研究者データベース

渡部 要一(ワタベ ヨウイチ)
公共政策学連携研究部 公共政策学部門 公共政策学分野
教授

基本情報

所属

  • 公共政策学連携研究部 公共政策学部門 公共政策学分野

職名

  • 教授

学位

  • 博士(工学)(東京工業大学)

連絡先

  • watabeeng.hokudai.ac.jp

ホームページURL

J-Global ID

研究キーワード

  • 地盤環境   長期圧密   埋立て   廃棄物   地盤調査   軟弱粘土   Reclamation   Waste   Geotechnical Investigation   Soft Clay   

研究分野

  • 社会基盤(土木・建築・防災) / 土木環境システム
  • 社会基盤(土木・建築・防災) / 地盤工学

職歴

  • 2016年10月 - 現在 北海道大学 大学院 工学研究院 環境フィールド工学部門 教授
  • 2016年04月 - 現在 National Institute of Maritime, Por and Aviation Technology Geotechnical Engineering Department, Port and Airport Research Instituite Director
  • 2016年03月 - 2016年09月 国立研究開発法人 海上・港湾・航空技術研究所 港湾空港技術研究所 地盤研究領域長
  • 2015年04月 - 2016年03月 国立研究開発法人 港湾空港技術研究所 地盤研究領域長
  • 2012年04月 - 2016年03月 Port and Airport Research Institute Geotechnical Engineering Field Director
  • 2012年04月 - 2015年03月 独立行政法人 港湾空港技術研究所 地盤研究領域長
  • 2010年04月 - 2012年03月 独立行政法人 港湾空港技術研究所 地盤研究領域 土質研究チームリーダー
  • 2008年04月 - 2012年03月 Port and Airport Research Institute Soil Mechanics and Geo-environment Group Leader
  • 2008年04月 - 2010年03月 独立行政法人 港湾空港技術研究所 地盤・構造部 地盤研究領域 土質研究チームリーダー
  • 2003年04月 - 2008年03月 独立行政法人 港湾空港技術研究所 地盤・構造部 土質研究室長
  • 2003年04月 - 2008年03月 Port and Airport Research Institute Soil Mechanics and Geo-environmnt Laboratory Head
  • 2001年04月 - 2003年03月 独立行政法人 港湾空港技術研究所 地盤・構造部 主任研究官
  • 2001年04月 - 2003年03月 Port and Airport Research Institute Soil Mechanics and Geo-environment Laboratory Senior Researcher
  • 2001年01月 - 2001年03月 国土交通省 港湾技術研究所 土質部 主任研究官
  • 1998年04月 - 2001年03月 Port and Harbour Research Institute, Ministry of Transport, Japan Geotechnical Engineering Division Senior Research Engineer
  • 1998年04月 - 2000年12月 運輸省 港湾技術研究所 土質部 主任研究官
  • 1997年03月 - 1999年03月 カナダ・ラヴァル大学 Post Doctoral Fellow
  • 1997年03月 - 1999年03月 Laval University, Canada Post-doctoral Fellow
  • 1995年04月 - 1998年03月 運輸省 港湾技術研究所 土質部 土性研究室 研究官
  • 1995年04月 - 1998年03月 Port and Harbour Research Institute, Ministry of Transport, Japan Soil Mechanics Laboratory Reseach Engineer

学歴

  • 1992年04月 - 1995年03月   東京工業大学
  •         - 1995年   東京工業大学大学院   理工学研究科   土木工学専攻(博士後期)
  • 1990年04月 - 1992年03月   東京工業大学
  •         - 1992年   東京工業大学大学院   理工学研究科   土木工学専攻(修士)
  • 1986年04月 - 1990年03月   東京工業大学
  •         - 1990年   東京工業大学   工学部   土木工学科
  •         - 1986年   東京都立白鴎高等学校

所属学協会

  • 国際地盤工学会   土木学会   地盤工学会   Japanese Geotechnical Society   Japan Society of Civil Engineers   

研究活動情報

論文

  • Yoichi Watabe, Shinji Sassa, Takashi Kaneko, Yukio Nakata
    SOILS AND FOUNDATIONS 57 5 760 - 775 2017年10月 [査読有り][通常論文]
     
    Coral gravel soils are composite soils comprised of large fragments of finger coral and fine particles from silt matrixes. When the amount of coral fragments is small, the mechanical behavior of the coral gravel soil is mainly governed by the silt matrixes, and when the amount of coral fragments is large, the mechanical behavior is mainly governed by the coral fragments. Undisturbed samples, called high-quality samples in the present study, were collected at large-scale coastal construction sites in Okinawa Prefecture and Kagoshima Prefecture, Japan. A series of triaxial CD-tests was conducted in the laboratory to evaluate the mechanical characteristics of coral gravel soils. The test results were examined from various viewpoints to find a common governing parameter for the mechanical behavior of coral gravel soils. It was anticipated that it would be difficult to interpret the mechanical behavior of the high-quality samples in a uniform manner because undisturbed coral gravel soils, in the form of natural sediments, are generally very heterogeneous. To provide a reference for the parametric interpretation of the test results showing the remarkable features of coral gravel soils, such as interlocking and particle crushing, the test data newly obtained for the high-quality samples were compared to the previous test results obtained for reconstituted mixtures having various volumetric percentages of coral fragments. It was found that an intergranular void ratio corresponding to 0.075 mm, in which particles finer than a grain size of 0.075 mm (i.e., particles of clay and silt) are regarded as voids, can be employed as a useful parameter in evaluating the shear strength of both reconstituted and undisturbed coral gravel soil samples. (C) 2017 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.
  • Antonio Bispo, Lizzi Andersen, Denis A. Angers, Martial Bernoux, Michel Brossard, Lauric Cécillon, Rob N.J. Comans, Joop Harmsen, Knut Jonassen, Frank Lamé, Caroline Lhuillery, Stanislav Maly, Edith Martin, Angus E. Mcelnea, Hiro Sakai, Yoichi Watabe, Thomas K. Eglin
    Frontiers in Environmental Science 5 Article 41 2017年07月12日 [査読有り][通常論文]
     
    Soil is a key compartment for climate regulation as a source of greenhouse gases (GHGs) emissions and as a sink of carbon. Thus, soil carbon sequestration strategies should be considered alongside reduction strategies for other greenhouse gas emissions. Taking this into account, several international and European policies on climate change are now acknowledging the importance of soils, which means that proper, comparable and reliable information is needed to report on carbon stocks and GHGs emissions from soil. It also implies a need for consensus on the adoption and verification of mitigation options that soil can provide. Where consensus is a key aspect, formal standards and guidelines come into play. This paper describes the existing ISO soil quality standards that can be used in this context, and calls for new ones to be developed through (international) collaboration. Available standards cover the relevant basic soil parameters including carbon and nitrogen content but do not yet consider the dynamics of those elements. Such methods have to be developed together with guidelines consistent with the scale to be investigated and the specific use of the collected data. We argue that this standardization strategy will improve the reliability of the reporting procedures and results of the different climate models that rely on soil quality data.
  • Takashi TSUCHIDA, Takatoshi NOGUCHI, Yoichi WATABE
    Japanese Geotechnical Journal 12 1 135 - 149 2017年
  • Yoichi Watabe, Shinji Sassa
    JOURNAL OF COASTAL RESEARCH 32 6 1389 - 1401 2016年11月 [査読有り][通常論文]
     
    An extensive pattern of sandbars within a flood-tidal delta complex can be seen at the tidal inlet of Lake Tofutsu, one of the lagoons located along the Okhotsk Sea in Hokkaido, Japan. The primary aim of this study was to investigate the sequential sedimentation history of these sandbars. The shear-wave velocity structure, which is equivalent to the stiffness variation, of these sandbars was examined using a surface-wave method called the multichannel analysis of surface waves (MASW) to identify and describe the stratigraphy of the flood-tidal delta at the tidal inlet of Lake Tofutsu. The MASW results demonstrated that even though the sandbars appeared to comprise the same sandy material, the sediment under the sandbars had a very varied stratigraphy, comprising the river-borne muddy sediment derived from the upstream side of the lagoon and wave-induced marine sandy sediment derived from the coastal sand of the Okhotsk Sea. The second aim of this study was to verify the sedimentation history described on the basis of the MASW results through laboratory testing of sediment samples collected at characteristic points along the MASW array. The sampling method was modified to be applicable to low-cost sediment investigation at tidal flats and was conducted by human power without the aid of an engine. The collected samples were examined in the laboratory to obtain the depth profiles of grain size distribution and carbon 14 dating. The results obtained from the sampling are consistent with the sequential sedimentation history evaluated by MASW.
  • 渡部 要一, 佐々 真志, 金子 崇, 橋本 裕司
    土木学会論文集B3(海洋開発) 72 2 I_449 - I_454 公益社団法人 土木学会 2016年 
    浚渫土砂に覆砂が施された人工干潟において,多チャンネル型表面波探査(MASW)による継続的モニタリングを実施し,物性の変化をせん断波速度によって把握してきた.干出時にジオフォンを使って実施してきたこれまでの調査では,圧密沈下によって干潮時にも水没するようになったエリアのモニタリングは継続できなくなってしまう.そこで本研究では,人工干潟の維持管理にMASWを適用する上での課題となる水没エリアへの対応を目的として,水没してしまった(あるいは将来水没するであろう)エリアにおいてハイドロフォンを使ったMASWの適用を試みた.ハイドロフォンを使ったMASWの結果は,ジオフォンを使ったMASWの結果とほぼ同様のものが得られたが,軟弱層での減衰の影響を受けやすく,覆砂厚を薄く評価する傾向があること,軟弱層の厚さを捉えられない傾向があることに留意が必要である.
  • Yoichi Watabe, Serge Leroueil
    INTERNATIONAL JOURNAL OF GEOMECHANICS 15 5 2015年10月 [査読有り][通常論文]
     
    A practical use of the isotache concept in creep settlement prediction is newly introduced in this study. The isotache concept introduces a unique relationship between the strain and the consolidation pressure corresponding to the strain rate in association with viscosity. The authors have proposed a method to simply introduce the isotache concept, which uses a compression curve normalized by preconsolidation pressure [epsilon-log(sigma'/sigma(p)')] and a strain rate dependency relationship between the preconsolidation pressure (sigma(p)') and strain rate ((epsilon) over dot = d epsilon/dt). The strain rate dependency relationship is modeled as an equation based on power law. According to the authors' method, the slope of the strain rate dependency relationship (log sigma(p)'-log epsilon(over dot)), which coincides with C-alpha e/C-c, can be calculated as a function of strain rate, showing that C-alpha e/C-c is not constant but decreases with decreasing strain rate. In engineering practice, consolidation settlement is generally estimated based on the compression curve obtained from the 24-h incremental loading oedometer test, which corresponds to a strain rate of about 1x10(-7) s(-1). Using the compression index C-c at the consolidation pressure and initial void ratio e(0), creep settlement can be easily calculated as a function of C-c = (1+e(0)) and in situ strain rate (several orders of magnitude smaller than 1x10(-7) s(-1)). This work is made available under the terms of the Creative Commons Attribution 4.0 International license, http://creativecommons.org/licenses/by/4.0/.
  • Yoichi Watabe, Shinji Sassa, Takashi Kaneko, Yukio Nakata
    SOILS AND FOUNDATIONS 55 5 1233 - 1242 2015年10月 [査読有り][通常論文]
     
    Coral gravel soils, which are composite soils consisting of finger-coral fragments and silt matrix, are often found in coastal regions of subtropical islands. In this study, for reconstituted soils with various volumetric percentages of coral fragments up to 44% (coral particle fraction of 59%) as the densest package, a series of triaxial CU-bar and CD tests was conducted to study the determination method for the soil design parameters in consideration of the interaction between the soil skeleton, consisting of coral fragments, and the silt matrix. For samples with volumetric percentages of coral fragments less than 20% (coral particle fraction of 31%), the shear strength obtained from the CD tests was slightly larger than that obtained from the CU-bar tests; however, the difference between the two tests was very small. For samples with volumetric percentages of fragments more than 20% (coral particle fraction of 31%), the shear strength obtained from the CU-bar tests was significantly overestimated because of the unrealistically large negative excess pore pressure in the field corresponding to significant dilation. The shear strength obtained from the CD tests also showed a similar tendency corresponding to volume expansion; however, these values are much smaller than those obtained from the CU-bar tests. For the samples with a dense package of coral fragments, shear resistance angle 0 was much larger than that for normal soils; however, it tended to decrease in association with the particle crush of coral fragments. The tendency of the particle crush was visually evidenced through CT-images taken before and after the triaxial tests. The soil parameters were significantly influenced by the volumetric percentages of the coral fragments in association with particle interaction and particle crush, when the percentage was more than 20% (coral particle fraction of 31%) for the coral gravel soils examined in this study. (C) 2015 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
  • 高橋英紀, 佐々真志, 森川嘉之, 渡部要一, 高野大樹
    港湾空港技術研究所報告 54 2 21-23,25-50 - 50 港湾空港技術研究所 2015年09月 [査読無し][通常論文]
  • Yoichi Watabe, Kunio Saitoh
    SOILS AND FOUNDATIONS 55 2 276 - 283 2015年04月 [査読有り][通常論文]
     
    When a clay sample is reconstituted from a slurry state to a normally consolidated state, a higher initial water content generally derives a higher void ratio in e-logp relationship. However, in undisturbed Holocene clay samples collected from a soil layer under the seabed, Void ratio is much higher than that for the reconstituted, even though the reconstituted sample was consolidated from a sample slurry state with a very high initial water content. Therefore, the higher void ratio for undisturbed Holocene clay cannot be explained by the initial water content. There must be another key factor to explain the higher void ratio for undisturbed Holocene clay. In this study, the difference between the microfabric of deposited clay from suspension state and reconstituted clay from a slurry state is investigated to clarify the key factors contributing to the higher void ratio. The clay in this study is Osaka Bay Holocene clay sampled from 15 to 19 in below the seabed. Sedimentation tests from the suspension state were carried out in various conditions of initial water content, salt concentration, and pH. A series of sedimentation tests was carried out with two types of hollow cylinders: an observation glass cylinder with an inner diameter of 60 mm and a height of 400 mm (specimen height of 350 mm), and a cylindrical acrylic container with an inner diameter of 100 mm and a height of 1800 into (specimen height of 1500 mm). In the 100-mm diameter cylinder, the deposited sample was consolidated by a pressure of 19.6 kPa, then mounted in an oedometer ring with an inner diameter of 60 mm and a height of 20 mm. An incremental loading oedometer test was then carried out up to 39.2 kPa. The microfabric of the consolidated specimen was observed by scanning electron microscope (SEM) and quantitatively investigated by mercury intrusion porosimeter (MIP). It was shown that the high void ratio of natural clay deposit is not only due to the high initial water content but also to the sedimentation process with flocculation. This plays an important role in the formation of the microfabric of natural clay deposits characterized by a significantly higher Void ratio than reconstituted samples. (C) 2015 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
  • 野口孝俊, 渡部要一, 土田孝
    土木学会論文集F4(建設マネジメント) 71 1 33 - 43 2015年03月15日 [査読有り][通常論文]
  • 新舎 博, 米谷 宏史, 高 将真, 熊谷 隆宏, 渡部 要一
    地盤工学ジャーナル 10 2 173 - 186 The Japanese Geotechnical Society 2015年 
    局所的に中間砂層が堆積している粘土地盤の圧密沈下を評価する際には,中間砂層の存在が地盤全体の沈下に及ぼす影響を明らかにする必要がある。中間砂層の堆積状況を詳細に把握するためには,密な間隔での土質調査が不可欠であり,本文では,前半部分でドレーン打設時のマンドレル貫入抵抗の記録を活用して,中間砂層の堆積分布を詳細に把握する方法を提案した。次に,中間砂層の影響を考慮した一次元圧密解析と三次元FEM圧密解析を行い,実測と解析の沈下量を比較して,中間砂層が沈下に与える影響について考察した。その結果,ここで述べる方法により,中間砂層が沈下に及ぼす影響を大筋で把握できることが明らかとなった。
  • 奥田 一弘, 土田 孝, 渡部 要一, 上野 一彦, 金子 崇, 村上 博紀
    地盤工学ジャーナル 10 3 343 - 358 The Japanese Geotechnical Society 2015年 
    福島第一原発事故により発生した廃棄物と除染発生土を対象とした海面処分場の構造について検討を行った。海面処分場の護岸と遮水工は長期にわたり汚染水の流出を防止する機能を維持する必要があり,この間に発生する可能性があるレベル2相当の巨大地震時に対しても安全性と機能の維持が求められる。本研究では,重力式護岸と鋼管矢板二重締切り内に土質系遮水材を充填した遮水工による構造とし,両者の間に幅広の裏込めを設けて分離する護岸断面を提案した。遠心載荷模型実験,模型振動台実験,数値解析による護岸と遮水矢板の変形量を検討した結果,静的震度0.25として港湾の基準で設計した構造は,レベル2地震においても遮水工の変形が十分に小さく抑えられており,遮水機能を維持できると考えられることがわかった。
  • Yoichi Watabe, Takashi Kaneko, Shinji Sassa
    15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability 547 - 551 2015年 [査読有り][通常論文]
     
    Coral gravel soils, which are composite soils consisting of finger-coral fragments and silt matrix, are often found in coastal regions of sub-tropical islands. In this study, for reconstituted soils with various coral gravel fractions up to 44% that was the densest package, a series of triaxial CU-bar and CD tests was conducted to study determination method for soil design parameters in consideration of interaction between soil skeleton consisted of coral fragments and silt matrix. The soil parameters were significantly influenced by volumetric percentage of coral fragments in association with particle interaction and particle crush, when the percentage was larger than 20% for the coral gravel soils examined in this study.
  • Yoichi Watabe, Shinji Sassa
    15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability 1784 - 1789 2015年 [査読有り][通常論文]
     
    The Tokyo Haneda Airport has been developed by land reclamation since 1931. When we look back its history, dredged soils have been effectively used at the offshore expansion project (1984-2007) and the D-runway project (2007-2010). In the offshore expansion project, a dredged clay deposit in ultra-soft state was converted into an airport island. Because of softness of the dreaded soil, continuity of the vertical drains under large consolidation settlement, as well as large lateral soil movement, had to be concerned. In the D-runway project, lightweight treated soils of dredged clay were effectively used to reduce earth pressure on the seawall. To efficiently conduct large-scale placement, pneumatic mixing method was very useful. At the joint structure between the reclamation and piled pier sections, air-foam treated lightweight soil was placed as backfill, because more lightness was strongly required to ensure the stability.
  • Yoichi Watabe, Shinji Sassa, Takashi Kaneko, Kazuhiko Ueno, Koichi Yamada
    6th Japan-China Geotechnical Symposium, SJGS 2015 30 - 34 2015年 [査読有り][通常論文]
     
    Dredged soils from navigation channel or anchorage area have been used in reclamation of artificial intertidal flats in Japan. Immediately after the reclamation, because the dredged clay filled in the intertidal flat has not consolidated, a safety assessment system is strongly required to avoid depression of foot into an extremely soft soil at a place where sand capping is significantly thin. In addition, temporal variation of the dredged soils filled in the intertidal flats has not been clarified yet. In this study, a follow up research at an artificial intertidal flat in Tokuyama-Kudamatsu Port, Yamaguchi, Japan, was periodically conducted for several years since its completion of reclamation in 2008. Shear wave velocity obtained by MASW in the extremely soft sediments was only 25 m/s. Gradual increase with elapsed time in shear strength of dredged soil layer was mostly caused by chemical bonding (thixotropy effect) rather than densification (consolidation). Because MASW can describe both the thickness of sand capping and softness of the dredged soils, this technology is useful to assess the safety of artificial intertidal flats.
  • Yoichi Watabe, Hiroshi Shinsha, Hiroshi Yoneya, Changjin Ko
    SOILS AND FOUNDATIONS 54 5 1006 - 1017 2014年10月 [査読有り][通常論文]
     
