hand side of the quarry is deformed owing to floor excavation and/or shear sliding. The rock slope is presently stable because the magnitude of the rate of displacement decrease is small and no acceleration is observed. - Stability of shale at a slope
AKM Badrul Alam, Yoshiaki Fujii, Naveel Islam, Md Abdur Rahman, Ashiq Al Hasan, Md Abid Hasan
IOP Conference Series: Earth and Environmental Science, 861, 6, 062010, 062010, IOP Publishing, 2021年10月01日, [査読有り]
英語, 研究論文(学術雑誌) - Development of a 3-D Dynamic Fracture Process Analysis code to Simulate Intermediate Loading Rate
D. Fukuda, S.H. Cho, G.J. Min, H.Y. Liu, K. Kodama, F. Fujii
IOP Conference Series: Earth and Environmental Science, 861, 4, 042075, 042075, IOP Publishing, 2021年10月01日, [査読有り]
英語, 研究論文(学術雑誌) - Geomechanical analysis of formation deformation and permeability enhancement due to low-temperature CO2 injection in subsurface oil reservoirs
Khurshid, I, Fujii, Y
Journal of Petroleum Exploration and Production, 11, 1915, 1923, 2021年03月, [査読有り]
英語 - Modelling of dynamic rock fracture process using the finite-discrete element method with a novel and efficient contact activation scheme
Daisuke Fukuda, Hongyuan Liu, Qianbing Zhang, Jian Zhao, Jun-ichi Kodama, Yoshiaki Fujii, Andrew Hin Cheong Chan
International Journal of Rock Mechanics and Mining Sciences, 138, 104645, 104645, Elsevier BV, 2021年02月, [査読有り]
英語, 研究論文(学術雑誌), Within the framework of combined finite-discrete element method (FDEM), we propose a novel and efficient semi-adaptive contact activation approach (semi-ACAA). The semi-ACAA adaptively activates contact calculations for continuum solid elements around the cohesive element which has just been subjected to shear softening while its softening function has just satisfied a prescribed threshold. The semi-ACAA is implemented in a three-dimensional (3D) FDEM code parallelized based on general-purpose graphic processing units (GPGPU) to model dynamic fracture processes of marbles in dynamic Brazilian tensile strength (BTS) and uniaxial compressive strength (UCS) tests. The semi-ACAA not only overcomes spurious fracturing mode associated with FDEM simulations using ACAA but also is more physically sound and computationally efficient compared with brute-force contact activation approach (BCAA), which has been prevalent in FDEMs with intrinsic cohesive zone model (ICZM)-based cohesive elements. Furthermore, it is proven that the spurious fracturing mode is caused by unphysical movements of mesh due to missing contacts during the shear softening of cohesive elements instead of the sudden activation of contact force calculations as indicated in some literature. Finally, a series of simulations of the dynamic BTS and UCS tests conducted by split Hopkinson pressure bar (SHPB) facility reveals that, if the threshold is set to around unity, not only the spurious fracturing mode can be overcome but also the modelling precision of stress waves in intact rocks can be improved. The speed-up times of semi-ACAA compared with BCAA are between 1.23 and 13.5 depending on the intensity of shear cracking in the simulations including mixed-mode cracking. Since the proposed semi-ACAA is simple and can be easily implemented into any FDEM codes with ICZM-based cohesive elements, it is expected to accelerate future developments and applications of FDEM with ICZM-based cohesive elements in rock dynamics such as drilling and blasting. - Mechanical Properties of Acid-corroded Sandstone Under Uniaxial Compression
Shuguang Li, Yingming Wu, Runke Huo, Zhanping Song, Yoshiaki Fujii, Yanjun Shen
Rock Mechanics and Rock Engineering, 54, 1, 289, 302, Springer Science and Business Media LLC, 2021年01月, [査読有り]
英語, 研究論文(学術雑誌) - Laboratory Investigation on the Permeability Variation of Fractured Inada Granite by Multiple Transient Axial Stress Disturbances
Sophea Boeut, Yoshiaki Fujii, Jun-Ichi Kodama, Daisuke Fukuda, Anjula Dassanayake, Badrul A. K. M. Alam
Pure and Applied Geophysics, 177, 11, 5385, 5396, Springer Science and Business Media LLC, 2020年11月, [査読有り]
英語, 研究論文(学術雑誌), A persistent increase in the permeability of rock mass caused by transient stress disturbances could explain the variation in groundwater level caused by earthquakes in the far-fields, increase in petroleum production due to artificial vibrations, induction of small earthquakes by seismic waves in intermediate and far-fields, etc. However, the effect of transient stress disturbances on rock permeability has not yet been fully clarified. In this study, the permeability of triaxially fractured Inada granite under multiple transient disturbances in axial stress was measured to clarify the effects of the transient stress disturbances on the fractured rock permeability. In the experiments, the permeability of fractured Inada granite decreased with time. However, the permeability increased with each series of axial stress disturbances whose amplitude was 3 MPa or larger. The degree of increase in permeability increased with the axial stress disturbance amplitudes. The increased permeability decreased with time and the duration in which the permeability decreased to its value before the disturbances was longer for larger axial stress disturbance amplitudes. The increase in permeability could be employed to enhance oil and gas productions, prevent large earthquakes, reroute underground water flow, etc. - Development of a Numerical Simulator for 3-D Dynamic Fracture Process Analysis of Rocks Based on Hybrid FEM-DEM Using Extrinsic Cohesive Zone Model
Daisuke Fukuda, Erina Nihei, Sang-Ho Cho, Sewook Oh, Yoshitaka Nara, Jun-ichi Kodama, Yoshiaki Fujii
MATERIALS TRANSACTIONS, 61, 9, 1767, 1774, Japan Institute of Metals, 2020年09月01日, [査読有り]
英語, 研究論文(学術雑誌), The combined finite-discrete element method (FDEM) is one of the promising hybrid methods that has attracted much interest for the numerical simulations of complex fracture processes of rocks. The mainstream FDEM simulators developed to date are based on the intrinsic cohesive zone model (ICZM) in which cohesive elements are inserted into all the boundaries of continuum solid elements at the onset of simulations, and a penalty elastic behavior must be incorporated to model the intact deformation of rocks. However, previous studies have not systematically discussed the effect of the introduction of the penalty elastic behavior on the precision of intact stress wave propagation, and this paper discusses this concern. This paper applies an FDEM based on the extrinsic cohesive zone model (ECZM) as an alternative to the FDEM(ICZM). An advantage of the FDEM(ECZM) is first presented through a three-dimensional (3D) numerical modeling of a dynamic tension test. In addition, the effect of considering the anisotropy of wave propagation in granite, which has been neglected in all the previous works using the FDEM, is investigated through the 3D FDEM(ECZM) simulation of a dynamic Brazilian test using a split-Hopkinson pressure bar apparatus. Through the presented numerical simulations, we can conclude that the FDEM(ECZM) is a useful alternative to FDEM(ICZM) for numerical simulations of complex dynamic fracture processes of rocks. - Complete slaking collapse of dike sandstones by fresh water and prevention of the collapse by salt water
Yoshiaki Fujii, Shiori Saito, Teppei Oshima, Jun ichi Kodama, Daisuke Fukuda, Shokichi Sakata, Kagemi Uchida, Hiroyuki Matsumoto, Anjula B.N. Dassanayake
International Journal of Rock Mechanics and Mining Sciences, 131, 2020年07月, [査読有り]
研究論文(学術雑誌), © 2020 Elsevier Ltd Slaking is a well-known process, in which the surface of rock masses consisting of rocks such as mudstone, shale, etc. show rapid and complete disintegration when they are subjected to drying and then wetting with fresh water. On the other hand, dried sandstones even if they contain clay minerals such as smectite, etc., usually do not exhibit complete disintegration when they are soaked in fresh water. Instead, they usually show a strength decrease. Their slaking durability is tested by rotating them in a drum which is partially immersed in fresh water and eventually measuring the decrease in weight. On the other hand, it was found that some of the Paleogene sandstones from Kushiro Coal Mine in Japan, were completely disintegrated when they were immersed in fresh water followed by drying, but they were not collapsed when saline water was used instead of the fresh water. It was also shown that sandstones containing calcite did not show the complete breakdown even in fresh water. To understand the complete collapse of sandstones in fresh water and prevention of the collapse by salt water, sandstones sampled from Neogene dikes and Cretaceous at the mine were immersed in pure and salt water with Shikotsu welded tuff for comparison. Only dike sandstones showed a complete collapse in pure water and 3% salt water. Dike sandstone further showed severe time-dependent damage in salt water whose salinity was less than 7%. The results were explained by the dissolution of halite, swelling pressure of montmorillonite, osmotic pressure, etc. - Extrinsic Cohesive Zone Modelを用いた岩石の3次元動的破壊過程解析法の開発に関する基礎的検討
福田大祐, 二瓶恵理菜, 趙祥鎬, 呉世旭, 奈良禎太, 児玉淳一, 藤井義明
材料, 69, 3, 228, 235, 2020年03月, [査読有り]
日本語, 研究論文(学術雑誌) - Development of a 3D Hybrid Finite-Discrete Element Simulator Based on GPGPU-Parallelized Computation for Modelling Rock Fracturing Under Quasi-Static and Dynamic Loading Conditions
Daisuke Fukuda, Mojtaba Mohammadnejad, Hongyuan Liu, Qianbing Zhang, Jian Zhao, Sevda Dehkhoda, Andrew Chan, Jun ichi Kodama, Yoshiaki Fujii
Rock Mechanics and Rock Engineering, 53, 3, 1079, 1112, 2020年03月01日, [査読有り]
英語, 研究論文(学術雑誌), © 2019, Springer-Verlag GmbH Austria, part of Springer Nature. As a state-of-the-art computational method for simulating rock fracturing and fragmentation, the combined finite-discrete element method (FDEM) has become widely accepted since Munjiza (2004) published his comprehensive book of FDEM. This study developed a general-purpose graphic-processing-unit (GPGPU)-parallelized FDEM using the compute unified device architecture C/C ++ based on the authors’ former sequential two-dimensional (2D) and three-dimensional (3D) Y-HFDEM IDE (integrated development environment) code. The theory and algorithm of the GPGPU-parallelized 3D Y-HFDEM IDE code are first introduced by focusing on the implementation of the contact detection algorithm, which is different from that in the sequential code, contact damping and contact friction. 3D modelling of the failure process of limestone under quasi-static loading conditions in uniaxial compressive strength (UCS) tests and Brazilian tensile strength (BTS) tests are then conducted using the GPGPU-parallelized 3D Y-HFDEM IDE code. The 3D FDEM modelling results show that mixed-mode I–II failures are the dominant failure mechanisms along the shear and splitting failure planes in the UCS and BTS models, respectively, with unstructured meshes. Pure mode I splitting failure planes and pure mode II shear failure planes are only possible in the UCS and BTS models, respectively, with structured meshes. Subsequently, 3D modelling of the dynamic fracturing of marble in dynamic Brazilian tests with a split Hopkinson pressure bar (SHPB) apparatus is conducted using the GPGPU-parallelized 3D HFDEM IDE code considering the entire SHPB testing system. The modelled failure process, final fracture pattern and time histories of the dynamic compressive wave, reflective tensile wave and transmitted compressive wave are compared quantitatively and qualitatively with those from experiments, and good agreements are achieved between them. The computing performance analysis shows the GPGPU-parallelized 3D HFDEM IDE code is 284 times faster than its sequential version and can achieve the computational complexity of O(N). The results demonstrate that the GPGPU-parallelized 3D Y-HFDEM IDE code is a valuable and powerful numerical tool for investigating rock fracturing under quasi-static and dynamic loading conditions in rock engineering applications although very fine elements with maximum element size no bigger than the length of the fracture process zone must be used in the area where fracturing process is modelled. - Time-dependence of mechanical behavior of Shikotsu welded tuff at sub-zero temperatures
Jun ichi Kodama, Yoshitaka Mitsui, Syohei Hara, Daisuke Fukuda, Yoshiaki Fujii, Atsushi Sainoki, Murat Karakus
Cold Regions Science and Technology, 168, 2019年12月, [査読有り]
英語, 研究論文(学術雑誌), © 2019 Elsevier B.V. A series of uniaxial compression and creep tests were performed on dry and wet specimens of Shikotsu welded tuff at −20 °C (−4 °F) to examine the time-dependence of the mechanical behavior of frozen rock. The impact of the water content of the specimens on the time-dependence of mechanical behavior was also investigated. The uniaxial compressive strengths (UCSs) of the frozen wet specimens strongly depended on the loading rate, and were greater than those of the frozen dry specimens at strain rates greater than 4.2 × 10−5 s−1. However, the creep lives of the frozen wet specimens were shorter than those of the frozen dry specimens at stress levels of less than 13.4 MPa (52% of the UCSs of the frozen wet specimens). Deformation behavior induced by pore ice was observed in the frozen wet specimens. The stress–strain behavior transitioned from brittle to ductile as the strain rate increased, and the ratio of the tertiary creep region was relatively larger. The strains of the frozen wet specimens were significantly larger than the frozen dry specimens. These results demonstrated that understanding the time-dependent deformation of frozen rock is crucial for the assessment of the long-term stability of rock slopes in cold regions, as pore ice strongly affected the failure process of the frozen wet specimens. - Development of a GPGPU-parallelized hybrid finite-discrete element method for modeling rock fracture
Fukuda Daisuke, Mohammadnejad Mojtaba, Liu Hongyuan, Dehkhoda Sevda, Chan Andrew, Cho Sang-Ho, Min Gyeong-Jo, Han Haoyu, Kodama Jun-ichi, Fujii Yoshiaki
INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, 43, 10, 1797, 1824, WILEY, 2019年07月, [査読有り]
英語, 研究論文(学術雑誌), The hybrid finite-discrete element method (FDEM) is widely used for engineering applications, which, however, is computationally expensive and needs further development, especially when rock fracture process is modeled. This study aims to further develop a sequential hybrid FDEM code formerly proposed by the authors and parallelize it using compute unified device architecture (CUDA) C/C++ on the basis of a general-purpose graphics processing unit (GPGPU) for rock engineering applications. Because the contact detection algorithm in the sequential code is not suitable for GPGPU parallelization, a different contact detection algorithm is implemented in the GPGPU-parallelized hybrid FDEM. Moreover, a number of new features are implemented in the hybrid FDEM code, including the local damping technique for efficient geostatic stress analysis, contact damping, contact friction, and the absorbing boundary. Then, a number of simulations with both quasi-static and dynamic loading conditions are conducted using the GPGPU-parallelized hybrid FDEM, and the obtained results are compared both quantitatively and qualitatively with those from either theoretical analysis or the literature to calibrate the implementations. Finally, the speed-up performance of the hybrid FDEM is discussed in terms of its performance on various GPGPU accelerators and a comparison with the sequential code, which reveals that the GPGPU-parallelized hybrid FDEM can run more than 128 times faster than the sequential code if it is run on appropriate GPGPU accelerators, such as the Quadro GP100. It is concluded that the GPGPU-parallelized hybrid FDEM developed in this study is a valuable and powerful numerical tool for rock engineering applications. - Analysis of Vibration Response Law of Multistory Building under Tunnel Blasting Loads
Huo, R., Li, S., Song, Z., Fujii, Y., Lei, S., Mao, J., Tian, S., Miao, Z.
Advances in Civil Engineering, 2019年02月, [査読有り] - Effects of clay zone on deformation of a cut rock slope in an open-pit limestone quarry
Clement A. Amagu, U. Rith, J. Kodama, D. Fukuda, Y. Fujii, H. Iwasaki, S. Ikegami
5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future, YSRM 2019, 389, 394, 2019年
研究論文(国際会議プロシーディングス), To ensure safe and effective productive operations in an open-pit limestone quarries, measurements and continuous monitoring of rock slope displacement is essential in order to assess slope stability. This is because instability of rock slopes may results in slope failures, consequently, leads to economic risks and fatal accidents in the quarries. Therefore, understanding the mechanism of rock slope deformation and factors that influence the rock slope stability is extremely important. In the previous study, the effects of regional rock stress on elastic deformation due to excavation and backfilling has been cleared. Furthermore, the effects of changes in temperature, rainfall and snow melt have also been investigated. Although past works provided valuable information on characterization of rock slope deformation by analysis of 3D displacement data; however, none of them has addressed the influence of geological formation including deterioration of clay zone existing on rock slope in the quarries, which could exhibit reduction in the strength and deformability of the rock slopes due to its high plasticity, weak strength and high sensitivity to the variation in water content. Therefore, this paper discusses a numerical investigation on the effects of deterioration of the existing clay on deformation of a cut rock slope formed in the quarries using 2D finite element method in terms of reduction in Young's modulus of the clay. The deformation mechanism is discussed, including the analysis of rock slope displacement measured by automated polar system (APS). This shows that change in distance which lies between 20-100mm decreases gradually with time for 5 years. The simulated results reveal the characteristics of deformation modes as forward and downward displacement of the cut rock slope. This resulted from deterioration effects of the clay rock existing at the foot wall of the rock slope. - Recent development and application of hybrid finite-discrete element simulator for rock failure process
D. Fukuda, M. Mohammadnejad, H. Liu, H. Haoyu, J. Kodama, Y. Fujii
5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future, YSRM 2019, 304, 309, 2019年
研究論文(国際会議プロシーディングス), The combined finite–discrete element method (FDEM) has been widely used for various engineering applications including the field of rock engineering as one of the promising hybrid methods since this method can simulate the processes of intact/continuous rock deformation, transition from continuum to discontinuum (i.e., rock fracturing) and discontinuous interactions between material surfaces (e.g., rock fragmentation). However, this method is notorious for its computationally expensive nature, especially when modeling rock fracture processes under quasi-static loading. The authors have recently developed a 2–dimensional/3–dimensional(3D) Y-HFDEM code through a research collaboration between university of Tasmania and Hokkaido university. An important feature of this code includes the incorporation of parallelization scheme using a general-purpose-graphics-processing-unit (GPGPU) to achieve a good speed-up of FDEM simulations of rock fracture processes, and the 3D Y-HFDEM code can achieve up to 284 times speed-up compared with the sequential code if it is run on appropriate GPGPU accelerators. In addition, the code is free for non-commercial/non-military applications, which should be useful for many young researchers in the field of rock engineering. This paper demonstrates our recent developments/achievements based on the Y-HFDEM code especially by introducing 3D modeling of rock fracture processes in uni- and tri-axial compression tests using 3D Y-HFDEM code since the number of applications of 3D FDEM for this class of problems has been very limited. One important issue regarding on the timing of contact activation is also discussed. - Application of peridynamics to dynamic fracture process analysis of rock-like materials
D. Fukuda, J. Kodama, Y. Fujii, S. H. Cho, H. Liu, A. Chan
Rock Dynamics Summit - Proceedings of the 2019 Rock Dynamics Summit, RDS 2019, 685, 690, 2019年
研究論文(国際会議プロシーディングス), Peridynamics (PD) has recently attracted significant attentions from researchers in the field of computational mechanics because it can model complex fracture process with relative ease even for 3D dynamic fracture problems. However, the number of its applications to dynamic fracture problems of rock-like materials has been very limited. This paper presents the application of a self-devolved 2D/3D PD simulator based on mesh-free particle discretization scheme. To overcome the significant computational burden of the PD, we implemented a PD simulator with a parallelization scheme utilizing general purpose graphic processing unit (GPGPU). The developed code is verified first using some benchmark simulations. Then, by applying the code to 2D/3D dynamic fracture problems of rock-like materials assuming high loading rate such as detonation and deflagration phenomena, the applicability and future task of the developed PD simulator are demonstrated. - Investigation of rockburst in deep underground mines, a case study of Mufulira mine, Copperbelt, Zambia
P. Sinkala, M. Nishihara, Y. Fujii, D. Fukuda, J. Kodama, E. Chanda
53rd U.S. Rock Mechanics/Geomechanics Symposium, 2019年, [査読有り]
研究論文(国際会議プロシーディングス), Copyright 2019 ARMA, American Rock Mechanics Association. Mufulira mine has been in operation since 1933. The mine is situated in the Copperbelt region of Zambia, which is predominantly rich in copper and cobalt mineralization. Since the beginning of 1970s, the mine has been recording incidents of rockbursts and applying various efforts to find mitigation measures for rockbursts. Recently, an M2.8 rockburst occurred in the mining drive at 1440 meter level underground on 16 January, 2018. In order to understand the mechanism of the rockburst, three major steps were taken. These were field geotechnical investigation, followed by uniaxial compression tests, and finally stress analysis. Under field investigations, scan-line mapping of joints indicated few major joint sets in the surrounding rock mass to the rockburst location. Stress analysis showed very high stresses in the chain pillars and low stress concentration at the rockburst site during initial stages of mining. But later, stress levels gradually increased with mining. It was therefore concluded that fracturing of the relatively intact rock mass around the mining drive under gradual stress increase by mining could be the cause of the rockburst. - Effects of transient axial stress or pore pressure disturbances on the permeability of Shikotsu welded tuff
S. Boeut, Y. Fujii, J. Kodama, D. Fukuda, A. B.N. Dassanayake
53rd U.S. Rock Mechanics/Geomechanics Symposium, 2019年, [査読有り]
