研究者詳細 - 野田　利弘

論文 - 野田　利弘

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Localized/enormous seismic damage of subsurface ground induced by the stratum irregularity 国際誌

Nakai, K. and Noda, T.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) 頁： 1d-0092 2020年9月

Numerical analysis on aftershock-induced liquefaction of sandy ground with water-level raised by main shock 国際誌

Yoshikawa, T. and Noda, T.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) 頁： 4b-0051 2020年9月

液状化地盤中の電柱の沈下および傾斜の抑制に対するドレーン化工法の適用性検証査読有り

伊藤広和，石丸真，中井健太郎，野田利弘

地盤工学ジャーナル 15 巻 ( 3 ) 頁： 643 - 652 2020年9月

担当区分：最終著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：地盤工学会

2011年東北地方太平洋沖地震の影響により，関東地方でも広範囲に液状化が発生し，多数の電柱が沈下・傾斜の被害を受けた。都市部では電柱は狭小な場所に設置される場合が多いため対策範囲が限られており，また液状化地域だけでも膨大な数量の電柱が施設されているため，安価で簡易な対策工法の開発が望まれている。本研究では排水工法に着目し，砂地盤の液状化時における電柱の沈下・傾斜の抑制を目的として，電柱にドレーン孔を設ける工法を新たに考案した。電柱底部，および電柱底部・地中部側面にドレーン孔を設けた模型を用いて遠心力模型実験を行ったところ，沈下量・傾斜量ともにドレーン化の程度に応じて小さくなり，電柱のドレーン化は液状化地盤の電柱の沈下・傾斜に対して一定の効果があることを実証した。

DOI： https://doi.org/10.3208/jgs.15.643

Scopus

Deformation-failure mechanism of saturated fill slopes due to resonance phenomena based on lg shaking-table tests (vol 55, pg 1668, 2018)

Murao Hidehiko, Nakai Kentaro, Noda Toshihiro, Yoshikawa Takahiro

CANADIAN GEOTECHNICAL JOURNAL 57 巻 ( 8 ) 頁： 1263 - 1263 2020年8月

堤防の浸透破壊に関する模型実験の空気～水～土連成有限変形シミュレーション査読有り

吉川高広，野田利弘，小高猛司，崔瑛

土木学会論文集 A2(応用力学) 75 巻 ( 2 ) 頁： I_379 - I_388 2020年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）

平成24年7月の九州北部豪雨による矢部川堤防の決壊は，高透水性の基礎地盤における局所的なパイピングをきっかけとして発生し，“越流なき破堤”として大きな衝撃を与えた．平成25年7月に発生した子吉川堤防の法すべりと梯川堤防の法崩れも，高透水性の基礎地盤に起因する被災と考えられている．本論文では，高透水性基礎地盤を有する河川堤防の浸透破壊メカニズム解明を目指し，空気～水～土骨格連成有限変形解析コードを用いて，透水模型実験の数値シミュレーションを実施した．その結果，実験において浸透破壊した場合としなかった場合の違いを表現できることを示した．また，本解析コードを用いてケーススタディを実施するとともに，土骨格の弾塑性構成モデルにサクションの効果を考慮することによる浸透破壊挙動への影響についても考察した．

DOI： 10.2208/jscejam.75.2_I_379

小規模な浮き型格子状地盤改良による既設小規模構造物の液状化被害の低減効果査読有り

森河由紀弘，中井健太郎，中谷一貴，武田祐輔，前田健一，野田利弘

土木学会論文集 A2(応用力学) 75 巻 ( 2 ) 頁： I_329 - I_339 2020年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）