    The dredged soil dumped into a reclamation facility is generally heterogeneous he reclamation is executed using hydraulic transportation through pipes, large particles will be deposited around their outlets, and fine particles will be deposited apart from those outlets, resulting in significant grain size segregation. Therefore, ground improvement by applying a preload or vacuum to the dredged soil deposit with prefabricated vertical drains (PVDs) may result in an unexpected differential settlement. In the present study, partial sandy layers in a dredged soil deposit were identified as three-dimensional information using the penetration resistance of the mandrel in the PVD installation, which was recorded as dense information for a wide region. It was clarified that the depth profile of the penetration resistance of the mandrel in the PVD installation was useful for investigating the soil stratigraphy, because it is closely related to the depth profile of the tip resistance in cone penetration tests (CPTU). The relative penetration resistance, defined as the penetration resistance eliminating the data trend that reflects the effects of the overburden stress, shear strength, sleeve friction and buoyance, is useful for identifying the partial sandy layers in a dredged soil deposit. A classification equation was proposed for identifying the partial sandy layers. Firstly, the depth profile without the sandy layer was approximated, and then the threshold value of 1.0 MN/m(2) was used to identify the partial sandy layer. To verify the availability of this proposed method, the depth profiles were compared with the results of CPTU tests. In addition, the predicted settlement, calculated on the basis of the stratigraphy obtained using the penetration resistance of the PVDs, was compared with the ground surface profile leveled after vacuum consolidation. (C) 2014 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
  • Shinji Sassa, Soonbo Yang, Yoichi Watabe, Naoto Kajihara, Yoshitake Takada
    JOURNAL OF SEA RESEARCH 85 336 - 342 2014年01月 [査読有り][通常論文]
     
    Sandy beach ecology has progressed rapidly with the emergence of several theories developed on the basis of understanding of hydrodynamic and morphodynamic processes on sandy beach habitats. However, the possible role of dynamic geophysical processes in the sediments remains poorly understood. The present study aims to explore the role of such geophysical processes in the sediments in forming the habitat environment and how they influence the species distributions. We conducted sets of integrated observations and surveys on intertidal and supratidal geophysical environments and the distributions of three amphipod and isopod species at four exposed sandy beaches located on the Japan Sea coast of Niigata Prefecture, Japan. The field results combined with a series of laboratory soil tests demonstrate that suction governed the variability of habitat environments observed, involving the degree of saturation, density, and hardness of the cross-shore intertidal and supratidal sediments, depending on the severity of the suction-dynamics-induced sediment compaction. While the observed species abundances were consistent with existing theories relating to intertidal and supratidal species, the observed magnitudes of suction were responsible for the distribution limits of the amphipods Haustorioides japonicus and Talorchestia brito and the isopod Excirolana chiltoni manifested consistently throughout the different beaches. The results of controlled laboratory experiments and field tests further revealed three distinctive suction-induced mechanisms, associated with their burrowing and physiology and the stability of the burrows. The novel role of such suction-induced geophysical processes in forming the habitat environment and influencing the species distributions may advance our understanding of sandy beach ecology in intertidal and supratidal zones. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
  • S. Sassa, Y. Watabe, S. Yang, T. Kuwae
    SOILS AND FOUNDATIONS 53 2 246 - 258 2013年04月 [査読有り][通常論文]
     
    The present study aims to pioneer a new cross-disciplinary research field which we call "Ecological Geotechnics". Recent findings about the salient geophysics involved in intertidal sediments made it possible to closely investigate the linkage between the waterfront geoenvironment and the ecology of intertidal flats. The results of a comprehensive set of field observations, surveys and controlled laboratory experiments demonstrated that the waterfront suction, which remained thus far unexplored in soil mechanics, and the associated geoenvironments govern the performances of the basic living activities of various representative creatures involving crabs, bivalves and birds. Furthermore, these results are discussed and substantiated in light of a successful habitat restoration project showing that such waterfront geoenvironment plays a pivotal role in the habitat selection for the benthos diversity. Hence, the present findings are expected to facilitate a new horizon for performance-based geoenvironmental assessments, design and management for the conservation and restoration of habitats with rich natural ecosystems in intertidal zones. (C) 2013 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
  • 新舎 博, 宮本 健児, 渡部 要一
    土木学会論文集B3(海洋開発) 69 2 I_970 - I_975 Japan Society of Civil Engineers 2013年 
    浚渫土を処分して形成された沿岸域の埋立地盤の中には,透水係数の大きい中間砂層が存在していることが多い.こうした埋立地盤を真空圧密で改良すると,中間砂層を通じて埋立地外の水を多量に吸引し,圧密改良効果そのものが著しく低減するのではないか,という懸念がある.そこで,中間砂層からの吸引水がある場合を想定して,粘土地盤の真空圧密効果を室内実験で明らかにすることを試みた.実験は中間砂層からの吸引水量をPBD1本あたり2ℓ/minと設定し,吸引水量がある場合とない場合の圧密実験を実施した.両者の沈下曲線を比較すると,大きな差がないことから,2ℓ/minの吸引水量が圧密へ及ぼす影響は小さいことが明らかとなった.また,PBDの許容通水量についても,負圧作用時の吸水試験の結果を基に考察した.
  • Yoichi Watabe, Shinichiro Imamura, Takashi Tsuchida
    Indian Geotechnical Journal 43 2 127 - 136 2013年 [査読有り][通常論文]
     
    In order to improve the seismic capacity of a caisson type quay wall, lightweight backfill method is often used in practice. However, the interaction between the caisson and lightweight backfill is not yet clear due to its high complexity. In this study, a series of centrifuge shaking tests, in which a strong model box was used with the model ground made of relatively dense sand, was conducted to investigate failure mechanism, earthquake induced earth pressure, force equilibrium, etc. Width of the lightweight backfill was varied as a parameter. In the case with sand backfill, active failure in the backfilled sand occurred, while in the cases with lightweight backfill, two independent active failures occurred in the sand regions behind the lightweight backfill and caisson. Horizontal displacement of the caisson during seismic shaking was significantly decreased by lightweight backfill, because earth pressure between the caisson and backfill was reduced. Effect of the inverted trapezoidal lightweight backfill to decrease the horizontal displacement is much higher than that of the rectangular lightweight backfills, when the slope of the inverted trapezoid is milder than that of active failure surface in the sand. © 2013 Indian Geotechnical Society.
  • Yoichi Watabe, Shinji Sassa
    SOILS AND FOUNDATIONS 52 3 411 - 429 2012年06月 [査読有り][通常論文]
     
    Intertidal flats are key elements in marine environments; they provide regions of rich bioactivity and also have the function of water purification. In the present study, the shear wave velocity structures of intertidal flats were explored by a surface wave method called the multichannel analysis of surface waves (MASW), which is a very useful method for surveying the sedimentary stratigraphy of various intertidal flats, in order to evaluate the cross-shore and the along-shore sedimentary stratigraphy. Field surveys were carried out in sandflats, mudflats, and subtropical tidal flats during spring tides in summer, when these flats were exposed. In the sandflats, the sedimentary stratigraphy evaluated by MASW (as distributions of the shear wave velocity/stiffness) and by physical soil tests (as distributions of the void ratio) can be explained as being a consequence of the cyclic elastoplastic contraction of the soils that are subjected to a variety of suction dynamics under the tide-induced groundwater table fluctuations. In the mudflats, the soil stiffness was extremely homogeneous, although a variation in the void structure was observed in association with the grain-size distributions, because suction did not develop in the soil. In the subtropical intertidal flats, lime rock was clearly identified beneath the soil sediments. A spectrum analysis in the cross-shore direction was carried out in order to quantitatively characterize the dominant wavelength for the variations in both shear wave velocity and morphological ground surface profiles of intertidal flats with various scales and soil types. In the intertidal flats with a multibar-trough structure, dominant wavelengths in the range 40-90 m were obtained corresponding to the unit length of the bar-trough structure, while in the mudflat or the huge-scale homogeneous sandflat, no dominant wavelength was obtained. In the subtropical tidal flats, the dominant wavelength was strongly influenced by protruding lime rock rather than by the morphological ground surface profile. (C) 2012 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
  • Yoichi Watabe, Kaoru Udaka, Yukio Nakatani, Serge Leroueil
    SOILS AND FOUNDATIONS 52 3 449 - 464 2012年06月 [査読有り][通常論文]
     
    The consolidation characteristics interpreted with the isotache concept have been studied by many researchers, including the authors. The aim of most of these studies has been to calculate secondary consolidation with high accuracy in order to evaluate the long-term settlement of large-scale structures. In a previous study, the long-term consolidation characteristics of Osaka Bay clay, collected from the construction site of the Kansai International Airport, were examined, and a simplified method based on the isotache concept, using a compression curve and the relationship between the consolidation yield stress (preconsolidation pressure) and the strain rate, was proposed. The former and the latter were obtained from constant rate of strain consolidation (CRS) tests and long-term consolidation (LT) tests, respectively. The latter is expressed by an equation with three isotache parameters. In addition, it is noteworthy that the isotache parameters can be commonly determined for the Osaka Bay clays retrieved from various depths up to 300 m below the seabed. In the present study, the proposed method was applied to worldwide clays with various characteristics using the common values for the isotache parameters determined for the Osaka Bay clays. It was found that the long-term consolidation behavior of those worldwide clays can be well characterized by the proposed method, along with the common values for the isotache parameters. (C) 2012 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
  • Yoichi Watabe, Takatoshi Noguchi, Yoshio Mitarai
    Journal of ASTM International 9 4 2012年04月 [査読有り][通常論文]
     
    Recently, a new runway designated "D-runway" was constructed at Tokyo Haneda Airport. In this project, a large amount of cement treated lightweight soils made from very soft and mildly contaminated dredged clay was used. In this paper, a seawall structure using a cement treated lightweight soil made from dredged clay is introduced and the quality control of these soils in the construction work is discussed. Two types of lightweight soils, "pneumatic mixing cement treated soil" and "air-foam treated lightweight soil," were used as backfill in the seawall structures. Design and quality control of the lightweight soils were carried out, and the seawall structures were successfully constructed. The shear strength and bulk density of the lightweight soils placed in the sites met the required specifications in design. Copyright © 2012 by ASTM International.
  • F. Yamada, N. Kobayashi, Y. Shirakawa, Y. Watabe, S. Sassa, A. Tamaki
    JOURNAL OF WATERWAY PORT COASTAL AND OCEAN ENGINEERING-ASCE 138 2 172 - 180 2012年03月 [査読有り][通常論文]
     
    Fine-grained sediment budgets based on the monthly bed level and net sediment flux monitoring from October 2006 to October 2007 are estimated to examine the relative contributions of tides and river discharge to mud transport on an intertidal flat adjacent to a river mouth in a semiclosed sound. The estimated sediment budgets are interpreted using the water mass balance equation and the horizontal tidal current pattern measured using high frequency (HF) radar. The intertidal flat accreted during normal discharge conditions are primarily attributable to the alongshore sediment flux toward the river mouth. However, the flat was eroded when the large offshore suspended sediment transport occurred on the flat during the large river discharge. The net alongshore tidal current causes alongshore sediment fluxes toward the river mouth on this intertidal flat adjacent to the river mouth. These findings may be specific to this site, but an adopted comprehensive approach may be applicable to other sites. DOI: 10.1061/(ASCE)WW.1943-5460.0000108. (C) 2012 American Society of Civil Engineers.
  • 上野 一彦, 菊原 紀子, 山田 耕一, 渡部 要一
    土木学会論文集B3(海洋開発) 68 2 I_1079 - I_1084 Japan Society of Civil Engineers 2012年 
    近年,浚渫粘性土を利用した人工干潟の造成が各地で試みられている.軟弱な浚渫粘性土を揚土し,表層を覆砂する構造であり,地盤改良も施さないことから,干潟造成時には地盤の安定性に配慮した施工技術が要求される.また,施工後においては圧密沈下が生じる.
    本研究では徳山下松港内に整備が進められている大島人工干潟を対象に施工方法を紹介するとともに,干潟造成後から約3年間にわたり人工干潟の地盤環境の変化について調査した結果について,圧密沈下解析結果と合わせて報告する.
  • 直井 恒雄, 渡部 要一, 新舎 博, 日高 征俊, 白神 新一郎
    土木学会論文集B3(海洋開発) 68 2 I_498 - I_503 Japan Society of Civil Engineers 2012年 
    東京都の新海面処分場Cブロックにおいて,真空圧密を利用した粘性土層の減容化事業を実施した.対象となる粘性土層は,均質な在来粘土層とその上に処分した砂分を多く含む浚渫土層である.本減容化事業では事前予測沈下量の90%以上の沈下量を目標として工事を実施しているが,浚渫土層の中に存在する中間砂層の堆積分布を正確に把握し,沈下量の評価に反映する必要があった.そこで,本文ではドレーン打設時のマンドレル貫入抵抗値から中間砂層の堆積分布を詳細に把握した.また,減容化のための圧密挙動に関しては,中間砂層を排水層とみなした圧密理論と実際の沈下挙動を比較し,予測沈下計算方法が十分に適用できることを明らかにした.
  • Yoichi Watabe, Takatoshi Noguchi, Yoshio Mitarai
    CONTAMINATED SEDIMENTS: RESTORATION OF AQUATIC ENVIRONMENT, VOL 5 1554 15 - 31 2012年 [査読有り][通常論文]
     
    Recently, a new runway designated "D-runway" was constructed at Tokyo Haneda Airport. In this project, a large amount of cement treated lightweight soils made from very soft and mildly contaminated dredged clay was used. In this paper, a seawall structure using a cement treated lightweight soil made from dredged clay is introduced and the quality control of these soils in the construction work is discussed. Two types of lightweight soils, "pneumatic mixing cement treated soil" and "air-foam treated lightweight soil," were used as backfill in the seawall structures. Design and quality control of the lightweight soils were carried out, and the seawall structures were successfully constructed. The shear strength and bulk density of the lightweight soils placed in the sites met the required specifications in design.
  • Yoichi Watabe, Takatoshi Noguchi
    SOILS AND FOUNDATIONS 51 6 1003 - 1018 2011年12月 [査読有り][通常論文]
     
    Tokyo International Airport (Haneda Airport) is a domestic hub-airport in Japan; however, the increasing number of passengers has brought it close to its capacity. In addition, there has been strong demand for the development of an international-flight network. Consequently, a new runway, called the "D-runway," was planned and constructed from March 2007 to October 2010. Because some of the D-runway runs through a river mouth, a hybrid structure consisting of piled pier and reclamation fill was adopted. To overcome the geotechnical difficulties in constructing this hybrid structure on the soft clay deposit, various technologies in design and construction were adopted. This paper provides an outline of the project, the ground investigation, and the design of the D-runway structure from a geotechnical engineering view point. From the results of the site investigation, the stratigraphic model at the site was clarified. For the clay layers, a representative depth-profile for each soil parameter was determined. Some local soil properties which tended to be overlooked when only employing an engineering point of view can be appropriately captured by linking the geological and geotechnical information. In the construction of the D-runway, not only the ground improvement technologies (SD, SCP, and CDM) but also the new developed construction materials (the pneumatic mixing of cement treated soil and air-foam treated lightweight soil) were utilized. In the-D-runway project, various technologies used in previous airport constructions were brought together and applied to the ground investigation, design, construction work, and even maintenance. The construction of the D-runway was completed safely, rapidly, and economically, and it came into use on 21 October 2010, on schedule.
  • Shinji Sassa, Yoichi Watabe, Soonbo Yang, Tomohiro Kuwae
    PLOS ONE 6 9 2011年09月 [査読有り][通常論文]
     
    The response of bivalves to their abiotic environment has been widely studied in relation to hydroenvironmental conditions, sediment types and sediment grain sizes. However, the possible role of varying geoenvironmental conditions in their habitats remains poorly understood. Here, we show that the hardness of the surficial intertidal sediments varies by a factor of 20-50 due to suction development and suction-induced void state changes in the essentially saturated states of intertidal flats and beaches. We investigated the response of two species of bivalves, Ruditapes philippinarum and Donax semigranosus, in the laboratory by simulating such prevailing geoenvironmental conditions in the field. The experimental results demonstrate that the bivalve responses depended strongly on the varying geoenvironmental conditions. Notably, both bivalves consistently shifted their burrowing modes, reducing the burrowing angle and burial depth, in response to increasing hardness, to compensate for the excessive energy required for burrowing, as explained by a proposed conceptual model. This burrowing mode adjustment was accompanied by two burrowing criteria below or above which the bivalves accomplished vertical burrowing or failed to burrow, respectively. The suitable and fatal conditions differed markedly with species and shell lengths. The acute sensitivities of the observed bivalve responses to geoenvironmental changes revealed two distinctive mechanisms accounting for the adult-juvenile spatial distributions of Ruditapes philippinarum and the behavioral adaptation to a rapidly changing geoenvironment of Donax semigranosus. The present results may provide a rational basis by which to understand the ensuing, and to predict future, bivalve responses to geoenvironmental changes in intertidal zones.
  • Yoichi Watabe, Hiroyuki Saegusa, Hiroshi Shinsha, Takashi Tsuchida
    Proceedings of the Institution of Civil Engineers: Ground Improvement 164 3 189 - 200 2011年08月 [査読有り][通常論文]
     
    Airfoam-treated lightweight soil is lightweight and provides for the early age development of shear strength and effective utilisation of dredged soils. This paper summarises a 10 year follow-up study of the lightweight soils that were placed as backfill at the seawall in Kobe Port Island and Tokyo International airport. These two sites are the early case examples of constructions undertaken in 1996 including the recovery project after the Kobe earthquake disaster and the offshore expansion project of the Tokyo International airport. Sampling and laboratory testing were carried out to investigate the physical and mechanical properties in order to compare the initial material condition. The depth profiles of the soil parameters such as bulk density, water content, pH, calcium content, shear strength, needle penetration resistance, compressive yield stress and compression index were examined. Consequently, it was confirmed that the physical and mechanical properties of the airfoam-treated lightweight soil satisfied their required performance criteria, indicating that the lightweight soil had sufficient durability for use as geomaterial for construction in coastal areas.
  • Y. Watabe, K. Yamada, K. Saitoh
    GEOTECHNIQUE 61 3 211 - 219 2011年03月 [査読有り][通常論文]
     
    In this study, a series of incremental loading oedometer tests and microscopic observations is carried out in order to investigate the influence of sand/bentonite fractions on hydraulic conductivity and compressibility. If sand particles do not form a skeletal structure, and each particle is independent in the clay matrix, an additive fraction of sand causes a decrease in the compressibility; however, it does not affect the hydraulic conductivity under the same consolidation pressure. The additive fraction of bentonite contributes to a decrease in the hydraulic conductivity, even for clayey materials. In addition, the relationship between the pore-size parameter, which represents the pore entrance size distribution, and the hydraulic conductivity is discussed using a probabilistic model known as the general capillary model.
  • 佐々 真志, 渡部 要一, 梁 順普
    土木学会論文集B2(海岸工学) 66 1 1096 - 1100 Japan Society of Civil Engineers 2010年 
    The present study aims at examining the processes of benthic habitat selection as induced by optimal burrowing and geoenvironnmental gradients. We utilized a newly developed eco-geoenvironment-water tank in order to clarify the response of benthos to a wide variety of geoenvironments involving both optimal and critical conditions, OP and CR, for burrowing of sand-bubbler crab, Scopimera globosa. The results indicate that the benthos placed in the OP swiftly started burrowing, by contrast, the benthos placed in the CR migrated toward the OP to burrow there. Furthermore, the predicted patch formation based on our proposed optimal-burrowing-model is found to be well consistent with what has been manifested in the field. These results demonstrate that the burrowing benthos actively selects the suitable geoenvironments for their burrowing, thereby generating patch formation. Hence, the present finding will alter the current perspective of habitat selection based on optimal-foraging-model and will facilitate a new horizon of ecohabitat management in the future.
  • 渡部 要一, 佐々 真志, 林 宏一, 山田 耕一
    土木学会論文集B2(海岸工学) 66 1 1406 - 1410 Japan Society of Civil Engineers 2010年 
    Most of the artificial intertidal flats are filled with dredged clay and have a sand capping. Immediately after the construction, because the dredged clay has not consolidated, a safety assessment system is strongly required to avoid a person who is caught in a soft clay layer at a place where sand capping is significantly thin. The authors have applied MASW method to various types of intertidal flats, and confirmed that the MASW is very useful method to efficiently survey the stratigraphy of intertidal flats. In this study, the MASW was applied to three intertidal flats: an artificial flat which was immediately after the filling; an artificial flat which was about ten years after the filling; and a natural muddy flat which has deposited over many years. Through these investigations, it was confirmed that MASW technology is useful to evaluate the safety of artificial intertidal flats.
  • S. Sassa, Y. Watabe
    PHYSICAL MODELLING IN GEOTECHNICS, VOLS. 1 AND 2 1483 - 1488 2010年 [査読有り][通常論文]
     