研究論文(国際会議プロシーディングス), Copyright 2019 ARMA, American Rock Mechanics Association. A persistent increase in the permeability of a rock mass caused by transient stress disturbances, when they exist, can explain the change in groundwater level as well as the petroleum production by seismic waves in the far-field. However, it has yet to be clarified whether the transient stress disturbances induce an increase or decrease in the rock permeability. To clarify the effects of transient stress disturbances on the rock permeability, permeability measurements were carried out on intact and triaxially fractured Shikotsu welded tuff, both before and after the occurrence of axial stress or pore pressure transient disturbances. Based on the experimental results, both types of stress disturbances showed an increasing effect on the permeability for fractured rocks. However, only the pore pressure disturbances showed an increasing effect for intact rocks. It can be estimated that rock masses consisting of glassy pyroclastic rock may exhibit an increase in the permeability through disturbances in the transient stress. - Variation in the permeability of intact and fractured rocks due to transient disturbances in axial stress or pore pressure
Sophea Boeut, Teppei Oshima, Yoshiaki Fujii, Jun Ichi Kodama, Daisuke Fukuda, Hiroyuki Matsumoto, Kazumi Uchida, Anjula B.N. Dassanayake
Advances in Civil Engineering, 2019, 2019年, [査読有り]
研究論文(学術雑誌), © 2019 Sophea Boeut et al. A persistent increase in the permeability of rock mass caused by transient stress disturbances, if present, could explain the variation in the groundwater level in far fields, increase in petroleum production caused by earthquakes or artificial vibrations in enhanced oil recovery, and induction of earthquakes by seismic waves in intermediate and far fields. However, it has not been verified whether the transient stress disturbances induce an increase or decrease in the rock permeability. In this study, the permeability values of intact and triaxially fractured Kushiro Cretaceous sandstone and Shikotsu welded tuff were measured before and after transient axial stress or pore pressure disturbances to clarify the effects of transient stress disturbances on rock permeability. According to the experimental results, the stress disturbances showed either decreasing or increasing effects on the permeability depending on the rock type and experimental conditions. However, when focusing on the fractured rocks rather than the intact ones, which would be more important in field applications, the argillaceous Kushiro Cretaceous sandstone mainly exhibited decreasing effects and the glassy Shikotsu welded tuff mainly exhibited increasing effects. - Influences of Water Vapor on Roof Fall Accidents in Selected Underground Coal Mines in Malawi
Umali M. Yasidu, Yoshiaki Fujii, Jun Ichi Kodama, Daisuke Fukuda, George J. Maneya, Johnson Dandadzi, Anjula B.N. Dassanayake
Advances in Civil Engineering, 2019, 2019年, [査読有り]
研究論文(学術雑誌), © 2019 Umali M. Yasidu et al. To develop affordable countermeasures against the roof falls, the accident records of Mchenga Mine were investigated as the first step. Based on the accident records, it was found that roof falls occurred most in April and May. Humidity measurements were taken both in the underground mine and at surface, and humidity peak appeared in April. The accident occurrence and the underground humidity had a positive correlation in which no roof falls could be expected under a humidity of less than a certain value. Effect of humidity on the indirect tensile strength of the rock samples collected from the mine was investigated, and it showed that the indirect tensile strength decreased with humidity. The diffusion coefficient was measured for the rock samples collected from Mchenga Mine as well as from Kaziwiziwi Mine, and the migration of water vapor into rock mass in the roof was calculated for Mchenga case. It was clarified that the weakening of tensile strength was transmitted upward at several centimeters per day from the immediate roof. This could explain the slight difference of the accident peak in April and May from the humidity peak in April. Introducing fresh and dry outside air, if possible, will not only improve the working environment but also contribute to a decrease in roof falls. - Effect of acid-temperature-pressure on the damage characteristics of sandstone
Li, S, Huo, R, Fujii, Y, Ren, D, Song, Z
Int. J. Rock Mech. Min. Sci., 122, 2019年, [査読有り]
英語, 研究論文(学術雑誌) - Tangent modulus method – An original method to measure in-situ rock stress
Y. Fujii, M. Makasi, J. Kodama, D. Fukuda, K. Goto, S. Kumakura, M. Kanaoka, A. B.N. Dassanayake
Tunnelling and Underground Space Technology, 82, 148, 155, 2018年12月, [査読有り]
英語, 研究論文(学術雑誌), © 2018 Elsevier Ltd This paper proposed Tangent Modulus Method (TMM) which is an improved oriented core method to determine in-situ rock stresses. In this approach, the cylindrical specimens prepared along different directions from thick core samples were uniaxially compressed twice to a given stress level. The stress value of the bending point in the first loading cycle of the stress-tangent modulus curve is considered as the normal component of the in-situ rock stress along the drilled direction of the specimen. Four types of rocks from soft porous tuff and sandstone to hard crystalline granite was investigated to evaluate the potential of this method. The effects of changes in strain rate, temperature, water content, confining and pore pressure, and stresses larger than the preload on the stress value of the bending point were experimentally investigated on preload specimens to investigate their influence on TMM. Comparison of the stress measurement results by TMM and an overcoring method at AK tunnel in Hokkaido, Japan was also performed to validate the TMM. - Water drainage from Kushiro Coal Mine decreased on the day of all M ≥ 7.5 earthquakes and increased thereafter
Yoshiaki Fujii, Yoshihisa Ichihara, Hiroyuki Matsumoto, Jun Ichi Kodama, Daisuke Fukuda, Anjula B.N. Dassanayake
Scientific Reports, 8, 1, 2018年12月01日, [査読有り]
研究論文(学術雑誌), © 2018, The Author(s). The amount of water drainage from Kushiro Coal Mine in Hokkaido, Japan decreased on the day of all M ≥ 7.5 earthquakes with epicenters within 300 km of the mine during the monitoring period and increased after these earthquakes. This is a valuable finding which would give us a clue to understand pre- and post-seismic rockmass behaviors and contribute for progress in earthquake prediction in future. - Prevention of Catastrophic Volcanic Eruptions, large earthquakes underneath big cities, and giant earthquakes at subduction zones
Yoshiaki Fujii, Morteza Sheshpari, Jun ichi Kodama, Daisuke Fukuda, Anjula B.N. Dassanayake
Sustainability (Switzerland), 10, 6, 2018年06月07日, [査読有り]
英語, 研究論文(学術雑誌), © 2018 by the authors. Catastrophic volcanic eruptions, large earthquakes beneath big cities, or giant earthquakes at subduction zones are apparently the biggest problems facing the sustainability of human society. However, imminent prediction methods for these events have never been established, except that volcanic eruptions can only be predicted by exceptional efforts by dedicated researchers. Even if a prediction method has been established, the method cannot significantly reduce infrastructure damage, although it could slightly reduce the number of fatalities. On the other hand, prevention of eruptions or earthquakes could significantly reduce, not only the number of fatalities, but also infrastructure damage. Therefore, the authors propose (1) gradual energy release by supercritical power generation to prevent catastrophic eruptions; (2) gradual seismic energy release by injecting water into seismic sources to prevent large earthquakes beneath big cities; and (3) exploding existing nuclear warheads underground to prevent giant earthquakes at subduction zones. Necessary technical developments, costs, risks, and problems will also be explained. - UCG模型試験における破砕炭と塊炭の燃焼・ガス化特性の比較
児玉淳一, 立川多久登, 中良介, 濱中晃弘, 板倉賢一, 出口剛太, 福田大祐, 藤井義明
J. MMIJ, 134, 7, 91, 98, 2018年, [査読有り]
日本語, 研究論文(学術雑誌) - Influence of transient stress disturbances on permeability of kushiro cretaceous sandstone
Sophea Boeut, Teppei Oshima, Yoshiaki Fujii, Jun ichi Kodama, Daisuke Fukuda, Hiroyuki Matsumoto, Kazumi Uchida
ISRM International Symposium - 10th Asian Rock Mechanics Symposium, ARMS 2018, 2018年
研究論文(国際会議プロシーディングス), There are several case studies in which vibration produced by earthquakes or underground explosion affected the level and temperature of ground water, petroleum production, etc. These might be due to the change in permeability by transient stress disturbances creating new pathways, clearing particles clogging the pore spaces of the existing pathways. This paper investigated on the permeability change of intact and triaxially fractured Kushiro Cretaceous sandstone by transient axial and pore pressure disturbances. In the room temperature, the specimens dimensioned 30 mm in diameter and 60 mm in length were triaxailly compressed under 1 MPa of pore water pressure, and 3-15 MPa of confining pressures. The permeability was measured before (kI: intact rock) and after (kDI: disturbed intact rock) transient stress disturbances for pre-failure rock and before (kP: post-failure rock) and after (kDP: disturbed post-failure rock) transient stress disturbances for post-failure rock. Under 0-11 MPa of the axial stress disturbance amplitudes, the permeability of the specimens decreased from kI to kDI and from kP to kDP due to the disturbance, yet it increased from kDI to kP resulted in rock failure. The permeability of pre-failure rock decreased larger with confining pressure and time; however, the decrease amount was almost constant by the disturbance amplitudes. For post-failure, the decrease amount of permeability became higher with the axial stress disturbances. This clarifies that the permeability of fractured Kushiro Cretaceous sandstone decreased by axial stress disturbance. Under pore pressure disturbance amplitudes of 0.2 to 1.8 MPa, in the pre-failure regime, the permeability decreased at the lower disturbance amplitudes, but increased at higher disturbance amplitude. The permeability continued to increase by rock failure, though, in the post-failures, the permeability decreased by the pore pressure disturbances. The increase might be utilized for the enhanced methane gas recovery. - Study of factors behind rock slope displacement at Higashi Shikagoe limestone quarry, Japan
Chimwemwe Nelson Bandazi, Rith Uy, Jun-ichi Kodama, Yoshiaki Fujii, Daisuke Fukuda, Hiroshi Iwasaki, Sanshirou Ikegami
GEOMECHANICS AND GEODYNAMICS OF ROCK MASSES (EUROCK2018), VOLS 1 AND 2, 479, 484, CRC PRESS-BALKEMA, 2018年
英語, 研究論文(国際会議プロシーディングス), Ensuring safe and productive operations in open pit mining entails undertaking displacement measurement of rock slopes to determine their stability. At Higashi Shikagoe limestone quarry in Hokkaido, Japan, Automated Polar System (APS) was installed to monitor rock slope displacement. The site is geologically complex and is subject to a wide variety of weather conditions due to its location in a cold region of Japan where winter temperatures can drop to -18 degrees C and snow depths of about 80 to 90 cm are often measured. In this study, APS data was used to characterize rock slope deformation and identify its driving forces. Analysis of displacement data revealed changes in tendencies of displacement during warm and cold periods. Numerical analysis using linearly elastic and isotropic models of the quarry showed that excavation and backfilling were not the main causes of measured displacement. It was found that snowfall and snowmelt had an influence on rock slope displacement. - Underground structures in Mars excavated by tunneling methods for sheltering humans
Morteza Sheshpari, Yoshiaki Fujii, Takuya Tani
TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY, 64, 61, 73, PERGAMON-ELSEVIER SCIENCE LTD, 2017年04月, [査読有り]
英語, 研究論文(学術雑誌), Humans can inhabit other planets in future by advancement in science and technology, starting by closest ones and moving to farther planets. There are some projects underway currently for human settlement on Mars such as Mars-one project or new proposals by NASA. In this paper, possibility of creating and using underground structures in Mars for sheltering humans against harsh environment and dangerous rays goes under investigation. Primary locations such as Arsia Mons for early settlement on Mars was investigated providing its appropriate conditions. Numerical analysis for tunneling to create underground space was conducted considering different spatial orientation of main discontinuities such as fault and joints in Martian gravity. It was inferred that tunneling in near surface Martian rocks is not susceptible to major failures and instabilities. Frozen water in Mars climate, and low gravity result in lower amounts of required cohesion value to keep tunneling structure stable in different scenarios of discontinuities in Martian rocks. It was concluded that underground structures are among the best options for residing humans on Mars and sheltering them against harsh climate by providing insulation and creating enough thickness of burden rock mass against dangerous cosmic and solar rays. (C) 2017 Elsevier Ltd. All rights reserved. - Effect of humidity on tensile strength of rocks in selected underground coal mines in Malawi
U. M. Yasidu, Y. Fujii, D. Fukuda, J. Kodama, G. Maneya
51st US Rock Mechanics / Geomechanics Symposium 2017, 1, 696, 704, 2017年
研究論文(国際会議プロシーディングス), One of the major challenges facing coal mines in Malawi is occurrence of hanging roof falls during the rainy season. Following this, the effect of humidity on the tensile strength of coal bearing rocks, arkose sandstone and fine-grained sandstone from Mchenga underground coal mine, was studied aiming to clarify the mechanism of roof fall in the underground mines and proposing countermeasures against the roof falls. Rock samples from the mine were treated in varying humidity levels. Some specimens were oven dried at 80°C and a desiccant was used to attain low humidity. Moderate humidity was obtained using magnesium-nitrate-hexahydrate, high humidity was achieved by pure water and some specimens were vacuum saturated. Subsequently, Brazilian test was carried out to obtain indirect tensile strength along the sedimentary plane. For comparison, Neogene tuffaceous Kimachi sandstone from Japan was also tested, following the same conditions. It was confirmed that indirect tensile strength of the rocks decreased with increase in humidity. The sensitivity of indirect tensile strength to humidity for arkose and fine grained sandstones was 12% or 29% larger than that for Kimachi sandstone. The stronger sensitivity for Mchenga roof rocks would be because the rocks contain illite, whose strength is very sensitive to water, while Kimachi sandstone contains only less sensitive zeolite for clay minerals. - Comparison of FEM-based 3-D dynamic fracturing simulations using intrinsic and extrinsic cohesive zone models
D. Fukuda, E. Nihei, S. H. Cho, S. W. Oh, J. Kodama, Y. Fujii
4th ISRM Young Scholars Symposium on Rock Mechanics, YSS 2017, 2017-May, 106, 110, 2017年
研究論文(国際会議プロシーディングス), Smeared crack approach coupled with cohesive zone model has been an attractive way for the realistic simulations of dynamic fracturing of rocks and frequently utilized in the framework of the Finite Element Method (FEM). In many cases, cohesive elements (CEs) with initially-zero-thickness are inserted at the onset of numerical simulations and these are used to express the dynamic fracturing, which is called “intrinsic cohesive zone model (ICZM)”. However, since the ICZM must introduce penalty terms to express the intact behavior of the CEs, this tends to render higher compliance of bulk rock, resulting in smaller wave propagation speed. In this paper, by introducing a so-called “extrinsic cohesive zone model (ECZM)”, which adaptively inserts the CEs, we compared the results of 3-D dynamic fracturing simulations by the ICZM and ECZM using the experimental data obtained from the dynamic spalling test for rocks. Using the same Young’s modulus, Poisson’s ratio, density and strengths estimated from the experiments, our results suggest that the outcome of the ICZM and experiment showed large discrepancy especially for the intact stress wave propagation while the ECZM showed good agreement with the experiment. Therefore, our results could have some implications on the current situation in which more and more simulations using the ICZM such as in hybrid FEM-DEM have been applied to rock fracture mechanics problems. - 3D numerical analysis of time-dependent behavior of a tunnel constructed with conventional support system
H. Arima, A. Sainoki, D. Fukuda, J. Kodama, Y. Fujii, H. Murayama, H. Niwa, K. Okazaki
4th ISRM Young Scholars Symposium on Rock Mechanics, YSS 2017, 2017-May, 265, 268, 2017年
研究論文(国際会議プロシーディングス), In Hokkaido prefecture, Japan, a number of road mountain tunnels constructed with conventional support systems are still in use. In one of the tunnels, the progressive damage evolution and large deformation of the tunnel wall were observed. The present study investigates its mechanism and the effectiveness of the conventional support system. In order to simulate the time-dependent behavior of the target tunnel, a variable-compliance-type constitutive equation is employed and implemented into FLAC3D. A 3D numerical model reproducing the actual ground surface topography is constructed. Using the numerical model and constitutive equation, the time-dependent damage evolution and resultant deformational behavior are simulated whilst considering combinations of the conventional support system members, namely steel sets, concrete lining and invert concrete. The analysis results show that concrete invert installation is the most effective measure to suppress and control the damage evolution and deformation of the tunnel wall. The concrete lining is the second effective, alleviating the deformation taking place on the tunnel wall and crown. It is then revealed that steel sets do not significantly contribute to suppressing the damage evolution. The analysis result also indicates that axial stresses originally acting on the steel sets are re-distributed to the concrete lining and invert concrete, proving that the two support members can work more effectively than steel sets in the aspect of controlling the time-dependent damage evolution of the surrounding rock mass. - Kimachi sandstone does not have to fail under larger stress
Y. Wang, Y. Fujii, D. Fukuda, J. Kodama
Rock Mechanics and Rock Engineering: From the Past to the Future, 1, 159, 164, 2016年
研究論文(国際会議プロシーディングス), Series of uniaxial compression tests combining constant strain rate and four patterns of cyclic loading were carried out on Kimachi sandstone to clarify the timing of rock failure. It was found that rock failure timing was random in triangular, reverse triangular and small amplitude triangular loading tests and all rocks failed during larger strain in large amplitude triangular loading tests. The results suggest that rock specimens did not have to fail under larger strain when the stress amplitude was smaller than a certain value and gave us clues to explain why rocks do not always fail under larger stress. The mechanism behind the experimental results was explained based on strain rate-dependent rock strength and fatigue damage. - Kimachi sandstone does not have to fail under larger stress
Y. Wang, Y. Fujii, D. Fukuda, J. Kodama
ISRM International Symposium - EUROCK 2016, 159, 164, 2016年
研究論文(国際会議プロシーディングス), Series of uniaxial compression tests combining constant strain rate and four patterns of cyclic loading were carried out on Kimachi sandstone to clarify the timing of rock failure. It was found that rock failure timing was random in triangular, reverse triangular and small amplitude triangular loading tests and all rocks failed during larger strain in large amplitude triangular loading tests. The results suggest that rock specimens did not have to fail under larger strain when the stress amplitude was smaller than a certain value and gave us clues to explain why rocks do not always fail under larger stress. The mechanism behind the experimental results was explained based on strain rate-dependent rock strength and fatigue damage. - Effect of buttress on reduction of rock slope sliding along geological boundary
Ryota Moriya, Daisuke Fukuda, Jun-ichi Kodama, Yoshiaki Fujii
OPERATIONAL AND ENVIRONMENTAL MINE HEALTH AND SAFETY PRACTICE AND INNOVATION, 121, 126, MCGILL UNIV, 2016年, [査読有り]
英語, 研究論文(国際会議プロシーディングス), In open-cut limestone mines in Japan, huge rock slopes with a geological boundary between limestone and bedrock have been formed by mining activities. In addition, latent sliding plane near the toe of the slopes may be formed through the development of damaged zones with an increase in size of the rock slope. It has been reported that inelastic time-dependent sliding deformation of rock slopes along both the geological boundary and the latent sliding plane can occur. In this case, one of the countermeasures to suppress sliding deformation is an application of rock buttress to the slope surface where the sliding is taking place. However, the effect of rock buttress on reduction of the rock slope sliding has not yet been clarified. In this paper, the effect of rock buttress on reduction of the rock slope sliding is discussed based on a 2-dimensional finite element analysis using a non-linear visco-elastic model. The results indicate that (i) the degree of deterioration of sliding plane at the time of the application of rock buttress significantly affects the expected life of rock slope, (ii) there is an optimum height for rock buttress,, (iii) larger Young's modulus of rock buttress results in a longer expected life of rock slope, and (iv) the balance of increase and decrease of normal and shear stresses on the sliding plane by buttress is important and the obtained results can be changed by the difference of friction angle and the geometry of the sliding plane. - Analytical model to determine optimal fluid injection time ranges for increasing fluid storage and oil recovery: A reservoir compaction approach
Ilyas Khurshid, Yoshiaki Fujii, Jonggeun Choe
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING, 135, 240, 245, ELSEVIER SCIENCE BV, 2015年11月, [査読有り]
英語, 研究論文(学術雑誌), Reservoir compaction and pore collapse are induced with fluids (oil, gas, and water) productions. They are responsible for both recovery and environmental problems. Our objective is to develop a generic integrated framework for reservoir compaction to determine optimal time ranges of fluids (CO2 or water) injection in a reservoir for increasing oil recovery and their storage. The framework consists of a model with a methodology. We derive the model using the concept of body-centered pores in a cubic lattice at microscopic level. The model describes the relationship between porosity and stresses, and estimates reservoir compaction as a function of fluid withdrawal, time, and stresses.