我が国では度重なる大地震を教訓に重要構造物の耐震化は推進されてきた．しかしながら，今もなお，十分な対策が行われていない戸建住宅の液状化被害は深刻である．これまで多くの液状化対策工法が研究されてきたが，その多くは原地盤を対象としており，戸建住宅などにも経済的に適用可能であり，且つ効果的な液状化対策工法については十分な検討が行われているとは言い難い．そこで，本研究では戸建住宅などにも適用可能な液状化対策として，小規模な浮き型格子状地盤改良の対策効果について検討を行った．本検討は構造物の不等沈下を伴わない限定的な条件ではあるが，1G場での模型実験や数値解析を用いた検討の結果，格子間隔を基礎幅の1.2倍以内に制限することで，改良深度が基礎幅の2倍程度の浅く小規模な浮き型格子状地盤改良でも構造物の沈下被害を抑制可能であること分かった．

DOI： 10.2208/jscejam.75.2_I_329

戸建て住宅の液状化被害に及ぼす隣家の影響査読有り

中井健太郎，野田利弘，大庭拓也

土木学会論文集 A2(応用力学) 75 巻 ( 2 ) 頁： I_401 - I_410 2020年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）

東北地方太平洋沖地震では，特に千葉県浦安市の埋立て地盤で甚大な液状化被害が発生し，多くの戸建て住宅が不同沈下の被害を受けた．しかし，既存の液状化対策工法は，施工面積およびコストの面から戸建て住宅への適用は難しく，小規模構造物に対する新しい工法の開発が期待されている．効果的な対策工法提案のためには，戸建て住宅の液状化被害の発生メカニズムを解明することが重要となるが，戸建て住宅の特徴としては，構造物が近接して立地していることが挙げられる．そこで本研究では，戸建て住宅の液状化被害発生メカニズムの解明の第一歩として，液状化被害に及ぼす隣家の影響について，数値解析的に検討した．その結果，①構造物1 棟単独評価の場合は傾斜せずに安定を保っても，隣接家屋を考慮すると互いに影響し合って傾倒被害が生じ得ること，②隣接家屋がある場合でも，構造物の傾倒向きや隣接家屋の影響範囲については，建物1 棟単独の変位ベクトルの向きで判断できることが示唆された．

DOI： 10.2208/jscejam.75.2_I_401

UNDRAINED CYCLIC SHEAR BEHAVIOR OF CLAY UNDER DRASTICALLY CHANGED LOADING RATE 国際誌

Khan Imran, Nakai Kentaro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE 18 巻 ( 66 ) 頁： 16 - 23 2020年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：International Journal of GEOMATE

The earthquake damage prediction is mainly focused on the seismic instability of sandy foundations although the clayey foundation could also be vulnerable to earthquake damage. Moreover, it is known that clayey soil shows a marked loading rate dependency in monotonic shear behavior due to its low permeability. Therefore, this paper aims to determine the undrained cyclic shear behavior of clayey soil under a drastically changed loading rate. Reconstituted clayey samples were subjected to undrained cyclic triaxial compression/extension tests with loading rate from 1.0Hz to 0.0042Hz by stress control, and 0.01%/min by strain control. The cyclic loading was stopped when the double amplitude exceeded 5%. Then, the specimen was left for a while in an undrained condition, until the value of pore water pressure converged. Results revealed that as the loading rate decreases, the number of cycles that corresponds to DA=2% and 5% also decreased. Therefore, the degree of strain evolution varies depending on the loading rate and the undrained shear strength also varies depending on the cyclic loading rate. This is because when the cyclic loading rate was high; the pore water did not migrate sufficiently, leading to the non-uniform distribution of the excess pore water pressure inside the specimen. However, the final values of excess pore water pressure after the homogenization process was the same regardless of the loading rate. This means that if sufficient time is left after cyclic loading, the final mean effective stress value becomes equal regardless of the loading rate.