    This paper reports our recent findings from physical modelling for Ecological Geotechnics: a new cross-disciplinary research field encompassing ecology and geotechnics. The physical modelling highlights the role of geophysical environments in association with groundwater level in benthic ecology of intertidal flats. Specifically, we designed and performed a series of 1g prototype scale chamber experiments in order to simulate the geophysical environmental characteristics of tidal flat soils and to closely examine the response of benthos to it. The results demonstrate that the waterfront suction and related geophysical environments were responsible for the manifestation of the threshold, optimum, and critical conditions for the burrowing activity of benthos. Furthermore, the results are substantiated by the relevant field evidence concerning the natural selection of habitats of benthos diversity. These findings indicate that such physical modelling will facilitate geoenvironmental design and management for conservation and restoration of habitats with diverse benthos activity in intertidal zones.
  • Tomohiro Kuwae, Eiichi Miyoshi, Shinji Sassa, Yoichi Watabe
    MARINE ECOLOGY PROGRESS SERIES 406 281 - 289 2010年 [査読有り][通常論文]
     
    Predators may have a series of alternative foraging modes. Under the food resource maximization hypothesis, predators are expected to shift between foraging modes such that they attain the highest intake rate in response to prey availability and constraints varying with environmental conditions. To test this hypothesis, we measured foraging action rate (actions per unit time), capture rate (captures per unit time), and intake rate (amount of energy and nutrients per unit time) for 2 foraging modes, pecking (feeding on epifauna at the sediment surface) and probing (feeding on infauna by inserting the bill into the sediment), in dunlin Calidris alpina on an intertidal sandflat. The birds chose their foraging mode to attain higher feeding success, i.e. individuals that obtained higher capture and intake rates by pecking allocated a higher proportion of foraging effort to pecking, and vice versa. The birds shifted foraging mode from probing to pecking with increased time after emersion. The shift may be related to decreasing efficiency of probing due to increases in the costs of energy and time caused by decreasing sediment penetrability (increasing hardness) with time after emersion. Our in situ study empirically suggests that, while environmental constraints reduce the predators' foraging mode flexibility, the birds show individual-based appropriate adjustments in their foraging mode to attain a higher intake rate at a given time and patch. This extends the ideal forager model for patch choice into foraging mode choice.
  • Yoichi Watabe, Masanori Tanaka, Yoshiaki Kikuchi
    SOILS AND FOUNDATIONS 49 6 827 - 839 2009年12月 [査読有り][通常論文]
     
    The Japanese design code for port facilities was revised in April 2007, and a performance-based reliability design method was introduced. This report introduces a new practical method, which has been adopted in the annex of the design code, to evaluate soil parameters. The new method uses a correction factor corresponding to the coefficient of data variation. In this method, the characteristic value automatically reflects the variation of the derived values in association with the testing method and the reliability of the data interpretation. Compared to the lower limit of 95% confidence interval, which is widely adopted in general design codes such as Eurocode 7 and JGS4001, the characteristic value determined by this method is conservative when the number of data entries is larger than 10. This tendency is caused by the concept, in which characteristic values always reflect the data variation, even though the number of data entries are significantly large. Generally, data variation in the depth profile can be reduced when the depth distribution is appropriately modeled. Also, data variation can be reduced by adopting a more reliable soil test. Accordingly, any efforts to reduce the variation are awarded in this new design code.
  • Yoichi Watabe, Masanori Tanaka, Hiroyuki Saegusa, Hiroshi Shinsha, Takashi Tsuchida
    Journal of ASTM International 6 4 2009年04月 [査読有り][通常論文]
     
    Airfoam-treated soli is lightweight and provides for the early age development of shear strength and effective utilization of dredged soils. This paper summarizes a 10-year follow-up study of the lightweight soils that were placed as backfill at the seawall in Kobe Port Island and Tokyo International Airport. These two sites are the early case examples of construction undertaken in 1996 including the recovery project after the Kobe earthquake disaster and the offshore expansion project of the Tokyo International Airport. Sampling and laboratory testing were carried out in order to investigate the physical and mechanical properties to compare the initial material condition. The depth profiles of the soil parameters such as bulk density, water content, pH, Ca content, shear strength and needle penetration resistance were examined. Consequently, it was confirmed that the physical and mechanical properties of the airfoamtreated lightweight soil satisfied their required performances, indicating that the lightweight soil has sufficient durability for use as geomaterlal for construction in coastal areas. Copyright © 2009 by ASTM International.
  • 渡部 要一, 佐々 真志
    土木学会論文集B2(海岸工学) 65 1 1441 - 1445 公益社団法人 土木学会 2009年 
    This study aims to develop a new technology in order to evaluate temporospatial geomorphology and outline of the sedimentation stratigraphy in a small intertidal flat. A small unmanned aerial vehicle (UAV) with a compact digital camera was applied to take aerial photographs in the intertidal flat. Because the water surface of the intertidal flat is tranquil, the waterline (water's edge) evaluated by aerial photograph taken from the UAV corresponds to a very precise contour of the intertidal flat. In addition, a geophysical exploration named as the multi-channel analysis of surface waves (MASW) was applied to investigate the sedimentation stratigraphy of the flat. The shear wave velocity structure obtained by MASW, corresponding to the stiffness distribution of the sediments, was consistent with the soil slices sampled by handy geo-slicer.
  • 渡部 要一, 佐々 真志, 林 宏一
    土木学会論文集B2(海岸工学) 65 1 1096 - 1100 公益社団法人 土木学会 2009年 
    In this study, shear wave velocity structures of sandy flats, muddy flats, and subtropical flats were evaluated by means of multi-channel analysis of surface waves (MASW). Spectrum analysis along the cross-shore direction was carried out in order to quantitatively characterize the dominant wavelength for the variations of both shear wave velocity and morphological structures of intertidal flats with various scales and soil types. In the intertidal flats with multi bar-trough structure, dominant wavelengths in a range of 40 to 90 m were obtained, while in the muddy flat or huge-scale homogeneous sandy flat, any dominant wavelength was not obtained. In subtropical intertidal flats, the dominant wavelength was strongly influenced by prominent lime rock rather than the morphological surface variation.
  • 佐々 真志, 渡部 要一, 梁 順普
    土木学会論文集B2(海岸工学) 65 1 1116 - 1120 公益社団法人 土木学会 2009年 
    We investigated in detail the performance and mechanics of self-burial activities of bivalves, Japanese Littleneck, from juvenile to adult, by utilizing our new approach encompassing ecology, geophysics and geotechnics. The observed speeds, angles and depths of the self-burial were all governed by the bed surface shear strength irrespective of the types of materials. The increase in the surface shear strength induced the mode shift from the vertical self-burial to inclined and/or partial self-burial, ultimately reaching the non-self-burial state. This self-burial mode shift can be consistently explained by the proposed conceptual model in view of required energy principle. There exists an optimal stage of growth, at which the bivalves can achieve the highest capabilities, below or above which the self-burial capabilities decrease continuously.
  • 佐々 真志, 渡部 要一, 梁 順普
    土木学会論文集B2(海岸工学) 65 1 1226 - 1230 公益社団法人 土木学会 2009年 
    The paper describes an interspecific comparison of burrowing capabilities of benthic fauna in tidal flats. By utilizing our new approach in Ecological Geotehcnics, we simulated and varied surface shear strengths of bed materials, to which we observed the responses of six species of invertebrates that belong to Arthropoda, Mollusca, and Annelida. The results demonstrate that for each of the burrowing activities there exist optimal, transitional and critical surface shear strengths, which are found to differ considerably between species, body sizes and weights. We have constructed a chart by which to examine such difference in the burrowing capabilities in an integrated manner in light of the associated geophysical environments in the field. This chart provides fresh important insights into natural selection of habitats of benthic fauna in tidal flats.
  • 渡部 要一, 佐々 真志, 林 宏一, 小林 耕一
    土木学会論文集B2(海岸工学) 65 1 661 - 665 公益社団法人 土木学会 2009年 
    At the entrance of the Tofutsu Lake, which is one of the lagoons located along the Okhotsk Sea in Hokkaido, sand bars have been significantly developed. The objective of this study is to evaluate the sequential sedimentation history of the sand bars by means of MASW (Multi-channel Analysis of Surface Waves) technology. We found out that the sedimentation stratigraphy under the sand bars were significantly different from muddy to sandy, even though the sand bars apparently consisted of the same sandy material. From the shear wave velocity structure obtained in this study, we successfully restored the sequential sedimentation process. Also, the sedimentation history was consistent with an old aerial photograph and memories of local inhabitants.
  • 金田一広, 渡部要一, 山崎浩之, 新舎博, 椎名貴彦
    地盤工学ジャーナル(Web) 4 3 245-258 (J-STAGE) - 258 The Japanese Geotechnical Society 2009年 [査読無し][通常論文]
     
    浚渫粘土を骨格構造が高位なものと仮定して,SYSカムクレイモデルを用いた水~土連成有限変形計算で,真空圧密による地盤改良の効果について調べた.真空圧を載荷することで地盤内の有効応力が増加し,骨格構造の劣化を伴う圧縮によって間隙が小さくなることを示した.真空圧密工法はドレーンを通じて地盤深部まで真空圧を伝達するため,改良域全般に効果がある反面,改良域以外での卓越したせん断ひずみの発生を引き起こす可能性があることを示した.さらに,真空圧密工法の適用現場を取り上げ,このモデルを用いた事例解析を行った.沈下・時間関係や,地表面沈下,さらに,側方変位について整合した結果が得られたことから,有限要素法を用いた変形予測の可能性が示された.
  • Shinji Sassa, Yoichi Watabe
    GEOPHYSICAL RESEARCH LETTERS 36 2009年01月 [査読有り][通常論文]
     
    The persistent nature of intertidal sand bars has been the subject of much speculation concerning the hydrodynamic mechanisms involved, but its origin remains enigmatic. Here, we introduce salient geophysics in contrast to the physics of fluids above the sediments. The geophysical evidence combined with theoretical modeling and analysis demonstrates that the geodynamic processes ensuing during exposure periods have a profound impact, yielding the persistent nature of the intertidal bars under severe hydrodynamic forcing which would otherwise lead to unstable bar behavior. The feedback between the effects of the dynamics of suction, i.e. negative pore water pressure relative to atmospheric air pressure, and sediment transport and morphology is found to play a crucial role in the intertidal bar morphodynamics. Our finding may fundamentally alter the current perspective, leading to a new level of understanding, of sediment transport and bar behavior at waterfronts that are ubiquitous in rivers, estuaries, and coastal seas. Citation: Sassa, S., and Y. Watabe (2009), Persistent sand bars explained by geodynamic effects, Geophys. Res. Lett., 36, L01404, doi:10.1029/2008GL036230.
  • Yoichi Watabe, Kaoru Udaka, Yoshiyuki Morikawa
    SOILS AND FOUNDATIONS 48 4 495 - 509 2008年08月 [査読有り][通常論文]
     
    The consolidation characteristics of clay, based on the isotache concept in which the strain rate effect is considered, have been studied by many researchers. Most of these studies are aimed at calculating the secondary consolidation with high accuracy in order to evaluate the long-term settlement of large structures. In this study, as the first step toward improving the accuracy of the evaluation of long-term settlement at the Kansai International Airport, the consolidation characteristics of Osaka Bay clay are examined and organized based on the isotache concept. This study proposes a simplified model based on the isotache concept by using a compression curve and the relationship between the consolidation yield stress and the strain rate. The former and the latter are obtained from the constant rate of strain consolidation (CRS) tests and long term consolidation (LT) tests, respectively. The latter is expressed by an equation with three isotache parameters. This model is very practical because it requires a minimum of only one CRS test and one LT test. It is widely applicable to the Osaka Bay clay. The isotache parameters used in this model can be commonly determined for the Osaka Bay clays retrieved from various depths at the Kansai International Airport.
  • Yoichi Watabe, Kaoru Udaka, Masaki Kobayashi, Takechiho Tabata, Tsuyoshi Emura
    SOILS AND FOUNDATIONS 48 4 547 - 561 2008年08月 [査読有り][通常論文]
     
    The objective of this study is to empirically clarify the scale effect in long-term consolidation behavior. Frictional pressure loss arising at the interface between the consolidation ring and the specimen must be considered, when the specimen thickness increases. This study uses a special oedometer that can evaluate the quantity of the frictional pressure loss. Incremental loading oedometer tests are carried out in order to evaluate the frictional pressure loss in the normal oedometer test using a specimen with a height of 20 mm. The frictional pressure loss ratio generally exceeds 0.2 when the consolidation pressure is less than approximately 300 kPa, rather than the overconsolidation range. Consequently, a series of inter-connected type consolidation tests, in which the frictional pressure loss can be minimized by limiting the thickness of each specimen element, are carried out in order to investigate the scale effect of the specimen thickness in the range of 20-200 mm. The end of primary consolidation (EOP) can be clearly identified in the excess pore pressure dissipation. The law of squared H is essentially valid for the pore water pressure dissipation. However, the EOP becomes unclear in the strains when the specimen thickness decreases. The compressive strain at the EOP stays constant or slightly increases with the specimen thickness.
  • Yoichi Watabe, Shinji Sassa
    MARINE GEOLOGY 252 3-4 79 - 88 2008年07月 [査読有り][通常論文]
     
    Intertidal flats are key elements in marine environments; they consist of regions with rich bioactivity and also contribute to water purification. Recently, it has been demonstrated that benthic activities in intertidal flats are closely related to geoenvironmental characteristics. The purpose of this study is to investigate the tidal flat stratigraphy which should be strongly affected by the geoenvironmental characteristics. We examined the shear wave velocity/stiffness structures of intertidal flats by a surface wave method called the multichannel analysis of surface waves (MASW) in order to identify and describe the cross-shore and alongshore tidal flat stratigraphy. Field surveys were carried out on a natural sandflat, natural mudflat, and artificial layered sand-mud flat during the spring tides in summer when these flats were exposed. The MASW has proved to be a very useful method to effectively survey the stratigraphy of various types of intertidal flats. This method is widely acceptable to nature because it does not have any harmful impacts. The tidal flat stratigraphy obtained by the MASW was consistent with the morphological soil structures that manifested themselves under relevant geoenvironmental dynamics. In the sandflat, the formation of stratigraphy obtained by the MASW (as distributions of the shear wave velocity/stiffness) and by soil sampling and physical soil tests (as distributions of the void ratio) can be attributed to the cyclic elastoplastic contraction of the soils that are subjected to various suction dynamics under tide-induced groundwater table fluctuations. In the mudflat, although a variation in the void structure was observed in association with grain size distributions, the soil stiffness was extremely homogeneous because suction did not occur in the soil. In the small-scale artificial layered sand-mud flat, which contained dredged muddy soil with a sand capping, the artificially layered tidal flat stratigraphy was clearly identified by the MASW. The groundwater table dynamics were equivalent to those in the natural large-scale sandflat, indicating that the geoenvironmental characteristics were successfully recreated, even though it had a layered sand-mud stratigraphy. (C) 2008 Elsevier B.V. All rights reserved.
  • Shinji Sassa, Yoichi Watabe
    Journal of Geophysical Research: Earth Surface 112 1 2007年03月24日 [査読有り][通常論文]
     
    In this paper we present and discuss the role of the dynamics of suction, that is, negative pore water pressure relative to atmospheric air pressure, in the evolution of intertidal sandy flats. This is done through the combined use of field evidence, laboratory experiments, and a theoretical model. Field observations were performed in the estuary of Obitsu River located in the east coast of Tokyo Bay, Japan. Laboratory experiments were performed in a calibration chamber as well as in a laterally scaled model flat subjected to water/groundwater level variations. The present study demonstrates that the suction dynamics associated with the tide-induced groundwater level variations play a substantial role in the temporospatial evolutions of voids, stiffness, and surface shear strength in cyclically exposed and submerged soil. The suction-induced void state changes are a consequence of cyclic elastoplastic contraction of the soil and are accompanied by distinct morphological changes, despite the lack of significant surface shear stresses acting on the soil. Such soil behavior occurs in regions where suction develops above the groundwater level during low tides and strongly depends on the way in which such suction develops. Discussions are made on how these suction dynamics effects could contribute, via feedback involved in surface transport processes, to the overall morphological evolution of cross-shore intertidal flat soils. Copyright 2007 by the American Geophysical Union.
  • 熊谷 隆宏, 土田 孝, 大坪 政美, 渡部 要一, 五明 美智男, 塩田 耕司
    地盤工学ジャーナル 2 3 223 - 235 The Japanese Geotechnical Society 2007年 
    液性限界を超える高い含水比を持つ軟弱な底泥が,波浪作用により流動化するとき, 周期的な波圧の作用に起因して,引張応力および主応力の回転に伴うせん断応力が地盤内に作用し,亀裂が発生する。スメクタイトを含有する浚渫泥では,変形追随性が高く,亀裂周囲の粘土部の性状は塊状で保持されながら,局所的に発生した亀裂が深度方向に発達していく延性的性質が現れることを明らかにするとともに,これまで,解明されていなかった亀裂の発生による圧密促進メカニズムを実験および解析により解明した。
  • Y Watabe, Y Itou, MS Kang, T Tsuchida
    SOILS AND FOUNDATIONS 44 6 53 - 67 2004年12月 [査読有り][通常論文]
     