On the basis of the model developed, we propose a methodology named failure-line method to determine the critical point of irreversible brittle pore collapse. Thus, the best fluid injection time range is before touching this critical point. We use inversion analysis to determine, compare and validate our results with experimental and field data available, and found a good match. As a result, the developed model and methodology can be an efficient and cost effective tool to investigate the effect of production on reservoir compaction, variation in porosity, and to determine an optimal time range for fluid injection. The model assumes that there are no consistent capillary and gravity forces. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved. - Fractured Rock Permeability as a Function of Temperature and Confining Pressure
A. K. M. Badrul Alam, Yoshiaki Fujii, Daisuke Fukuda, Jun-ichi Kodama, Katsuhiko Kaneko
PURE AND APPLIED GEOPHYSICS, 172, 10, 2871, 2889, SPRINGER BASEL AG, 2015年10月, [査読有り]
英語, 研究論文(学術雑誌), Triaxial compression tests were carried out on Shikotsu welded tuff, Kimachi sandstone, and Inada granite under confining pressures of 1-15 MPa at 295 and 353 K. The permeability of the tuff declined monotonically with axial compression. The post-compression permeability became smaller than that before axial compression. The permeability of Kimachi sandstone and Inada granite declined at first, then began to increase before the peak load, and showed values that were almost constant in the residual strength state. The post-compression permeability of Kimachi sandstone was higher than that before axial compression under low confining pressures, but lower under higher confining pressures. On the other hand, the permeability of Inada granite was higher than that before axial compression regardless of the confining pressure values. For the all rock types, the post-compression permeability at 353 K was lower than at 295 K and the influence of the confining pressure was less at 353 K than at 295 K. The above temperature effects were observed apparently for Inada granite, only the latter effect was apparent for Shikotsu welded tuff, and they were not so obvious for Kimachi sandstone. The mechanisms causing the variation in rock permeability and sealability of underground openings were discussed. - A new approach to evaluate effective stress coefficient for strength in Kimachi sandstone
A. B. N. Dassanayake, Yoshiaki Fujii, Daisuke Fukuda, Jun-ichi Kodama
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING, 131, 70, 79, ELSEVIER SCIENCE BV, 2015年07月, [査読有り]
英語, 研究論文(学術雑誌), This paper is devoted to the experimental investigation of effective stress coefficient for peak and residual strengths of saturated Kimachi sandstone. Authors have described the Modified Failure Envelope Method (MFEM), which can be used to obtain the effective stress coefficients for peak and residual strengths (alpha(-Peak) and alpha(-Residual)). The effective stress coefficients for intact and fractured Kimachi sandstone (alpha(-Biot's) and alpha(-Fractured)) were also evaluated using conventional methods, and the data were compared with the coefficient values obtained by MFEM for the peak and residual strengths. The effective stress coefficient for intact rock, alpha(-Biot's) decreased with increasing confining pressure, and was in the range 1 > alpha(-Biot's) > 0.8. The effective stress coefficient for fractured rock, alpha(-Fractured), was larger than that for intact rock and was close to unity. The effective stress coefficient calculated for peak strengths, alpha(-Peak), using both the single and multistage MFEMs, decreased with increasing effective confining pressure and was in the range 0.8 > alpha(-Peak) > 0.4. For residual strength states, effective stress coefficient, alpha(-Residual), was between the peak strength value and that for intact rock. Based on the results, multistage MFEM is suitable for obtaining an effective stress coefficient for the peak strength, alpha(-Peak). An equation to obtain the effective stress coefficient from total confining pressure and pore pressure, and a method to choose the coefficients for elastic stress analyses and failure evaluations for intact rock structures or structures in rock mass were proposed. (C) 2015 Elsevier B.V. All rights reserved. - Time-dependent mechanical behaviors of frozen welded tuff
J. Kodama, Y. Mitsui, T. Sugawara, D. Fukuda, Y. Fujii, S. Hara
13th ISRM International Congress of Rock Mechanics, 2015- MAY, 1, 10, 2015年
研究論文(国際会議プロシーディングス), Surfaces of rock slopes in cold regions often become frozen in winter. Therefore, understanding time-dependent behavior of frozen rock, as well as that of unfrozen rock, is important for long-term stability assessment of rock slopes. In this study, a series of uniaxial compression tests and creep tests were carried out on Shikotsu welded tuff under dry and water-saturated conditions at -20°C to clarify time-dependent strength and deformation of the frozen rock. The influence of water content on them also was investigated. It was found that the amount of deformation of the water-saturated specimen was much greater than that of the dry specimen. It also was found that the creep behavior of the water-saturated specimen was similar to that of polycrystalline ice. These show that deformation of the water-saturated specimen is strongly affected by pore ice. The UCS of the water-saturated specimen was approximately equal to that of the dry specimen at a strain rate below 4.2×10-6/s, and its value was about 17 MPa. However, the former increased up to 26 MPa at 4.2×10-4/s with loading rate, whereas there was little increase in the latter. This means that the UCS of the water-saturated specimen was always greater than that of the dry specimen at higher strain rates. The creep life of water-saturated specimens was longer than that of the dry specimens at stress level greater than 15 MPa. These results of UCS and creep life show that inclusion effect due to presence of pore ice plays an important role on strength of the water-saturated specimen. Creep life of the non-failure specimen that was loaded for more than three days was estimated by the relationship between creep life and axial strain rate at 10 s on failure specimens. It was found that creep life of the water-saturated specimens was shorter than that of the dry specimen at stress levels less than 14 MPa. This suggests that estimation of creep life of frozen rock under water-saturated condition is important for the stability assessment of frozen rock slopes. It was clear that the loading-rate dependency of UCS was related to the stress-level dependency of creep life in both dry and wet conditions. This indicates that there are common fracture mechanism in creep and uniaxial compression tests. It also indicates that the creep life can be estimated by the relationship between the UCS and the loading rate. The time dependencies of the water-saturated specimen were in good agreement with those of polycrystalline ice. This confirms that pore ice strongly affects the strength of the water-saturated specimens as, well as the deformation behavior. - Giant earthquakes are occurring at lunar phases specific to each subduction zone
Y. Fujii, J. Kodama, D. Fukuda
13th ISRM International Congress of Rock Mechanics, 2015- MAY, 1, 10, 2015年
研究論文(国際会議プロシーディングス), Here, we statistically proved that giant earthquakes occur at lunar phases specific to each subduction zone. Enough attention during the lunar period, especially when seismicity is occurring, will significantly reduce damage from giant earthquakes. Two case studies in which giant earthquakes occurred after seismicity in dangerous lunar phases were discussed, and the mechanisms underlying why giant earthquakes occur around neap tide at some subduction zones were explained by prohibition of giant earthquake occurrences due to high strain rates at spring tides at N-S subduction zones. The prohibition was statistically proven for uniaxial creep tests on Inada granite with slight stress disturbances. - Evaluation of 3-D Strain Distribution in Lignite Based on Image Analysis
D. Fukuda, M. Maruyama, J. Kodama, Y. Fujii, N. Aramaki, K. Kaneko, Y. Nara
ISRM Congress 2015 (The 13th. International Congress of Rock Mechanics), 2015- MAY, 394, 10, 2015年, [査読有り]
英語, 研究論文(国際会議プロシーディングス), Evaluation of three dimensionally non-uniform strain distribution in rocks under various conditions such as in water or under freeze-thaw cycles is of significant importance to understand their complex deformations and fracturing mechanisms. For this purpose, we developed an image analysis method which can evaluate or "measure" the three dimensional (3-D) strain distribution in rocks. The proposed method utilizes the 3-D images of rock under initial and deformed configurations, which are obtained by some imaging techniques such as X-ray computed tomography (X-rayCT). In the proposed method, the obtained 3-D images are divided into multiple sub-regions of interest. For each sub-region, the strain is evaluated utilizing 3-D affine transform with unknown coefficients to be determined. In the first step, 3-D voxel level displacements at multiple representative points in each sub-region are computed by 3D digital volume correlation technique between the comparison images and the initial-guess of the transform coefficients are obtained. In the second step, referring to the initial-guess of unknown transform coefficient, they were optimized in sub-voxel level by finding optimum digital volume correlation between the comparison images, which can evaluate the transform coefficients with higher precision. From the calculated transform coefficients, the strain was directly obtained through the spatial derivative of displacement based on affine transform. In this paper, along with the description of the proposed method, the evaluation of deformation in a lignite specimen due to immersion in water was presented as an application example. As the 3-D imaging technique, micro-focus X-rayCT was applied. The result showed that the induced dilatational strain field due to the initiation and extension of cracks in the specimen was clearly captured. Therefore, authors believe that the proposed method can be applicable to various problems in rock mechanics. - 地層内バイオメタン生産技術に関する過酸化水素を用いた石炭系材料の有機物分解及び内部構造の経時変化
荒牧憲隆, 玉村修司, 田中翔, 川崎了, 藤井義明, 金子勝比古
地盤工学ジャーナル, 10, 3, 391, 401, The Japanese Geotechnical Society, 2015年, [査読有り]
日本語, 研究論文(学術雑誌) - The Deformation Modes of Rock Slopes due to Excavation in Mountain-Type Mines
Najib, Daisuke Fukuda, Jun-Ichi Kodama, Yoshiaki Fujii
MATERIALS TRANSACTIONS, 56, 8, 1159, 1168, JAPAN INST METALS, 2015年, [査読有り]
英語, 研究論文(学術雑誌), This paper discusses an investigation of mining-induced elastic deformation of a cut rock slope formed in a mountain-type mine using a two-dimensional finite element method. The horizontal elastic deformation mechanism is discussed, including the effects of the Poisson's ratio, slope angle and progression of the excavation. The results show a clear dependence of the deformation modes characterized by extension, contraction or shear distortion of rock mass, on these three effects, in which the direction of rock movement at the surface due to excavation was opposite. Four effects contribute to the deformation mechanism in mountain-type mines: the Poisson effect (PE), the distributed load effect (DLE), bending effects and shear distortion. Forward surface displacement of the cut rock slope was found to occur during the early stages of excavation due to the release of horizontal compressive stresses due to bending effects around the middle of the mountaintop. As the excavation progresses, forward or backward horizontal surface displacement was found to occur due to PE or DLE, respectively, which depends on the Poisson's ratio in the subsequent stages of excavation. Asymmetric stress release due to excavation affects the horizontal deformation of the mountain, and induces a moment enhancing the backward displacement due to shear distortion. It should be noted that the direction of the surface displacement of the rock slope could change from forward to backward as the excavation progresses, even though the rock slope may be stable. This is very important in the interpretation of surface displacement monitoring using the Automated Polar System and/or Global Positioning System. In the interpretation of the internal displacement measured using extensometers, we should consider extension during the early stages of excavation, followed by slight contraction during the latter stages, as a sign of a stable cut rock slope in a mountain type mine. - 凍結融解履歴を受ける泥質片岩と花崗岩の変形挙動と破壊プロセス
児玉淳一, 畔原孝典, 福田大祐, 藤井義明
Zairyo/Journal of the Society of Materials Science, Japan, 63, 3, 219, 226, Society of Materials Science Japan, 2014年, [査読有り]
日本語, 研究論文(学術雑誌), Fracture processes of argillaceous schist and granite subjected to freeze-thaw cycles were investigated based on their deformation behaviors. It was found that argillaceous schist showed apparent anisotropy in deformation. Significant extensile strain was observed in the direction perpendicular to the cleavage plane around -3°C in freezing process on the water-saturated specimen, followed by extensile plastic strain at the end of the cycle. No apparent extension and anisotropy were found on the water-saturated specimen of granite, but decrease in contraction rate was seen at -3°C in freezing process with AE activity. The extensile plastic strain of both rocks gradually increased with the number of freeze-thaw cycles, but magnitude of the plastic strain on argillaceous schist was much greater than that of granite. These results indicate that there might be common mechanism in fracture process between both rocks, but significant differences in deterioration rate. Deterioration of argillaceous schist is much faster because fracture mainly develops by extension of well-developed cleavage in the rock. It was concluded that weak plane such as cleavage strongly affected deterioration of rocks by freeze-thaw cycle. © 2014 The Society of Materials Science, Japan. - Effects of confining pressure on the permeability of three rock types under compression
A. K. M. Badrul Alam, Masaki Niioka, Yoshiaki Fujii, Daisuke Fukuda, Jun-ichi Kodama
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 65, 49, 61, PERGAMON-ELSEVIER SCIENCE LTD, 2014年01月, [査読有り]
英語, 研究論文(学術雑誌), Triaxial tests were conducted on three different rocks, under confining pressures of 1-15 MPa at 295 K using an ultra-compact triaxial cell. The samples were held for 24 h under the target consolidation pressure, and then constant strain-rate compression was applied measuring permeability. The structural changes were measured by thin section image analysis and micro-focus X-ray computed tomography. For the Shikotsu welded tuff, the permeability decreased monotonously with axial compression, mainly due to pore collapse. For the Kimachi sandstone, the permeability first decreased with increasing axial stress, then began to increase when the total lateral strain recovered its value before the application of confining pressure, and then maintained an almost constant value in the post-peak region. The minimum and final permeability decreased with increasing confining pressure mainly due to compaction and large plastic deformation of clay cementing materials. For the lnada granite, the tendency of permeability change during axial compression was almost the same as for the Kimachi sandstone. The final permeability was larger than that before compression, and the permeability decreased with smaller confining pressure mainly due to a decrease in the number and width of rupture planes and the absence of axial cracks from biotite. The permeability, however, increased under larger confining pressures mainly due to the formation of subrupture planes caused by the high stress concentration at the rough and stiff rupture plane under large confining pressure. (C) 2013 Elsevier Ltd. All rights reserved. - Numerical study on fracturing process in rock by blasting a cylindrical charge
D. Fukuda, J. Ikezawa, K. Kaneko, J. Kodama, Y. Fujii
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014, 784, 791, 2014年
研究論文(国際会議プロシーディングス), In blasting, cylindrical charge is generally applied in terms of energy efficiency. The dynamic fracturing in rock due to detonation of high-explosive involves quite fast process and extremely complex fracturing pattern. In addition, detailed fracturing process is generally not observable. Thus, blasting design tends to be based on empirical knowledge or law. It is also well known that fracturing process envisioned here depends on the applied pressure wave forms characterized by such as detonation property and amount of applied explosive. These in turn make the design optimization of blasting quite difficult and, even for the simplest blasting problem with a single free face, the fracturing mechanism has not been clarified yet. Therefore, it is of paramount importance to investigate the fracturing process due to blasting in detail for various types of applied pressure wave forms. For this purpose, application of numerical simulation is one of the most promising approaches. This paper proposed a method for the simulation of dynamic fracturing process through axisymmetric finite element formulation in which the initiation, propagation, branching and coalescence of fractures in heterogeneous rock can be analyzed. In particular, blasting a cylindrical charge through bottom priming in a cylindrical rock specimen was analyzed considering the difference of load configuration characterized by length of applied explosive. It was clarified that the resultant fracturing patterns were strongly dependent on the length of applied explosive. In addition, cross-shaped fractures occurring on the free face were successfully simulated by the proposed method, which were observed in the field-scale blasting with a cylindrical charge. Therefore, the applicability of the proposed method was validated and it can give a deep insight for understanding the dynamic fracturing process in rock due to blasting with a cylindrical charge. - Observation of fracture process of rocks subjected to freeze-thaw cycles using X-ray CT
J. Kodama, M. Nakaya, Y. Nara, T. Goto, D. Fukuda, Y. Fujii, K. Kaneko
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014, 628, 634, 2014年
研究論文(国際会議プロシーディングス), Understanding fracture process of rocks exposed to freeze-thaw cycles is a fundamental issue for stability assessment of a rock fill dam as well as a rock slope, especially in cold weather regions. In this study, cyclic freeze-thaw tests were carried out on rock samples in order to characterize fracture propagation by freeze-thaw action. The fracture process was characterized by macroscopic observation by digital camera and changes in water absorption. Fracture initiation and propagation inside of the specimen were also observed using X-ray CT scanner. It was found that the fracture process depends on the rock type. For rocks which possess preferred orientation of pre-existing fractures and remarkable anisotropy in P-wave velocity, only one fracture propagated dominantly and split the rock specimen in half. Gradual increase in aperture of the fracture was observed not only on surfaces but also inside of the specimen. On the other hand, for isotropic rock, propagation and branching of several fractures occurred and rock samples were split into several parts. These fracture processes were confirmed by change in water absorption. Water absorption of the anisotropic rock tended to increase gradually with freeze-thaw cycles, but suddenly decreased to the initial value at the occurrence of split. In contrast, water absorption of the isotropic rock continued to increase even after sample split occurred. - Significant differences in effective stress coefficient for rocks within elastic region and peak and residual strengths
A. B.N. Dassanayake, Y. Fujii, D. Fukuda, J. Kodama
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014, 141, 150, 2014年
研究論文(国際会議プロシーディングス), The values of the effective stress coefficients (α) for intact and fractured rocks were evaluated for three different rocks by conventional method and compared for peak and residual strengths evaluated by Modified Failure Envelope Method (MFEM), which was developed by the authors. For Kimachi Sandstone, intact rock α values decreased with confining pressure and varied between 1 and 0.8. α value for fractured rock of the same sandstone was higher than the intact rock, reaching nearly one. α value for peak strength decreased from 0.8 to 0.4 with effective confining pressure under both single and multi stage MFEMs. For residual strength state, α value was between that for the peak strength and that for the intact rock. For Inada Granite, α value for intact rock decreased with confining pressure from 0.9 to 0.7. α value for fractured rock was higher than that for intact rock and nearly one. Value for peak strength was obtained only by multistage test and decreased from 0.8 to 0.2 with confining pressure. The value for residual strength could not be obtained. For Shikotsu Welded Tuff, the α value for intact rock slightly decreased from 0.95 to 0.90 with increasing confining pressure. The value for fractured rock was higher than α for intact rock and nearly one. MFEM could not be effectively used to determine the values for peak and residual strengths possibly due to pore collapse. From the above results, it can be concluded that the multistage MFEM is very effective to obtain the value for peak strength. The choice of coefficient values was proposed for stress analysis and failure evaluation, in intact rock structures or structures in rock mass. - Uniaxial compressive strength of Shikotsu welded tuff and Bibai sandstone at sub-zero temperature
S. Hara, J. Kodama, Y. Fujii, D. Fukuda, Y. Mitsui, T. Sugiura
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014, 151, 159, 2014年
研究論文(国際会議プロシーディングス), Understanding strength and deformation of frozen rock is important for stability assessment of a rock slope in cold weather regions because surfaces of the rock slope often get frozen in winter. In this study, strength and deformation of frozen rock specimens of Shikotsu welded tuff and Bibai sandstone were investigated by uniaxial compression test at -20oC (253 K). Failure processes of both rocks were also considered based on their deformation behaviors. Larger deformation of wet specimens was found than that of dry ones in both rocks due to pore ices plastic deformation. However, it was found that the effect of water content on strength depends on rock type. UCS of wet specimens of Shikotsu welded tuff was greater than that of dry ones. In contrast, UCS of wet specimens was smaller on Bibai sandstone. The former phenomenon can be interpreted by inclusion effect of presence of pore ice. The latter phenomenon can be explained due to stress corrosion by unfrozen water or reduction in friction coefficient of crack surfaces by pore ice. - Investigation of rock slope deformation modes due to excavation on mountain type mine
Najib, D. Fukuda, J. Kodama, Y. Fujii
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014, 1737, 1744, 2014年
研究論文(国際会議プロシーディングス), Prediction of rock slope deformation is significantly important for stability assessment. In particular, if the deformation under a stable state of a rock slope is successfully predicted, the slope stability can be evaluated by comparison of predicted and observed deformations. Based on this point of view, some researchers have successfully shown that the rock slope due to floor excavation in a pit -type mine can be expressed by elastic deformation. However, rock slope deformation due to excavation in the case of mountain type mine has not been cleared yet. In this study, the elastic deformation due to excavation of a mountain type mine was investigated by 2 dimensional (2-D) finite element method (FEM). Considering the possibility that the characteristics of deformation measured by extensometer show the dependancy on its insertion direction and location, the displacements along horizontal, tilted and vertical lines assuming the extensometers at the different insertion locations were simulated for various Poissons ratios. In the horizontal and tilted directions, the rock slope formed is always extended by the progress of excavation. It is found that the magnitude of displacement tends to decrease with the increasing distance from the excavated region and the magnitude of displacement at small Poisson's ratio is greater than that at large Poisson's ratio. In the vertical direction, neither apparent increase nor decrease in the displacement with depth can be found and the magnitude of displacement at small Poisson's ratio is greater than that at large Poisson's ratio. Two locations of measurement by an extensometer were considered at the top of the slope and at the lower part of the slope. The extended deformation of rock slope was always found by an extensometer installed into the horizontal and tilted directions on mountain type mine. In addition, both those directions showed that the magnitude of relative displacement decreased with the increase in depth and Poisson's ratio. In case of the vertical direction, the rock slope formed by excavation showed predominant contraction and relative extension by an installed extensometer at earlier and subsequent steps of excavation, respectively. Magnitude of the contraction and extension at v of 0.4 and v of 0.1, respectively, were greater. The extensometer became insensitive to excavation with the progress of excavation in all directions of displacement measurement. - Temperature-confining pressure coupling effects on the permeability of three rock types under triaxial compression
A. K. M. B. Alam, Y. Fujii, D. Fukuda, M. Niioka
ROCK ENGINEERING AND ROCK MECHANICS: STRUCTURES IN AND ON ROCK MASSES, 131, 136, CRC PRESS-TAYLOR & FRANCIS GROUP, 2014年, [査読有り]
英語, 研究論文(国際会議プロシーディングス), Triaxial compression tests were carried out at 295K and 353K under confining pressure of 1-15 MPa for Shikotsu welded tuff, Kimachi sandstone and Inada granite. The samples were kept for 24 hr consolidation and then axial compression was applied measuring permeability. Permeability decreased monotonously for Shikotsu welded tuff. The permeability decreased first, began to increase before peak load and showed almost constant value in the residual strength state for Kimachi sandstone and Inada granite. Permeability decreased by failure for Shikotsu welded tuff. It increased due to failure under low confining pressures but decreased under high confining pressures for Kimachi sandstone. It increased due to failure for Inada granite. The permeability at 353K was lower than that at 295K for all of the three types of rock. The mechanisms of the permeability decrease are also shown. - Biot's effective stress coefficient of rocks for peak and residual strengths by modified failure envelope method
A. B. N. Dassanayake, Y. Fujii
ROCK ENGINEERING AND ROCK MECHANICS: STRUCTURES IN AND ON ROCK MASSES, 155, 160, CRC PRESS-TAYLOR & FRANCIS GROUP, 2014年, [査読有り]
英語, 研究論文(国際会議プロシーディングス), Kimachi sandstone and Shikotsu welded tuff were tested in single and multistage triaxial tests to determine the Biot's effective stress coefficient (alpha). Pure water saturated 30 mm in diameter and length of 60 mm cylindrical test specimens were introduced for triaxial compression, with strain rate at 10(-5) s(-1). For Kimachi sandstone, alpha value for peak strength decreased with effective confining pressure. a values for residual strength were almost constant and larger than the case of peak strength. For Shikotsu welded tuff, only two data points were obtained for peak strength due to pore collapse and alpha value for residual strength decreased with effective confining pressure. The multistage test has given a fair evaluation of the coefficient for peak strength of Kimachi snadstone. Number of specimens and variation from specimen to specimen can be reduced by using multistage tests although further considerations are required to obtain the coefficient for residual strength. - Estimation of regional stress state and Young's modulus by back analysis of mining-induced deformation
J. Kodama, T. Miyamoto, S. Kawasaki, Y. Fujii, K. Kaneko, P. Hagan
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 63, 1, 11, PERGAMON-ELSEVIER SCIENCE LTD, 2013年10月, [査読有り]
英語, 研究論文(学術雑誌), A method to evaluate regional stress state and Young's modulus by analyzing the mining-induced deformation of ground is proposed. The effect of changes in regional strain state due to tectonic plate motion can be accounted for using the proposed method. Mining-induced deformation can manifest itself as changes in ground surface geometry resulting from mining activity. There are three underlying factors that can contribute to the deformation, these being: displacement induced by the effect of gravity; displacement induced by the effect of horizontal regional strain; and, incremental change in the horizontal regional strain. Both regional strain and Young's modulus can be simultaneously estimated, because the displacement induced by the regional strain is independent of the Young's modulus and the displacement induced by the gravity is inversely proportional to the Young's modulus. The relative displacement arising from the mining excavation at the Torigatayama limestone mine in Japan has been measured by GPS. Both the regional stress state and Young's modulus were estimated by back analysis of the relative displacement using a 3-D finite element method. It was shown that back analysis based on changes in distance between the measurement points provides a more reliable estimation than that could be achieved based on the direct relative displacement. (C) 2013 Elsevier Ltd. All rights reserved. - The effects of water content, temperature and loading rate on strength and failure process of frozen rocks
J. Kodama, T. Goto, Y. Fujii, P. Hagan
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 62, 3, 1, 13, PERGAMON-ELSEVIER SCIENCE LTD, 2013年09月, [査読有り]
英語, 研究論文(学術雑誌), The effects of water content, temperature and loading rate on the strength and failure process of rock at sub-zero temperatures were investigated and are presented in this paper. Over the range of temperatures studied there was little change observed in the properties of dry rock. The presence of water in the rock, however, resulted in a marked increase in rock strength and the fracture initiation stress. Rock strength increased with amount of water present and the rate of load application, with the effect being exacerbated at the colder temperatures. Interestingly, the changes in strength were not uniform as there was a greater rate of increase in the tensile strength of rock with temperature than compressive strength. It is postulated that these changes in mechanical properties may be explained in part by a reduction in the stress concentration within the interstitial spaces and cracks of the rock samples tested. (C) 2013 Elsevier Ltd. All rights reserved. - 一軸引張応力下における稲田花崗岩の疲労特性と寿命予測
児玉淳一, 高坂恒輔, 福田大祐, 藤井義明
J. MMIJ, 129, 7, 418, 424, The Mining and Materials Processing Institute of Japan, 2013年, [査読有り]
日本語, 研究論文(学術雑誌), Uniaxial tension cyclic loading and creep tests were carried out on Inada granite aiming to clarify effects of stress amplitude and loading rate on fatigue behavior. Relationship between fatigue life, deformation behavior and AE activity were also examined. It was found that time to failure in cyclic loading test became shorter than that in creep test for low applied stress. This indicates stress amplitude has a significant effect on fatigue failure. The amount of fatigue damage per cycle increased with decrease in loading rate when the same maximum stress was applied. This is thought to be cause of decrease in fatigue life with decrease in loading rate. On the other hand, the amount of fatigue damage per cycle and fatigue life did not depend on loading rate when the same maximum stress ratio, which was normalized by the uniaxial tensile strength at each loading rate, was applied. Fatigue life of a specimen showing less strain increment tended to be longer and the relationship between the minimum value in the strain increment and fatigue life was represented by a line regardless of loading rate and maximum stress. AE event rate as well as strain increment was inversely proportion to life expectancy before failure. Ratio of AE event rate in unloading to loading began to increase just before failure. These results show that strain increment and AE event are useful parameter to predict fatigue failure. - 凍結した支笏溶結凝灰岩の力学的挙動の時間依存性
三井善孝, 児玉淳一, 原翔平, 菅原隆之, 福田大祐, 藤井義明
J. MMIJ, 129, 7, 425, 432, The Mining and Materials Processing Institute of Japan, 2013年, [査読有り]
日本語, 研究論文(学術雑誌), Understanding time-dependent deformation of frozen rock is significant for the assessment of long-term stability of rock slopes in cold region. In this study, to clarify the time-dependent deformation of frozen rock and influence of water content on the deformation, a series of uniaxial compression tests and creep tests were carried out on Shikotsu welded tuff under the dry and wet conditions at -20℃ (-4°F). The uniaxial compressive strength (UCS) of frozen wet specimens was approximately equal to that of frozen dry specimens at the strain rate below 4.2×10-6/s. However, the former was greater than the latter at higher strain rates. The creep life of frozen wet specimens was longer than that of frozen dry specimens at the stress level above 13.4 MPa. On the other hand, the former was shorter than the latter at lower stress levels. Deformation of frozen wet specimens was larger than that of frozen dry specimens. The frozen dry and wet specimens showed different axial strain rate-axial creep strain curves. These differences could be explained by the presence of pore ice. Therefore, water content of rock should be considered for the assessment of long-term stability of rock slopes in cold region. - 岩石の強度に対して応力状態が影響するメカニズムを明らかにするための三次元弱面モデル
藤井義明, 児玉淳一, 福田大祐
J. MMIJ, 129, 7, 467, 471, The Mining and Materials Processing Institute of Japan, 2013年, [査読有り]
日本語, 研究論文(学術雑誌), The 3-D weakness plane model was developed to clarify the mechanisms of influences of various stress states on the strength of rocks. The model assumes numerous planes of weakness whose directions are uniformly distributed in a rock; each plane slips or opens based on the Coulomb criterion with a tension cut-off; and the rock is regarded as failed when the ratio of the failed plane number to that of all planes reaches a certain value. The equal strength parameters were assigned to all planes and no complicated statistical functions are used. The model was applied to true triaxial compression, uniaxial tension, Brazilian and extension tests. The model was very simple but the effects of a stress state, namely, nonlinear increase of peak stress with small intermediate principal stress and nonlinear decrease with large intermediate principal stress in true triaxial tests, larger tensile strength by Brazilian tests than uniaxial tensile tests and the bilinear nature of peak stress in extension tests, were simulated very well. Distributions of stress and failed planes on the Schmidt net increased the understanding of the mechanism of the stress state effects on rock strength. - Sub-zero温度領域における支笏溶結凝灰岩と美唄砂岩の一軸圧縮強度と破壊プロセス
児玉淳一, 原翔平, 三井善孝, 藤井義明
J, MMIJ, 129, 1, 21, 28, The Mining and Materials Processing Institute of Japan, 2013年, [査読有り]
日本語, 研究論文(学術雑誌), Strength and deformation of frozen rocks were investigated by uniaxial compression test and cyclic loading test at -20°C. Failure processes of Shikotsu welded tuff and Bibai sandstone were considered based on their deformation behaviors. Larger deformation of wet specimen was found than that of dry specimen in both rocks due to pore ices plastic deformation. However, effect of water content on strength depends on type of rocks. UCS of wet specimens of Shikotsu welded tuff was greater than that of dry specimens. In contrast, UCS of wet specimens was smaller on Bibai sandstone. The former phenomenon can be interpreted by inclusion effect of pore ice. The latter phenomenon can be explained due to stress corrosion by unfrozen water or reduction in friction coefficient of crack planes by pore ice. - 若材齢トンネル吹付けコンクリートの変形特性に関する研究
谷卓也, 青木智幸, 小川豊和, 武田均, 藤井義明
J. MMIJ, 128, 3, 113, 120, 資源・素材学会, 2012年03月, [査読有り]
日本語, 研究論文(学術雑誌), Uniaxial compression tests and multi-stage stress relaxation tests for specially prepared young-age tunnelshotcrete were carried out. Comparing to previous studies, clip gauges were determined to be the best toevaluate elastic moduli of young-age tunnel shotcrete. Uniaxial compressive strength and 33% secantmodulus were larger than those of base concrete till 1 day, however, they became less than those of baseconcrete after then. Uniaxial compressive strength and 33% secant modulus till 1day showed a linearrelationship. This means that 33% secant modulus could be determined from uniaxial compressive strengthwhich is routinely determined at tunnel construction sites. In the multi-stage stress relaxation test,displacing rate significantly affected 33% secant modulus. This will result in significant change in support response to rock mass deformation. Stress decrease by yielding and stress increase with curing time even after the yielding were observed for slow loading multi-stage tests. The above findings will help to design reasonable tunnel supports through precise stress analyses around tunnel faces. - 本当に二酸化炭素は減らすべきか?