DOI： 10.21660/2020.66.07893

Web of Science

Scopus

EXPERIMENTAL RESEARCH ON DEVELOPMENT/DIMINISHING OF ANISOTROPY AND ITS EFFECT ON MECHANICAL BEHAVIOR OF CLAY 査読有り国際誌

Khan Imran, Nakai Kentaro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE 18 巻 ( 65 ) 頁： 9 - 14 2020年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：International Journal of GEOMATE

Anisotropy refers to the directional dependence of material properties. The knowledge of development/diminishing of anisotropy are very important, to understand the true behavior of naturally deposited soil. The anisotropy of clays and silty clay intimately connected with their structure, which depends on the environmental conditions during which the soil is deposited as well as the stress changes subsequent to deposition. In this paper, triaxial tests were carried out using the vertical and the horizontal extraction specimen of the reconstituted clay and silty clay, for accumulating experimental facts of development of anisotropy during the preliminary consolidation process and the influence of the anisotropy on the shear behavior. Pre-consolidation pressure of 200kPa applied to induced initial anisotropy. Undrained shear triaxial test was performed with different isotropic stresses on clay (50 to 1800kPa) and silty clay (50,300 and 600kPa), and undrained shearing was carried out under constant axial strain rate of 0.0056(mm/min). Vertical sample shows larger peak strength as compared to horizontal, because of the development of anisotropy on the compression side. As the confining pressure increases, the difference between peak strength of vertical and horizontal becomes smaller and smaller which indicate that the anisotropy diminished and intensity ratio decreases. By comparing clay and silty clay, silty clay materials lose their anisotropy at lower confining pressure (600kPa) as compared to clay materials (1800kPa). Therefore, the grain sizes have significant effect on the developing and diminishing of anisotropy. Another important fact observed was, critical state index is decreasing and becomes constant as confining pressure increases.

DOI： 10.21660/2020.65.4729

Web of Science

Scopus

An analytical consideration on aftershock-induced expansion of liquefaction damage of sandy ground with groundwater-level rise due to main shock 国際誌

Noda T., Yoshikawa T.

16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 2020年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019

Extensive liquefaction damage was observed in the 2011 off the Pacific coast of Tohoku Earthquake over a wide range of reclaimed coastal land. It is reported that in Chiba Prefecture, the large aftershock that occurred 29 minutes after the main shock extended the liquefaction damage in sandy ground. In this paper, using a soil-water-air coupled finite deformation analysis code incorporating the elasto-plastic constitutive equation SYS Cam-clay model, it is shown that the groundwater level rises due to the main shock and that during the aftershock, this groundwater level rise could cause extended liquefaction damage. A special point of emphasis made in this paper is that the results described here could not have been obtained without using the soil-water-air coupled elasto-plastic finite deformation analysis. This is because 1) the generation of positive excess pore water pressure is attributed to the soil contractancy which is described by its elasto-plasticity; 2) determination of behavior of unsaturated soil needs to be based on a three phase system analysis; and 3) settlement/displacement of the ground needs to be calculated precisely by sequential computation in a finite deformation regime.

Scopus

Correction: Deformation–failure mechanism of saturated fill slopes due to resonance phenomena based on 1g shaking-table tests (Can. Geotech. J., 55(11), 1668-1681, 2018, 10.1139/cgj-2017-0385) 国際誌

Murao H., Nakai K., Noda T., Yoshikawa T.

Canadian Geotechnical Journal 57 巻 ( 8 ) 2020年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Canadian Geotechnical Journal

Replace Fig. 10 with the figure shown herein, where labels “(a)” and “(b)” have been added; and “ch.3 (upper)”, “ch.2 (middle)”, and “ch.1 (lower)” in part (b) of the figure have been replaced with “ch.6 (upper)”, “ch.5 (middle)”, and “ch.4 (lower)”, respectively.(Image presented).

Scopus

Numerical simulation of Riedel shear bands formation considering effects of geometrical barrier on strike-slip fault 国際誌

Toyoda T., Noda T., Yamada S., Asaoka A.