    Air-foam treated lightweight geo-material (LGM), which is a mixture of dredged clay, cement, and air-foam, has been developed and utilized for various coastal structures, in order to reduce both overburden stress acting on an underground structure (tunnel, buried pipe, etc.) and lateral earth pressure acting on. a retaining structure (quay wall, seawall, shore protection, etc.). In this study, one-dimensional compression behavior of the LGM was investigated in microscopic point of view with scanning electron microscope, optical CCD digital microscope, color laser 3-D profile microscope and mercury intrusion porosimetry (MIP). Though air-foam bubbles with diameters in a range of 200-500 mum are observed in the microscopic images, these sizes are not well reflected in the pore entrance size distribution by MIP because of the very small pore entrances. In MIP, there are in total three pore groups for LGM as in ranges of greater than 10 mum, 0.5-10 mum, and less than 0.5 mum. The group of the largest size corresponds to the air-foam bubbles, the one of the smallest size corresponds to the intra-pores in aggregates, and the one of the middle size corresponds to the inter-pores between the particle aggregates. When compression pressure increases, the observable air-foam bubbles primarily decreases; then the inter-pores between aggregates slightly decreases under a large compression pressure, but the intra-pores in aggregates do not decrease so much.
  • 上田 正樹, 伊野 同, 山田 耕一, 吉野 久能, 渡部 要一
    地盤工学研究発表会 発表講演集 39 2295 - 2296 公益社団法人 地盤工学会 2004年 
    鋼管矢板継手部に土質系変形追随遮水材を用いた場合について,実海域で施工築造した鋼管矢板壁試験体により遮水性能確認試験を行った。試験の概要と現在までに得られた遮水性能について報告する。 今回の試験結果より,管理型廃棄物処分場の遮水壁に求められる遮水性能が得られていることが確認された。
  • 福田 賢二郎, 上田 正樹, 渡部 要一, 杉原 広晃
    地盤工学研究発表会 発表講演集 39 2267 - 2268 公益社団法人 地盤工学会 2004年 
    底面遮水基盤の存在しない海面管理型廃棄物処分場の建設の際には、底面に遮水基盤を構築し廃棄物を投入しなければならないという構造上の基準が定められている。本論文は、人工的に構築した粘性土の遮水基盤上に廃棄物が投入され、処分場が廃止された後に跡地利用として構造物を建築する際に、打設する基礎杭が人工的に構築した遮水基盤の遮水性能に及ぼす影響について確認した実験の報告である。実験は、1/25、1/5スケールの遮水基盤を実験土槽に作製し、模型杭打設前後での透水量を計測して遮水係数の算出を行ない杭打設による影響を調べた。
  • 池田 昌弘, 喜田 浩, 渡部 要一
    地盤工学研究発表会 発表講演集 39 2291 - 2292 公益社団法人 地盤工学会 2004年 
    遮水性能の向上を目的とし、継手部に溶接を用いたBOX型鋼矢板について、実海域で施工築造したBOX型鋼矢板壁試験体により遮水性能確認試験を行った。試験の概要と現在までに得られた遮水性能について報告する。今回の試験結果より、管理型廃棄物処分場の遮水壁に求められる遮水性能が得られていることが確認された。
  • 木下 雅敬, 鳥崎 肇一, 瀬尾 彰, 渡部 要一
    地盤工学研究発表会 発表講演集 39 2293 - 2294 公益社団法人 地盤工学会 2004年 
    遮水性能向上を目的とし、あらかじめアスファルトを充填した鋼管矢板継手について,実海域で施工築造した鋼管矢板壁試験体により遮水性能確認試験を行った。試験の概要と現在までに得られた遮水性能について報告する。今回の試験結果より管理型廃棄物処分場の遮水壁に求められる遮水性能が得られていることが確認された。
  • 岡 由剛, 沖 健, 小澄 省三, 渡部 要一
    地盤工学研究発表会 発表講演集 39 2285 - 2286 公益社団法人 地盤工学会 2004年 
    遮水性能向上を目的とした継手に空隙部を有する遮水用鋼矢板について,実海域で施工築造した鋼矢板壁試験体により遮水性能確認試験を行った。試験の概要と現在までに得られた遮水性能について報告する。今回の試験結果より,管理型廃棄物処分場の遮水壁に求められる遮水性能が得られていることが確認された。
  • 渡部 要一, 山田 耕一, 吉野 久能, 鳥崎 肇一, 沖 健, 喜田 浩
    地盤工学研究発表会 発表講演集 39 2297 - 2298 公益社団法人 地盤工学会 2004年 
    海面処分場の鉛直遮水工の開発・提案が進められてきたが,これまでは,室内における要素レベルでの遮水性能の評価が多かった.しかし,鉛直遮水工の多くは,陸上に比べて難しい海上での施工となることから,実海域における施工性ならびに遮水性能の評価は,工法の信頼性を評価する上で重要である.本研究では,鋼(管)矢板による遮水壁を構築するために,膨潤性遮水材,膨潤性ゴム,粘土系遮水材,アスファルト,モルタル,溶接等を組み合わせた新しい工法について,施工性と遮水性能を評価するために実海域での実証実験を行った.本報では,実海域実証実験の概要について示し,今後の成果の活用方法などについて取りまとめる.
  • 鳥崎 肇一, 岡 由剛, 喜田 浩, 柿本 龍二, 渡部 要一
    地盤工学研究発表会 発表講演集 39 2289 - 2290 公益社団法人 地盤工学会 2004年 
    遮水性能向上を目指した改良継手(漏洩防止ゴム板付き継手)を持つ鋼管矢板について,実海域で施工築造した試験体により遮水性能確認試験を行った。試験の概要と現在までに得られた遮水性能について報告する。今回の試験結果より本工法について管理型廃棄物処分場の遮水壁に求められる遮水性能が得られていることが確認された。
  • 新舎 博, 渡部 要一, 合川 聖二郎, 谷口 利久
    地盤工学研究発表会 発表講演集 39 751 - 752 公益社団法人 地盤工学会 2004年 
    港湾・空港において、気泡混合処理土の施工が数多く実施されている。気泡混合処理土は原料土の含水比を調整して調整泥土を作製し、次に固化材と事前発泡させた気泡を混合して作製するものである。 本文は、こうした施工事例の中から、原料土が細粒土系の設計配合について整理し、考察したものである。その結果、(1)調整泥土の含水比は液性限界の約2.8倍に調整している事例が多いこと、(2)設計強度の確保においては、気泡混合処理土内の水量と気泡量を加えた間隙量が重要な要因の1つであること、(3)設計強度が200kN/m2以上の確保において、固化材添加量は約80~150kg/m3の範囲にあること、などが明らかとなった。
  • 竹村 知子, 渡部 要一
    地盤工学研究発表会 発表講演集 39 295 - 296 公益社団法人 地盤工学会 2004年 
    粘土の微視的構造に関する研究において,近年,電子顕微鏡(SEM)による画像観察が活用されるようになった.しかし,高倍率で特定の対象物を観察したSEM画像では,その土の微視的な構造全体を代表しているとは言い難い.本研究では,大阪湾の海底(深度約20mと105m)から採取した(それぞれの長さ0.8mのサンプラー1本分ずつ)乱さない試料について,長さ25mmにつき8ヶ所ずつ計256ヶ所,倍率500~5000の4画像ずつ合計1024画像をSEMによって観察し,Scion Imageを用いて画像解析を行った.Scion Imageでは画像の濃さを256階調で表し,あるしきい値を設定して二値化することによって白黒の比率を求める.各観察倍率での白黒の比率の変化をばらつきを考慮して求め,対象とした粘土の代表的な構造を観察する場合の倍率の上限について考察した.
  • 山田 耕一, 鵜飼 亮行, 伊野 同, 土田 孝, 渡部 要一
    海洋開発論文集 19 177 - 182 Japan Society of Civil Engineers 2003年 
    In recent year, the capacity of the disposal space of waste is running short. Accordingly, construction of new disposing site is needed.
    The standard of impervious structure about a disposal site was defined by the law 1999. However, with the past technology about impervious sea wall, it is very difficult to construct this type of structure meeting this law. Then, we proposed new structure and material about impervious sea wall, which maintains the performance of water interception over long period. This research paper reports the result of the field experiment about impervioussea wall structure with clayey water interception material.
  • 木村 誠, 今井 五郎, 上野 一彦, 土田 孝, 渡部 要一
    地盤工学研究発表会 発表講演集 38 2417 - 2418 公益社団法人 地盤工学会 2003年 
    近年,廃棄物処分場用地を陸域に確保することが困難になっており,海面埋立型の廃棄物処分場に期待が寄せられている.そこで海域に建設される管理型廃棄物処分場の底面遮水に着目し,土質材料を用いて廃棄物荷重による圧密に伴う止水性を実験的に検討した.配合設計の確立を困難にしている原因は,配合ごとに異なるe-logk関係が存在するというその関係の一般性の欠如にある.本研究では正規化間隙比によって透水係数との配合によらない一義的な関係(e/eL-logk)を得た.その関係を用いて,現場の初期応力状態に基づく簡易的な配合設計方法を構築した.
  • 上野 一彦, 渡部 要一, 斎藤 邦夫, 土田 孝, 山田 耕一
    地盤工学研究発表会 発表講演集 38 2419 - 2420 公益社団法人 地盤工学会 2003年 
    浚渫粘土を母材料とした遮水材料の開発が行われているが,一般に砂分含有量のばらつきが見られる.また,砂分の含有は流動性を高くして施工性を高めると同時に,圧密による体積収縮を小さくするために,積極的に砂分を添加する可能性も考えられる.そこで,砂分含有量が遮水性能に与える影響を明らかにする必要があることから,浚渫粘土に砂を加えた砂分含有量調整土に対して,砂分含有量の変化が圧縮性や遮水性に与える影響について圧密試験を通じて検討を行った.その結果,砂や比較的大きなシルト分が,粘土のマトリックスの中に骨格を形成することなく浮いている程度であれば,砂分含有量の増加は間隙比を小さくして圧密沈下抑制に寄与し,かつ遮水性にはほとんど影響しないことが明らかとなった.なお,実験した材料では,名古屋粘土:新潟砂の比率が10:20で砂が骨格を形成し始めており,このとき粘土分含有量(0.005mm以下)は16%,砂分含有量(0.075mm以上)は70%であった.
  • 山田 耕一, 上野 一彦, 羽田 晃, 土田 孝, 渡部 要一
    海洋開発論文集 18 77 - 82 Japan Society of Civil Engineers 2002年 
    The standard of impervious structure were specified with the law about a disposal site revisedin 1999. However, with the past material and method, it cannot respond enough. Then, we are grappling with development of a impervious material and a impervious method and a impervious structure newer than several year before. This paper explains the new deformation following impervious material and the new impervious structure.
  • 上野 一彦, 山田 耕一, 羽田 晃, 土田 孝, 渡部 要一, 長江 泰史, 桑原 蒸二
    地盤工学研究発表会 発表講演集 37 2427 - 2428 公益社団法人 地盤工学会 2002年
  • 羽田 晃, 山田 耕一, 上野 一彦, 土田 孝, 渡部 要一, 阿部 勝久
    地盤工学研究発表会 発表講演集 37 2429 - 2430 公益社団法人 地盤工学会 2002年
  • H Tanaka, KK Hamouche, M Tanaka, Y Watabe, S Leroueil, Fournier, I
    GEOTECHNICAL SITE CHARACTERIZATION, VOLS 1 AND 2 439 - 444 1998年 [査読有り][通常論文]
     
    The Japanese fixed piston sampler has been tested in a sensitive Champlain sea clay deposit. A series of laboratory tests has been performed on samples obtained with this sampler and the results are compared with those of similar tests performed on samples taken with the Laval sampler used with two different procedures: the conventional and the modified. It appears that the Japanese sampling technique provides sample quality similar to the conventional Laval sampling and slightly lower than the modified Laval technique.

作品等

  • 設置回収型ドレーン工法の開発に関する研究
    2002年 -2004年
  • 軟弱地盤における安定・変形解析手法の高度化に関する研究
    2002年 -2004年
  • 鋼製護岸の遮水性能に関する研究
    2002年 -2003年
  • 海面における管理型廃棄物最終処分場の遮水工法の開発に関する研究
    2001年 -2003年
  • 年代効果を有する洪積粘土の力学特性に関する研究
    1997年

その他活動・業績

  • 棚谷 灯子, 所 立樹, 渡部 要一, 桑江 朝比呂 港湾空港技術研究所報告 = Report of the Port and Airport Research Institute 57 (2) 3 -5,7-33 2018年06月
  • 渡部 要一, 金子 崇, 佐々 真志 港湾空港技術研究所報告 = Report of the Port and Airport Research Institute 55 (3) 3 -19 2016年09月
  • 渡部 要一, 金子 崇, 佐々 真志 港湾空港技術研究所報告 55 (2) 61 -74 2016年06月
  • Yoichi Watabe, Kunio Saitoh SOILS AND FOUNDATIONS 56 (2) 325 -326 2016年04月 [査読無し][通常論文]
  • Y. Nakata, Y. Watabe Geomechanics from Micro to Macro, Vols I and II 281 -284 2015年 [査読無し][通常論文]
     
    This paper presents one dimensional compression behaviour of the assembly containing cylindrical crushable gravels modeled by DEM. The DEM gravels were represented as the agglomerate of spherical elements as forming cylindrical shape. A degraded bonding was introduced in order to provide the variability of stiffness and strength. The assemblies of DEM cylindrical gravels were applied to one dimensional compression. The compression behaviour was discussed on three effects such as cylindrical geometry, sedimentation condition and gravels contents over stress level with crushing.
  • 渡部 要一, 菊池 喜昭, 新舎 博 地盤工学シンポジウム論文集 地盤工学会 編 59 675 -680 2014年
  • 佐々 真志, 渡部 要一, 梁 順普, 桑江 朝比呂 地盤工学会誌 62 (8) 48 -48 2014年
  • 渡部 要一, 佐々 真志 基礎工 = The foundation engineering & equipment, monthly : 土木・建築基礎工事と機材の専門誌 41 (9) 90 -92 2013年09月
  • 渡部 要一, 佐々 真志 地盤工学会誌 = / the Japanese Geotechnical Society 61 (8) 49 -49 2013年08月01日
  • Yoichi Watabe, Kaoru Udaka, Yukio Nakatani, Serge Leroueil SOILS AND FOUNDATIONS 53 (2) 360 -362 2013年04月 [査読無し][通常論文]
  • Ecological Geotechnics
    Sassa, S, Watabe, Y, Yang, J, Kuwae, T ISSMGE Bulletin 7 (3) 23 -33 2013年 [査読無し][通常論文]
  • 梁 順普, 佐々 真志, 渡部 要一 土木学会論文集. B2, 海岸工学 67 (2) 986 -990 2011年
  • 渡部 要一, 佐々 真志, 山田 文彦 土木学会論文集. B2, 海岸工学 67 (2) 1361 -1365 2011年
  • 渡部 要一, 佐々 真志, 桑江 朝比呂 港湾空港技術研究所報告 49 (3) 157 -196 2010年09月
  • 佐々 真志, 渡部 要一 地盤工学会誌 = / the Japanese Geotechnical Society 58 (1) 48 -49 2010年01月01日
  • 佐々 真志, 梁 順普, 渡部 要一, 梶原 直人, 高田 宜武 土木学会論文集B2(海岸工学) 66 (1) 1126 -1130 2010年 [査読無し][通常論文]
     
    Benthos such as Amphipoda living in coastal sandy sediments are important food organisms for fish, but, factors controlling their distributions remain poorly understood. Here, we aim to solve this question by introducing our new approach encompassing ecology, geophysics and hydraulics / geotechnics. We performed sets of integrated observations / surveys and analyses concerning the in situ intertidal geoenvironments and the benthos distributions at three natural coasts. The results demonstrate that the waterfront suction governs the variety of the habitat environments, involving a range of the degree of saturation, stiffness and void state, and the manifestation of the peak and critical area of densities for the three dominant species are uniquely determined by the magnitudes of such suction which are found to be particular to species throughout the coasts. These findings will effectively contribute to the conservation and management of fishery resources at sandy coasts.
  • Yoichi Watabe, Shinji Sassa Geotechnical Special Publication (210) 1013 -1022 2010年 [査読無し][通常論文]
     
    A significant development of sandbars can be seen at the entrance of Lake Tofutsu, one of the lagoons located along the Okhotsk Sea in Hokkaido, Japan. The purpose of this study is to investigate the sequential sedimentation history of these sandbars. We examined the shear-wave velocity and stiffness structures of these sandbars using a surface wave method called the multichannel analysis of surface waves (MASW) in order to identify and describe the stratigraphy of the sediments at the entrance of Lake Tofutsu. We discovered that even though the sandbars appear to be composed of the same sandy material, the subsoil under the sandbars has a very varied sedimentation stratigraphy, consisting of muddy soil derived from the upstream of the lake and sandy soil derived from the coastal sand of the Okhotsk Sea. On the basis of the shear-wave velocity structure obtained in this study, we successfully determined the sequential sedimentation process. © 2010 American Society of Civil Engineers.
  • Yoichi Watabe, Kaoru Udaka, Masaki Kobayashi, Takechiho Tabata, Tsuyoshi Emura SOILS AND FOUNDATIONS 49 (5) 824 -825 2009年10月 [査読無し][通常論文]
  • 渡部 要一, 田中 政典, 佐々 真志 港湾空港技術研究所報告 48 (2) 83 -101 2009年06月
  • 佐々 真志, 渡部 要一, 桑江 朝比呂 海岸工学論文集 55 1171 -1175 2008年10月
  • 触り心地の本質, 特集「港の五感」を科学する
    渡部要一 港湾, 日本港湾協会 Vol.85 (1月号) 2008年 [査読無し][通常論文]
  • 港湾・空港の維持管理・更新技術
    渡部要一 土と基礎 Vol.56 (No.2) 8 -11 2008年 [査読無し][通常論文]
  • Sassa, S, Watabe, Y Marine Ecology Progress Series Vol.354 191 -199 2008年 [査読無し][通常論文]
  • 渡部要一, 佐々真志 土木学会論文集B Vol.64 (No.1) 24 -29 2008年 [査読無し][通常論文]
     
    本研究では,任意時刻に低空で自律飛行できる小型のUAV(無人飛行機)を活用し,搭載した小型デジタルカメラで撮影した航空写真により干潟微地形を効率的に時空間評価する手法を開発し,その適用性を検討した.干潟の水際近傍の水面は,波浪の影響が極めて小さく穏やかであることが特徴である.このような特徴を活かし,高分解能な低空からの航空写真撮影で潮位とともに変化する水際線を捉えることにより,きわめて平坦な干潟地盤の微地形を効率的かつ精密に把握できることがわかった.高分解能な航空写真が得られれば底生生物の巣穴やその密度等をも捉えることができ,干潟微地形と干潟の動植物とを関連づけるような研究においても今後の活用が期待できる.
  • Shinji Sassa, Yoichi Watabe MARINE ECOLOGY PROGRESS SERIES 354 191 -199 2008年 [査読無し][通常論文]
     
    The role of physical processes in sediments in the response of macroinfauna remains largely unknown, in contrast to the role of waves and swash conditions. This study was motivated by our recent finding on the physics involved in intertidal sediments and aims to explore the link between geophysics and ecology. Field observations were performed on an intertidal sand flat on the east coast of Tokyo Bay, Japan. The results indicate that the development of suction (s), i.e. negative pore water pressure relative to atmospheric air pressure, was closely linked to the behaviour of the sand bubbler crab Scopimera globosa (Crustacea: Ocypodidae) and was the trigger responsible for the onset of its burrowing activity. Three series of laboratory burrowing experiments were performed by simulating the relevant geophysical environment prevailing in the intertidal flat sediment. The results demonstrate that the burrowing performance of S. globosa depended strongly on the state of s in association with the groundwater level. Notably, under a given sediment porosity, burrows started to develop and reached peak depth when s was present initially, but declined rapidly with increased s. The effective cohesion and stiffness of the sediment produced by the s were responsible for the manifestation of the threshold, optimum, and critical conditions for the development of the burrows. The present results imply that the s and related geophysical environmental conditions may have an important contribution to the natural selection of habitats of macroinfauna in intertidal zones.
  • Takashi Tsuchida, Yi Xin Tang, Yoichi Watabe SOILS AND FOUNDATIONS 47 (4) 731 -748 2007年08月 [査読無し][通常論文]
     
    An artificial lightweight soil has been developed as a backfill to reduce the earth pressure behind port and harbor structures. To reduce the unit weight lightening ingredient such as air foam or EPS beads is mixed within slurry of dredged soft clay, while cement is used as stabilizer to warrant compressive strength. This experimental study aims to characterize the strength and deformation properties of lightweight treated soil cured in water pressure. Samples of two types of lightweight treated soil mixed with air foam or EPS were cured under various pressures, and subjected to undrained shearing tests on triaxial apparatus modified to detect volumetric change. Though high pressures inevitably compress lightener and consequently incur increment in unit weight, pressured curing did not reduce the compressive strength, q(max) = (sigma(a) - sigma(c))(max). It was also found that the deformation modulus E-50 greatly decreases with relative confining pressure sigma(c)/sigma(max). The lightweight soils maintained relatively large residual strengths, showing no significant sign of brittle failure as often confronted in unconfined compression test. It was observed that the critical state line exists when subjected to ultimate strains, and that the peak deviator stress envelop was identified in effective stress path plane for air foam mixed cases alone. K-0-consolidation tests were conducted on modified triaxial apparatus, showing that K-0 values from the quasi one dimensional tests decline to as small as 0.1 to 0.15 around axial strain of 0.5 similar to 1% at near yielding points. Poisson's ratios based on both undrained shearing and K-0-consolidation are compared in consistent tendency with minimal values of 0.1 to 0.2 near the identical yielding points. Yet it is revealed from the obtained compression curves that the compressibility increases drastically by some 100-fold when comparing before and after yielding for lightweight treated soil. This fact strikes the importance of not overloading lightweight treated soil by its compressive strength.
  • Yoichi Watabe, Yasunori Shiraishi, Tomohide Murakami, Masanori Tanaka SOILS AND FOUNDATIONS 47 (4) 701 -716 2007年08月 [査読無し][通常論文]
     
    Samples collected from both Holocene and Pleistocene layers in Osaka Bay were examined in this study. The objective of this study is to evaluate variations of soil parameters in a sample length of about one meter. The retrieved samples from EL. (elevation) -37.5 to -38.5 m and from EL. -125.5 to -126.5 m with a length of about one meter were divided into every 25 mm long to trim consolidation specimens. Variations of soil parameters obtained from laboratory tests were evaluated. Clay microfabric was also evaluated by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The clay layers are relatively homogeneous with variation coefficient CV in a range of 0.025 to 0.12 for the consolidation parameters (e, p '(c), C-c and c(v)). CV of void ratio e is only 0.025 to 0.056. In contrast, CV values of the other consolidation parameters are significantly greater than this, but the average is less than 0.1. It can be concluded that CV of soil consolidation parameters for the homogeneous natural clay deposits dealt in this study is less than about 0.1. These variations are mainly influenced by sedimentary environment. Even the soil is said to be homogeneous, because the specimen size for the laboratory tests is sufficiently large in consideration of microscopic heterogeneity obtained from SEM and MIP.
  • Takashi Tsuchida, Yi Xin Tang, Yoichi Watabe SOILS AND FOUNDATIONS 47 (4) 731 -748 2007年08月 [査読無し][通常論文]
     