藤井 義明
Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan, 128, 4, 218, 223, 資源・素材学会, 2012年03月, [査読有り]
日本語, 研究論文(学術雑誌), In order to clarify whether we should reduce anthropogenic carbon dioxide emission or not, interaction between 5 potential problems to survival of human, namely, water shortage, food crises, exhaustion of energy and mineral resources, global warming and population increase were investigated. Population increase was the origin of the 5 problems and increase in ODA for women education etc. to accelerate population stabilization was proposed. Unreasonable reduction of carbon dioxide is harmful to human future and should be stopped. Instead, it was suggested not to increase carbon dioxide by accelerating population stabilization and improving efficiency of coal power plants in US, India and China. Prevention of population decrease, increase in self-sufficiency ratio of foods, secure energy and mineral resources, development of such domestic energy resources as underground coal gasification, coal bed methane, deep coal, methane hydrate and sea uranium, and reduction of earthquake damage were proposed as the key points to a better future of Japan. - 破壊後の圧密による岩石の透水性変化に関する研究
熊倉 聡, 石島 洋二, 藤井 義明, 児玉 淳一
Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan, 128, 4, 163, 172, 資源・素材学会, 2012年03月, [査読有り]
日本語, 研究論文(学術雑誌), EDZ (Excavatin Damaged Zone) may appear around underground repositories. Permeability of rock massin EDZ would be greater than that of surrounding rock mass and sealability of rock mass would be deteriorated. Countermeasures for the sealability deterioration would induce increase in construction andmaintenance costs. However, if sealability recovers with time under pressure, the costs would be reduced.The objective of this study is to clarify whether sealability recovery of clastic rocks exists or not. Toaccomplish the objective, Kimach sandstone, Toyotomi siliceous mudstone and Inada granite were fractured under triaxial compressive stress state and consolidated in the residual strength state. Hydraulicconductivity increased with failure and decreased by the consolidation to 0.3-0.6 times that just after failure or 0.9-1.5 times that before axial loading for Kimachi sandstone. Similar results were obtained forToyotomi siliceous mudstone where the ratios were 0.4 and 0.6. Ratios for Inada granite were 0.2 and 16.These results mean that a strong sealability recovery was confirmed for the clastic rocks and a weak sealability recovery for Inada granite. - Effect of temperature and confining pressure on permeability during deformation and failure of shikotsu welded tuff
Alam A.K.M. Badrul, Masaki Niioka, Yoshiaki Fujii, Jun-ichi Kodama, Takayuki Sugawara
ISRM Regional Symposium - 7th Asian Rock Mechanics Symposium, ARMS 2012, 563, 572, International Society for Rock Mechanics, 2012年
英語, 研究論文(国際会議プロシーディングス), Permeability variation during deformation and failure in triaxial test was considered for Shikotsu welded tuff. Pure water saturated cylindrical test specimens of 30 mm in diameter and length of 60 mm with constant flow rate method at 0.3 ml/min was introduced for compression, with strain rate of 10-5 s-1 on the consolidated samples under 1 MPa, 5 MPa, 10 MPa and 15 MPa for 24 hours until the axial strain reached at 10% in 22ºC and 80ºC. Permeability at the end of 15 MPa consolidation was lower than those of under 1-10 MPa. In compression (i) permeability basically decreased with slight disturbances around peak load points due to rapid volumetric change (ii) under 1 MPa the permeability was larger, compare to 5-15 MPa confining pressure at 22ºC (iii) no apparent confining pressure dependency was observed at 80ºC. The permeability was lower at 80ºC than 22ºC. However, more water flow is expected for the same pore pressure gradient at 80ºC due to lower viscosity of water. - Effect of loading rate on strength and failure process of frozen welded tuff
J. Kodama, Y. Fujii, T. Goto, P. Hagan
ISRM Regional Symposium - 7th Asian Rock Mechanics Symposium, ARMS 2012, 638, 645, International Society for Rock Mechanics, 2012年
英語, 研究論文(国際会議プロシーディングス), The effects of loading rate on the strength of frozen rock as well as the failure process at sub-zero temperatures were investigated. There was a marked difference observed in the fracture initiation stress and rock strength between frozen dry rock samples and frozen rock that contained water. There was no significant change observed in strength parameters of dry rock whereas in frozen rock containing water, rock strength increased with loading rate. Interestingly the magnitude of the change in strength was much greater for tensile strength than compressive strength of wet rock. It is postulated that these changes in mechanical properties may be explained in part by a reduction in the stress concentration within the interstitial spaces and cracks of the rock. - Abandoned roadways aged up to 50 years observed in Kushiro Coal Mine, Japan
Y. Fujii, T. Sugawara, J. Kodama, Y. Ishijima, T. Kiyama, M. Takada, Y. Ichihara, S. Kumakura, T. Narita, M. Sawada, E. Nakata
HARMONISING ROCK ENGINEERING AND THE ENVIRONMENT, 975, 978, CRC PRESS-TAYLOR & FRANCIS GROUP, 2012年, [査読有り]
英語, 研究論文(国際会議プロシーディングス), 95 abandoned old roadways up to 50 years old and 300m deep were observed at Kushiro Coal Mine. Large plastic deformations as roof deflection and/or floor heave closed most roadways although a few roadways were remain open. Such in-situ measurements as Rayleigh wave velocity, permeability etc. were carried out. Rayleigh wave velocity in the closed roadway was approx. half the virgin rock mass. Permeability of closed roadway was 40 times greater than that for virgin rock mass. This suggests that 1/40 sealability can be expected even a rock cavern in clastic rocks completely collapsed. This would be much better than rock cavern in crystalline rocks in which much less sealability is expected when completely collapsed. - Mechanical properties of abandoned and closed roadways in the Kushiro Coal Mine, Japan
Yoshiaki Fujii, Yoji Ishijima, Yoshihisa Ichihara, Tamotsu Kiyama, Satoshi Kumakura, Michihiko Takada, Takayuki Sugawara, Takashi Narita, Jun-ichi Kodama, Masataka Sawada, Eiji Nakata
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 48, 4, 585, 596, PERGAMON-ELSEVIER SCIENCE LTD, 2011年06月, [査読有り]
英語, 研究論文(学術雑誌), The objective of this research is to clarify the mechanical properties and self-healing ability of the Excavation Damaged Zone (EDZ) around rock caverns in clastic-rock. Observations of nearly one hundred closed roadways up to fifty years old, which can be regarded as very severe EDZs with no initial sealability and are up to 300 m deep in clastic-rock, were made at the Kushiro Coal Mine, Japan, to accomplish the objective. Most old roadways were closed, though a few remain open. Closure of old roadways was mainly due to roof deflection and/or floor heave. Large plastic deformations dominated; however, severe fractures were seldom observed in closed old roadways. Rayleigh wave velocity and hydraulic conductivity in the closed old roadways were in the range of 0.3-1.2 km/s and 5 x 10(-7)-1 x 10(-7) m/s, respectively, and those in EDZ and EdZ (Excavation disturbed Zone) around recently excavated roadways were 1.1-1.8 km/s and 1 x 10(-8)-5 x 10(-8) m/s, respectively. The extent of EDZ around the present tailgate was in the range of 1-5 m. Mechanical excavation and prevention from water are suggested as the key points for long-term maintenance of rock repositories. Pressurization from inside the cavern to decrease the permeability of EDZ is proposed for maintenance of rock repositories in medium-hard clastic-rock masses at similar depths for long periods. (C) 2011 Elsevier Ltd. All rights reserved. - The role of atmospheric nuclear explosions on the stagnation of global warming in the mid 20th century
Yoshiaki Fujii
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, 73, 5-6, 643, 652, PERGAMON-ELSEVIER SCIENCE LTD, 2011年04月, [査読有り]
英語, 研究論文(学術雑誌), This study suggests that the cause of the stagnation in global warming in the mid 20th century was the atmospheric nuclear explosions detonated between 1945 and 1980. The estimated GST drop due to fine dust from the actual atmospheric nuclear explosions based on the published simulation results by other researchers (a single column model and Atmosphere-Ocean General Circulation Model) has served to explain the stagnation in global warming. Atmospheric nuclear explosions can be regarded as full-scale in situ tests for nuclear winter. The non-negligible amount of GST drop from the actual atmospheric explosions suggests that nuclear winter is not just a theory but has actually occurred, albeit on a small scale. The accuracy of the simulations of GST by IPCC would also be improved significantly by introducing the influence of fine dust from the actual atmospheric nuclear explosions into their climate models; thus, global warming behavior could be more accurately predicted. (C) 2011 Elsevier Ltd. All rights reserved. - Analysis of natural rock slope deformations under temperature variation: A case from a cool temperate region in Japan
Azania Mufundirwa, Yoshiaki Fujii, Nariaki Kodama, Jun-ichi Kodama
COLD REGIONS SCIENCE AND TECHNOLOGY, 65, 3, 488, 500, ELSEVIER SCIENCE BV, 2011年03月, [査読有り]
英語, 研究論文(学術雑誌), In this paper, natural rock slope deformation across fractures predominantly in a chert rock mass was monitored using six surface fracture displacement sensors, and the deformations arising from thermal stresses were predicted using (5 m x 5 m) two-dimensional (2D) finite element (FE) plane strain analysis coupled with a model for rock mass expansion due to freezing of pore water. A new and simple method to minimize displacement proportional to temperature (due to thermal response of chert rock mass and sensor) was proposed. By applying the method, the corrected displacement, u', can be well recognized. Under u', clear rock mass movement, which could be related to fracture growth, was observed. In addition, progressive fracture opening and closure were noted. Results from this study indicate insignificant influences of weather conditions on fracture/rock mass movement. Furthermore, under numerical analysis (FE), in the rock mass model (with 1-m deep fracture), tensile stresses that were large enough to induce fracture growth appeared at the fracture tip when temperature lowered. And in the rock slope model (with 1-m deep fracture), small tensile stresses, which were sufficient to cause fracture growth along the planes of weakness, were observed. This research suggests that freezing effects on deformation of chert rock mass are insignificant, and we tentatively suggest that thermal fatigue predominantly caused the permanent fracture deformations. (C) 2010 Elsevier B.V. All rights reserved. - 凍結融解作用を受ける岩石の破壊プロセスと耐久性の評価
児玉 淳一, 中谷 匡志, 奈良 禎太, 後藤 龍彦, 藤井 義明, 金子 勝比古
Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan, 127, 3, 117, 126, 資源・素材学会, 2011年02月, [査読有り]
日本語, 研究論文(学術雑誌), Durability evaluation of rocks subjected to freezing-and-thawing is important for stability assessment of a rock fill dam as well as rock slopes, especially in cold weather regions. In this study, freezing-and-thawing tests up to 300 cycles were carried out on twelve kinds of rock samples in order to characterize fracture propagation by freezing-and-thawing and evaluate the durability, and fracture propagation was observed. The fracturing process was characterized by macroscopic observation by digital camera and changes in physical properties. Fracture initiation and propagation in the specimen were also observed by using X-ray CT. It was found that the fracturing process depends on the rock type. For rocks which possess preferred orientation of pre-existing fractures and anisotropy of tensile strength, only one fracture propagated dominantly and split the rock sample in half. On the other hand, for isotropic rock, propagation of several fractures occurred and rock samples were split into several parts. Additionally, spalling continuously progressed once the loss of weight exceeded 5% for isotropic rocks because fractures had developed throughout the specimen. This result indicates that freezing-and-thawing cycles at 5% weight loss is assumed to be the spalling initiation. Therefore, we can conclude that the number of freezing-and-thawing cycles to the spalling initiation is the important indicator of the durability evaluation. It was also pointed out that both supply capacity of water to the crack tip and crack growth resistance affect the durability, because the tensile strength divided by the percentage of water absorption is in good correlation with the number of cycles to the spalling initiation. It is concluded that the durability can be easily evaluated by both tensile strength and the percentage of water absorption. - 三軸圧縮破壊過程における岩石の透水性に封圧が及ぼす影響に関する研究
高田迪彦, 藤井義明, 児玉淳一
J. MMIJ, 127, 3, 151, 157, 資源・素材学会, 2011年, [査読有り]
日本語, 研究論文(学術雑誌), The permeability of Kimachi sandstone in triaxial compression failure process was investigated by laboratory experiments. Tests were carried out under a constant confining pressure of between 5.0 and 15.0 MPa with a constant pore pressure of 2.0 MPa until axial strain reached approximately 5.0%. The stress-strain relation was linear under low differential stress and gradually became nonlinear as peak differential stress approached. In the tests under confining pressure of 5.0 and 7.5 MPa, the permeability decreased in the elastic region and then increased as the peak strength approached. The permeability continued to increase at first in residual strength region, and then it decreased at axial strain of approximately 4.0%. In the tests conducted under higher confining pressure, the variation in the permeability was small until axial strain of 5.0%. It appeared that failure types were different depending on confining pressure from the observation of the thin sections made from the specimens after tests. In the tests under 5.0 MPa confining pressure, a macroscopic fault occurred in the test pieces. On the other hands it did not occur in the tests under higher confining pressures. It was suggested in the elastic FEM analyses that the failure types were influenced by the end constraint. - 凍結融解作用を受ける岩石の破壊プロセスと耐久性の評価
児玉 淳一, 中谷 匡志, 奈良 禎太, 後藤 龍彦, 藤井 義明, 金子 勝比古
J. MMIJ, 127, 3, 117, 126, The Mining and Materials Processing Institute of Japan, 2011年, [査読有り]
日本語, 研究論文(学術雑誌), Durability evaluation of rocks subjected to freezing-and-thawing is important for stability assessment of a rock fill dam as well as rock slopes, especially in cold weather regions. In this study, freezing-and-thawing tests up to 300 cycles were carried out on twelve kinds of rock samples in order to characterize fracture propagation by freezing-and-thawing and evaluate the durability, and fracture propagation was observed. The fracturing process was characterized by macroscopic observation by digital camera and changes in physical properties. Fracture initiation and propagation in the specimen were also observed by using X-ray CT. It was found that the fracturing process depends on the rock type. For rocks which possess preferred orientation of pre-existing fractures and anisotropy of tensile strength, only one fracture propagated dominantly and split the rock sample in half. On the other hand, for isotropic rock, propagation of several fractures occurred and rock samples were split into several parts. Additionally, spalling continuously progressed once the loss of weight exceeded 5% for isotropic rocks because fractures had developed throughout the specimen. This result indicates that freezing-and-thawing cycles at 5% weight loss is assumed to be the spalling initiation. Therefore, we can conclude that the number of freezing-and-thawing cycles to the spalling initiation is the important indicator of the durability evaluation. It was also pointed out that both supply capacity of water to the crack tip and crack growth resistance affect the durability, because the tensile strength divided by the percentage of water absorption is in good correlation with the number of cycles to the spalling initiation. It is concluded that the durability can be easily evaluated by both tensile strength and the percentage of water absorption. - A new practical method for prediction of geomechanical failure-time
A. Mufundirwa, Y. Fujii, J. Kodama
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 47, 7, 1079, 1090, PERGAMON-ELSEVIER SCIENCE LTD, 2010年10月, [査読有り]
英語, 研究論文(学術雑誌), Predicting the failure-time of geo-hazards is an important rock mechanics problem. We first evaluated the validity of the INVerse-velocity (INV) method to predict failure-time of rock mass and landslides. This method utilizes rates of displacement or strain to predict the actual failure-time (T(f)), so the value of total displacement or strain before "failure" is not crucial. Second, we developed a new method for computing failure-time predictions based on the SLOpe (gradient) to predict Tf, termed the SLO method. Finally, a simple conceptualised model representing "safe" and "unsafe" predictions was proposed.
To validate these hypotheses, prediction of rock mass failure in the Asamushi and Vaiont landslides (in situ studies) was conducted. Furthermore, laboratory conditions were incorporated into the research, which include predictions using circumferentials train and axial strain from uniaxial compression creep test on Shikotsu welded tuff (SWT), and predictions of failure-time for Inada granite under Brazilian creep tests. It was found that the SLO method is better than the INV method; SLO gave safe predictions in all the cases. In contrast, INV tends to give unsafe predictions(predicted failure-time Tfp > Tf). Our findings reveal that predictions using circumferential strain are better than those made using axial strain for SWT, and notably, given failure with very short tertiary creep, the methods tend to show limited reliability. However, the SLO method could find extensive application in predicting failure-timeofgeo-hazards, for instance, roof wall failure in mines, etc. (c) 2010 Elsevier Ltd. All rights reserved. - 応力下におけるNaCl結晶の自由面溶解に関する分子動力学法を用いた検討
高田 迪彦, 藤井 義明
J. MMIJ, 126, 3, 72, 77, The Mining and Materials Processing Institute of Japan, 2010年, [査読有り]
日本語, 研究論文(学術雑誌), The effect of stress on free surface dissolution of NaCl was investigated. Stress and elastic constants near the {001} surface of NaCl crystal were calculated using a classical molecular dynamics simulation. The normal stress in the first layer of the free surface was calculated as approximately 2.25 GPa (tension) on the assumption that the bulk stress was 0. The elastic constants of the first layer were also different from those of the bulk. Based on the results, it is estimated that molar Gibbs free energy of the first layer will increase by tension, and decrease by compression. Namely, NaCl crystal is expected to become easier to dissolve by tension and harder to dissolve by compression. This qualitatively coincides with the experiments on NaCl free surface dissolution under loading. - Prediction of rock mass failure-time of geo-hazards
A. Mufundirwa, Y. Fujii
ROCK MECHANICS IN CIVIL AND ENVIRONMENTAL ENGINEERING, 567, 570, CRC PRESS-TAYLOR & FRANCIS GROUP, 2010年, [査読有り]
英語, 研究論文(国際会議プロシーディングス), Can we predict failure-time of geo-hazards? Prediction of geo-hazards, for instance, rock mass failure, landslides, etc., is still a challenge to date in the rock mechanics field. Geo-hazards still pose a major threat to life and major loss in terms of economics. The focal point of our research is to predict failure-time of geo-hazards. Firstly, the authors evaluated the validity of the Inverse-velocity (INV) method to predict failure-time of rock mass and landslides. Secondly, two methods for computing predictions were also evaluated: (I) based on non-linear approximation (NLA), and (2) on the slope (gradient) to compute T(f),, termed the SLO method, which will be described in detail in the paper. The concept of "safe" and "unsafe" predictions was developed to classify predictions. With this in mind, prediction of failure case histories and rock specimens in the laboratory is presented. It was realised that SLO is better than the INV method. - 幌延地域に分布する珪質岩に対する幾つかの岩盤応力測定法の適用性と推定された応力状態
真田 祐幸, 丹生屋 純夫, 松井 裕哉, 藤井 義明
J. MMIJ, 125, 10/11, 530, 539, The Mining and Materials Processing Institute of Japan, 2009年, [査読有り]
日本語, 研究論文(学術雑誌), Understanding initial stress condition in deep underground is important for such construction as rock cavern for geological disposal of HLW and underground power plant. Neogene sedimentary rock is widely distributed in Japan. There are only a few studies of initial stress measurement in Neogene sedimentary rock mass in Japan due to difficulty of measurement. Evaluation of initial stress condition around Horonobe Underground Research Laboratory Project was carried out in order to understand initial stress condition and applicability of AE, DSCA and hydraulic fracturing (HF) methods to Neogene sedimentary rock. Initial stress values obtained from AE method is smaller than overburden pressure due to time dependency of Kaizer effect. It would be difficult to use AE method as initial stress measurement method for Horonobe Siliceous rocks. Principal stress values by DSCA are similar to those by HF tests. Directions of maximum horizontal principal stresses are approximately in E-W and corresponded to HF results.