16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019

Displacements of strike-slip faults generate Riedel shear bands and flower structures at the surface ground above the faults. This paper aims to simulate deformation of strike-slip deformation of the surface ground considering jogs as geometrical imperfections. Analyses are based on the GEOASIA with SYS Cam-clay model that considers overconsolidation, which allows us to simulate softening behavior of brittle materials. Since the analytical results consider the presence of jogs, fractal shear zones (duplexes), P-shear, R/R'-shear, outer shear/splay shear, and tulip/palm-tree structures are successfully simulated. Furthermore, in terms of the scale effect, Riedel shear bands fractally appear when setting same overconsolidation ratio at the bottom of models.

Scopus

Numerical simulation of Riedel shear bands formation considering effects of geometrical barrier on strike-slip fault 国際誌

Toyoda Tomohiro, Noda Toshihiro

Proc. of the 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering (16ARC) 頁： JGS-064 2019年10月

記述言語：英語

Soil-water-air coupled elasto-plastic finite deformation simulation of unsaturated silt triaxial test using void ratio-dependent soil water retention model 国際誌

Yoshikawa Takahiro, Noda Toshihiro

Proc. of the 7th Asia-Pacific Conference on Unsaturated Soils (AP-UNSAT2019) 頁： EA56 2019年8月

記述言語：英語

A soil-water-air coupled finite deformation analysis of unsaturated silt triaxial tests, which were conducted by Kodaka et al. (2006), was performed considering the triaxial test not as an element test but as an initial and boundary value problem. The analysis can deal with suction effect accounting it in the elasto-plastic constitutive equation, SYS Cam-clay model. A series of processes of suction variation, isotropic consolidation, and exhausted-drained shearing were simulated beginning from a single initial condition and using a single set of material constants. The results showed that considering ceramic disc permeability was required to reproduce well both the mechanical and hydraulic behavior. Accordingly, it is suggested that a laboratory test result should be seized as the solution for an initial and boundary value problem. In addition, to experimentally clarify that the ceramic disc permeability is comparatively low, unsaturated silt triaxial tests were conducted using both a ceramic disc and a micro-porous membrane for suction control.

An analytical study on expansion of liquefaction damage during aftershock induced by groundwater-level rise due to main shock 国際誌

Noda Toshihiro, Yoshikawa Takahiro

Proc. of the 7th Asia-Pacific Conference on Unsaturated Soils (AP-UNSAT2019) 頁： EA59 2019年8月

担当区分：筆頭著者記述言語：英語

Development and verification of a soil-water coupled finite deformation analysis based on u-w-p formulation with fluid convective nonlinearity 査読有り国際誌

Noda Toshihiro, Toyoda Tomohiro

SOILS AND FOUNDATIONS 59 巻 ( 4 ) 頁： 888 - 904 2019年8月

気水分離方式を含む真空圧密工法の地盤改良効果に関する数値解析的検証査読有り

山田正太郎, 肥後隼大, 野田利弘, 中野正樹

土木学会論文集C（地圏工学） 75 巻 ( 5 ) 頁： 303 - 315 2019年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）

真空圧密工法において課題となる沈下に伴う気密シート直下の水圧増加を抑制するために，気水分離方式と称される手法が開発されている．これまでに同手法がより高い減圧効果を発揮することは実証されているが，同工法の変形抑制効果については十分に議論されていない．そこで本研究では，同方式を含む真空圧密工法の変形抑制効果を明らかにすることを主な目的に，水～土連成解析を実施し，主として次の知見を得た．1) 気水分離型真空圧密工法は，高いプレロード効果を有するため，真空ポンプ停止後の沈下を顕著に抑制する．2) 一方で，通常型真空圧密工法も，大沈下が生じ，気密シート直下の水圧が上昇するようなケースであっても，側方変位の抑制などに高い効果を発揮する．3) 通常型・気水分離型ともに，既往の施工実績以上に短期での施工が可能である．

DOI： https://doi.org/10.2208/jscejge.75.303

NON-CONTACT ESTIMATION OF STRAIN PARAMETER-TRIGGERING LIQUEFACTION 査読有り国際誌

Uy Erica Elice S., Noda Toshihiro, Nakai Kentaro, Dungca Jonathan R.