    An artificial lightweight soil has been developed as a backfill to reduce the earth pressure behind port and harbor structures. To reduce the unit weight lightening ingredient such as air foam or EPS beads is mixed within slurry of dredged soft clay, while cement is used as stabilizer to warrant compressive strength. This experimental study aims to characterize the strength and deformation properties of lightweight treated soil cured in water pressure. Samples of two types of lightweight treated soil mixed with air foam or EPS were cured under various pressures, and subjected to undrained shearing tests on triaxial apparatus modified to detect volumetric change. Though high pressures inevitably compress lightener and consequently incur increment in unit weight, pressured curing did not reduce the compressive strength, q(max) = (sigma(a) - sigma(c))(max). It was also found that the deformation modulus E-50 greatly decreases with relative confining pressure sigma(c)/sigma(max). The lightweight soils maintained relatively large residual strengths, showing no significant sign of brittle failure as often confronted in unconfined compression test. It was observed that the critical state line exists when subjected to ultimate strains, and that the peak deviator stress envelop was identified in effective stress path plane for air foam mixed cases alone. K-0-consolidation tests were conducted on modified triaxial apparatus, showing that K-0 values from the quasi one dimensional tests decline to as small as 0.1 to 0.15 around axial strain of 0.5 similar to 1% at near yielding points. Poisson's ratios based on both undrained shearing and K-0-consolidation are compared in consistent tendency with minimal values of 0.1 to 0.2 near the identical yielding points. Yet it is revealed from the obtained compression curves that the compressibility increases drastically by some 100-fold when comparing before and after yielding for lightweight treated soil. This fact strikes the importance of not overloading lightweight treated soil by its compressive strength.
  • Yoichi Watabe, Yasunori Shiraishi, Tomohide Murakami, Masanori Tanaka SOILS AND FOUNDATIONS 47 (4) 701 -716 2007年08月 [査読無し][通常論文]
     
    Samples collected from both Holocene and Pleistocene layers in Osaka Bay were examined in this study. The objective of this study is to evaluate variations of soil parameters in a sample length of about one meter. The retrieved samples from EL. (elevation) -37.5 to -38.5 m and from EL. -125.5 to -126.5 m with a length of about one meter were divided into every 25 mm long to trim consolidation specimens. Variations of soil parameters obtained from laboratory tests were evaluated. Clay microfabric was also evaluated by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The clay layers are relatively homogeneous with variation coefficient CV in a range of 0.025 to 0.12 for the consolidation parameters (e, p '(c), C-c and c(v)). CV of void ratio e is only 0.025 to 0.056. In contrast, CV values of the other consolidation parameters are significantly greater than this, but the average is less than 0.1. It can be concluded that CV of soil consolidation parameters for the homogeneous natural clay deposits dealt in this study is less than about 0.1. These variations are mainly influenced by sedimentary environment. Even the soil is said to be homogeneous, because the specimen size for the laboratory tests is sufficiently large in consideration of microscopic heterogeneity obtained from SEM and MIP.
  • Takashi Tsuchida, Yi Xin Tang, Yoichi Watabe, Katsumasa Ishikura SOILS AND FOUNDATIONS 47 (2) 219 -235 2007年04月 [査読無し][通常論文]
     
    The bearing capacity for composite breakwater's mound is considered as a problem of foundation stability. Expected displacement due to mound failure under eccentric inclined load by repeating wave forces is estimated. The displacement is calculated by the use of angular motion equation along virtual failure arc, similarly to Newmark's method in earthquake engineering. A computation program, which takes into account various conditions for individual breakwater, was developed. It has been found that the relationship between the expected displacement and the design safety factor of bearing capacity varies with the ratio of breadth to height for the caisson box. If an allowable expected deformation in service life is introduced in breakwater design, it is prospective to reduce caisson breadth especially in the cases of larger breadth height ratios. The program was used in back analysis of case of breakwater failure that occurred in Tomakomai west port. The settlements of caissons, ranging from 7 cm to 45 cm, were observed after a series of typhoons. By using the high wave record, and accounting for the effect of wave force increase due to incompletely armored wave-breaking blocks, the calculated settlements and horizontal displacements were in agreement with the range of deformations observed in spite of considerable scatter.
  • Takashi Tsuchida, Yi Xin Tang, Yoichi Watabe, Katsumasa Ishikura SOILS AND FOUNDATIONS 47 (2) 219 -235 2007年04月 [査読無し][通常論文]
     
    The bearing capacity for composite breakwater's mound is considered as a problem of foundation stability. Expected displacement due to mound failure under eccentric inclined load by repeating wave forces is estimated. The displacement is calculated by the use of angular motion equation along virtual failure arc, similarly to Newmark's method in earthquake engineering. A computation program, which takes into account various conditions for individual breakwater, was developed. It has been found that the relationship between the expected displacement and the design safety factor of bearing capacity varies with the ratio of breadth to height for the caisson box. If an allowable expected deformation in service life is introduced in breakwater design, it is prospective to reduce caisson breadth especially in the cases of larger breadth height ratios. The program was used in back analysis of case of breakwater failure that occurred in Tomakomai west port. The settlements of caissons, ranging from 7 cm to 45 cm, were observed after a series of typhoons. By using the high wave record, and accounting for the effect of wave force increase due to incompletely armored wave-breaking blocks, the calculated settlements and horizontal displacements were in agreement with the range of deformations observed in spite of considerable scatter.
  • Shinji Sassa, Yoichi Watabe JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 112 (F1) F01003 -F01003 2007年02月 [査読無し][通常論文]
     
    [1] In this paper we present and discuss the role of the dynamics of suction, that is, negative pore water pressure relative to atmospheric air pressure, in the evolution of intertidal sandy flats. This is done through the combined use of field evidence, laboratory experiments, and a theoretical model. Field observations were performed in the estuary of Obitsu River located in the east coast of Tokyo Bay, Japan. Laboratory experiments were performed in a calibration chamber as well as in a laterally scaled model flat subjected to water/groundwater level variations. The present study demonstrates that the suction dynamics associated with the tide-induced groundwater level variations play a substantial role in the temporospatial evolutions of voids, stiffness, and surface shear strength in cyclically exposed and submerged soil. The suction-induced void state changes are a consequence of cyclic elastoplastic contraction of the soil and are accompanied by distinct morphological changes, despite the lack of significant surface shear stresses acting on the soil. Such soil behavior occurs in regions where suction develops above the groundwater level during low tides and strongly depends on the way in which such suction develops. Discussions are made on how these suction dynamics effects could contribute, via feedback involved in surface transport processes, to the overall morphological evolution of cross-shore intertidal flat soils.
  • Masanori Tanaka, Yoichi Watabe, Masafumi Miyata, Saiichi Sakajo SOILS AND FOUNDATIONS 47 (1) 131 -139 2007年02月 [査読無し][通常論文]
     
    The 4th runway of Tokyo Haneda International Airport is now under planning. The distributions of weak layer, bearing layer and their engineering characteristics must be clarified to some extent. Prior to detailed foundation investigations leading to for detailed designs and constructions. New soil investigations of boring, sampling and laboratory tests were conducted in this area. Using these data and the past boring data from the database, the whole 3D ground was visualized by the 3D soil layer estimation system, that we have proposed. Subsequently, the 3D ground for the runway could be successfully modeled. This 3D model is very useful to recognize the general soil layer compositions for planning the detailed soil investigations on their test items, depths and numbers. Furthermore, this result is expected to reduce the costs regarding numerical analysis, design and construction.
  • Shinji Sassa, Yoichi Watabe JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 112 (F1) F01003 -F01003 2007年02月 [査読無し][通常論文]
     
    [1] In this paper we present and discuss the role of the dynamics of suction, that is, negative pore water pressure relative to atmospheric air pressure, in the evolution of intertidal sandy flats. This is done through the combined use of field evidence, laboratory experiments, and a theoretical model. Field observations were performed in the estuary of Obitsu River located in the east coast of Tokyo Bay, Japan. Laboratory experiments were performed in a calibration chamber as well as in a laterally scaled model flat subjected to water/groundwater level variations. The present study demonstrates that the suction dynamics associated with the tide-induced groundwater level variations play a substantial role in the temporospatial evolutions of voids, stiffness, and surface shear strength in cyclically exposed and submerged soil. The suction-induced void state changes are a consequence of cyclic elastoplastic contraction of the soil and are accompanied by distinct morphological changes, despite the lack of significant surface shear stresses acting on the soil. Such soil behavior occurs in regions where suction develops above the groundwater level during low tides and strongly depends on the way in which such suction develops. Discussions are made on how these suction dynamics effects could contribute, via feedback involved in surface transport processes, to the overall morphological evolution of cross-shore intertidal flat soils.
  • Masanori Tanaka, Yoichi Watabe, Masafumi Miyata, Saiichi Sakajo SOILS AND FOUNDATIONS 47 (1) 131 -139 2007年02月 [査読無し][通常論文]
     
    The 4th runway of Tokyo Haneda International Airport is now under planning. The distributions of weak layer, bearing layer and their engineering characteristics must be clarified to some extent. Prior to detailed foundation investigations leading to for detailed designs and constructions. New soil investigations of boring, sampling and laboratory tests were conducted in this area. Using these data and the past boring data from the database, the whole 3D ground was visualized by the 3D soil layer estimation system, that we have proposed. Subsequently, the 3D ground for the runway could be successfully modeled. This 3D model is very useful to recognize the general soil layer compositions for planning the detailed soil investigations on their test items, depths and numbers. Furthermore, this result is expected to reduce the costs regarding numerical analysis, design and construction.
  • 渡部要一, 三枝弘幸, 植田智幸, 土田 孝, 御手洗義夫, 新舎 博 土木学会論文集C No.1 (Vol.63) 237 -248 2007年 [査読無し][通常論文]
     
    近年,軽量化によりもたらされる高い付加価値に期待して,気泡混合処理土は沿岸域工事での施工実績を着実に伸ばしている.しかしながら,気泡混合処理土は不適切な現場環境の下では劣化が進行し,甚大な損傷を受ける可能性も有している.本研究では,気泡混合処理土が沿岸域での工事において,本格的に利用された初期の代表事例である神戸港ポートアイランドおよび東京国際空港の護岸工事を取り上げ,劣化の有無を把握するために,打設から約10年間にわたり実施してきた一連の追跡調査結果を取りまとめた.当該事例の気泡混合処理土は沿岸域の実際の現場環境の下で,10年経過した今日でも安定した材料特性が維持されており,かつ,特段の劣化兆候も見られないことを確認し,土木材料として十分な長期耐久性を有していることを実証した.
  • 渡部要一, 植田智幸, 三枝弘幸, 田中政典, 菊池喜昭 土木学会論文集C Vol.63 (No.2) 553 -565 2007年 [査読無し][通常論文]
  • 渡部要一, 木下雅敬, 山田耕一, 沖 健 土木学会論文集C Vol.63 (No.3) 662 -676 2007年 [査読無し][通常論文]
  • 佐々真志, 渡部要一, 川野泰広, 中島謙二郎, 吉田秀樹 海洋開発論文集 23 507 -512 2007年 [査読無し][通常論文]
     
    This paper describes an integrated methodology to evaluate the tidal flat geoenvironments and its application to natural and artificial muddy flats. The proposed methodology enables quantitative assessment of the dynamics of thermal and geophysical environments that were found to vary significantly under given tidal and meteorological conditions. The temporal and spatial variations of suction, void state and surface shear strength of the artificial flat soils were particularly noteworthy, occasionally yielding unfavorable geophysical environments to benthos habitats. The present method may thus provide a rational basis for adaptive geoenvironmental management so as to facilitate the favorable performance of diverse benthos activity.
  • 佐々真志, 渡部要一, 石井嘉一 海岸工学論文集 第54巻 1151 -1155 2007年 [査読無し][通常論文]
     
    In this paper we describe and clarify the mechanisms of water retention dynamics in intertidal sandy flats and beaches. This was done by performing field observations, laboratory experiments and theoretical analyses, which developed in an interactive manner. The combined results demonstrate that the difference in the water retention dynamics for sandy flats and beaches arises from the difference in pore water migrations that take place around air entry suctions for both types of the soils. Furthermore, it is found that for a given sandy soil, there exists a critical ground water level above which the degree of saturation does not decline. Two quantitative index are proposed for assessing and creating such water retention fields. The results obtained can directly apply to the design and management of artificial sandy flats.
  • 佐々真志, 渡部要一 海岸工学論文集 第54巻 1196 -1200 2007年 [査読無し][通常論文]
  • 渡部要一, 佐々真志, 河野健二 海岸工学論文集 第54巻 1166 -1170 2007年 [査読無し][通常論文]
     
    In an area of Buzen Sea intertidal flat, multi-bar-trough structure is developed in both cross-shore direction with a long interval and along-shore direction with a short interval. We carried out geophysical investigation and geotechnical soil tests along the multi-bar-trough structure, and clarified that the softness and the density are closely related to the ground surface profile and water/groundwater level during a period of exposure. Relatively denser and stiffer sedimentary structures at bar regions are consistent with our explanation on the formation mechanism; i. e. denser and stiffer structures are explained as a consequence of accumulated contraction caused by effective stress associated with suction corresponding to a low groundwater level at 0.2 to 0.3m deep from the ground surface during the period of exposure.
  • 渡部要一, 三枝弘幸, 植田智幸, 椎名貴彦, 白石保律, 村上智英 地盤工学ジャーナル Vol.2 (No.4) 311 -318 2007年 [査読無し][通常論文]
  • 水野健太, 土田 孝, 小林正樹, 渡部要一 土木学会論文集C Vol.63 (No.4) 936 -953 2007年 [査読無し][通常論文]
  • Influence of sedimentation process on microfabric of clay deposit
    Watabe, Y, Ishii, H, Kang, M.-S, Saitoh, K Proceedings of the 13th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, Kolkata 97 -100 2007年 [査読無し][通常論文]
  • Influence of sedimentation process on microfabric of clay deposit
    Watabe, Y, Ishii, H, Kang, M.-S, Saitoh, K Proceedings of the 13th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, Kolkata 97 -100 2007年 [査読無し][通常論文]
  • Y Watabe, JP LeBihan, S Leroueil GEOTECHNIQUE 56 (4) 273 -284 2006年05月 [査読無し][通常論文]
     
    A probabilistic model including some previous probabilistic studies is proposed to evaluate hydraulic conductivity from pore entrance size distribution. The model considers multi-pores in series of paths through capillary networks in the soil fabric. The average number of connected pores is a representative value of the fabric, greater than two but not too large. The hydraulic conductivity of three glacial tills from northern Quebec with different grain-size distributions has been examined by horizontal permeability tests in saturated conditions, and suction tests with vertical permeability measurement in unsaturated conditions. The hydraulic conductivity is strongly influenced by compaction conditions corresponding to different microfabrics. The model is applicable not only in saturated conditions but also in unsaturated conditions with different microfabrics.
  • Y Watabe, JP LeBihan, S Leroueil GEOTECHNIQUE 56 (4) 273 -284 2006年05月 [査読無し][通常論文]
     
    A probabilistic model including some previous probabilistic studies is proposed to evaluate hydraulic conductivity from pore entrance size distribution. The model considers multi-pores in series of paths through capillary networks in the soil fabric. The average number of connected pores is a representative value of the fabric, greater than two but not too large. The hydraulic conductivity of three glacial tills from northern Quebec with different grain-size distributions has been examined by horizontal permeability tests in saturated conditions, and suction tests with vertical permeability measurement in unsaturated conditions. The hydraulic conductivity is strongly influenced by compaction conditions corresponding to different microfabrics. The model is applicable not only in saturated conditions but also in unsaturated conditions with different microfabrics.
  • 講座 土構造物のメンテナンス 5. 空港における点検と維持管理
    渡部要一 土と基礎 Vol.54 (No.7) 55 -62 2006年 [査読無し][通常論文]
  • 鋼製壁による遮水構造の性能に関する現地実証実験
    渡部要一, 山田耕一, 沖 健 基礎工 Vol.34 (No.7) 57 -59 2006年 [査読無し][通常論文]
  • 港湾施設の設計・施工における地盤調査計画
    渡部要一, 田中政典 基礎工 Vol.34 (No.8) 21 -24 2006年 [査読無し][通常論文]
  • 地盤環境モニタリングコーンの開発
    渡部要一, 土田 孝, 織田幸伸, 田中政典 基礎工 Vol.34 (No.9) 66 -68 2006年 [査読無し][通常論文]
  • SGM軽量土工法における最近の取組み
    渡部要一 土木技術 Vol.61 (No.10) 53 -58 2006年 [査読無し][通常論文]
  • 鋼製遮水壁の遮水性能と適用性に関する研究
    渡部要一, 吉野久能, 柿本龍二, 山田耕一, 鵜飼亮行, 沖 健, 岡 由剛, 喜田 浩, 永尾直也, 望月 武, 木下雅敬 港湾空港技術研究所資料 (No. 1142) 2006年 [査読無し][通常論文]
  • 佐々真志, 渡部要一 港湾空港技術研究所報告 Vol.45 (No.4) 61 -107 2006年 [査読無し][通常論文]
  • 熊谷隆宏, 上田正樹, 池野勝哉, 渡部要一, 佐々真志 海岸工学論文集 第53巻 436 -440 2006年 [査読無し][通常論文]
     
    干潟の地盤環境の形成過程を解明する上では, 干出と冠水を繰り返す潮間帯における圧密特性を明らかにすることが重要である. 本研究では, 潮間帯における地盤環境の形成過程の解明に向けて, 高透水性の中間砂礫層が存在するような場合の自然干潟をも含む条件を設定し, 潮位変動下の圧密実験を実施した.さらに, Sekiguchi・Ohta (1977) の弾塑性および弾・粘塑性構成則を適用し, 潮汐作用下の圧密挙動を定量的に評価できる有限要素解析手法を提案する. また, 適用性を検証した解析モデルを用いて, 水平排水層が存在する場合に, 堆積粘性土地盤の干潮位からの地盤面の高さが自重圧密沈下特性に与える影響を評価した.
  • 渡部要一, 下迫健一郎, 浅沼丈夫, 稲垣正芳, 諫山太郎 海岸工学論文集 第53巻 821 -825 2006年 [査読無し][通常論文]
     
    防波堤の信頼性設計手法として, 簡易ビショップ法による支持力検討に, Newmarkの方法とモンテカルロシミュレーションを組み込み, マウンドの期待沈下量を算出する手法が提案されている. しかし, 大変形時の計算誤差が大きく, 検証事例も少ないことから, 計算パラメータの整理が不十分な状況にあった. そこで本研究では被災時大変形に対応するために, 合理的な沈下量算出手法となるように改良して耐波安定実験結果に対して適用した結果, 二次元弾塑性変形解析結果とも整合する変形量が得られることがわかった. 設計上の最重要項目である円弧滑りの解析目標安全率として0.8を得るとともに, 3つの被災事例によりその妥当性を検証した.
  • 佐々真志, 渡部要一 海岸工学論文集 第53巻 1061 -1065 2006年 [査読無し][通常論文]
     
    本研究は, 砂質干潟における生態土砂環境場の評価・設計法の開発を目標として, 底生生物の住活動と土砂物理環境の関わりを解明することを目的としている. 具体的には, 盤洲干潟における代表的な巣穴底生生物であるコメツキガニを対象として, 現地動態観測により, 巣穴住活動が地下水位・サクションの動態と密接にリンクしていることを明らかにした. 干潟表層土砂の硬軟や強度の形成に重要な役割を担うサクションと相対密度を制御した一連の室内生物実験により, 巣穴住活動の性能を支配する臨界・最適・限界土砂環境場の存在を見出した. 得られた知見を活用して, 良好な住活動を満足しうる生態土砂環境場の設計を提示した.
  • 渡部要一, 佐々真志 海岸工学論文集 第53巻 1236 -1240 2006年 [査読無し][通常論文]
     