In HF, rod type and wire-line type systems were compared. Workability of rod type was much better than wire-line type. However, re-opening pressure were not able to be precisely measured in case of rod type system due to the large compliance of the packers and rods. Horizontal maximum and minimum principal stresses increase linearly in HF results. Deviatoric stress is acting at shallow depth. Initial stress condition approaches hydrostatic condition with depth. Direction of maximum horizontal principal stress was in E-W direction which was similar to tectonic movement around Horonobe URL by triangular surveying. - 堆積履歴が幌延地域に分布する珪質岩の力学的特性や微視的構造変化に及ぼす影響
真田 祐幸, 丹生屋 純夫, 松井 裕哉, 藤井 義明
J. MMIJ, 125, 10/11, 521, 529, The Mining and Materials Processing Institute of Japan, 2009年, [査読有り]
日本語, 研究論文(学術雑誌), As part of the research and development program on geological disposal of high-level radioactive waste Japan Atomic Energy Agency is implementing the Horonobe URL Project. This paper shows the results obtained from the laboratory tests carried out to understand mechanical properties of Horonobe siliceous rocks for site characterization. Accordingly, the relationship among microscopic observation, sedimentary history and mechanical properties of Horonobe siliceous rocks was discussed in this paper. Such laboratory tests as uniaxial compression test, triaxial compression test, isotropic consolidation test were carried out. Uniaxial compression tests were carried out for specimen sampled at about 50 m interval of eleven deep boreholes more than 500 m deep from the ground surface. Triaxial compression tests including isotropic consolidation test were also carried out using cores of the boreholes. The triaxial tests were carried out under drained and undrained conditions since change in pore structure was expected for the sedimentary soft rocks with large effective porosity. Physical and mechanical properties showed significant variations along the burying depth due to dissolution of the minute porosity in diatom occured from increasing of overburden, temperature etc. The consolidated undrained and drained triaxial compression tests showed different behaviors of strain-softening, pore pressure and dilatancy between diatomaceous and siliceous mudstones. Stress-strain behavior changed from strain-softening to ductile behavior under high confining pressure and pore pressure increased gradually even after peak strength for diatomaceous mudstone. On the other hand, for siliceous mudstone strain-softening behavior was observed and pore pressure decreased rapidly after peak stress regardless of confining pressure value. Diatomaceous mudstone yielded under hydrostatic pressure of 10 MPa in isotropic consolidation test. This yielding was regarded as pore collapse based on the variation of hydraulic conductivity which was estimated from variation of volumetric strain in isotropic consolidation test, effective porosity and microscopic observation before and after the yielding. - 凍結状態にある登別溶結凝灰岩の強度と破壊プロセスに与える温度と載荷速度の影響
児玉 淳一, 後藤 龍彦, 藤井 義明
J. MMIJ, 125, 9, 472, 480, 2009年, [査読有り]
研究論文(学術雑誌) - 北海道大学工学部環境社会工学科資源循環システムコースにおける教育改善の取り組み
藤井義明, 広吉直樹, 原田周作, 金子勝比古
工学教育, 56, 5, 36, 41, Japanese Society for Engineering Education, 2008年, [査読有り]
日本語, 研究論文(学術雑誌), Department of Resources Engineering, Faculty of Engineering, Hokkaido University, which was renamed to Course of Sustainable Resources Engineering in 2005, was established in 1972 based on Department of Mining. Number of coal mines in Japan rapidly decreased at that time by the governmental policy and the department was not popular with students from the beginning. Students with very low GPA (Maximum GPA was 1.6 in 1981, for example) were distributed to the department and the department was filled with full of dull students. Teachers also lost eagerness for high quality education. A negative spiral was formed and the situation went worse and worse. As time goes, attempts were made to revolutionize the department. One is "Curriculum Petit Committee" . And the other is "Committee for Education System Improvement" . These two committees significantly improved the education in the department. As a result, the department was filled with full of vivid students, and teachers. For exampe, in 2007, students′ maximum, minimum and average GPA was 3.3, 2.0 and 2.5, respectively, - 接線ヤング率法の三つの岩種に対する適用性と同方法における封圧の影響
藤井 義明, 大高 憲道, 中川 嘉文, 児玉 淳一
J. MMIJ, 124, 2, 120, 128, The Mining and Materials Processing Institute of Japan, 2008年, [査読有り]
日本語, 研究論文(学術雑誌), The tangent modulus method was applied to pre-loaded cylindrical specimens of Shikotsu welded tuff, Inada granite and Kimachi sandstone. It was clarified that the tangent modulus method could be applied to the rocks. A positive correlation was observed between the preloading duration and the maximum delay time at which the preloaded stress was determined with the error less than 20% for Shikotsu welded tuff and Inada granite although the correlation was not confirmed for Kimachi sandstone due to small number of specimens. The confirmed maximum delay time for each rock was 42 days for Shikotsu welded tuff, 21 days for Inada granite and 28 days for Kimachi sandstone based on clip gage.
The stress at bending point in uniaxial cyclic loading for triaxially pre-loaded Kimachi sandstone decreased as confining pressure in the preloading increased. Kimachi sandstone and Shirahama sandstone were triaxially preloaded and triaxially cyclic loaded under decreased or increased confining pressure. The stress at bending point decreased with decrease of confining pressure for Shirahama sandstone. No apparent change was observed for Kimachi sandstone. Bending points were not observed for Shirahama sandstone under increased confining pressure. On the other hand, the stress at bending point decreased with increase of confining pressure for Kimachi sandtsone.
The physical phenomena utilized to detect stress memory in tangent modulus method was explained based on a model which consisted of two springs and a slider. One spring represents the elasticity of rock. Another spring and the slider are connected in parallel and represent inelasticity due to irreversible closure of voids. Decrease of tangent modulus at the preloaded stress was well simulated by the model. - 釧路コールマインに見られる旧坑の閉塞状況と閉塞機構
石島 洋二, 藤井 義明, 市原 義久, 児玉 淳一
J. MMIJ, 124, 6/7, 435, 444, The Mining and Materials Processing Institute of Japan, 2008年, [査読有り]
日本語, 研究論文(学術雑誌), Kushiro Coal Mine in Kushiro, Japan is now excavating coal seams at a shallower level than before. Approximately 100 old workings, which were excavated about 50 years ago, were observed at either longwall coal faces or sidewalls of roadways. Most of them were completely closed with a few exceptions, which were in open condition without severe deformation. Two thirds of the observed old workings were closed mainly by roof sagging. The sagged roofs were either deflected or plugged in. Development of the tension cracks were observed in the deflected roof. One third of the old workings were closed mainly by floor heaving, mostly accompanied by the severe deflection.
Complete closure of the old workings can be attributed to the following two reasons: One is rock stress of considerable magnitude composed from the initial one and the induced one due to mining. Another is weakening of the sedimentary rocks surrounding the opening due to increase of the water content brought mainly by the supply of water detached from the injected filling material with high water content. It is certain that the two mechanisms work simultaneously to the closure of the old workings, but the latter is considered to be prior to the former in its effect. - 原位置計測と坑内観察に基づく釧路コールマインにおける閉塞した空洞内の諸状態
石島 洋二, 藤井 義明, 市原 義久, 木山 保, 高田 迪彦, 菅原 隆之, 熊倉 聡
J. MMIJ, 124, 6/7, 445, 451, The Mining and Materials Processing Institute of Japan, 2008年, [査読有り]
日本語, 研究論文(学術雑誌), In-situ measurements were conducted at closed old roadways in Kushiro Coal Mine in Kushiro, Japan. Based on the results of the P-wave velocity and permeability obtained at the closed old roadways, the material comprising deformed rock mass, filler, plastically deformed clay and softened rocks, with which the closed old roadways are filled, is judged to have the same quality with that of weak rock mass. This nature could be brought by the stress of small magnitude which has loaded the closed old roadways.
In-situ monitoring of stress induced in the longwall goaf revealed that the crushed rocks in goaf have been receiving stress of fair magnitude, which could bring their consolidation. This anticipation was confirmed by the observation of the closed old goaf abandoned about 52 years ago that the crushed rocks have been consolidated to such extent that the machining surface created by the drum shearer is smooth and self supported.
A suggestion was proposed for reasonable design and construction of rock caverns which could maintain mechanical stability for a long time in such sedimentary rock masses as ones encountered in Kushiro Coal Mine. - 凍結状態にある岩石の強度と変形・破壊挙動
児玉 淳一, 後藤 龍彦, 藤井 義明
Journal of MMIJ, 124, 12, 733, 740, The Mining and Materials Processing Institute of Japan, 2008年, [査読有り]
日本語, 研究論文(学術雑誌), Understanding mechanical behavior of frozen rocks is useful for evaluating the stability of rock slopes in cold regions. In this study, uniaxial compression tests and Brazilian tests were carried out on frozen rock specimens of welded tuff and andesite under -20°C temperature. The fracture process was examined by observing deformation behaviors and AE activities. Effects of water saturation degree on strength and deformability were also investigated. The main results are as follows.
1) The fracture process of the frozen rock was similar to that of non-frozen rock and was divided into the following regions. (I) Closure of cracks and pores. (II) Elastic deformation. (III) Fracture initiation and stable fracture propagation. (IV) Unstable fracture propagation. Also, stress levels at the beginning of the region (III) increased with the degree of water saturation.
2) Both strength and strain at peak stress increased as the degree of water saturation increased. The relations between them were able to be approximated by a straight line. Brittleness of rocks decreased with the degree of water saturation since indirect tensile strength was more sensitive to the degree of water saturation than uniaxial compressive strength.
3) The mechanical effect of frozen pore water was considered with an inclusion model. The model predicted the observed phenomenon. Namely, increment in fracture initiation stress, due to frozen pore water in uniaxial tension, was always higher than that in uniaxial compression. The increase in strength was thought to result from relaxation of stress concentration around pores. - パイロット孔壁変形法の開発と室内試験
李 基夏, 石島 洋二, 菅原 隆之, 藤井 義明
Journal of MMIJ, 123, 6/7, 336, 341, The Mining and Materials Processing Institute of Japan, 2007年, [査読有り]
日本語, 研究論文(学術雑誌), The theory and a probe of the pilot hole wall deformation method, which is a 3-dimensional stress measurement method based on the stress relief principle, were developed. A pilot hole is drilled from the bottom of a borehole and the stress measurement probe is inserted into the pilot hole. The borehole is advanced as the overcoring and the changes in the radius of the pilot hole in three directions and in the axial lengths between the borehole bottom and the pilot hole wall along four axial lines are measured by cantilever type-displacement sensors. The differences between the displacements by the elastic stress analysis and those measured by using the probe were within 3% in the uniaxial compression test of an acrylic resin plate having a hole. The stress components which were applied to a cubic Kimachi sandstone specimen with an inclined borehole were evaluated by using the probe within the error of 6% the applied maximum principal stress in a biaxial loading test. - 接線ヤング率の変化に基づく岩盤応力の推定に関する基礎実験
藤井 義明, 大高 憲道, 中川 嘉文, 児玉 淳一
資源と素材, 122, 10/11, 483, 488, The Mining and Materials Processing Institute of Japan, 2006年, [査読有り]
日本語, 研究論文(学術雑誌), Tangent modulus method was investigated as one of core-based methods for rock stress measurement and was compared to DRA method. It was clarified that the preloaded stress level was accurately estimated as the stress level at the bending point on the stress-tangent modulus curve by the tangent modulus method. Relationship between duration of load application and maximum delay time for stress memory was investigated by carrying out the both methods. The bending point gradually became vague as the delay time increased in the both methods. The accuracy of estimated stress level of the preloading was almost the same for the both methods. It was shown that the preloaded stress level was accurately estimated from the rock specimen which had been preloaded for approximately one week and had been left for approximately six weeks. - 封圧下で一方向に伸び変形を受ける岩石の変形・破壊挙動に関する研究
藤井 義明, 上原 洋次郎
資源と素材, 122, 6/7, 330, 337, The Mining and Materials Processing Institute of Japan, 2006年, [査読有り]
日本語, 研究論文(学術雑誌), Extension tests on Shirahama sandstone (blocks I and II) and Shikotsu welded tuff were carried out under confining pressure. Tensile strength increased and then decreased for Shirahama sandstone block I and Shikotsu welded tuff. It decreased or unaffected with confining pressure for Shirahama sandstone block II. Absolute value of lateral strain at peak load point increased with confining pressure and that in uniaxial compression tests distributed in the similar manner on the confining pressure-strain value plot. Absolute value of axial strain at peak load point increased with confining pressure except for Shirahama sandstone block I. 50% tangent Young's modulus increased with confining pressure and that in uniaxial compression tests distributed in a similar manner on the confining pressure-Young's modulus plot. Effect of confining pressure on Poisson's ratio was unclear. Residual strength decreased with confining pressure except for Shirahama sandstone block I. Results of Brazilian tests distribute upper limit of results in extension test under confining pressure on the confining pressure-tensile strength plot except Shirahama sandstone block II which distributed above the extension test results. The effect of confining pressure on tensile strength was roughly explained by assuming a number of discontinuities whose strength was represented by Coulomb criterion and whose angle was different with each other. - A Modeling Method on Fractal Distribution of Cracks in Rocks using AE Monitoring
Watanabe, Y, Itakura, K, Sato, K, Fujii, Y, Balusu, R, Guo, H, Luo, X
J. Acoustic Emission, 23, 119, 128, 2005年, [査読有り]
英語, 研究論文(学術雑誌) - Consideration of fracture growth initial fracture at the surface of from an inclined slit and inclined rock and mortar in compression
Y Fujii, Y Ishijima
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 41, 6, 1035, 1041, PERGAMON-ELSEVIER SCIENCE LTD, 2004年09月, [査読有り]
英語, 研究論文(学術雑誌) - 「稲田花崗岩と白浜砂岩の水中における緩やかな亀裂進展現象に対する温度の影響」
小玉齊明, 藤井義明, 藤田泰之, 石島洋二
『土木学会論文集』, 778, III-69, 195, 204, 公益社団法人 土木学会, 2004年, [査読有り]
日本語, 研究論文(学術雑誌), 1℃, 40℃, 80℃の3通りの温度における水中でダブルトーション試験を行い, 緩やかな亀裂進展現象に対する温度の影響を調べた. その結果, 温度が上昇するに従い, 応力腐食指数が減少すること, 同レベルの応力拡大係数に対する亀裂速度が増加することを確認した. これらについて反応速度論に基づいた活性化エネルギーの評価を行い, 一軸圧縮試験, 圧裂引張試験, 破壊靱性試験の結果と比較した. また, 緩やかな亀裂進展における温度の影響の要因として, 応力腐食の熱活性化の他に水の影響を挙げ, 有限要素法による熱応力解析を実施し, 亀裂観察によるフラクタル次元の評価, ガラス供試体を用いた試験結果等もあわせて, 試験結果について考察した. - 水中における稲田花崗岩と白浜砂岩の変形・破壊挙動に対する温度の影響
小玉斉明, 藤井義明, 藤田泰之, 石島洋二
資源と素材, 119, 8, 461, 468, The Mining and Materials Processing Institute of Japan, 2003年, [査読有り]
日本語, 研究論文(学術雑誌), Uniaxial compression test, Brazilian test and fracture toughness test were carried out for Inada granite and Shirahama sandstone in pure water controlling the water temperature between 0 °C and 80 °C and the loading rate between 1.67 × 10-7 m / s and 5.00 × 10-4 m / s. The uniaxial compressive strength, Poisson's ratio, Indirect tensile strength and stress intensity factor decreased with the temperature for the both two rocks. This tendency was clearer for Inada granite. Critical compressive strain value (axial strain value at peak load point) of Shirahama sandstone also decreased with temperature. However, the effect of temperature on the critical extensile strain (radial strain at peak load point) was not clear for the both two rocks. Young's modulus seemed to take the peak value at 20 °C or 40 °C. These results were explained based on thermal stress due to anisotropy and difference of thermal expansion coefficient between the mineral grains, stress corrosion and change in viscosity of water. - 「圧縮を受ける岩盤の自由表面近傍における亀裂成長挙動に関する考察」
藤井 義明, 堀場 夏峰, 石島 洋二
『資源と素材』, 118, 3/4, 157, 164, The Mining and Materials Processing Institute of Japan, 2002年, [査読有り]
日本語, 研究論文(学術雑誌), Uniaxial compression tests were carried out on rock specimens which were modeled on a bench cut-quarry or cliffs of various shapes in order to clarify behavior of near-surface crack growth in rock mass. Exfoliations at highly compressed parts and detachments of convex parts as results of crack growth were observed in the experiments. Numerical simulation on crack growth based on 2D-DDM was carried out in order to explain the experimental results. The authors proposed a new criterion for crack growth since predictions by using widely known Sih's maximum tensile stress theory were slightly different from the observed results. The new method takes shear stress as well as tensile stress near crack tip into account and gave results that were similar to the observation. A series of compression tests on rock and mortar specimens having a slit or an initial crack was conducted in order to clarify the applicability of the new method. Profiles of the most observed cracks were similar to predictions by the proposed method. - 「北海道の急崖を構成する岩石の力学的特性」
藤井 義明, 宮下 尚志, 石島 洋二, 川北 稔
『地盤工学会論文報告集』, 42, 3, 129, 136, The Japanese Geotechnical Society, 2002年, [査読有り]
日本語, 研究論文(学術雑誌) - 自然乾燥状態および湿潤状態における登別溶結凝灰岩のクリープ変形とクリープ寿命
児玉淳一, 後藤龍彦, 藤井義明, 吉田豊, 板倉賢一
『資源と素材』, 117, 9, 718, 724, The Mining and Materials Processing Institute of Japan, 2001年, [査読有り]
日本語, 研究論文(学術雑誌), Not only axial strain but also lateral strain were measured during creep tests on Noboribetsu welded tuff under air-dried and water-saturated conditions in which the water contents of specimens were regulated about 0.3% and 17%, respectively. Creep rupture strength under water-saturated condition was smaller than that under air-dried condition. The difference in them was comparable to that in uniaxial compressive strength under both conditions. The axial and lateral strain rates decreased linearly with time in a log-log plot in the primary stage. They increased until a rupture occurs after the strain rates had reached the minimum magnitude. Creep failure time tended to increase as the "decrease rates of the strain rates" in the primary stage increased. Creep failure time and the life after the minimum strain rate increased as the minimum magnitude in the strain rates decreased. In the tertiary stage, the strain rates were inversely proportional to residual life. These relationships were represented by the same curves regardless of the water content. Therefore, the creep failure time would be successfully estimated from the behaviors of either axial or lateral strain rate regardless of the water content by using the experimental results. Thin sections of the specimens that had experienced various levels of the creep deformation were prepared and observed under a microscope. Nucleation of cracks and pores that distributed along the loading axis in the matrix were observed for specimens that had been just before the rupture. - 「白浜砂岩の変形・破壊挙動に及ぼす水と載荷速度の影響」
藤田泰之, 藤井義明, 石島洋二
『資源と素材』, 116, 7, 565, 571, The Mining and Materials Processing Institute of Japan, 2000年, [査読有り]
日本語, 研究論文(学術雑誌), Uniaxial compression tests, Brazilian tests and fracture toughness tests were carried out on dry and wet specimens of Shirahama sandstone at several loading rates. Effects of water in the uniaxial compression tests were as follows: (1) UCS and Young's modulus decreased by 42 % to 47 % and 42 % to 46 %, respectively; (2) Poisson's ratio increased slightly; and, (3) No obvious effects were observed on the critical strains. Effects of loading rate were as follows: (1) UCS and Young's modulus decreased as loading rate decreased; (2) No obvious effects were observed on Poisson's ratio; and, (3) Critical compressive strain and the absolute value of the critical extensile strain decreased as loading rate decreased. It was clarified in the fracture toughness and Brazilian tests that the fracture toughness / indirect tensile strength decreased by 70 % to 80 % / 52 % to 72 %, respectively, and that a positive linear correlation was observed between fracture toughness / indirect tensile strength and logarithm of loading rate, respectively. Mechanisms of the above observations were discussed based on the breakage of interlocking between such mineral particles as quartz and plagioclase. Breakage of cementing by illite was also considered. - 「非造構性の節理に起因する岩盤崩壊の機構-北海道積丹半島セタカムイ崩壊-」
永田秀尚, 藤井義明
『地形』, Vol. 21, No. 2, 169, 191, 2000年, [査読有り]
研究論文(学術雑誌) - Circumferential strain behavior during creep tests of brittle rocks
Y Fujii, T Kiyama, Y Ishijima, J Kodama
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 36, 3, 323, 337, PERGAMON-ELSEVIER SCIENCE LTD, 1999年04月, [査読有り]
英語, 研究論文(学術雑誌), Creep tests were carried out on Inada granite under confining pressure and on dry and wet specimens of Kamisunagawa sandstone. Distinctive points Q(A) (the point where the axial strain rate reaches a minimum), Q(C) (the point where the magnitude of circumferential strain rate reaches a minimum) and R-C (the point where the magnitude of circumferential strain acceleration begins to increase) were defined. Dependency of the strain values at the distinctive points on creep stress, confining pressure and water presence was examined. Circumferential strain at Q(C) or P-C was not affected by creep stress for both rocks. Peak load points were observed in reloading stress-strain curves when reloading was carried out before Q(C) for Kamisunagawa sandstone. Circumferential strain values at peak load during reloading coincided with critical extensile strain, which is defined as circumferential strain value at peak load during constant strain rate tests and is insensitive to confining pressure, water presence, and anisotropy, although slightly affected by strain rate. Load increased slightly or did not increase when reloading was carried out after R-C for both rocks. R-C in creep tests scattered around unloading stress-strain curves from peak load during constant strain rate tests for Kamisunagawa sandstone. These observations suggest that Q(C) and P-C in creep tests are closely related to the peak load points during constant strain rate tests. Circumferential strain would be used as a condition-insensitive damage indicator of rock in creep tests as well as in constant strain rate tests. (C) 1999 Elsevier Science Ltd. All rights reserved. - Circumferential strain behavior during creep tests of brittle rocks
Y. Fujii, T. Kiyama, Y. Ishijima, J. Kodama
International Journal of Rock Mechanics and Mining Sciences, 36, 3, 323, 337, Elsevier Science Ltd, 1999年, [査読有り]
英語, 研究論文(学術雑誌), Creep tests were carried out on Inada granite under confining pressure and on dry and wet specimens of Kamisunagawa sandstone. Distinctive points QA (the point where the axial strain rate reaches a minimum), QC (the point where the magnitude of circumferential strain rate reaches a minimum) and RC (the point where the magnitude of circumferential strain acceleration begins to increase) were defined. Dependency of the strain values at the distinctive points on creep stress, confining pressure and water presence was examined. Circumferential strain at QC or RC was not affected by creep stress for both rocks. Peak load points were observed in reloading stress-strain curves when reloading was carried out before QC for Kamisunagawa sandstone. Circumferential strain values at peak load during reloading coincided with critical extensile strain, which is defined as circumferential strain value at peak load during constant strain rate tests and is insensitive to confining pressure, water presence, and anisotropy, although slightly affected by strain rate. Load increased slightly or did not increase when reloading was carried out after RC for both rocks. RC in creep tests scattered around unloading stress-strain curves from peak load during constant strain rate tests for Kamisunagawa sandstone. These observations suggest that QC and RC in creep tests are closely related to the peak load points during constant strain rate tests. Circumferential strain would be used as a condition-insensitive damage indicator of rock in creep tests as well as in constant strain rate tests. - Examination of a rock failure criterion based on circumferential tensile strain
Y Fujii, T Kiyama, Y Ishijima, J Kodama
PURE AND APPLIED GEOPHYSICS, 152, 3, 551, 577, BIRKHAUSER VERLAG AG, 1998年10月, [査読有り]
英語, 研究論文(学術雑誌), Uniaxial compression, triaxial compression and Brazialian tests were conducted on several kinds of rock, with particular attention directed to the principal tensile strain. In this paper we aim to clarify the effects of the experimental environment-such as confining pressure, loading rate, water content and anisotropy-on the critical tensile strain, i.e., the measured principal tensile strain at peak load.
It was determined that the chain-type extensometer is a most suitable method for measuring the critical tensile strain in uniaxial compression tests. It is also shown that the paper-based strain gage, whose effective length is less than or equal to a tenth of the specimen's diameter and glued on with a rubber-type adhesive, can be effectively used in the Brazilian tests.
The effect of confining pressure P-C on the critical tensile strain epsilon(TC) in the brittle failure region was between -0.02 x 10(-10) Pa-1 and 0.77 x 10(-10) Pa-1. This pressure sensitivity is small compared to the critical tensile strain values of around -0.5 x 10(-2). The strain rate sensitivities partial derivative epsilon(TC)/partial derivative{log(d\epsilon\/dt)} were observed in the same way as the strength constants in other failure criteria. They were found to be from -0.10 x 10(-3) to -0.52 x 10-3 per order of magnitude in strain rate in the triaxial tests. The average magnitude of the critical tensile strain epsilon(TC) increased due to the presence of water by 4% to 20% for some rocks, and decreased by 22% for sandstone. It can at least be said that the critical tensile strain is less sensitive to water content than the uniaxial compressive strength under the experimental conditions reported here. An obvious anisotropy was observed in the P-wave velocity and in the uniaxial compressive strength of Pombetsu sandstone. It was not observed, however, in the critical tensile strain, although the data do show some variation.