INTERNATIONAL JOURNAL OF GEOMATE 16 巻 ( 57 ) 頁： 82 - 88 2019年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：International Journal of GEOMATE

The strain parameter-triggering liquefaction is usually determined by implementing cyclic strain approach with a corresponding laboratory experiment. These parameters are threshold shear strain, cyclic shear strain and cyclic shear strain that would trigger liquefaction. In this study, non-contact measurement technique was implemented to estimate and monitor the development of the mentioned parameters. In this technique, a mirrorless camera and Lucas and Kanade pyramidal optical flow algorithm were utilized to track the movement of the particles. The camera was first calibrated to eliminate the errors from the lens and the scene as well. Furthermore, curvature correction was applied because the sample tested has a curved profile. The comparison was made with the loose and medium dense conditions. The samples were tested under a consolidated undrained cyclic triaxial test at 2.4, 1.6 and 0.8 mm strain amplitudes. The confining pressures used were 50, 100 and 200 kPa. Based on the results, a non-contact measurement technique can estimate the parameters. A range of values was established due to the non-homogeneous movement of the soil.

DOI： 10.21660/2019.57.4722

Web of Science

Scopus

Development of Disaster Response Applications and Improvements in Regional Disaster Prevention Capacity Based on Collaborative Information Use 国際誌

Noda Toshihiro, Yamori Katsuya, Harada Kenji

JOURNAL OF DISASTER RESEARCH 14 巻 ( 2 ) 頁： 375 - 386 2019年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Disaster Research

For alleviation of damage and rapid recovery following a widespread large-scale disaster, responses are needed that remain effective with limited human and material resources. To achieve this, it is imperative to prepare ahead for a collaborative response of agencies and organizations in the region at risk. In Theme 7 of Cross-ministerial Strategic Innovation Promotion Program(SIP) for Enhancement of Societal Resiliency against Natural Disasters, the research and development of the application technology and the experiments of its social implementation have proceeded under the perspectives of the following sub-themes to cooperate with the citizens, local governments and industries and make the regional disaster response possible under the regional cooperation. Theme 7-1 aims to enhance the regional resilience targeting the areas of industrial clusters and the areas with high risk of tsunami, supposing a large-scale disaster caused by the Nankai megathrust earthquake. Theme 7-2 aims to develop the support technology to response to and mitigate effectively the urban-type complex disaster triggered by the earthquake disaster by the earthquake that directly hits Tokyo area etc. and the flood by torrential rain etc., taking the urban Metropolitan area into consideration. In this paper the abovementioned efforts are outlined and the matters to be mentioned especially and stressed in Theme 7-1 are pointed out.

DOI： 10.20965/jdr.2019.p0375

Web of Science

Scopus

堤防の浸透破壊に関する模型実験の空気～水～土連成有限変形シミュレーション査読有り

吉川高広，野田利弘，小高猛司，崔瑛

土木学会論文集 A2(応用力学) 75 巻 ( 2 ) 頁： I_379 - I_388 2019年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）

平成24年7月の九州北部豪雨による矢部川堤防の決壊は，高透水性の基礎地盤における局所的なパイピングをきっかけとして発生し，“越流なき破堤”として大きな衝撃を与えた．平成25年7月に発生した子吉川堤防の法すべりと梯川堤防の法崩れも，高透水性の基礎地盤に起因する被災と考えられている．本論文では，高透水性基礎地盤を有する河川堤防の浸透破壊メカニズム解明を目指し，空気～水～土骨格連成有限変形解析コードを用いて，透水模型実験の数値シミュレーションを実施した．その結果，実験において浸透破壊した場合としなかった場合の違いを表現できることを示した．また，本解析コードを用いてケーススタディを実施するとともに，土骨格の弾塑性構成モデルにサクションの効果を考慮することによる
浸透破壊挙動への影響についても考察した．

DOI： https://doi.org/10.2208/jscejam.75.2_I_379

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