    本研究では, 多様な土質で構成された砂質干潟・泥質干潟・砂泥二層干潟地盤において, 一般的な土質特性の調査に加え, 地球物理学的手法の一つである表面波探査の適用を試みた.その結果, 表面波探査は, 地盤の硬軟を表すせん断波速度の分布を定量的に把握することにより, 干潟地盤の堆積構造を効率的に評価できる有効な手法であることが確認できた.硬軟分布や間隙分布として定量化された干潟土砂堆積構造の形成要因について考察した結果, 波浪や潮汐流を通じて土砂が堆積した後, 潮汐に伴う地下水位変動に起因したサクション動態に基づく土骨格の繰返し弾塑性変形の帰結として, 堆積構造を定量的に説明できることが明らかとなった.
  • ノルウェー・オンソイ粘土の工学的性質
    田中政典, 渡部要一, 亀井健史, 冨田龍三 地盤と建設 Vol.24 (No.1) 35 -42 2006年 [査読無し][通常論文]
  • Physical and theoretical modelling of the dynamics of tidal flat geo-environments with their morphological impacts
    Sassa, S, Watabe, Y Proceedings of the International Conference on Physical Modelling in Geotechnics, Hong Kong 1285 -1290 2006年 [査読無し][通常論文]
  • Seismic performance of anchored sheet pile quay wall
    Watabe, Y, Imamura, S, Hirano, T, Kishi, M, Yamamura, K Proceedings of the International Conference on Physical Modelling in Geotechnics, 6th ICPMG, Hong Kong 1119 -1124 2006年 [査読無し][通常論文]
  • Geotechnical heterogeneity of undisturbed clay samples retrieved from Osaka Bay
    Watabe, Y, Tanaka, M Proceedings of the International Conference on Civil and Environmental Engineering, ICCEE-2006 57 -66 2006年 [査読無し][通常論文]
  • Watabe, Y, Sassa, S Oceans’06, MTS/IEEE, Boston, ISBN: 1-44244-0115-1 6 pages 2006年 [査読無し][通常論文]
  • Soil parameters used in the new design code of port facilities in Japan
    Watabe, Y, Tanaka, M, Kikuchi, Y Proceedings of the International Symposium on New Generation Design Codes for Geotechnical Engineering Practice, TAIPEI2006, ISBN 981-270-382-9, Session VI: Geotechnical Uncertainties and Variabilities 10 pages 2006年 [査読無し][通常論文]
  • Characterization of alluvial deposits in Mekong Delta,
    Takemura, J, Watabe, Y, Tanaka, M Proceedings of the 2nd International Workshop on Characterisation and Engineering Properties of Natural Soils Vol.3 1805 -1829 2006年 [査読無し][通常論文]
  • Physical and theoretical modelling of the dynamics of tidal flat geo-environments with their morphological impacts
    Sassa, S, Watabe, Y Proceedings of the International Conference on Physical Modelling in Geotechnics, Hong Kong 1285 -1290 2006年 [査読無し][通常論文]
  • Seismic performance of anchored sheet pile quay wall
    Watabe, Y, Imamura, S, Hirano, T, Kishi, M, Yamamura, K Proceedings of the International Conference on Physical Modelling in Geotechnics, 6th ICPMG, Hong Kong 1119 -1124 2006年 [査読無し][通常論文]
  • Geotechnical heterogeneity of undisturbed clay samples retrieved from Osaka Bay
    Watabe, Y, Tanaka, M Proceedings of the International Conference on Civil and Environmental Engineering, ICCEE-2006 57 -66 2006年 [査読無し][通常論文]
  • Y. Watabe, S. Sassa OCEANS 2006, VOLS 1-4 728 -+ 2006年 [査読無し][通常論文]
     
    In the present study, we explored the capability of a surface wave method, called here MASW (Multi-channel Analysis of Surface Waves) in evaluating the cross-shore and along shore sedimentary structures of intertidal flats. Field surveys were carried out at sandy, muddy, and sand-mud layered flats, when these flats were exposed during spring tides in summer. The present method has proved very useful to investigate the sedimentary structures of various types of intertidal flats. The formation processes of the intertidal sedimentary structures can be explained as a consequence of cyclic elastoplastic contraction of soils that are subjected to a variety of suction dynamics under the tide-induced ground water table fluctuations.
  • Soil parameters used in the new design code of port facilities in Japan
    Watabe, Y, Tanaka, M, Kikuchi, Y Proceedings of the International Symposium on New Generation Design Codes for Geotechnical Engineering Practice, TAIPEI2006, ISBN 981-270-382-9 (Session VI: Geotechnical Uncertainties and Variabilities) 10 pages 2006年 [査読無し][通常論文]
  • Characterization of alluvial deposits in Mekong Delta,
    Takemura, J, Watabe, Y, Tanaka, M Proceedings of the 2nd International Workshop on Characterisation and Engineering Properties of Natural Soils Vol.3 1805 -1829 2006年 [査読無し][通常論文]
  • 渡部要一 基礎工 Vol. 33 (No.12) 61 -64 2005年 [査読無し][通常論文]
  • 渡部要一 自然災害科学 Vol.24 (No.3) 221 -226 2005年 [査読無し][通常論文]
  • 粘土の強度増加に関する考察と柳井粘土の土質調査結果による検証
    鈴木耕司, 田中洋輔, 安原一哉, 渡部要一 第50回地盤工学シンポジウム論文集 137 -142 2005年 [査読無し][通常論文]
  • 土田 孝, 熊谷隆宏, 池野勝哉, 渡部要一, 五明美智男 海岸工学論文集 第52巻 451 -455 2005年 [査読無し][通常論文]
     
    本研究では, 粘性土地盤の堆積・形成過程の中の影響因子である波浪に着目し, 波浪による粘土地盤の応答や圧密特性を明らかにすることを目的として, 水理模型実験を行った. さらに, 実験で得られた結果を用いて, 底泥上を進行する波の減衰特性を評価すると同時に, 底泥の動的応答, 圧密特性を評価する波浪-底泥の相互作用解析手法を構築した. 実験結果を用いて, 構築した解析手法の適用性の検証を行った結果, 波高減衰, 底泥内の土圧および間隙水圧変動, 含水比およびせん断強度の時間変化を精度良く評価できることが分かった.
  • 佐々真志, 渡部要一 海岸工学論文集 第52巻 981 -985 2005年 [査読無し][通常論文]
     
    自然砂質干潟における干潟地盤内のサクションを核とした土砂物理環境の連動過程を捉えることに世界で初めて成功した. 現地観測結果に基づき, 干出時の地表からの温度蒸発, サクション勾配による水分供給, 土中塩分集積過程が連動した干潟土砂の保水機構を明らかにした. さらに, 沖側水位変動を制御した干潟模型実験と干潟地盤環境動態の理論モデル化/シミュレーションの有機的な連携を通じて, 岸沖方向における地下水面の繰返し変動にともなうサクション動態が, 岸沖干潟地盤の表層構造ならびに微地形の顕著な変化を引き起こすことを明らかにした.
  • Modeling of consolidation characteristics of clays for settlement prediction of Kansai International Airport
    Kobayashi, M, Furudoi, T, Suzuki, S, Watabe, Y Proceedings of the Symposium on Geotechnical Aspects of Kansai International Airport 65 -76 2005年 [査読無し][通常論文]
  • The dynamics of tidal flat geo-environments in an estuary
    Sassa, S, Watabe, Y Proceedings of the 5th International Conference on Coastal Dynamics, American Society of Civil Engineers 12 pages 2005年 [査読無し][通常論文]
  • Geophysical characterization of intertidal sedimentary environments, sand, mud and sand-mud layered flats
    Watabe, Y, Sassa, S Proceedings of International Symposium on Fluvial and Coastal Disasters, ISBN4-9902861-0-3 (Paper No.13) 1 -10 2005年 [査読無し][通常論文]
  • Y. Watabe, K. Saltoh Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering, Vols 1-5 615 -618 2005年 [査読無し][通常論文]
     
    For mixtures of a dredged clay and a sand in various ratios, the compressibility and the hydraulic conductivity were investigated by carrying out the incremental loading consolidation test (oedometer test), scanning electron microscopic observation (SEM), and mercury intrusion porosimetry test (MIP), in consideration of influence of sand fraction on the compressibility and the hydraulic conductivity. The followings were derived as conclusions: If the sandy particles do not make a skeletal structure and each particle independents in the clay matrix, increasing sand fraction contributes to decrease the compressibility, but does not affect on the hydraulic conductivity, under the same overburden stress. In this study, some evidences of sandy skeletal structure were observed in the specimens, whose clay (less than 0.005 mm) and sand (larger than 0.075 mm) fractions are smaller than 16.5% and larger than 68.6%, respectively.
  • Modeling of consolidation characteristics of clays for settlement prediction of Kansai International Airport
    Kobayashi, M, Furudoi, T, Suzuki, S, Watabe, Y Proceedings of the Symposium on Geotechnical Aspects of Kansai International Airport 65 -76 2005年 [査読無し][通常論文]
  • The dynamics of tidal flat geo-environments in an estuary
    Sassa, S, Watabe, Y Proceedings of the 5th International Conference on Coastal Dynamics, American Society of Civil Engineers 12 pages 2005年 [査読無し][通常論文]
  • Geophysical characterization of intertidal sedimentary environments, sand, mud and sand-mud layered flats
    Watabe, Y, Sassa, S Proceedings of International Symposium on Fluvial and Coastal Disasters, ISBN4-9902861-0-3 (Paper No.13) 1 -10 2005年 [査読無し][通常論文]
  • Watabe, Y. and Saitoh, K.
    Proceedings of the, h, International Conference on Soil Mechanics, Geotechnical Engineering, Osaka Influence of sand fraction on compressibility and hydraulic conductivity of clayey soils 615 -618 2005年 [査読無し][通常論文]
  • Tanaka, H, Kang, M.-S, Watabe, Y Soils and Foundations 44 (6) 39 -51 2004年12月 [査読無し][通常論文]
     
    Soil samples were recovered from the Osaka basin, where Holocene as well as Pleistocene marine clays are thickly deposited. It is found from X-ray diffraction analysis that the component of clay minerals for these clay layers is almost identical through all depths. This fact suggests that the origin of these sediments has not been drastically changed through at least more than 1,000,000 years. Using data obtained by oedometer tests, this paper examines ageing effects on consolidation properties. It is found that void ratio for the Pleistocene clays keeps large even under high in situ effective overburden pressure (p'(vo)). Salinity of pore fluid decreases with depth and becomes nearly zero at depths deeper than 70 m. However, the change in salinity does not give any influences on the index properties, suggesting that the relatively large void ratio for the Pleistocene clays is caused by other reasons than leaching. It is also found that the Pleistocene clays reveal no particular differences in consolidation properties, but fundamentally similar to those of Holocene clays. There is no distinguished difference in the overconsolidation ratio (OCR), non-linearity of the e - log p' relation after yield consolidation pressure including the maximum compression index (C-cmax) and the hydraulic conductivity (k). The only prominent difference in the Osaka Pleistocene clays, compared to the Holocene clay, is relatively small void ratio due to the large p'(vo).
  • H Tanaka, MS Kang, Y Watabe SOILS AND FOUNDATIONS 44 (6) 39 -51 2004年12月 [査読無し][通常論文]
     
    Soil samples were recovered from the Osaka basin, where Holocene as well as Pleistocene marine clays are thickly deposited. It is found from X-ray diffraction analysis that the component of clay minerals for these clay layers is almost identical through all depths. This fact suggests that the origin of these sediments has not been drastically changed through at least more than 1,000,000 years. Using data obtained by oedometer tests, this paper examines ageing effects on consolidation properties. It is found that void ratio for the Pleistocene clays keeps large even under high in situ effective overburden pressure (p'(vo)). Salinity of pore fluid decreases with depth and becomes nearly zero at depths deeper than 70 m. However, the change in salinity does not give any influences on the index properties, suggesting that the relatively large void ratio for the Pleistocene clays is caused by other reasons than leaching. It is also found that the Pleistocene clays reveal no particular differences in consolidation properties, but fundamentally similar to those of Holocene clays. There is no distinguished difference in the overconsolidation ratio (OCR), non-linearity of the e - log p' relation after yield consolidation pressure including the maximum compression index (C-cmax) and the hydraulic conductivity (k). The only prominent difference in the Osaka Pleistocene clays, compared to the Holocene clay, is relatively small void ratio due to the large p'(vo).
  • 村上朋子, 竹村次朗, 野坂知正, 渡部要一 第39回地盤工学研究発表会発表講演集 39 153 -154 2004年 [査読無し][通常論文]
     
    ベトナムハイフォンにおいて固定ピストン式(FPS)およびシェルビー式(Shelby)シンフォールサンプリングにより採取した軽く過圧密された粘性土(OCR約2)試料に対して行った一連の圧密試験(標準圧密、定ひずみ試験)の結果、試験機関、サンプリング方法等により圧密特性(e-logp,圧密係数等)に違いが現れた。これについて検討するために、圧密試験前に試料に先行的に圧縮ひずみを与え(軸ひずみ2-4%)、その後圧密供試体を作成し、標準圧密試験を行った。あわせて、初期供試体と圧密リングに隙間を与えた条件でも圧密試験を行い、これらが圧密試験結果に与える影響についても調べた。その結果、4%まででは先行ひずみの影響はFPSサンプルである程度現れるのに対し、Shelbyサンプルではほとんど見られないこと、供試体とリングとの隙間(供試体周辺の乱れ)がe-logpに与える影響が確認にできた。
  • 竹村次朗, BuiTanMan, 渡部要一, 田中政典 第39回地盤工学研究発表会講演概要集 39 155 -156 2004年 [査読無し][通常論文]
     
    ベトナム国ハイフォンにおいて固定ピストン式(FPS)およびシェルビー式(Shelby)シンフォールサンプリングにより軽く過圧密された粘性土(OCR約2)試料を採取し、2種の試料に対して、ベトナム2機関、日本1機関においてに室内試験を実施した。本報告はその共通試験の中の圧密試験結果についてのものである。試験結果から、FPSとShelby試料の差を確認することができたが、それ以上に試験機関の差が大きく現れ、ある機関の結果では圧密降伏応力(Py)が有効土被り圧を下回るといった結果となった。圧密試験時の有効土被り圧までの間隙比変化とpyとの関係を調べるとこの間隙比変化が大きなほどpyが小さくなり、再圧密時の間隙比変化が乱れの指標として有効であることが確認できた。
  • SGM軽量土工法, 特集:軟弱地盤対策
    渡部要一 土木技術 Vol. 59 (No. 8) 93 -99 2004年 [査読無し][通常論文]
  • 渡部要一 基礎工 Vol.32 (No.12) 19 -22 2004年 [査読無し][通常論文]
  • Microscopic evaluation of 1-D compression for air-form treated lightweight geo-material
    Watabe, Y, Itou, Y, Kang, M.-S, Tsuchida, T Proceedings of the A. W. Skempton Memorial Conference 1183 -1192 2004年 [査読無し][通常論文]
  • History of geotechnical database for port and airport construction in Japan
    Watabe, Y, Tanaka, M Proceedings of the International Conference on Engineering Practice and Performance of Soft Deposits, IS-Osaka 2004 409 -414 2004年 [査読無し][通常論文]
  • S. Shibuya, S. Yamashita, Y. Watabe, D. C. F. Lo Presti Geotechnical and Geophysical Site Characterization Vols 1 and 2 167 -185 2004年 [査読無し][通常論文]
     
    Quasi-elastic stiffness (QES) in shear behaviour of geomaterials is discussed. Recent developments in measurement of QES of natural ground by a means of in-situ seismic survey, together with comparable measurement of elastic wave velocities in the laboratory are outlined. Application of combined insitu/lab measurements is discussed with reference to the interlink between QES and strengths, the quality of laboratory sample and the in-situ 'structure' of natural sedimentary clay. Two case records, each demonstrating the importance of in-situ seismic survey are described: these are i) prediction of soft clay ground deformation associated with deep excavation in Bangkok Metro project, and ii) geotechnical site investigation performed at leaning tower of Pisa in September 2003.
  • Y. Watabe, M. Tanaka, J. Takemura Geotechnical and Geophysical Site Characterization Vols 1 and 2 1765 -1772 2004年 [査読無し][通常論文]
     
    A series of site investigations, which consisted of Japanese sampling, piezo-cone penetration test (CPTU), Marchetti's flat dilatometer test (DMT), hydraulic fracture test (HFT) and seismic cone penetration test (SCPT), was carried out at Ariake (Japan), Bangkok (Thailand) and Hai-Phong (Vietnam). A Japanese thin-walled tube sampler with fixed piston was used for the sampling. K-0-consolidation test in a triaxial cell was carried out for the sampled specimens. For representative undisturbed clay samples, K-0-consolidation and K-0-overconsolidation tests (i.e., SHANSEP test) were consecutively carried out to obtain K (stress ratio) - OCR (overconsolidation ratio) relationship. Using the profile of OCR obtained from a series of CRS (constant rate of strain) consolidation tests, a K-value corresponding to the OCR can be evaluated as the in-situ K-0. The K-0-values obtained from SHANSEP test, DMT and HFT are compared well.
  • Microstructure of clay observed by SEM in consideration of specimen preparation method
    Watabe, Y, Hikiyashiki, H, Kang, M.-S, Tanaka, M, Takemura, T Proceedings of the 15th Southeast Asian Geotechnical Conference, Bangkok 21 -26 2004年 [査読無し][通常論文]
  • On the homogeneity of undisturbed clay samples retrieved from Osaka Bay
    Watabe, Y, Takemura, T, Shiraishi, Y, Murakami, T Proceedings of the 57th Canadian Geotechnical Conference/ the 5th Joint IAH-CNC/CGS Conference, Québec Session7E Page 1-8 2004年 [査読無し][通常論文]
  • Watabe, Y, Itou, Y, Kang, M.-S, Tsuchida, T Soils and Foundations 44 (6) 53 -67 2004年 [査読無し][通常論文]
  • Microscopic evaluation of 1-D compression for air-form treated lightweight geo-material
    Watabe, Y, Itou, Y, Kang, M.-S, Tsuchida, T Proceedings of the A. W. Skempton Memorial Conference 1183 -1192 2004年 [査読無し][通常論文]
  • History of geotechnical database for port and airport construction in Japan
    Watabe, Y, Tanaka, M Proceedings of the International Conference on Engineering Practice and Performance of Soft Deposits, IS-Osaka 2004 409 -414 2004年 [査読無し][通常論文]
  • S. Shibuya, S. Yamashita, Y. Watabe, D. C. F. Lo Presti Geotechnical and Geophysical Site Characterization Vols 1 and 2 167 -185 2004年 [査読無し][通常論文]
     
    Quasi-elastic stiffness (QES) in shear behaviour of geomaterials is discussed. Recent developments in measurement of QES of natural ground by a means of in-situ seismic survey, together with comparable measurement of elastic wave velocities in the laboratory are outlined. Application of combined insitu/lab measurements is discussed with reference to the interlink between QES and strengths, the quality of laboratory sample and the in-situ 'structure' of natural sedimentary clay. Two case records, each demonstrating the importance of in-situ seismic survey are described: these are i) prediction of soft clay ground deformation associated with deep excavation in Bangkok Metro project, and ii) geotechnical site investigation performed at leaning tower of Pisa in September 2003.
  • Y. Watabe, M. Tanaka, J. Takemura Geotechnical and Geophysical Site Characterization Vols 1 and 2 1765 -1772 2004年 [査読無し][通常論文]
     