A "tensiie strain criterion" was proposed, based on the above experimental results. This criterion signifies that stress begins to drop when the principal tensile strain reaches the critical tensile strain. The criterion is limited to use within the brittle failure region. The critical tensile strain contains an inelastic strain component as well as an elastic one. It is affected by the strain rate, however, it is relatively insensitive to the confining pressure, the presence of water and anisotropy. - 「半径方向の剛性の変化に注目した岩石の構成方程式」
藤井 義明, 石島 洋二
『資源と素材』, 114, 3, 169, 174, 資源・素材学会, 1998年, [査読有り]
日本語, 研究論文(学術雑誌), A linear equation between axial strain, circumferential strain and axial stress was found while performing compression tests on several kinds of rock. This equation means that in such laboratory tests the trace of axial strain, circumferential strain and axial stress is located on a plane in the three-dimensional space defined by these quantities. New constitutive equations were derived combining the above-mentioned equation with another equation which derived assuming that the stiffness in the radial direction decreases with radial expansion. Using the set of the newly-deduced constitutive equations, the effect of confining pressure on strength and strain-softening behavior including Class? can be simulated. Numerical results also show the decrease in radial stiffness due to crack existence. - 「あるV字谷におけるシーティングの力学的背景に関する研究」
藤井義明, 石島洋二, 堀場夏峰, 稲葉力
『資源と素材』, 114, 12, 869, 874, The Mining and Materials Processing Institute of Japan, 1998年, [査読有り]
日本語, 研究論文(学術雑誌), There are a considerable number of sheeting joints at a V-shaped valley in Japan, which is a construction site for a P-Dam. Sheeting joints could cause water leakage and reduce the strength of rock mass as a dam foundation. The mechanical backgrounds of sheeting joints were therefore investigated. In-situ stress measurement by the stress relief method revealed that maximum horizontal stress, which is almost perpendicular to the P-River, is about 12 MPa. This result coincides with results obtained by the Deformation Rate Analysis method. It was also clarified that the temperature in rock mass shows large day-variation as deep as 30 cm, and that a significant temperature gradient appears under direct sunlight. Through numerical analyses, it was determined that an inclined crack near a free surface can grow much longer than that in an infinite medium. From these points of view, it was considered that the sheeting joints are exfoliation as a result of crack propagation near the free surface under horizontal stress concentrated by the geometry of the V-shaped valley and periodically-acting horizontal thermal stress. - Prediction of coal face rockbursts and microseismicity in deep longwall coal mining
Y Fujii, Y Ishijima, G Deguchi
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 34, 1, 85, 96, PERGAMON-ELSEVIER SCIENCE LTD, 1997年01月, [査読有り]
英語, 研究論文(学術雑誌), A new method is proposed for predicting rockbursts, as well as microseismicity in deep longwall coal mining. The method is able to predict failure in the coal seam and in the rock mass by using 3-D elastic numerical stress analyses. These locations were compared with the results of microseismic monitoring. Fracturing intensity and its variation with respect to face advance were represented by the maximum shear seismic moment release rate.
The ''Seismic Moment Method'' was applied to three cases in the Horonai Coal Mine and in the Miike Coal Mine, Japan. The first case considered panels W8-5U and W8-5 in the Horonai Coal Mine at 1055 and 1125 m deep. Even though no rockburst occurred, areas where microseismic events were concentrated were predicted. It was also clear, by comparing calculated maximum shear seismic moment release rate to observed data, that the magnitude of the seismicity and its variation with respect to the face advance were also successfully predicted. The second case corresponded to panel W6-3 in the same mine from 915 to 985 m deep. Microseismic monitoring had not yet been introduced; however, the rockburst in this panel was successfully predicted as fracturing of coal seam elements al the coalface. The last case considered panels E3-E6 in the Miike Coal Mine at 600 and 650 m deep, respectively. The location and intensity of microseismicity were again predicted; in addition, toppling as well as rockbursts were also predicted.
Relations between the extent of the relief zone ahead of the coal face and the occurrence of rockbursts are discussed. An effective method to prevent rockburst hazard is also proposed. (C) 1997 Elsevier Science Ltd. - 「岩石のクリープ試験における周ひずみの挙動に関する研究」
藤井義明, 木山保, 大森瑞穂, 石島洋二
『資源と素材』, 113, 3, 162, 168, 資源・素材学会, 1997年, [査読有り]
日本語, 研究論文(学術雑誌) - 「長壁式採炭に伴う切羽周辺の地圧変化に関する地層模型試験」
後藤 龍彦, 児玉 淳一, 吉田 豊, 板倉 賢一, 藤井 義明
『資源と素材』, 112, 7, 439, 444, 資源・素材学会, 1996年, [査読有り]
日本語, 研究論文(学術雑誌) - 岩石の最大荷重点における最小主ひずみの正確な評価に関する研究
藤井 義明, 石島 洋二
資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan, 111, 9, 601, 606, 資源・素材学会, 1995年08月, [査読有り]
日本語, 研究論文(学術雑誌) - 太平洋炭礦における長壁式採炭切羽周辺の岩盤挙動に関する計測事例
後藤 龍彦, 松本 裕之, 藤井 義明, 児玉 淳一, 佐藤 干城, 出口 剛太
資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan, 111, 4, 213, 218, 資源・素材学会, 1995年04月, [査読有り]
日本語, 研究論文(学術雑誌) - 長壁式採炭払における炭壁圧出型山はねの応力解析に基づく予測
藤井 義明, 石島 洋二, 出口 剛太
資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan, 111, 1, 10, 16, 資源・素材学会, 1995年01月, [査読有り]
日本語, 研究論文(学術雑誌) - 長壁式採炭払における払面近傍の応力状態を簡便に評価し得る近似式
藤井 義明, 石島 洋二
資源と素材, 110, 7, 527, 532, 資源・素材学会, 1994年06月, [査読有り]
日本語, 研究論文(学術雑誌) - 岩盤表面に現れているき裂の深さを測定する方法
藤井 義明, 福島 猛, 石島 洋二
資源と素材, 110, 3, 233, 239, 資源・素材学会, 1994年03月, [査読有り]
日本語, 研究論文(学術雑誌) - 赤平炭を用いた室内試験からの考察 -坑道引立面付近の炭層状況と破壊挙動に関する研究-
後藤 龍彦, 藤井 義明, 佐藤 干城, 児玉 淳一
Journal of MMIJ, 110, 15, 1227, 1232, 資源・素材学会, 1994年
日本語 - 3対のカ-ブドジャッキを用いた2次元地圧変化計測の理論と室内試験
藤井 義明, 後藤 竜彦, 佐藤 干城
資源と素材, 109, 1, p37, 42, 資源・素材学会, 1993年01月, [査読有り]
日本語, 研究論文(学術雑誌) - APPLICATION OF DDM TO SOME ROCK PRESSURE PROBLEMS IN JAPANESE DEEP COAL-MINES
Y FUJII, Y ISHIJIMA, T GOTO
11TH INTERNATIONAL CONFERENCE ON GROUND CONTROL IN MINING - PROCEEDINGS, 414, 420, AUSTRALASIAN INST MINING & METALLURGY, 1992年, [査読有り]
英語, 研究論文(国際会議プロシーディングス) - 板状鉱床採掘に伴って生じる力学的擾乱の簡易計算法
藤井 義明, 石島 洋二
資源と素材, 107, 5, 253, 258, 資源・素材学会, 1991年04月, [査読有り]
日本語, 研究論文(学術雑誌) - Numerical simulation of microseismicity induced by deep longwall coal mining
Yoshiaki Fujii, Yoji Ishijima
Mining Science and Technology, 12, 3, 265, 285, 1991年, [査読有り]
英語, 研究論文(学術雑誌), To find an effective numerical simulation method for microseismicity induced by deep mining activity, results obtained by using four simulation methods, namely: (1) the energy release rate method, based on Cook's study
(2) the strain energy release rate method, developed by the authors
(3) the volume excess shear stress index method, based on Spottiswoode's study
and (4) the maximum shear seismic moment release rate method, developed here by the authors
were compared with the microseismicity in a Japanese deep longwall coal mine. The maximum shear seismic moment release rate method was discovered to be the best method, since the intensity of microseismicity in a longwall coal panel, its variation with the face advance and the distribution of microseismic events were well simulated. © 1991 Elsevier Science Publishers B.V. - 深部採炭に伴う微小地震活動とそのシミュレ-ション
藤井 義明, 石島 洋二
日本鉱業会誌, 104, 1204, p345, 351, 資源・素材学会, 1988年06月, [査読有り]
日本語, 研究論文(学術雑誌) - 3次元変位くい違い法--その原理と板状介在物ならびに近接累層問題への応用
石島 洋二, 藤井 義明
日本鉱業会誌, 103, 1198, p835, 840, 資源・素材学会, 1987年12月, [査読有り]
日本語, 研究論文(学術雑誌)
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福田大祐, 二瓶恵理菜, 趙祥鎬, 児玉淳一, 藤井義明, 資源・素材学会春季大会(Web), 2016, 2016年 - 氷点下における支笏溶結凝灰岩の力学的挙動
三井善孝, 三井善孝, 児玉淳一, 菅原隆之, 福田大祐, 藤井義明, 原翔平, 原翔平, 土木学会年次学術講演会講演概要集(CD-ROM), 70th, 2015年 - 傾斜した層構造を有するピット型鉱山における残壁の掘削変位の解析
森谷亮太, NAJIB, 福田大祐, 児玉淳一, 藤井義明, 資源・素材学会北海道支部春季講演会講演要旨集, 2015, 2015年 - 釧路地方の岩層メタンガスについて(3)
松本裕之, 内田景己, 藤井義明, 児玉淳一, 福田大祐, 尾原祐三, 佐藤晃, 吉永徹, 陳友晴, 鮎沢潤, 末永弘, 玉村修司, 資源・素材学会北海道支部春季講演会講演要旨集, 2015, 2015年 - 来待砂岩の強度のひずみ速度依存性は封圧とともに小さくなる
天羽啓太, 藤井義明, 児玉淳一, 福田大祐, 資源・素材学会北海道支部春季講演会講演要旨集, 2015, 2015年 - 釧路南東部の白亜系砂質頁岩の性状
児玉淳一, 藤井義明, 福田大祐, 高橋徹, 菅原隆之, 末永弘, 佐藤晃, 松本裕之, 内田景己, 資源・素材(Web), 2015, 2015年 - 1次元的および3次元的に冷却した岩石の氷点下における一軸圧縮試験
三井善孝, 児玉淳一, 菅原隆之, 福田大祐, 藤井義明, 資源・素材学会春季大会(Web), 2015, 2015年 - 釧路コールマインにおける排水量は,北海道東方沖並びに釧路沖においてM7.5以上の地震が発生する直前に減少し,発生後に増加した
藤井義明, 児玉淳一, 福田大祐, 市原義久, 松本裕之, 資源・素材学会春季大会(Web), 2015, 2015年 - 押え盛石による残壁の滑り変形の抑制効果に関する検討
福田大祐, 安藤健太, 児玉淳一, 藤井義明, 資源・素材学会春季大会(Web), 2015, 2015年 - 釧路コールマインにおける白亜系砕屑岩の浸透率の計測
高橋徹, 菅原隆之, 藤井義明, 児玉淳一, 福田大祐, 松本裕之, 内田景己, 資源・素材学会春季大会(Web), 2015, 2015年 - 釧路コールマインにおける砂質頁岩のガス浸透率
高橋徹, 菅原隆之, 藤井義明, 児玉淳一, 福田大祐, 松本裕之, 内田景己, 資源・素材学会北海道支部春季講演会講演要旨集, 2014, 2014年 - 函館市豊崎町における落石メカニズム解明を目的とした長期モニタリング対象の旧道岩盤斜面を構成する岩石の特徴
冨樫晃平, 小玉齊明, 山真典, 菅原隆之, 畠山葵, 福田大祐, 加藤昌治, 川崎了, 藤井義明, 資源・素材学会春季大会(Web), 2014, 2014年 - 海洋潮汐力に起因する比較的大きいひずみ速度による略南北走向の沈み込み帯での大潮における巨大地震発生の抑制
藤井義明, 杉本拓也, 福田大祐, 児玉淳一, 資源・素材学会春季大会(Web), 2014, 2014年 - 岩石表面への氷の付着強度の測定
三井善孝, 赤羽一輝, 児玉淳一, 菅原隆之, 福田大祐, 藤井義明, 資源・素材学会春季大会(Web), 2014, 2014年 - Sub-zero温度領域における美唄砂岩のクリープ試験
赤羽一輝, 三井善孝, 児玉淳一, 菅原隆之, 福田大祐, 藤井義明, 資源・素材学会春季大会(Web), 2014, 2014年 - 岩石のピーク応力と残留強度における有効応力係数の値とそれらの応用
藤井義明, ANJULA Dassanayake, 福田大祐, 児玉淳一, 資源・素材(Web), 2014, 2014年 - 繰り返し引張載荷を受ける稲田花崗岩の破壊サイクル数の予測
藤井義明, 児玉淳一, 福田大祐, 資源・素材, 2013, 2013年 - いくつかの岩石における三軸圧縮下の変形・破壊に伴う浸透率の変化とそれに対する封圧と温度の影響
藤井義明, ALAM A.K.M. Badrul, 福田大祐, 児玉淳一, 資源・素材, 2013, 2013年 - 寒冷地の露頭岩盤における表面亀裂の長期的な挙動
小玉, 齊明, 藤井, 義明, 菅原, 隆之, 第41回岩盤力学に関するシンポジウム講演集, 41, 153, 156, 2012年01月12日
第41回岩盤力学に関するシンポジウム(土木学会)、2012年1月12日(木),13日(金)、土木会館、東京, 土木学会, 日本語 - 2-331 北大工学部資源循環システムコースにおけるFD((17)ファカルティ・ディベロップメント,口頭発表論文)
藤井 義明, 五十嵐 敏文, 廣吉 直樹, 工学教育研究講演会講演論文集, 23, 59, 538, 539, 2011年08月22日
公益社団法人日本工学教育協会, 日本語 - 若材齢吹付けコンクリートの粘弾性挙動を考慮した支保効果の検討
谷 卓也, 小川 豊和, 青木 智幸, 藤井 義明, 春季大会講演集. I, 資源編, 19, 1, 131, 132, 2007年03月29日
日本語 - 長壁式採炭切羽周辺における原位置透気試験
木山 保, 熊倉 聡, 西本 壮志, 石島 洋二, 市原 義久, 田澤 宏, 菅原 隆之, 藤井 義明, 春季大会講演集. I, 資源編, 19, 1, 113, 114, 2007年03月29日
日本語 - 釧路コールマインにおける旧坑の透水性に関する研究
高田 迪彦, 菅原 隆之, 藤井 義明, 木山 保, 石島 洋二, 市原 義久, 春季大会講演集. I, 資源編, 19, 1, 117, 118, 2007年03月29日
日本語 - 破壊した来待砂岩の透水性変化に関する研究
熊倉 聡, 木山 保, 西本 壮志, 石島 洋二, 藤井 義明, 春季大会講演集. I, 資源編, 19, 1, 111, 112, 2007年03月29日
日本語 - 第三紀堆積岩の風化変質評価 : 釧路コールマイン坑内と地表岩石試料の比較
米田 哲朗, 藤井 義明, 市原 義久, 石島 洋二, 春季大会講演集. I, 資源編, 18, 1, 159, 160, 2006年03月27日
日本語 - 新しい方式の応力変化測定装置を用いた地圧測定 : 釧路コールマインにおける事例
成田 孝, 藤井 義明, 菅原 隆之, 犬飼 尚志, 石島 洋二, 市原 義久, 春季大会講演集. I, 資源編, 18, 1, 105, 106, 2006年03月27日
日本語 - 釧路コールマインにおける旧坑とその周囲の力学的状態
藤井 義明, 菅原 隆之, 犬飼 尚志, 米田 哲朗, 木山 保, 石島 洋二, 成田 孝, 市原 義久, 春季大会講演集. I, 資源編, 18, 1, 103, 104, 2006年03月27日
日本語 - 数種の岩石の凍結融解および凍上に伴う変形挙動
小玉斉明, 赤川敏, 藤井義明, 石島洋二, 岩盤力学に関するシンポジウム講演論文集, 35th, 2006年 - 76.トンネル施工における付加体の特殊性と地山分類の一例(地山分類・評価,岩石・岩盤物性・解析,岩盤分類(2),口頭発表)
後藤 和則, 亀石 暁, 小板橋 重一, 河田 孝志, 木崎 健治, 藤井 義明, 研究発表会講演論文集, 18, 271, 274, 2006年
日本応用地質学会, 日本語 - AE計測による3次元き裂分布モデルの構築とその応用
渡部 義範, 板倉 賢一, 佐藤 一彦, 藤井 義明, BALUSU Rao, GUO Hua, LUO Xun, 春季大会講演集. I, 資源編, 17, 1, 177, 178, 2005年03月28日
日本語 - 稲田花こう岩と白浜砂岩のクリープ挙動に対する温度の影響
小玉斉明, 藤井義明, 石島洋二, 岩盤力学に関するシンポジウム講演論文集, 34th, 2005年 - 釧路コールマインにおいて現れる旧坑
藤井義明, 資源 素材学会平成17年度春季大会講演要旨集 (I) 資源編, 2005年 - 水中における稲田花崗岩と白浜砂岩のクリープ変形挙動に及ぼす水温の影響
小玉 齊明, 中川 嘉文, 藤井 義明, 石島 洋二, 春季大会講演集. I, 資源編, 15, 1, 87, 88, 2003年03月27日
日本語 - 組み合わせ応力が岩石のクリープ挙動に及ぼす影響について
石島 洋二, 藤井 義明, 深田 直之, 一般発表(研究・業績発表)講演要旨集, 2001, 1, 115, 116, 2001年03月01日
日本語 - 圧縮応力を受ける傾斜したスリット先端からのき裂成長挙動に関する研究
中村 貫太, 藤井 義明, 石島 洋二, 一般発表(研究・業績発表)講演要旨集, 2000, 1, 71, 72, 2000年03月29日
日本語 - 周囲水溶液のpHが白浜砂岩の変形・破壊挙動に及ぼす影響
藤田 泰之, 藤井 義明, 石島 洋二, 一般発表(研究・業績発表)講演要旨集, 2000, 1, 146, 147, 2000年03月29日
日本語 - ロックボルトの支保効果の機構に関する研究 -ボルトを設した岩盤模型の2軸圧縮間試験の結果とその解釈-
中間 茂雄, 石島 洋二, 藤井 義明, 出口 剛太, 一般発表(研究・業績発表)講演要旨集, 2000, 1, 81, 82, 2000年03月29日
日本語 - 圧縮応力を受けた稲田花崗岩のP波速度とき裂について
藤井 義明, 山田 志保子, 石島 洋二, 一般発表(研究・業績発表)講演要旨集, 1997, 1, 268, 268, 1999年03月25日
日本語 - 伸びひずみに伴い減少する変形係数に基づいた構成方程式のせん断場や厚肉円筒への応用
藤井 義明, 石島 洋二, 一般発表(研究・業績発表)講演要旨集, 1999, 1, 159, 160, 1999年03月
日本語 - ロックボルトの支保効果に関する研究 -付着要素を用いたロックボルトモデルの開発-
中間 茂雄, 石島 洋二, 藤井 義明, 出口 剛太, 一般発表(研究・業績発表)講演要旨集, 1999, 1, 76, 77, 1999年03月
日本語 - Effects of Pore Pressure on Critical Strains of Indiana Limestone
FUJII Yoshiaki, SCOTT JR. Thurman Eugene, ROEGIERS Jean-Claude, ISHIJIMA Yoji, 資源・素材, 1998, 1, 162, 162, 1998年11月
英語 - 空洞やピラーの模型試験-いくつかの変位測定の試み-
岡崎 達也, 溝井 敦史, 石島 洋二, 藤井 義明, 一般発表(研究・業績発表)講演要旨集, 1998, 1, 155, 155, 1998年03月30日
日本語 - 単軸圧縮下における岩石の微視的構造の変化に関する研究
山田 志保子, 藤井 義明, 石島 洋二, 一般発表(研究・業績発表)講演要旨集, 1996, 1, 169, 170, 1996年03月29日
日本語 - Material tests and stress analysis on the rock slope collapse at Toyohama Tunnel
藤井義明, Bulletin of the Natural Disaster Science Data Center, Hokakido, 11, 77, 89, 1996年 - 沿層坑道におけるロックボルトの支保効果に関する研究 : 模型試験と解析の比較
堀場 夏峰, 石島 洋二, 藤井 義明, 出口 剛太, 一般発表(研究・業績発表)講演要旨集, 1995, 1, 147, 147, 1995年03月28日
日本語 - 気乾状態と湿潤状態における上砂川砂岩のクリープ特性について
大森 瑞穂, 藤井 義明, 石島 洋二, 一般発表(研究・業績発表)講演要旨集, 1995, 1, 222, 222, 1995年03月28日
日本語
書籍等出版物
- Prime Archives in Sustainability: 2nd Edition
Nikologianni, A., Prevention of Catastrophic Volcanic Eruptions, Large Earthquakes underneath Big Cities, and Giant Earthquakes at Subduction Zones
Vide Leaf, 2021年, [共著] - シェールガス・オイルの採掘、貯蔵、輸送、転換技術と環境規制への対応
技術情報協会, 第2章第2節[2]
技術情報協会, 2015年02月, [共著] - 斜面崩壊対策技術
石川芳治, 藤井義明ら, 第1編第3章「岩盤斜面の崩壊メカニズム」
エヌ・ティー・エス, 2014年, [共著] - トンネルの変状メカニズム
(社)土木学会, 2003年 - 露天掘鉱山における残壁技術解説書
(社)資源・素材学会, 2003年 - 岩盤崩壊の発生機構と計測技術
社団法人地盤工学会北海道支部, 2000年 - Advances in Rock Mechanics
World Scientific Publishing, 1998年
講演・口頭発表等
- 3-D Analysis of Rock Slope Deformation at Higashi-shikagoe Limestone Quarry, Japan
Amagu, C. A, Zhang, C, Kodama, J, Shioya, K, Yamaguchi, T, Sainoki, A, Fukuda, D, Fujii, Y, Sharifzadeh, M
26th World Mining Congress, 2023年06月28日, 英語 - Development of a Blasting Simulator Considering Gas-Rock Interaction
Ikawa, W, Fukuda, D, Takahashi, Y, Saburi, T, Kubota, S, Kodama, J, Fujii, Y
International Symposium on Earth Resources Management and Environment (ISERME) 2022, 2022年12月02日, 英語 - An analysis of impact of weak formation on mining-induced deformation of rock slope
Amagu, C. A, Zhang, C, Kodama, J, Shioya, K, Yamaguchi, T, Sainoki, A, Fukuda, D, Fujii, Y, Sharifzadeh, M, Saydam, S
AUSRock, 2022年11月30日, 英語 - Potential of CMC to increase the stability of shale at a slope
Alam, A.K.M. B, Fujii, Y, Eidee, S. J, Ullah, A.S.M. W
ARMS12, 2022年11月23日, 英語, 口頭発表(一般) - 日本のエネルギー供給に対するロシアによるウクライナ侵攻の影響
綿谷椋多, 藤井義明
資源・素材2022(福岡), 2022年09月07日, 日本語, 口頭発表(一般) - In-situ tearing test at rock slope and non-destructive detection of potentially dangerous rock blocks by impact test
Fujii, Y, Kodama, N, Naito, T, Sugawara, T, Fukuda, D, Kodama, J
RocExs 2020 (7th International Workshop on Rockfall Protection), 2022年06月28日, 英語 - 送毛安山岩のピーク及び残留強度の載荷速度依存性
竹内洋翔, 藤井義明, 児玉淳一, 福田大祐
資源・素材学会北海道支部2022年度春季講演会, 2022年06月11日, 日本語, 口頭発表(一般) - 釧路コールマインにおけるルーム採炭時の応力擾乱に与える充てんの影響
木村礼音, 藤井義明, 児玉淳一, 福田大祐, 松本裕之
資源・素材学会北海道支部2022年度春季講演会, 2022年06月11日, 日本語, 口頭発表(一般) - 北海道・道北における地下バイオメタン鉱床造成/生産法: Ⅲ- 褐炭分解過程におけるマイクロバブル利用の可能性
木山保, 猪股英紀, 上野晃生, 玉澤聡, 玉村修司, 村上拓馬, 吉田邦彦, 山口眞司, 佐々木利基, 酒井智生, 藤井義明, 五十嵐敏文
資源・素材学会春季大会, 2022年03月07日, 日本語, 口頭発表(一般) - 北海道・道北における地下バイオメタン鉱床造成/生産法:Ⅱ- 原位置試験における流体の注入特性について
猪股英紀, 木山保, 上野晃生, 玉澤聡, 玉村修司, 村上拓馬, 吉田邦彦, 山口眞司, 佐々木利基, 酒井智生, 藤井義明, 五十嵐敏文
資源・素材学会春季大会, 2022年03月07日, 日本語, 口頭発表(一般) - ザンビア共和国の深部銅鉱山における山はねの予測
中山雄斗, 藤井義明, 児玉淳一, 福田大祐, パルドン シンカラ
資源・素材学会春季大会, 2022年03月07日, 日本語 - Effective Stress Coefficient Through MFEM and Confining Pressure Dependency of Bibai Sandstone
Dassanayake, A, Fujii, Y, Thirukumaran, A
2021 Moratuwa Engineering Research Confernce (MERCon), 2021年07月28日, 英語, 口頭発表(一般) - Mining-induced Subsidence Prediction by Displacement Discontinuity Method
Alam, A. K. M. B, Fujii, Y, Razo, S. A, Ahmed, S. M
ISERME 2020 (International Symposium on Earth Resources Management & Environnent), 2020年12月22日, 英語, 口頭発表(一般) - Failure Criterion based on Extensile Strain and Rock Failure Prediction by Displacement Rate
Fujii. Y
Special lecture at Xi'an University of Architecture & Technology, Xi'an, China, 2020年11月07日, 英語, 公開講演,セミナー,チュートリアル,講習,講義等
[招待講演] - Stability analysis of slopes in Aruwakkalu Limestone Mine during rain: A finite element approach
Thirukumaran, A, Dananjaya, L, Dilshan, T, Dassanayake, A, Jayawardane, C, Wickrama, M, Fujii, Y, Boeut, S
2020 Moratuwa Engineering Research Conference (MERCon), 2020年07月28日, 英語, 口頭発表(一般) - Effects of clay zone on deformation of a cut rock slope in an open-pit limestone quarry
Amagu, C, Rith, U, Kodama, J.-I, Fukuda, D, Fujii, Y, Iwasaki, H, Ikegami, S
ISRM2019 Specialized Conference YSRM2019 & REIF2019., 2019年12月, 英語, 口頭発表(一般)
2019年12月01日 - 2019年12月04日 - Water migration considering stress and temperature dependent permeability of fractured rocks and its approximation
Alam, A.K.M. B, Fujii Y
ISRM2019 Specialized Conference YSRM2019 & REIF2019, 2019年12月, 英語, 口頭発表(一般)
2019年12月01日 - 2019年12月04日 - Recent development and application of hybrid finite-discrete element simulator for rock failure process
Fukuda, D, Mohammadnejad, M, Liu, H, Haoyu, H, Kodama, J.-I, Fujii, Y
ISRM2019 Specialized Conference YSRM2019 & REIF2019, 2019年12月, 英語, 口頭発表(一般) - Observation of crack initiation and propagation in coal subjected to heating and cooling
Kodama, J, Naka, R, Minami, T, Sugawara, T, Hamanaka, A, Itakura, K, Deguchi, G, Fukuda, D, Fujii, Y
Future Mining 2019, 2019年11月20日, 英語, 口頭発表(一般) - Continuous measurements of rock slope displacement in an open-pit limestone quarry, Japan
Amagu, C, Uy, R, Kodama, J.-I, Fukuda, D, Fujii, Y, Iwasaki, H, Ikegami, S
International Symposium on Rock Mechanics and Engineering for Sustainable Energy-The 35th VSRM Anniversary, 2019年11月, 英語, 口頭発表(一般) - Control and Prevention of Catastrophic Disasters
Fujii. Y
Special lecture at Xi'an University of Architecture & Technology, Xi'an, China, 2019年09月10日, 英語, 公開講演,セミナー,チュートリアル,講習,講義等
[招待講演] - Investigation of Rockburst in Deep Underground Mines, A case study of Mufulira mine, Copperbelt, Zambia
Sinkala, P, Nishihara, M, Fujii, Y, Fukuda, D, Kodama, J
Annual Meeting of ARMA (American Rock Mechanics Association), 2019年06月23日, 英語, ポスター発表
[国際会議] - Effects of transient axial stress or pore pressure disturbances on the permeability of Shikotsu welded tuff
Boeut S, Fujii Y, Kodama J, Fukuda D, Dassanayake. A.B.N
Annual Meeting of ARMA (American Rock Mechanics Association), 2019年06月23日, 英語, ポスター発表
[国際会議] - Influence of transient stress disturbances on permeability of Kushiro Cretaceous sandstone
Boeut, S, Oshima, T, Fujii, Y, Kodama, J.-I, Fukuda, D, Matsumoto, H, Uchida, K
ARMS10 (10th Asian Rock Mehcnaics Symposium, The ISRM International Symposium for 2018), 2018年11月03日, 英語, 口頭発表(一般)
[国際会議] - Development of 2-D hybrid FEM/DEM method code using GPGPU
Fukuda, D, Mohammadnejad, M, Chan, A, Cho, S. H, Min, G. J, Kodama, J, Fujii, Y
ARMS10 (10th Asian Rock Mehcnaics Symposium, The ISRM International Symposium for 2018), 2018年10月31日, 英語, 口頭発表(一般)
[国際会議] - Study of factors behind rock slope displacement at Higashi Shikagoe limestone quarry
藤井 義明
European Rock mechanics Symposium(EUROCK2018), 2017年11月06日, 英語, 口頭発表(一般)
[国際会議] - Effect of Axial Stress Disturbances on Permeability of Kushiro Sandy Shale
Boeut, S, Oshima, T, Fujii, Y, Kodama, J, Fukuda, D, Matsumoto, H, Uchida, K
1st. International KAMPAI Symposium on Sustainable Management of Resources and Environment in the 21st. Century, 2017年11月06日, 英語, 口頭発表(一般)
[国際会議] - Water Vapour Diffusion in Sandstone during Rainy Season in Mchenga Underground Coal Mine, Malawi
Yasidu, U, Fujii, Y, Kodama, J, Fukuda, D, Dandadzi, J, Maneya, G
1st. International KAMPAI Symposium on Sustainable Management of Resources and Environment in the 21st. Century, 2017年11月06日, 英語, ポスター発表
[国際会議] - Geological Disposal of High-level Radioactive Waste in Japan and the Role of Rock Engineering
Fujii, Y
International Symposium on Earth Resources Management & Environmnet, 2017年08月29日, 英語, 口頭発表(招待・特別)
[招待講演], [国際会議] - Prevention of Catastrophic Volcanic Eruptions
Fujii, Y, Kodama, J, Fukuda, D, Dassanayake, A.B.N
International Symposium on Earth Resources Management & Environmnet, 2017年08月29日, 英語, 口頭発表(一般)
[国際会議] - Effect of Humidity on Tensile Strength of Rocks in Selected Underground Coal Mines in Malawi
Yasidu, U.M, Fujii, Y, Fukuda, D, Kodama, J, Maneya, G
51st U.S. Rock Mechanics Geomechanics Symposium, 2017年06月27日, 英語, 口頭発表(一般)
[国際会議] - Change in Permeability of Cretaceous Sandy Shale in Kushiro Coal Mine due to Axial Stress Disturbance
Boeut, S, Oshima, T, Fujii, Y, Kodama, J, Fukuda, D, Matsumoto, H, Uchida, K
2017 International Joint Symposium between CERI (Japan) and IEGS (Korea), 2017年06月25日, 英語, 口頭発表(一般)
[国際会議] - Effects of Confining Pressure on Strain Rate-Dependent Deformation and Failure of Kimachi Sandstone
Amo, K, Fujii, Y, Kodama J, Fukuda, D
ARMS9, 2016年10月19日, 英語, 口頭発表(一般)
[国際会議] - 3-D Analysis of Time-dependent Behavior of Tunnel Crossing Weak Rock Formation
Kodama, J, Tabata, S, Fukuda, D, Fujii, Y, Murayama, H, Niwa, H, Sainoki, A
ARMS9, 2016年10月18日, 英語, 口頭発表(一般)
[国際会議] - Kimachi Sandstone does not have to Fail under Larger Stress
Wang, Y, Fujii, Y, Fukuda, D, Kodama, J
EUROCK 2016, 2016年08月30日, 英語, 口頭発表(一般)
[国際会議] - Effect of Butress on Reduction of Rock Slope Sliding along Geologic Boundary
Moriya, R, Fukuda, D, Kodama, J, Fujii, Y
3rd. International Symposium on Mine Safety, Science and Engineering, 2016年08月30日, 英語, 口頭発表(一般)
[国際会議] - New Techniques for Monitoring and Analyzing the Stability of Steep Cliffs against Rock Falls
Fujii, Y, Maeda, S, Sugawara, T, Kodama, N, Miyashita, N
US Rock Mechanics/Geomechanics Symposium, 2016年06月28日, 英語, 口頭発表(一般)
[国際会議] - What Should We Do to Improve the Future for Humans?
Fujii, Y
ASEAN++, 2016年, 英語, 口頭発表(招待・特別)
[招待講演], [国際会議] - Time-dependent Mechanical Behaviors of Frozen Welded Tuff
Kodama, J, Mitsui, Y, Sugawara, T. Fukuda, D, Fujii, Y
ISRM Congress 2015, 2015年10月13日, 英語, 口頭発表(一般)
[国際会議] - Giant Earthquakes are Occurring at Lunar Phases Specific to Each Subduction Zone
Fujii, Y, Kodama, J, Fukuda, D
ISRM Congress 2015, 2015年10月12日, 英語, 口頭発表(一般)
[国際会議] - Evaluation of 3-D Strain Distribution in Lignite Based on Image Analysis
Fukuda, D, Maruyama, M, Kodama, J, Fujii,Y, Aramaki, N, Kaneko, K, Nara, Y
ISRM Congress 2015, 2015年10月11日, 英語, 口頭発表(一般)
[国際会議] - The Cause of Global Warming Stagnation in the 21st Century
Fujii, Y
The 8th International Conference on Earth Resources Technology, 2014年10月23日, 英語, 口頭発表(一般)
[国際会議] - Prediction of Time and Volume of Rock Failure by Slope Method
Fujii, Y, Mufundirwa, A, Kodama, J, Fukuda, D
The 3rd. International Conference on Advances in Mining and Tunneling, 2014年10月22日 - Sealability Recovery of Fractured Rocks by Post-failure Consolidation
Fujii, Y, Kumakura, S, Kaneko, K
ARMS8, 2014年10月15日, 英語, 口頭発表(一般)
[国際会議] - Creep Behavior of Frozen Shikotsu Welded Tuff
Mitsui, Y, Hara, S, Akabane, K, Kodama, J, Sugawara, T, Fukuda, D, Fujii, Y
ARMS8, 2014年10月14日, 英語, 口頭発表(一般)
[国際会議] - Significant Differences in Effective Stress Coefficient for Rocks within Elastic Region and Peak and Residual Strengths
藤井 義明
Dassanayake, A. B. N., Fujii, Y., Fukuda, D. and Kodama, J., 2014年10月14日, 英語, 口頭発表(一般)
[国際会議] - Uniaxial Compressive Strength of Shikotsu Welded Tuff and Bibai Sandstone at Sub-zero Temperature
Hara, S, Kodama, J, Fujii, Y, Fukuda, D, Mitsui, Y, Sugiura, T
ARMS8, 2014年10月14日, 英語, 口頭発表(一般)
[国際会議] - Investigation of Rock Slope Deformation Modes due to Excavation on Mountain Type Mine
Najib, Fukuda, D, Kodama, J, Fujii, Y
ARMS8, 2014年10月14日, 英語, 口頭発表(一般)
[国際会議] - Numerical Study on Fracturing Process in Rock by Blasting a Cylindrical Charge
Fukuda, D, Ikezawa, J, Kaneko, K, Kodama, J, Fujii, Y
ARMS8, 2014年10月14日, 英語, 口頭発表(一般)
[国際会議] - Shale Gas Extraction and CCS May Induce Serious Seismicity
Fujii, Y, Takahashi, K, Fukuda, D, Kodama, J
Workshop on Rock Engineering and Environment, 2014年10月13日, 英語, 口頭発表(一般)
[国際会議] - Consideration on the Tunnel Supporting Effectiveness of Shotcrete with a Time-dependent Viscoelastic Model,
Tani, T, Aoki, T, Ogawa, T, Fujii, Y
Computer Methods and Recent Advances in Geomechanics, 2014年09月25日, 英語, 口頭発表(一般)
[国際会議] - Temperature-Confining Pressure Coupling Effects on the Permeability of Three Rock types under Triaxial Compression
Alam, A. K. M. B, Fujii, Y, Fukuda, D, Niioka, M
EUROCK 2014, 2014年05月27日, 英語, 口頭発表(一般)
[国際会議] - Biot’s Effective Stress Coefficient of Rocks for Peak and Residual Strengths by Modified Failure Envelope Method
Dassanayake, A. B. N, Fujii, Y
EUROCK 2014, 2014年05月27日, 英語, 口頭発表(一般)
[国際会議] - Why Do Giant Earthquakes Occur at Lunar Phases Specific to Each Subduction Zone?
Fujii, Y, Ozaki, Y, Fukuda, D, Kodama, J
6th Int. Symp. on In-situ Rock Stres, 2013年08月21日, 英語, 口頭発表(一般)
[国際会議] - Effect of Confining Pressure on Permeability during Deformation and Failure of Several Rocks under Compression
Alam A.K.M. B, Niioka M, Fujii Y
47th US Rock Mechanics/ Geomechanics Symosium in San Fransisco, 2013年06月24日, 英語, 口頭発表(一般)
[国際会議] - Mechanisms of Falling Rock Formation at Steep Slope due to Temperature Perturbation
Keppetipola, S.S.S.S.M, Fujii Y, Kodama, N
47th US Rock Mechanics/ Geomechanics Symosium in San Fransisco, 2013年06月24日, 英語, 口頭発表(一般)
[国際会議] - An Analytical Study on the Effect of Weak Layer on the Long-term Behavior of Tunnels
Kodama, J, Mitsui, Y, Fukuda, D, Fujii, Y, Hagan, P
5th AUN/SEED/Net Regional Conference on Geological Engineering, 2013年01月15日, 英語, 口頭発表(一般)
[国際会議] - Effect of Temperature and Confining Pressure on Permeability during Deformation and Failure of Shikotsu Welded Tuff
Alam, B. A.K.M, Niioka, M, Fujii, Y. Kodama, J, Sugawara, T
ARMS7, 2012年10月16日, 英語, 口頭発表(一般)
[国際会議] - Date, Lunar Phase and Time of Giant Earthquakes might be Specified for Each Subduction Zone
Fujii, Y, Ozaki, Y
Seismological Society of America 2012 Annual Meeting, 2012年04月19日, 英語, ポスター発表
[国際会議] - Giant Eruptions did not Frequently Occur in the Periods When Giant Earthquakes Frequently Occurred and vice versa after 1900
Fujii, Y
Seismological Society of America 2012 Annual Meeting, 2012年04月18日, 英語, ポスター発表
[国際会議] - 自然はやんちゃ
藤井 義明
平成23年度北海道資源・素材フォーラム「北海道の地震・津波・噴火」, 2011年12月16日, シンポジウム・ワークショップパネル(指名) - Abandoned roadways aged up to 50 years observed in Kushiro Coal Mine, Japan
Fujii, Y, Sugawara, T, Kodama, J, Ishijima, Y, Kiyama, T, Takada, M, Ishihara, Y, Kumakura, S, Narita, T, Sawada, M, Nakata, E
12th. Int Congr. Rock Mech., 2011年10月18日, 英語, 口頭発表(一般)
[国際会議] - Analysis of Natural Rock Slope Deformations under Temperature Variation: A Case Study from Japan
Mufundirwa A, Fujii, Y, Kodama, N, Kodama, J
Slope Stability, 2011年09月20日, 英語, 口頭発表(一般)
[国際会議] - Foreshocks had been Observed since Two Days before the 2011 off the Pacific Coast of Tohoku Earthquake!