    A series of site investigations, which consisted of Japanese sampling, piezo-cone penetration test (CPTU), Marchetti's flat dilatometer test (DMT), hydraulic fracture test (HFT) and seismic cone penetration test (SCPT), was carried out at Ariake (Japan), Bangkok (Thailand) and Hai-Phong (Vietnam). A Japanese thin-walled tube sampler with fixed piston was used for the sampling. K-0-consolidation test in a triaxial cell was carried out for the sampled specimens. For representative undisturbed clay samples, K-0-consolidation and K-0-overconsolidation tests (i.e., SHANSEP test) were consecutively carried out to obtain K (stress ratio) - OCR (overconsolidation ratio) relationship. Using the profile of OCR obtained from a series of CRS (constant rate of strain) consolidation tests, a K-value corresponding to the OCR can be evaluated as the in-situ K-0. The K-0-values obtained from SHANSEP test, DMT and HFT are compared well.
  • Microstructure of clay observed by SEM in consideration of specimen preparation method
    Watabe, Y, Hikiyashiki, H, Kang, M.-S, Tanaka, M, Takemura, T Proceedings of the 15th Southeast Asian Geotechnical Conference, Bangkok 21 -26 2004年 [査読無し][通常論文]
  • On the homogeneity of undisturbed clay samples retrieved from Osaka Bay
    Watabe, Y, Takemura, T, Shiraishi, Y, Murakami, T Proceedings of the 57th Canadian Geotechnical Conference/ the 5th Joint IAH-CNC/CGS Conference, Québec Session7E Page 1-8 2004年 [査読無し][通常論文]
  • Watabe, Y, Itou, Y, Kang, M.-S, Tsuchida, T Soils and Foundations 44 (6) 53 -67 2004年 [査読無し][通常論文]
  • 渡部 要一, 土田 孝, 山田 耕一, 鵜飼 亮行 土と基礎 = Soil mechanics and foundation engineering 51 (8) 32 -33 2003年08月01日 
    Most wastes from large coastal cities are reclaimed into waste disposal sites in coastal areas, in Japan. Since technologies on seepage control structure have been developed for inland disposal sites, new technologies for coastal disposal sites are strongly demanded. This paper describes characteristic aspects of waste reclamation sites in coastal area and a development of new deformable material for seepage control, which is a mixture of the dredged clay and bentonite. In addition, some influences of sand fraction on the hydraulic conductivity were examined. Finally, the performance of seepage control structure was examined by an experimental proof test in Kure port, Hiroshima, Japan.
  • 土田 孝, 渡部 要一 土と基礎 = Soil mechanics and foundation engineering 51 (3) 37 -38 2003年03月01日
  • 渡部 要一, 田中 政典, 田中 洋行, 土田 孝 地盤工学会論文報告集 = Journal of the Japanese Geotechnical Society : soils and foundation 43 (1) 1 -20 2003年02月15日 
    A series of K_0-consolidation tests in a triaxial cell was carried out for marine clays collected from different areas in the world in order to investigate the behavior during K_0-consolidation tests and evaluate K_0-values that are required for laboratory tests with recompression techniques, FEM analysis using elasto-plastic constitutive equations, etc. It was confirmed that the famous equation K_<0NC> = 1-sinφ' is useful; however, the definition of φ' should be concerned. Inthe case using φ' corresponding to a critical state line, i.e. (q/p)_, the equation underestimates K_<0NC> by 0.05 ; in contrast, in the case using φ' corresponding to a peak strength, i.e. (q)_, the equation overestimates K_<0NC> by 0.05. This study proposes a procedure for estimating the in-situ K_0-value. For a representative undisturbed clay sample, K_0-consolidation and K_0-overconsolidation tests (i.e. SHANSEP test) are consecutively carried out to obtain the K-OCR relationship. Using the profile of OCR obtained from a series of oedometer tests, the K-value corresponding to the OCR can be calculated as the in-situ K_0. The K_0-values obtained from both the K_0-overconsolidation test corresponding to the OCR in the laboratory and the flat dilatometer test (DMT test) in the field compared well.
  • Y Watabe, M Tanaka, H Tanaka, T Tsuchida SOILS AND FOUNDATIONS 43 (1) 1 -20 2003年02月 [査読無し][通常論文]
     
    A series of K-0-consolidation tests in a triaxial cell was carried out for marine clays collected from different areas in the world in order to investigate the behavior during K-0-consolidation tests and evaluate K-0-values that are required for laboratory tests with recompression techniques, FEM analysis using elasto-plastic constitutive equations, etc. It was confirmed that the famous equation K-0NC = 1 - sin phi' is useful; however, the definition of phi' should be concerned. In the case using phi' corresponding to a critical state line, i.e. (q/P)(max), the equation underestimates K-0NC by 0.05; in contrast, in the case using phi' corresponding to a peak strength, i.e. (q)(max), the equation overestimates K-0NC by 0.05. This study proposes a procedure for estimating the in-situ Ko-value. For a representative undisturbed clay sample, K-0-consolidation and K-0-overconsolidation tests (i.e. SHANSEP test) are consecutively carried out to obtain the K-OCR relationship. Using the profile of OCR obtained from a series of oedometer tests, the K-value corresponding to the OCR can be calculated as the in-situ K-0. The K-0-values obtained from both the K-0-overconsolidation test corresponding to the OCR in the laboratory and the flat dilatometer test (DMT test) in the field compared well.
  • Y Watabe, M Tanaka, H Tanaka, T Tsuchida SOILS AND FOUNDATIONS 43 (1) 1 -20 2003年02月 [査読無し][通常論文]
     
    A series of K-0-consolidation tests in a triaxial cell was carried out for marine clays collected from different areas in the world in order to investigate the behavior during K-0-consolidation tests and evaluate K-0-values that are required for laboratory tests with recompression techniques, FEM analysis using elasto-plastic constitutive equations, etc. It was confirmed that the famous equation K-0NC = 1 - sin phi' is useful; however, the definition of phi' should be concerned. In the case using phi' corresponding to a critical state line, i.e. (q/P)(max), the equation underestimates K-0NC by 0.05; in contrast, in the case using phi' corresponding to a peak strength, i.e. (q)(max), the equation overestimates K-0NC by 0.05. This study proposes a procedure for estimating the in-situ Ko-value. For a representative undisturbed clay sample, K-0-consolidation and K-0-overconsolidation tests (i.e. SHANSEP test) are consecutively carried out to obtain the K-OCR relationship. Using the profile of OCR obtained from a series of oedometer tests, the K-value corresponding to the OCR can be calculated as the in-situ K-0. The K-0-values obtained from both the K-0-overconsolidation test corresponding to the OCR in the laboratory and the flat dilatometer test (DMT test) in the field compared well.
  • ベトナム国ハイフォン粘土の工学的性質
    田中政典, 渡部要一, 伊藤康成, 竹村次朗 第58回土木学会年次学術講演会講演概要集 III (1) 341 -342 2003年 [査読無し][通常論文]
  • Y Watabe, A Tanaka, H Tanaka, T Tsuchida SOFT GROUND ENGINEERING IN COASTAL AREAS pp.97-103 97 -103 2003年 [査読無し][通常論文]
     
    In this study, a series of K-0-consolidation tests in a triaxial cell was carried out for marine clays collected from different areas in the world. From the test results, in the case using phi' corresponding to (q/p)(max), the equation K-ONC = 1 - sin phi' proposed by Jaky (1944) underestimates K-ONC by 0.05; in contrast, in the case using phi' corresponding to (q)(max), the equation overestimates K-ONC by 0.05. For a representative undisturbed clay sample, K-0-consolidation and K-0-overconsolidation tests (i.e., SHANSEP test) were consecutively carried out to obtain K - OCR relationship. The K-value corresponding to the OCR can be calculated as the in-situ K-0.
  • Watabe, Y., Tsuchida, T., Kang, M.-S., Saitoh, K., Yamada, K. and Ueno, K.: Influence of sand fraction on the impermeability of seepage control clayey layer
    Proceedings of the 2nd International Symposium on Contaminated Sediments: Characterisation, Evaluation, Mitigation/Restoration, Monitoring and Performance, Québec pp.163-169 2003年 [査読無し][通常論文]
  • MS Kang, Y Watabe, T Tsuchida PROCEEDINGS OF THE THIRTEENTH (2003) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL 2 pp.385-392 385 -392 2003年 [査読無し][通常論文]
     
    This research reviewed and investigated the effect of drying and specimen preparation method for micro-structural observation and pore size distribution measurement according to various soils and test conditions, in utilizing Scanning Electron Microscope(SEM) and Mercury Intrusion Porosimetry(MIP), the major instruments for microscopic studies. Different types of soils, such as slurry state specimen of extremely high water content and reconstituted specimen from Honmoku clay, and undisturbed soils of Ariake and Osaka Pleistocene clays were used. For drying these soils, three types of drying methods such as air, oven and freeze drying were adopted for comparison. Through examining these results, it has been known that inappropriate adoption of drying method may lead to unrighteous understanding on the microstructure of fine-grained soils and that however, different drying method to the same specimen can be adopted on occasions depending on test purposes.
  • Y Watabe Proceedings of the Twelfth Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, Vol 1 and 2 pp.417-420 417 -420 2003年 [査読無し][通常論文]
     
    In Japan, a dredged clayey soil treated with a small quantity of cement has begun to be used to construct the slope of seawall structure. Recently, it has been utilized to an intermediate buffer layer between double-layered seepage control sheets of a waste reclamation landfill. In this study, mechanical characteristics and their variations of the cement treated soil with curing time were investigated by vane shear test, oedometer test, unconfined compression test, and triaxial CIU test. In addition, influences of curing conditions on desiccation crack were investigated. Finally, some practical instructions during the construction were pointed out.
  • Y Watabe, M Tanaka, T Tsuchida, H Tanaka DEFORMATION CHARACTERISTICS OF GEOMATERIALS pp.535-544 535 -544 2003年 [査読無し][通常論文]
     
    Some influences of ageing effect derived from secondary consolidation and cementation are observed in stress-strain relationship for natural clays. in this study, both Louiseville and Osaka Bay Pleistocene clays are dealt as aged and structured natural clays and their mechanical characteristics are investigated. In addition, cement treated soil is dealt as an artificially structured clay, and variation of its mechanical characteristics with curing time is investigated and compared with that of the natural clays. Finally, normalization by consolidation yield stress is attempted and discussed.
  • 渡部要一, 田中政典, 竹村次朗, 澁谷 啓: 国際化と日本の地盤調査技術
    地質と調査 2003年第4号, pp. 8-16 2003年 [査読無し][通常論文]
  • Watabe, Y., Tanaka, M. and Takemura, J.: Field and laboratory tests to evaluate the mechanical characteristics of Hai-Phong clay
    Pre-Proceeding of Hanoi GeoEngineering 2003 (International Workshop on GeoEngineering) pp.63-72 2003年 [査読無し][通常論文]
  • Watabe, Y., Tsuchida, T., Kang, M.-S., Saitoh, K., Yamada, K. and Ueno, K.: Influence of sand fraction on the impermeability of seepage control clayey layer
    Proceedings of the 2nd International Symposium on Contaminated Sediments: Characterisation, Evaluation, Mitigation/Restoration, Monitoring and Performance, Québec pp.163-169 2003年 [査読無し][通常論文]
  • MS Kang, Y Watabe, T Tsuchida PROCEEDINGS OF THE THIRTEENTH (2003) INTERNATIONAL OFFSHORE AND POLAR ENGINEERING CONFERENCE, VOL 2 pp.385-392 385 -392 2003年 [査読無し][通常論文]
     
    This research reviewed and investigated the effect of drying and specimen preparation method for micro-structural observation and pore size distribution measurement according to various soils and test conditions, in utilizing Scanning Electron Microscope(SEM) and Mercury Intrusion Porosimetry(MIP), the major instruments for microscopic studies. Different types of soils, such as slurry state specimen of extremely high water content and reconstituted specimen from Honmoku clay, and undisturbed soils of Ariake and Osaka Pleistocene clays were used. For drying these soils, three types of drying methods such as air, oven and freeze drying were adopted for comparison. Through examining these results, it has been known that inappropriate adoption of drying method may lead to unrighteous understanding on the microstructure of fine-grained soils and that however, different drying method to the same specimen can be adopted on occasions depending on test purposes.
  • Watabe, Y.: Utilization of dredged soil treated with small quantity of cement for waste reclamation landfill
    Proceedings of the 12th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, Singapore pp.417-420 2003年 [査読無し][通常論文]
  • Y Watabe, M Tanaka, T Tsuchida, H Tanaka DEFORMATION CHARACTERISTICS OF GEOMATERIALS pp.535-544 535 -544 2003年 [査読無し][通常論文]
     
    Some influences of ageing effect derived from secondary consolidation and cementation are observed in stress-strain relationship for natural clays. in this study, both Louiseville and Osaka Bay Pleistocene clays are dealt as aged and structured natural clays and their mechanical characteristics are investigated. In addition, cement treated soil is dealt as an artificially structured clay, and variation of its mechanical characteristics with curing time is investigated and compared with that of the natural clays. Finally, normalization by consolidation yield stress is attempted and discussed.
  • Watabe, Y., Tanaka, M. and Takemura, J.: Field and laboratory tests to evaluate the mechanical characteristics of Hai-Phong clay
    Pre-Proceeding of Hanoi GeoEngineering 2003 (International Workshop on GeoEngineering) pp.63-72 2003年 [査読無し][通常論文]
  • 姜 敏秀, 渡部 要一, 土田 孝 港湾空港技術研究所資料 (1032) 1 -25 2002年12月
  • 土田 孝, 渡部 要一, 織田 幸伸 港湾空港技術研究所資料 (1025) 1 -96 2002年06月
  • 土田 孝, 渡部 要一, 姜 敏秀 港湾空港技術研究所報告 41 (2) 45 -91 2002年06月
  • Watabe, Y., Tsuchida, T. and Adachi, K.: Undrained shear strength of Pleistocene clay in Osaka Bay.
    Journal of Geotechnical and Geoenvironmental Engineering, ASCE Vol.128, No.3, pp.216-226 2002年 [査読無し][通常論文]
  • Watabe, Y., Tsuchida, T., Imamura, S. and Satoh, T.: Stability of quay wall backfilled by lightweight geo-material during earth quake.
    Proceedings of the International Conference on Physical Modelling in Geotechnics, St-John’s pp.435-440 2002年 [査読無し][通常論文]
  • Watabe, Y., Tsuchida, T., Tanaka, M., Oda, Y. and Sakai, Y.: Geo-environmental cone penetrometer with efficient ground water sampling.
    Proceedings of the 4th International Congress on Environmental Geotechnics, Rio de Janeiro pp. 71-76 2002年 [査読無し][通常論文]
  • 渡部要一, 土田 孝, 斎藤邦夫, 山田耕一, 上野一彦: 粘土係遮水材料における微視構造と透水係数の関係.
    第47回地盤工学シンポジウム論文集 pp.381-388 2002年 [査読無し][通常論文]
  • 渡部要一, 土田 孝, 山縣延文, 今村眞一郎, 加藤繁幸: 軽量混合処理土を用いた護岸構造物の地震時安定性
    第11回日本地震工学シンポジウム論文集 pp.999-1002 2002年 [査読無し][通常論文]
  • Kang, M.S., Watabe, Y. and Tsuchida, T.: Effect of drying and preparation method on microscopic analysis on Pleistocene clays using mercury intrusion porosimetry
    Proceedings of the International Symposium on Soft Ground Engineering in Coastal Areas, Nakase Memorial Symposium, Yokosuka pp.73-78 2002年 [査読無し][通常論文]
  • Yamada, K., Ueno, K., Hada, A., Tsuchida, T., Watabe, Y. and Imai, G.: Development of clayey water interception material in a coastal disposal site
    Proceedings of the International Symposium on Soft Ground Engineering in Coastal Areas, Nakase Memorial Symposium, Yokosuka pp.193-200 2002年 [査読無し][通常論文]
  • Tsuchida, T., Watabe, Y., Yuasa, H. and Oda, Y.: Construction of seawall for waste landfill in Tachibana Port
    Proceedings of the International Symposium on Soft Ground Engineering in Coastal Areas, Nakase Memorial Symposium, Yokosuka pp.345-352 2002年 [査読無し][通常論文]
  • Watabe, Y., Tsuchida, T. and Adachi, K.: Undrained shear strength of Pleistocene clay in Osaka Bay
    Journal of Geotechnical and Geoenvironmental Engineering, ASCE Vol.128, No.3, pp.216-226 2002年 [査読無し][通常論文]
  • Watabe, Y., Tsuchida, T., Imamura, S. and Satoh, T.: Stability of quay wall backfilled by lightweight geo-material during earthquake.
    Proceedings of the International Conference on Physical Modelling in Geotechnics, St-John’s pp.435-440 2002年 [査読無し][通常論文]
  • Watabe, Y., Tsuchida, T., Tanaka, M., Oda, Y. and Sakai, Y.: Geo-environmental cone penetrometer with efficient ground water sampling.
    Proceedings of the 4th International Congress on Environmental Geotechnics, Rio de Janeiro pp. 71-76 2002年 [査読無し][通常論文]
  • Watabe, Y., Tanaka, M., Tanaka, H. and Tsuchida, T.: Evaluation of in-situ lateral earth pressure at rest for marine clay by means of triaxial cell
    Proceedings of the International Symposium on Soft Ground Engineering in Coastal Areas, Nakase Memorial Symposium, Yokosuka pp.97-103 2002年 [査読無し][通常論文]
  • Kang, M.S., Watabe, Y. and Tsuchida, T.: Effect of drying and preparation method on microscopic analysis on Pleistocene clays using mercury intrusion porosimetry
    Proceedings of the International Symposium on Soft Ground Engineering in Coastal Areas, Nakase Memorial Symposium, Yokosuka pp.73-78 2002年 [査読無し][通常論文]
  • Yamada, K., Ueno, K., Hada, A., Tsuchida, T., Watabe, Y. and Imai, G.: Development of clayey water interception material in a coastal disposal site
    Proceedings of the International Symposium on Soft Ground Engineering in Coastal Areas, Nakase Memorial Symposium, Yokosuka pp.193-200 2002年 [査読無し][通常論文]
  • Tsuchida, T., Watabe, Y., Yuasa, H. and Oda, Y.: Construction of seawall for waste landfill in Tachibana Port
    Proceedings of the International Symposium on Soft Ground Engineering in Coastal Areas, Nakase Memorial Symposium, Yokosuka pp.345-352 2002年 [査読無し][通常論文]
  • H Tanaka, DR Shiwakoti, O Mishima, Y Watabe, M Tanaka SOILS AND FOUNDATIONS 41 (4) 73 -87 2001年08月 [査読無し][通常論文]
     
    A site investigation program was carried out at the Yamashita site, Yokohama, Japan, by means of laboratory as well as field tests. It was found from the investigation that the clayey layer is overconsolidated with an OCR of about 2.0. It is evident from geological consideration that this overconsolidation may not have been caused by stress change, but was probably due to structure effects such as cementation or delayed consolidation. The physical and mechanical properties of the Yamashita clay is compared with those of Louiseville clay, a Champlain Sea Clay widely distributed in Quebec, eastern Canada, and a well known cemented clay. Louiseville clay was retrieved by Japanese sampler and transported to the Port and Harbour Research Institute (PHRI) for laboratory investigation. Comparison of the two clays shows that strength properties such as the stress-strain curve or stress path for both clays are very similar to each other. However, the pattern of the e-log p curve measured by Constant Rate of Strain oedometer, particularly beyond the yield consolidation pressure, is remarkably different between the two clays.
  • Y Watabe, T Tsuchida SOILS AND FOUNDATIONS 41 (4) 17 -24 2001年08月 [査読無し][通常論文]
     
    A data set of unconfined compression strengths of Osaka Bay Pleistocene clays collected from large depths tends to be much scattered. This is because of large stress release in the collected sample. In more detail, the two following factors are possibly considered. A residual effective stress larger than 98.1 kPa is apparently impossible in a fully saturated soil because a negative pressure greater than a vacuum is non-existent, and some cracks are created in a sample when extruding it from the sampler and during trimming. In this study, a series of suction and unconfined compression tests for samples collected from 40-200 In depths in Osaka Bay was carried out to investigate the relationship between the residual effective stress and the undrained shear strength. Suction larger than 98.1 kPa was measured in undisturbed samples collected from large depths by applying a back air pressure. The disturbance ratio defined by Okumura (1974) ranges from 1.5 to 3, implying that the samples show a small strength reduction of up to 15%. It is concluded that the quality of the undisturbed Pleistocene clay sample collected from a large depth is very good, if the effective stress is of concern and no crack is created. However, the unconfined compression strength of Osaka Bay Pleistocene clay tends to show a large variance due to the crack type disturbance that is created when trimming the specimen.
  • H Tanaka, DR Shiwakoti, O Mishima, Y Watabe, M Tanaka SOILS AND FOUNDATIONS 41 (4) 73 -87 2001年08月 [査読無し][通常論文]
     