Fujii, Y
Society of America, 2011 Annual Meeting, 2011年04月13日, 英語, ポスター発表
[国際会議] - Influence of Stress Larger than Preload but Acted for Shorter Duration in Tangent Modulus Method - A New Method to Measure In-situ Rock Stress
Fujii, Y, Kondo, K
ISRM International Symposium 2010 and 6th Asian Rock Mechanics Symposium, 2010年10月27日, 英語, 口頭発表(一般)
[国際会議] - Prediction of Rock Mass Failure-time of Geo-hazards
Mufundirwa A, Fujii, Y, Kodama, J
EUROCK 2010, 2010年06月18日, 英語, 口頭発表(一般)
[国際会議] - Influence of Atmospheric Nuclear Explosions on Climate Change
Fujii, Y
90th AMS Annual Meeting, 2010年01月20日, 英語, 口頭発表(一般)
[国際会議] - 今後100年くらいの間、人類が今と同じ程度の文化的生活を継続するために日本は何をすべきか
藤井 義明
資源・素材2009(札幌), 2009年09月, シンポジウム・ワークショップパネル(指名) - Development of Rock Stress Measurement Probe Based on The Pilot Hole Wall Deformation Method Laboratory Tests
Lee, K, Ishijima, Y, Fujii, Y, Koo, H
43rd. U.S. and 4th U.S. Canada Rock Mechanics Symposium, 2009年07月01日, 英語, 口頭発表(一般)
[国際会議] - Mechanical Properties of Siliceous Rocks around the Horonobe URL from Triaxial Compression and Isotropic Consolidation Tests
Sanada, H, Matsui, H, Fujii, Y
ISRM-Sponsored Int. Symp. Rock Mech, 2009年05月20日, 英語, 口頭発表(一般)
[国際会議] - Things Hidden by the Global Warming
Fujii, Y, Abe, H
3rd Int. Workshop and Conference on Earth Resources Technology, 2009年05月14日, 英語, 口頭発表(一般)
[国際会議] - New Methods for Prediction of Geomechanical Failure-time
Mufundirwa, A, Fujii, Y
Korean Rock Mechanics Symposium 2008, 2008年10月22日, 英語, 口頭発表(一般)
[国際会議] - Effects of strain rate and temperature on Tangent Modulus Method
Makasi M, Fujii Y
Korean Rock Mechanics Symposium 2008, 2008年10月22日, 英語, 口頭発表(一般)
[国際会議] - Increase in Sealability of Fractured Sedimentary Rock with Time
Fujii, Y
Int. Symp. Sealability of Geomaterials, 2005年07月22日, 英語, 口頭発表(招待・特別)
[国際会議] - A Modeling Method on Fractal Distribution of Cracks in Rocks Using AE Monitoring
Watanabe, Y, Itakura, K, Sato, K, Fujii, Y, Balusu, R, Guo, H, Luo, X
17th International Acoustic Emission Symposium, 2004年11月10日, 英語, 口頭発表(一般)
[国際会議] - The Effect of Temperature on the Mechanical Properties of Inada Granite and Shirahama Sandstone
Kodama, N, Fujii, Y, Ishijima, Y
The 1st Kyoto International Symposium on Underground Environment, 2003年03月18日, 英語, 口頭発表(一般)
[国際会議] - Numerical Simulation on Microseismicity due to Mining at One of the Collieries in Australia
Fujii, Y, Balusu, R, Deguchi, G, Ishijima, Y
20th Int. Conference on Ground Control in Mining, 2001年08月09日, 英語, 口頭発表(一般)
[国際会議] - A Study on the Mechanism of Slope Failure at Toyohama Tunnel
Ishijima, Y, Fujii, Y
NY Rocks '97, 1997年07月01日, 英語, 口頭発表(一般)
[国際会議] - 'Condition Insensitive Damage Indicator' for Brittle Rock
Fujii, Y, Ishijima, Y
NY Rocks '97, 1997年07月01日, 英語, 口頭発表(一般)
[国際会議] - 引張ひずみ規準について
藤井 義明
大深度地下空間開発技術研究講演会, 1994年10月07日, シンポジウム・ワークショップパネル(指名)
[招待講演], [国内会議] - A New Criterion for Brittle Failure of Rock
Fujii,Y, Kiyama,T, Ishijima,Y
MMIJ/AusIMM Joint Symp., 1994年10月, 英語, 口頭発表(一般)
[国際会議] - Application of DDM to Some Rock Pressure Problems in Japanese Deep Coal Mines
Fujii, Y, Ishijima, Y, Goto
11 th. Intl. Conf. on Ground Control in Mining, 1992年07月08日, 英語, 口頭発表(一般)
[国際会議] - Numerical Analysis of Maximum Shear Seismic Moment Release for Microseismicity Induced by Deep Coal Mining
Fujii,Y, Ishijima,Y
10 th. Int. Acoustic Emission Symp., 1990年10月, 英語, 口頭発表(一般)
[国際会議] - Criterion for Occurrence and Focal Mechanism of Seismic Events Around Underground Excavation
Sato,K, Fujii,Y
2nd. Intl. Symp. of Rockbursts and Seismicity in Mines, 1990年06月, 英語, 口頭発表(一般)
[国際会議] - Microseismicity Induced by Deep Coal Mining Activity
Ishijima, Y, Fujii, Y, Sato, K
6th. ISRM Congress, 1987年08月, 英語, 口頭発表(一般)
[国際会議] - Microseismic Activity Induced by Longwall Coal Mining
Sato, K, Fujii, Y, Ishijima, Y, Kinoshita, S
4 th. Conf. on Acoustic Emission / Microseismic Activity in Geologic Structures and Materials, 1985年10月, 英語, 口頭発表(一般)
[国際会議]
共同研究・競争的資金等の研究課題
- ピークおよび残留強度における岩石の有効応力係数
科学研究費助成事業
2014年04月01日 - 2017年03月31日
藤井 義明
改良破壊包絡線法を開発し、いくつかの岩石について適用した。同方法は、岩石の三軸圧縮試験結果から、有効応力に基づくピーク・残留強度条件式を矛盾なく表すことのできる、有効応力に依存した有効応力係数を逆算する手法であり、従来の破壊包絡線法と比べると、破壊条件式の仮定や試行錯誤が不要という利点を有する。
求めた有効応力係数は、全応力と間隙水圧の関数として定式化し、有限要素法に実装した。岩盤中に掘削された略円形の空洞周辺の有効応力と改良破壊接近度を解析し、有効応力係数の有効応力依存性を考慮することにより、破壊接近度を、より正確に評価することができることを確認した。
日本学術振興会, 基盤研究(C), 北海道大学, 26420840 - 岩石の絶対強度の解明とサブゼロ温度領域におけるその応用
科学研究費助成事業
2010年 - 2012年
児玉 淳一, 小玉 齊明, 藤井 義明, 中村 大
岩石を対象に,時間や環境の影響を受ない「絶対強度」の概念を提案するとともに,サブゼロ温度領域における岩石のクリープ変形,クリープ寿命に与える間隙氷の影響について検討した。その結果,支笏溶結凝灰岩に関しては,絶対強度の存在を明らかにすることはできなかったが,応力レベルが小さくなると乾燥供試体のクリープ寿命より含水飽和供試体のクリープ寿命の方が短くなるという工学的に重要な現象を見出した。
日本学術振興会, 基盤研究(C), 北海道大学, 22560805 - 破壊後岩石の圧縮に伴う透水性変化に関する研究
科学研究費助成事業
2010年 - 2012年
藤井 義明, 児玉 淳一
変形・破壊に伴う支笏溶結凝灰岩、来待砂岩、稲田花崗岩の浸透率の変化とそのメカニズムを明らかにすることを目的として、浸透率を計測しながらいくつかの封圧と温度の下で三軸圧縮試験を行い、凝灰岩や高封圧下の砂岩において、破壊により浸透率が小さくなること、ならびに、高温下で地下水量が増えることを明らかにした。これらの知見は、将来、安全かつ低コストな地下空洞建設に役立つものと期待される。
日本学術振興会, 基盤研究(C), 北海道大学, 22560804 - 岩石の載荷履歴と接線ヤング率の変化に対する諸条件の影響
科学研究費助成事業
2006年 - 2008年
藤井 義明
岩盤中に作用している応力の値を測定するための一手法である接線ヤング率法における諸条件の影響について来待砂岩を用いて検討し、一軸載荷で推定した屈曲点応力をそのまま原位置応力成分とみなすことはできないことがわかった。一方、原位置との温度の差は考慮しなくてよい、また、岩盤応力推定時のひずみ速度は極端に速く/遅くなければ応力の推定結果に大きく影響しない、ということがわかった。
日本学術振興会, 基盤研究(C), 北海道大学, 18560776 - 限界伸びひずみに対する温度の影響に関する研究
科学研究費助成事業
2000年 - 2001年
藤井 義明
温度が岩石の限界伸びひずみに及ぼす影響を明らかにすることを主な目的として0〜80℃の水中において稲田花崗岩と白浜砂岩を一軸圧縮試験、圧裂引張試験、CB試験、ダブルトーション試験に供した。本研究で得られた主な知見を以下に示す。
0℃から80℃への温度上昇の影響について稲田花崗岩では(1)一軸圧縮強度の平均値は6%減少した。(2)限界圧縮ひずみの平均値は6%減少した。(3)限界伸びひずみの平均値は絶対値で約3割増加した。(4)ヤング率の平均値は、40℃で最も大きくなり、0℃と80℃を比べると後者が14%小さかった。(5)ポアソン比の平均値は約2割減少した。(6)圧裂引張強度の平均値は16%減少した。(7)KCBの平均値は26%減少した。(8)80℃の温度上昇に対し、応力腐食指数は約5割減少した。
白浜砂岩では、(1)一軸圧縮強度の平均値は10%減少した。(2)限界圧縮ひずみの平均値は13%減少した。(3)限界伸びひずみの平均値は絶対値で3%減少した。(4)ヤング率の平均値は、20℃において最大になり、0℃と80℃では後者が13%小さい。.(5)ポアソン比の平均値は11%減少した。(6)圧裂引張強度の平均値は14%減少した。(7)KCBの平均値は11%減少した。(8)80℃の温度上昇に対し応力腐食指数は約2割減少した。
両岩石の差異として、強度や限界ひずみに対する温度の影響は概して稲田花崗岩に顕著に表れた。有限要素法による解析の結果、80℃の温度変化による熱応力の発生は、稲田花崗岩について粘土鉱物であるイライトが介在する白浜砂岩より2オーダー程度大きかった。この結果は、稲田花崗岩において限界ひずみに対する温度の影響が白浜砂岩より顕著であったことを裏付ける結果となった。
日本学術振興会, 基盤研究(C), 北海道大学, 12650911 - スムースブラスティングの最適化に関する研究
科学研究費助成事業
1998年 - 1999年
金子 勝比古, 加藤 昌治, 藤井 義明, 朝倉 國臣, 山本 雅昭, 平田 篤夫
本研究では,より高度なスムースブラスティングを実現させるための必要条件を理論的・実験的に解明することを目的とし,亀裂進展を考慮したスムースブラスティングのシミュレーションコードを開発するとともに、岩石実験と数値予測により,スムースブラスティングの影響因子を定量的に分析し,その最適設計条件について検討を加えた。得られた成果をまとめると以下のようである。
(1)岩石動的破壊の数値解析法を開発するとともに,発破設計における基本定数である岩石動的強度とその発現のメカニズムについて検討を加え,動的強度と静的強度の相違は,応力集中域の寸法と亀裂進展プロセスにあること,両者の強度の比は微視的強度分布の均一性係数に依存することなどを明らかにした。
(2)スムースブラスティングにおける亀裂進展プロセスと破断面形成プロセスを解析し,起爆時間精度と破断面平滑性および損傷圏寸法との関係を明らかにした。また,トンネル掘進の試験施工により,起爆時間精度を向上させることにより,岩盤損傷が抑制され,破断面の平滑性が向上することを確認した。
(3)スムースブラスティングの効果を定量評価するために,簡易PS検層により,損傷圏寸法を迅速に計測する方法を開発した。また,本手法を実際の発破施工現場に適用し,その有用性を確認した。
以上の結果から,高度なスムースブラスティングを実現させるためには,電子遅延式起爆システムなどにより起爆時間精度を向上させるとともに,発破後に損傷圏計測を実施し,その結果を薬量・孔間隔などの発破設計にフィードバックさせることが肝要であると考える。
日本学術振興会, 基盤研究(B), 北海道大学, 10450387 - 悪条件下の岩盤を対象とした地圧計測法の開発
科学研究費助成事業
1996年 - 1998年
石島 洋二, 菊池 慎二, 中村 章, 藤井 義明, 菊地 慎二
本研究では、多額の費用と日数を要する地圧測定をより簡易化し、また、測定の適応範囲を広げるために、開発すべき地圧測定法として、研究代表者が約25年前から理論を確立していた孔壁変形法を選んだ。本方法は、測定技術が追いつかずに放置されていたが、今回、研究費を得て技術開発に成功し、きわめて正確な測定結果が得られ、かつ従来困難であった悪条件下の岩盤にも適用し得る見通しが得られた。主な成果を箇条書きに述べる。
(1) 解析解に基づく孔壁変形法の観測方程式は極めて明快で簡潔なので、誤差の検出が容易で、クリープ挙動を示す岩盤にも適用できる。また、従来開発された測定法の中で感度係数の状態が最もよく、6成分の3次元応力が同一の正確さで評価できる。
(2) 40mm径の観測孔に埋設する計器として、3方向の孔径変化と軸ひずみを同時に測定する計器と、2方向の軸方向ずれ変位を測定する計器を開発した。これら2種の測定器を1本の観測孔で交互に使用することにより3次元応力が決定できる。
(3) 測定方式は機械式なので頑丈で、測定器を観測孔の所定の深度に容易に埋設することができる。また、埋設した直後から測定作業に取りかかれ、能率的である。さらに、耐水性があるので、水没状態の孔中での使用が可能である。
(4) 測定中に観測孔中の測定器と地表の測定装置を繋ぐケーブルを不要とする小型データーロガーを開発し、測定器に組み込むことに成功した。この成功によって、測定が失敗する確率が大幅に減少し、また、より深部の岩盤内での測定が可能になった。
(5) 圧縮強度が0.02〜0.08MPaの軟弱岩での下向き地圧測定に成功し、また、コアデスキングを起こすような高地圧帯での地圧測定に成功し、本測定法が悪条件に強いことを証明した。
日本学術振興会, 基盤研究(A), 北海道大学, 08555252 - 岩石破砕プロセスの三次元視化に関する研究
科学研究費助成事業
1996年 - 1997年
金子 勝比古, 加藤 昌治, 藤井 義明, 宗像 瑞恵, 小池 克明, 高島 和希, 尾原 祐三
本研究では,X線CTスキャナーを用いて岩石の破砕プロセスを可視化計測して、岩石破砕における亀裂進展プロセスに対する理論的アプローチを試みるとともに、岩盤表面における亀裂計測から岩盤内部の亀裂状態を推定する方法について検討を加えた。これらの成果はすでに学会誌および国際会議などに発表しているためこれらをまとめ報告書とした。報告書は3部から構成され、各部の成果は以下のようである。
(1)X線CTスキャナーにより、岩石の破壊進行に伴う内部構造変化の可視化計測を試みた。その結果、クラス2岩石における圧縮破壊プロセスはモード・の複合亀裂による断続的剥離破壊プロセスであることを明らかにした。また、静的破砕における亀裂の可視化計測により、プロセスゾーンの存在を確認するとともに、強度不均一性に依存した亀裂の選択プロセスを実験的に明らかにした。さらに、X線CTスキャナーを岩石内部構造評価に適用し、亀裂の先端構造、水の浸透フロントの可視化計測法を確立した。
(2)岩石破砕プロセスの破壊力学的解析法を提案するとともに、提案した方法を岩石破砕現象に適用し、岩石・岩盤の破壊プロセスを明らかにした。とくに、破壊プロセスや破壊形態は強度不均一性に密接に関係することを明らかにした。
(3)画像処理や数理地質学的手法により岩盤や岩体のスケールにおける亀裂分布を可視化表現する方法を開発するとともに、それらの結果から岩盤および岩体の透水性が評価ひれることを明らかにした。
日本学術振興会, 基盤研究(B), 08455487 - 岩石の応力下での微視的変形挙動に関する研究
科学研究費助成事業
1995年 - 1997年
石島 洋二, 中村 章, 藤井 義明
軸方向がリフト面、および、グレイン面に垂直な稲田花崗岩の円柱形供試体を単軸・三軸圧縮試験に供し、周ひずみが-0.05×10^<-2>〜-0.04×10^<-2>になった時点で除荷し、P波速度の測定とレプリカ法によるリフト面・グレイン面の観察を行った。
単軸の場合には無載荷の供試体より、載荷を経験した供試体の方が除荷後のP波速度が大きかった。一方、三軸の場合には、除荷後のP波速度は載荷に伴いやや減少した。
半径方向の除荷後のP波速度は載荷に伴い減少し、R軸(リフト面法線)方向やG軸(グレイン面法線)方向のP波速度はH軸(ハドウェイ面法線)方向のものより小さかった。同じ除荷時の周ひずみに対しては、単軸の方が三軸よりもP波速度が小さかった。一方、同じ永久周ひずみで比較すると、P波速度の値は、単軸と三軸とでほぼ等しかった。
レプリカ法と樹脂を含浸させた薄片を用いた供試体断面の観察を行った結果、レプリカ法は、鉱物種の判定が困難であるという欠点を有するものの、作製が簡単で、有色鉱物内のき裂も観察可能である等、き裂の検知能力は薄片と同程度であることがわかった。
リフト面・グレイン面におけるき裂密度は載荷に伴い増加した。同じ除荷時の周ひずみに対しては、三軸の方が単軸よりもき裂密度が小さかったが、同じ永久周ひずみで比較すると、き裂密度の値は、単軸と三軸とでほぼ同じであった。単軸の場合には、リフト面あるいはグレイン面に平行なクラックが多くみられたが、三軸の場合にはクラックの方向性は不明瞭であった。き裂密度とともにP波速度は減少したが、減少の割合破単軸よりも三軸の方が大きかった。測定方向の影響はみられなかった。
日本学術振興会, 基盤研究(B), 北海道大学, 07455405 - 1996年北海道古平町豊浜トンネル斜面崩落とその災害に関する調査研究
科学研究費助成事業
1996年 - 1996年
渡辺 輝夫, 藤井 義明, 播磨屋 敏生, 福田 正己, 川村 信人, 宇井 忠英
本研究は1996年2月10日午前8時頃,国道229号線の豊浜トンネル古平側(西側)坑口上部の急崖が崩落し,バスの乗員,乗客と自家用車の運転手20名が圧死した事故に関係する斜面崩落とその災害に関する調査研究である.地質,地形,地球物理,凍結岩盤の物性,気象などに関する研究がまとめられた.すでに1996年9月14日に,豊浜トンネル崩落事故調査委員会が調査報告書を北海道開発局局長に提出しているため,本研究は,その報告内容をふまえ,1996年10月以降に実施した.研究は,復旧工事との関係で今後永久に観察出来なくなる崩落斜面下部の観察を最重点として行なわれた.岩盤表層の凍結深度の変化と気象の関係を岩盤の凍結前から観察することも重点的に行なった.さらに,岩盤崩落の機構に関する考察を深めた.その結果,岩盤下部の表面構造は上部とは違っていることを明らかに出来た.また,崩落面下部では火山レキの破断が特徴的に見られたが,岩石圧裂引張実験から,6MPaで破断することが明らかとなった.これは,岩石上部に少なくとも300mは累重しなければ破断が生じない圧力である.したがって,レキの破断は特殊に応力がかかるか,地質時代にさかのぼる長い時間の出来事であると考えられる.研究はハイアロクラスタイト中の火山岩の全岩化学組成やスメクタイトの鉱物組成も明らかにした.岩石の応力解析の研究は,崖の鉛直面では粘着力の失われたある長さ以上の初期不連続面が不安定に成長すること,水平面では2次連続面が生じ,自由面に達することを明らかにした.凍結一融解の実験は調査地域の気象が岩石の脆弱化を招くことを明らかにした.地質の研究は,地質構造に規制された地下水の浸透面と枝わかれパイプ状の流路と地下水圧が崩落面の形成に関係し,過去の落石も同様の経過で崩落したものと推測された.
日本学術振興会, 基盤研究(C), 北海道大学, 08300013 - 引張ひずみに基づいた破壊規準に関する理論的研究
科学研究費助成事業
1995年 - 1995年
藤井 義明
材料科学の分野で広く用いられている分子動力学法(数値解析法の一種で、経験的ポテンシャルに基づいて原子1つ1つについて運動方程式を解いていく方法)を用いて10^<-9>mオーダーの寸法を有する微小なCuとNaClについて引張・圧縮時の変形・破壊挙動を解析した結果、巨視的スケールの材料試験と同じように、ひずみ軟化挙動を含む非線形な荷重-変位線図が得られた。
さらに、Cuについては以下の知見が得られた。(1)引張強温度が圧縮強度よりやや大きい、(2)引張試験時の大変形に伴いネッキングが観察される、(3)側圧による圧縮強度の増大が少ない、(4)圧縮試験における最大荷重点の偏差変位(せん断ひずみに対応する量)は側圧に依存しない。これらの特徴は巨視的な金属材料と一致する。
一方、NaClについては以下の知見が得られた。(5)引張強度が圧縮強度より小さい、(6)側圧により圧縮強度が、あたかもCoulombの破壊規準に従うように、増加する、(7)最大荷重点の載荷軸方向変位(軸ひずみに対応する)は側圧と共に増加するが、横方向変位(横ひずみに対応する)は側圧に依存しない。これらの特徴は巨視的な岩質材料と一致する。
もちろん、本研究で得られた結果がそのまま岩石に対して適用できるわけではないが、以上は、欠陥の無い極く微小な結晶でも巨視的材料にみられる特性を失っておらず、分子動力学法を岩石の変形・破壊のメカニズム解明に援用する価値があることを示唆している。クラックの導入により、さらに実際的な解析が可能になるものと期待される。SiO_2等の共有結合物質の解析は、当面の最も大きな課題として残された。先端的ないくつかの研究例を参考にして検討を続けていきたい。
日本学術振興会, 奨励研究(A), 北海道大学, 07751024 - 地層模型による空洞消滅に関する研究
科学研究費助成事業
1993年 - 1994年
石島 洋二, 藤井 義明, 中村 章
原型との相似則が高いレベルで満たされている多層構造を成す夾炭層岩盤模型を開発し、初期地圧が負荷された状態下にある地層中に空洞を掘削する2次元模型試験を実施した。模型試験結果は、少くとも深部炭鉱の地圧現象をよく再現していることが確認された。
次に、本模型試験により、深部の砕屑性堆積岩地層を掘削する場合、空洞の閉塞が進行し、やがて消滅すること、ならびに、空洞周囲には閉塞量の増大とともに緩み域が発達していくことが確認された。同時に、空洞が消滅し、空洞の天井と下盤、あるいは左右側壁が接触した時点から、地圧の回復と緩み域の圧密が生じることも明らかになった。
以上の結果から、高放射性廃棄物などの深地層処分への応用を考えた場合、砕屑性堆積岩の天然バリアーとしての能力に関して、次のことが推測される。すなわち、地層に期待される遮蔽能力は、空洞の開削時から低下し始め、空洞が消滅する前後で最低の水準になる。しかし、その後は緩み域の圧密の進行とともに次第に遮蔽能力が回復し、石化が充分進んだ段階では、空洞掘削前の地山状態と同じ水準になると予想される。空洞の充填は人工的な空洞消滅と解釈できるので、遮蔽能力の回復がより速やかに達成される。
したがって、砕屑性堆積岩地層の場合、空洞を開削してから、ある期間は遮蔽能力が低下するので、この間を人工的バリアーの遮蔽能力で補足する必要がある。本研究では、空洞開削から消滅までの期間を定量的に評価するには至らなかったが、現在考えられている人工的バリアーの遮蔽能力の発現期間よりは充分に小さいと推定される。したがって、砕屑性堆積岩盤は深地層処分の検討対象になり得る程度に遮蔽能力を有していると判断される。
日本学術振興会, 一般研究(B), 北海道大学, 05452314 - コアを用いた地圧計測法の高信頼性化に関する総合的研究
科学研究費助成事業
1992年 - 1993年
松木 浩二, 佐野 修, 瀬戸 政宏, 山本 清彦, 古住 光正, 藤井 義明
本研究では,コアを用いた地圧計測法の信頼性を向上させるため,8人の研究者により基礎的研究と実際の地圧計測を行った。釜石鉱山の550mレベルおよび250mレベルの坑道からボーリングにより得られたコアを各研究者に配付することにより,共通の試料によりラウンドロビン試験を行い,結果の比較を行った。地圧の評価は各研究者が以下に述べるようなそれぞれの方法で行った。藤井はreduced strainを用いないDRA法により,古住は,DRAまたはAE法およびそれらの併用法により,山本はDRAにより,瀬戸はAE法とDRA法の併用法により,及川はDSCA法および静水圧下のDRA法(PSHA)法により,佐野はDSCA法,DSA法および弾性波速度の異方性の評価により地圧計測を行い,また松木と小島はDRA法,DSCA法ASR法およびAE法の全てを用いて地圧計測を行った。これらの方法により得られた結果の総合的な比較・検討はまだ完全には行われていないが,現在までのところでは,それらはほぼ一致していたり,またかなり異なっていることもあった。ラウンドロビン試験により共通試料に対する各方法の結果を得るという本研究の当初の目的は達成されたが,これらの総合的評価は今後の課題として残った。基礎的研究については,山本は,DRAに基づく応力記憶について基礎的な研究を行い,非弾性ひずみの発生機構を微視破壊によるものと地殻応力下での応力の均一化によるものに分類し,DRAのメカニズムは後者であるとの仮定に基づき理論的研究を行った。松木と小島は,山本とは別の観点から,閉鎖き裂の力学的挙動に注目し,ガラス板にWing crackを有する閉鎖き裂を導入してモデル実験を行い,AEのカイザー効果のみならずDRAによる非弾性ひずみの急増も閉鎖き裂の力学的挙動に現れること,またそれらの挙動はき裂面の粗さに大きく依存することを見いだし,さらに閉鎖き裂の除荷に伴う逆滑りが時間依存的に起こることを明らかにして,DSCA法も含めて,全てのコアを用いた地圧計測法の背後にあるメカニズムが岩石中に含まれる閉鎖き裂の力学的挙動によって説明できる可能性があることを示した。
日本学術振興会, 総合研究(A), 東北大学, 04302052 - 炭鉱におけるガス突出に関する基礎的研究
科学研究費助成事業
1987年 - 1988年
佐藤 干城, 藤井 義明, 吉田 豊, 後藤 龍彦
本研究はガス突出機構を明確にするための基礎的研究として次の3点に着目し実験を行った。1つは石炭の突出型破壊試験、他は炭層ボーリングの穿孔挙動ならびに石炭に対する地圧とガス圧の相互作用についてである。これらの実験結果を以下に示す。
(1)塊状石炭サンプルを用い引立直前に高地圧帯が存在し、それにより石炭が破壊するプロセスを室内試験でモニタした。その結果から得られた破壊挙動は突出、逐次、流動型の3種に分類され、これらは地圧の大きさのみならず石炭の力学的性質に大きく依存したことがわかった。また破壊により多くの場合引立奥部に空洞が確認され、しかも坑道への流出炭と坑内で実際に発生したガス突出時の粉炭との粒度分布の間には良い一致が得られた。
(2)石炭供試体に外力を負荷した状態で穿孔試験を実施した。その結果、本実験条件下ではあるが、原位置炭層ボーリング時に観察された4つのパターンをほぼ得ることが出来、穿孔に伴う繰粉量の増加やジャミングの発生は石炭の破壊に起因することがわかった。それゆえテストボーリングの有効性を確認することが出来た。さらに室内試験と原位置ボーリングの対応関係から、穿孔時の繰粉重量変化やジャミング発生位置を正確にモニタすることにより、炭層内部の破壊状況をある程度把握することが可能である。
(3)芦別および赤平炭を対象に地圧とガス圧の相互作用の関連を明らかにするため、チッソガスを用い透過性および間隙ガス圧試験を実施した。その結果、石炭の透過性は静水圧の大きさに影響され、供試体に作用する静水圧が大きくなるほど透過性が悪くなることがわかった。またガス透過過程においてもAEの発生がモニタされた。有効封圧が同じ場合、変形や破壊挙動もほぼ同じ傾向を有することがわかった。
日本学術振興会, 一般研究(B), 室蘭工業大学, 62460181 - Deformation and Failure of Rock and Rock Mass
Grant-in-Aid for Scientific Research
1984年
競争的資金
その他
- 2012年12月 - 2012年12月
STVラジオときめきワイド、笹子トンネル事故に関連して北海道のトンネルについて電話インタビュー - 2012年11月 - 2012年11月
AIR G'(FM北海道)、北海道宝島において北海道の石炭鉱業についてインタビュー - 2012年04月 - 2012年04月
藤井義明(2012)、石炭エネルギー技術小特集「石炭等エネルギーの開発・利用」の発刊に寄せて、J. MMIJ, Vol. 128, Nos. 4/5, p. 178 - 2012年03月 - 2012年03月
北海道新聞2012年3月5日(月)夕刊、科学、無理なCO2削減やめよう - 2011年04月 - 2011年04月
Press release by Seismological Society of America on 2011 Meeting - 2010年04月 - 2010年04月
Scientists explore if we're in 'age of great quakes', U-T San Diego, by Gary Robbins, Apr. 10, 2011
Scientists explore if we're in 'age of great quakes', U-T San Diego, by Gary Robbins, Apr. 10, 2011 - 2008年06月 - 2008年06月
uhbスーパーニュース出演、北海道の石炭についてコメント - 2008年 - 2008年
Fujii, Y. (2008), Environmental Buisiness... E:VISION, Spring, 2008, p. 2 - 1997年 - 1997年
Fujii, Y. (1997), Circumferential Strain of Brittle Rocks Under Compression, ROCKbits, Rock Mechanics Research Center, The University of Oklahoma, Vol.4, No.1, p.3, Nov. 1997.