    A site investigation program was carried out at the Yamashita site, Yokohama, Japan, by means of laboratory as well as field tests. It was found from the investigation that the clayey layer is overconsolidated with an OCR of about 2.0. It is evident from geological consideration that this overconsolidation may not have been caused by stress change, but was probably due to structure effects such as cementation or delayed consolidation. The physical and mechanical properties of the Yamashita clay is compared with those of Louiseville clay, a Champlain Sea Clay widely distributed in Quebec, eastern Canada, and a well known cemented clay. Louiseville clay was retrieved by Japanese sampler and transported to the Port and Harbour Research Institute (PHRI) for laboratory investigation. Comparison of the two clays shows that strength properties such as the stress-strain curve or stress path for both clays are very similar to each other. However, the pattern of the e-log p curve measured by Constant Rate of Strain oedometer, particularly beyond the yield consolidation pressure, is remarkably different between the two clays.
  • 姜 敏秀, 土田 孝, 渡部 要一 港湾技術研究所報告 40 (2) 23 -44 2001年06月
  • 渡部 要一, 土田 孝, 引屋敷 英人 港湾技術研究所報告 40 (2) 3 -22 2001年06月
  • Watabe, Y.: Residual effective stress in undisturbed samples collected from very large depth.
    Proceedings of the International Symposium on Suction, Swelling, Permeability and Structure of Clays, IS-Shizuoka 2001 pp.95-100 2001年 [査読無し][通常論文]
  • 渡部要一, 土田 孝, 佐藤孝夫, 今村眞一郎, 加藤繁幸: 裏込めに軽量混合処理土を用いたケーソン式岸壁の地震時安定性について
    第26回地震工学研究発表会, 土木学会 pp.821-824 2001年 [査読無し][通常論文]
  • 土田 孝, 渡部要一, 佐藤孝夫, 今村眞一郎, 山村和弘: 分割法による地震時土圧の算定法とその適用性について
    第26回地震工学研究発表会, 土木学会 pp.733-736 2001年 [査読無し][通常論文]
  • Watabe, Y. and Tsuchida, T.: Comparative study on undrained shear strength of Osaka Bay Pleistocene Clay determined by several kinds of laboratory test.
    Soils and Foundations Vol.41, No.5, pp.47-59 2001年 [査読無し][通常論文]
  • 土木学会論文集 No.694, III-57, pp.331-342 2001年 [査読無し][通常論文]
  • Watabe, Y.: Residual effective stress in undisturbed samples collected from very large depth.
    Proceedings of the International Symposium on Suction, Swelling, Permeability and Structure of Clays, IS-Shizuoka 2001 pp.95-100 2001年 [査読無し][通常論文]
  • Watabe, Y. and Tsuchida, T.: Influence of stress release on sample quality of Pleistocene clay collected from large depth in Osaka Bay.
    Soils and Foundations Vol.41, No.4, pp.17-24 2001年 [査読無し][通常論文]
  • Watabe, Y. and Tsuchida, T.: Comparative study on undrained shear strength of Osaka Bay Pleistocene Clay determined by several kinds of laboratory test.
    Soils and Foundations Vol.41, No.5, pp.47-59 2001年 [査読無し][通常論文]
  • Watabe, Y., Furuno, T. and Tsuchida, T.: Mechanical properties of dredged soil treated with low quantity of cement (in Japanese).
    Journal of Geotechnical Engineering, JSCE No.694, III-57, pp.331-342 2001年 [査読無し][通常論文]
  • 織田 幸伸, 渡部 要一, 土田 孝 港湾技研資料 (975) 1 -15 2000年12月
  • Y Watabe, S Leroueil, JP Le Bihan CANADIAN GEOTECHNICAL JOURNAL 37 (6) 1184 -1194 2000年12月 [査読無し][通常論文]
     
    The paper examines the hydraulic conductivity of a nonplastic till from northern Quebec. It is shown that the hydraulic conductivity is strongly influenced by the compaction degree of saturation, and the variation of hydraulic conductivity with void ratio is influenced by compaction conditions. Determination of pore-size distributions and microphotographs provide evidence that changes in hydraulic conductivity are related to the fabric of the compacted specimens and macroporosity developing when the soil is compacted at degrees of saturation less than that at the optimum.
  • Y Watabe, S Leroueil, JP Le Bihan CANADIAN GEOTECHNICAL JOURNAL 37 (6) 1184 -1194 2000年12月 [査読無し][通常論文]
     
    The paper examines the hydraulic conductivity of a nonplastic till from northern Quebec. It is shown that the hydraulic conductivity is strongly influenced by the compaction degree of saturation, and the variation of hydraulic conductivity with void ratio is influenced by compaction conditions. Determination of pore-size distributions and microphotographs provide evidence that changes in hydraulic conductivity are related to the fabric of the compacted specimens and macroporosity developing when the soil is compacted at degrees of saturation less than that at the optimum.
  • Watabe, Y., Oda, Y. and Tsuchida, T.: Development of a geo-environmental cone penetrometer with efficient ground water sampling.
    Proceedings of the Workshop on Underwater Geoenvironmental Problems, KIG Forum2000, Kyoto pp.185-192 2000年 [査読無し][通常論文]
  • Y Watabe, T Tsuchida, K Adachi COASTAL GEOTECHNICAL ENGINEERING IN PRACTICE, VOL 1 pp.205-210 205 -210 2000年 [査読無し][通常論文]
     
    In the present study, the Recompression method proposed by Bjermm (1973) is examined for Pleistocene clay in Osaka Bay in order to evaluate the profile of its undrained shear strength. It is found that the strength increment ratio (su/sigma'(nu0)) ranges between 0.28 and 0.33 depending on the difference in definition of the extension strength. (su/sigma'(nu0)) is 0.33 when the extension strength is defined as a peak strength or a strength at axial strain of 15 %, while (su/sigma'(v0)) is 0.28 when the extension strength is defined as a strength at the same strain equivalent to the compression peak. To study the effects of shear strength obtained by the different definitions to the practice, stability analyses were carried out for a designed cross section of the seawall structure of the Kansai International Airport.
  • Y Watabe, T Tsuchida, T Furuno, H Yuasa COASTAL GEOTECHNICAL ENGINEERING IN PRACTICE, VOL 1 pp.739-745 739 -745 2000年 [査読無し][通常論文]
     
    In a construction of waste reclamation landfill, in Japan, cement treated dredged soil was utilized for an intermediate buffer zone between two layered impermeable sheets. Since waste reclamation landfill in coastal area is constructed on a thick impermeable clayey soil to secure its impermeability, it is required that the treated dredged soil must be deformable. In this study, mechanical characteristics, and these changes with curing time for cement treated soil are investigated by carrying out vane shear test, oedometer test, unconfined compression test, and isotropic and anisotropic consolidated undrained triaxial shear tests.
  • Watabe, Y., Oda, Y. and Tsuchida, T.: Development of a geo-environmental cone penetrometer with efficient ground water sampling.
    Proceedings of the Workshop on Underwater Geoenvironmental Problems, KIG Forum 2000, Kyoto pp.185-192 2000年 [査読無し][通常論文]
  • Y Watabe, T Tsuchida, K Adachi COASTAL GEOTECHNICAL ENGINEERING IN PRACTICE, VOL 1 pp.205-210 205 -210 2000年 [査読無し][通常論文]
     
    In the present study, the Recompression method proposed by Bjermm (1973) is examined for Pleistocene clay in Osaka Bay in order to evaluate the profile of its undrained shear strength. It is found that the strength increment ratio (su/sigma'(nu0)) ranges between 0.28 and 0.33 depending on the difference in definition of the extension strength. (su/sigma'(nu0)) is 0.33 when the extension strength is defined as a peak strength or a strength at axial strain of 15 %, while (su/sigma'(v0)) is 0.28 when the extension strength is defined as a strength at the same strain equivalent to the compression peak. To study the effects of shear strength obtained by the different definitions to the practice, stability analyses were carried out for a designed cross section of the seawall structure of the Kansai International Airport.
  • Y Watabe, T Tsuchida, T Furuno, H Yuasa COASTAL GEOTECHNICAL ENGINEERING IN PRACTICE, VOL 1 pp.739-745 739 -745 2000年 [査読無し][通常論文]
     
    In a construction of waste reclamation landfill, in Japan, cement treated dredged soil was utilized for an intermediate buffer zone between two layered impermeable sheets. Since waste reclamation landfill in coastal area is constructed on a thick impermeable clayey soil to secure its impermeability, it is required that the treated dredged soil must be deformable. In this study, mechanical characteristics, and these changes with curing time for cement treated soil are investigated by carrying out vane shear test, oedometer test, unconfined compression test, and isotropic and anisotropic consolidated undrained triaxial shear tests.
  • Y Watabe Characterization of Soft Marine Clays, A.A.Balkema pp.241-251 241 -251 1999年 [査読無し][通常論文]
     
    A series of K-0 consolidation tests and triaxial shear tests were conducted for undisturbed clay samples collected from various five areas in the world. Through investigating these test results, it is discussed on the locality of aging effect appearing on the characteristics of K-0 consolidation and triaxial shearing. For clays destructured by sufficient normally consolidation, it is not able to be observed any notable differences on mechanical properties for each clay. However, characteristics of natural intact clay's mechanical behaviour are so much influenced by structures which have developed due to properties of minerals and environment of depositing.
  • Y Watabe SOIL MECHANICS AND GEOTECHNICAL ENGINEERING, VOL 1 pp.145-148 145 -148 1999年 [査読無し][通常論文]
     
    A series of triaxial shear tests were conducted for normally consolidated clay, intact clay and mechanically overconsolidated clay samples collected from various five areas in the world. Through investigating these observed behaviour, it is discussed on the locality of aging effect appearing on the characteristics of triaxial shearing. For clays destructured by sufficient normally consolidation, it is not able to be observed any notable differences on mechanical properties for each clay. However, characteristics of natural intact clay's mechanical behaviour are so much influenced by structures which have developed due to properties of minerals and environment of depositing.
  • Watabe, Y.: Mechanical properties of K0-consolidation and shearing behaviour observed in triaxial tests for five worldwide clays –Drammen, Louiseville, Singapore, Kansai and Ariake clay–.
    Characterization of Soft Marine Clays, A.A.Balkema pp.241-251 1999年 [査読無し][通常論文]
  • Watabe, Y.: Comparative study on characteristics of triaxial shear of five worldwide marine clays.
    Proceedings of the 11th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, Seoul pp.145-148 1999年 [査読無し][通常論文]
  • 土田 孝, 福原 哲夫, 渡部 要一 港湾技研資料 (918) 1 -18 1998年09月
  • 渡部 要一, 土田 孝, 足立 格一郎 港湾技術研究所報告 37 (2) 59 -74 1998年06月
  • Tanaka, H., Hamouche, K.K., Tanaka, M., Watabe, Y., Leroueil, S. and Fournier, I.: Use of Japanese sampler in Champlain sea clay.
    Proceedings of the 1st International Conference on Site Characterization, Atlanta pp.439-444 1998年 [査読無し][通常論文]
  • 土田 孝, 渡部要一: 関西国際空港の地盤調査
    基礎工 Vol.26, No.3, pp.90-94 1998年 [査読無し][通常論文]
  • Tanaka, H., Hamouche, K.K., Tanaka, M., Watabe, Y., Leroueil, S. and Fournier, I.: Use of Japanese sampler in Champlain sea clay.
    Proceedings of the 1st International Conference on Site Characterization, Atlanta pp.439-444 1998年 [査読無し][通常論文]
  • 土木学会論文集 No.568, III-39, pp.227-240 1997年 [査読無し][通常論文]
  • Watabe,Y., Takemura,J. and Kimura,T.: Long term behavior of piled bridge abutments in soft clay subjected to backfill loading (in Japanese).
    Journal of Geotechnical Engineering, JSCE No.568, III-39, pp.227-240 1997年 [査読無し][通常論文]
  • Watabe, Y., Takemura, J. and Kimura, T.: Failure Mechanisms of clay deposits improved by SCP and Pile Foundations.
    Proceedings of the 2nd International Conference on Soft Soil Engineering, Nanjing pp.449-454 1996年 [査読無し][通常論文]
  • Watabe,Y., Takemura,J. and Kimura,T.: Failure Mechanisms of Clay Deposits Improved by SCP and Pile Foundations.
    Proc. of 2nd International Conference on Soft Soil Engineering, Nanjing pp.449-454 1996年 [査読無し][通常論文]
  • 渡部 要一, 竹村 次朗, 木村 孟 土木学会論文集 No.523, III-32, pp.111-123 (523) 111 -123 1995年 [査読無し][通常論文]
     
    軟弱地盤中に建設された杭基礎橋台の背面に裏込め盛土を築造する場合の地盤および杭基礎構造物の安定性を調べるために, 深さ方向に強度が増加する軟弱な正規圧密粘土地盤に対して, この種の安定問題に特に大きく影響すると考えられる, 杭間隔, 軟弱層厚, 杭先の拘束を種々変化させた実験条件の下で遠心模型実験を行った. また, 裏込めの土圧が橋台の側面に作用しないように仕切板を設置し, 軟弱地盤に生じる側方流動の影響のみを調べる実験も併せて行った. 一連の遠心模型実験の結果から, これら各種影響要因が軟弱地盤の安定性や変形のメカニズムおよび杭基礎構造物の変形挙動に与える影響を定性的に明らかにした.
  • Watabe,Y., Takemura,J. and Kimura,T.: Centrifuge model tests on interaction between soft clay and piled bridge abutments subjected to backfill loading (in Japanese).
    Journal of Geotechnical Engineering, JSCE No.523, III-32, pp.111-123 1995年 [査読無し][通常論文]
  • Watabe,Y., Takemura,J. and Kimura,T.: Stabilities of piled bridge abutments in soft clay subjected to backfill loading (in Japanese).
    Journal of Geotechnical Engineering, JSCE No.529, III-33, pp.177-189 1995年 [査読無し][通常論文]
  • T KIMURA, J TAKEMURA, Y WATABE, N SUEMASA, A HIROOKA THIRTEENTH INTERNATIONAL CONFERENCE ON SOIL MECHANICS AND FOUNDATION ENGINEERING, PROCEEDINGS, VOL 2 pp.721-724 721 -724 1994年 [査読無し][通常論文]
  • Kimura,T., Takemura,J., Watabe,Y., Suemasa,N. and Hirooka,A.: Stability of piled bridge abutments on soft clay deposits.
    Proc. of 13th ICSMFE, New Delhi pp.721-724 1994年 [査読無し][通常論文]
  • Takemura, T., Watabe, Y., Suemasa, N., Hirooka, A. and Kimura, T.: Stability of soft clay improved with sand compaction piles.
    Proceedings of the 9th Asian Regional Conference on Soil Mechanics and Foundation Engineering, Bangkok pp.543-546 1991年 [査読無し][通常論文]
  • Takemura,T., Watabe,Y., Suemasa,N., Hirooka,A. and Kimura,T.: Stability of soft clay improved with sand compaction piles.
    Proc. of 9th ARC ICSMFE, Bangkok pp.543-546 1991年 [査読無し][通常論文]
  • セメント系固化処理土への期待~浚渫土の有効活用~
    渡部要一 セメント新聞 (2006年11月27日) 5p [査読無し][通常論文]
  • サウンディング調査における技術の伝承~サンプリング調査と比較して~
    渡部要一 地質と調査 (2007第3号) 33 -36 [査読無し][通常論文]

受賞

  • 2019年 土木学会 論文賞
     港湾鋼構造物の海底土中部の電気防食特性および土壌抵抗率を考慮した電気防食設計に関する検討
  • 2016年 地盤工学会功労章
     
    受賞者: 渡部 要一
  • 2014年 Japanese Society of Geotechnical Engineering 地盤工学会論文賞(英文部門)
     Ecological geotechnics: Role of waterfront geoenvironment as habitats in the activities of crabs, bivalves, and birds for biodiversity restoration
  • 2014年 土木学会国際活動奨励賞受賞
     
    受賞者: 渡部 要一
  • 2013年 Japanese Society of Geotechnical Engineering 地盤工学会技術開発賞
     Sedimentary stratigraphy of natural intertidal flats with various characteristics 
    受賞者: 渡部要一
  • 2007年 The Ports and Harbours Association of Japan 日本港湾協会論文賞
     防波堤マウンドの期待変形量に関する研究 
    受賞者: 渡部要一;下迫健一郎;浅沼丈夫;稲垣正芳;諫山太郎
  • 2006年 Japan Society for Civil Engineers 海岸工学論文賞(土木学会)
  • 2001年 カナダ地盤工学会・キグレイ賞(学会賞)優秀論文 Honorable Mention for R.M.Quigley Award, (The Best Paper Published in the Canadian Geotechnical Journal)
  • 2001年 Honorable Mention for R.M.Quigley Award, Canadian Geotechnical Society.
  • 1996年 土木学会論文奨励賞
  • 1996年 手島記念研究賞・博士論文賞(東京工業大学博士論文賞)
  • 1996年 Japan Society of Civil Engineering's Praise for Outstanding Young Researchers.
  • 1996年 Tokyo Institute of Technology's Praise for Ph.D. thesis ("Tejima" Memorial Award).
  • 1992年 東京工業大学博士後期課程奨学金
  • 1992年 Ph.D. Scholarship Awarded by Tokyo Institute of Technology.

共同研究・競争的資金等の研究課題

  • 微視構造を核とした締固め土のパフォーマンス記述:盛土材料の耐侵食性向上を目指して
    科学研究費補助金 基盤研究(B)
    研究期間 : 2017年04月 -2020年03月 
    代表者 : 渡部 要一
  • 沿岸土砂堆積環境の連続一体調査手法の開発による堆積形成史復元
    科学研究費補助金 基盤研究(B)
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 渡部 要一
  • サンゴ礫混じり土の地盤定数評価手法の提案~サンゴ礫骨格とマトリックスの相互作用~
    科学研究費補助金 基盤研究(B)
    研究期間 : 2011年04月 -2014年03月 
    代表者 : 渡部 要一
  • 保全/修復を目的とした干潟地盤環境の評価と設計技術に関する研究
    科学研究費補助金 基盤研究(B)
    研究期間 : 2006年04月 -2009年03月 
    代表者 : 渡部 要一
  • Undrained Shear Test of Natural Soft Clay. Stability of Soft Clay Deposits. Engineering Characteristics of Cement Treated Dredged Soil and its Utilization. Influence of Compaction Conditions on Pore-size Distribution and Hydraulic Conductivity. Wast・・・
    Undrained Shear Test of Natural Soft Clay. Stability of Soft Clay Deposits. Engineering Characteristics of Cement Treated Dredged Soil and its Utilization. Influence of Compaction Conditions on Pore-size Distribution and Hydraulic Conductivity. Waste Reclamation Landfill and Geo-environmental Investigation

教育活動情報

主要な担当授業

  • 大学院共通授業科目(教育プログラム):JICA開発大学院連携プログラム
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : National land development, civil engineering, social infrastructure, life cycle management, urban planning, transportation, geotechnical engineering, water environment, bridge engineering, construction materials, sustainable development, technology transfer
  • 地盤防災特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : Geotechnical disaster, Earthquake, Settlement, Ground improvement, Ground contamination, Geoenvironment
  • 地盤防災特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : Geotechnical disaster, Earthquake, Settlement, Ground improvement, Ground contamination, Geoenvironment
  • 国際プロジェクト論
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 国際プロジェクト,基準の国際標準化,教育研究の国際化,土木技術者の国際性
  • 土の力学演習
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 土の基本的性質、土中水と浸透、地盤内応力と変形、土の圧縮と圧密、応力とテンソルの基礎、破壊基準、排水強度と非排水強度、土圧、斜面の安定、地盤の支持力
  • 土の力学Ⅰ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 土の基本的性質,土の分類,締固め,透水,地盤内応力,圧密
  • 土の力学Ⅱ
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 地盤のせん断強さ,土圧,土留め構造物,斜面安定,地盤の支持力,構造物基礎
  • 社会基盤と国土政策
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 社会基盤、国土政策、持続的発展、環境、維持管理
  • 技術政策学
    開講年度 : 2021年
    課程区分 : 専門職大学院
    開講学部 : 公共政策学教育部
    キーワード : 科学技術・イノベーション、公共政策、政策決定、政策実施、政策評価、ガバナンス、基本計画、テクノロジー(リスク)・アセスメント、リスク・マネジメント、リスク・コミュニケーション、規制政策、公共事業、国際標準化、インフラ整備、兵器開発、環境問題、知的財産権、AI(人工知能)、ディープ・ラーニング(深層学習)
  • 自然災害論
    開講年度 : 2021年
    課程区分 : 専門職大学院
    開講学部 : 公共政策学教育部
    キーワード : 自然災害 災害発生メカニズム 防災対策 水害 地震被害 津波被害 地盤災害 気象災害
  • 災害危機管理事例研究
    開講年度 : 2021年
    課程区分 : 専門職大学院
    開講学部 : 公共政策学教育部
    キーワード : 自然災害,地震,津波,洪水,火山噴火,斜面崩壊,土石流,危機管理


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