研究者詳細 - 野田　利弘

論文 - 野田　利弘

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New developments related to clarification of the mechanisms of ground deformation caused by earthquakes - In the wake of the Great East Japan Earthquake - 招待有り査読有り

Noda, T., Kazama, M. and Asaoka, A.

Journal of JSCE 5 巻 ( 1 ) 頁： 133-144 2017年3月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

The 2011 Great East Japan Earthquake caused massive ground damage, including liquefaction of sandy grounds, collapse of river levees and lands developed for housing, etc., particularly in regions across eastern Japan. Not only damage to 'currently unqualified' structures that did not conform to existing design standards and codes but also ground damage that could not be explained within the framework of conventional geomechanics and geotechnical engineering was observed. Particularly in the latter case, therefore, it has become necessary to develop new techniques in geomechanics without being restrained by the conventional framework. From the above standpoint, this paper reviews the research that has been carried out in the field of geotechnology after the Great East Japan Earthquake. More specifically, new knowledge relating to the mechanism of liquefaction damage at Urayasu City and other ground deformation caused by the earthquake is introduced, together with the results of research carried out on ground strengthening techniques.

DOI： 10.2208/journalofjsce.5.1_133

地盤－煙突構造物相互作用系の耐震性に及ぼす入力地震波の影響査読有り

中井健太郎，野田利弘

土木学会論文集 A2(応用力学) 73 巻 ( 2 ) 頁： I_409-I_418 2017年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

本論文では，液状化危険度の高い地盤上に実在する煙突を対象に，二次元平面ひずみ条件下での地震応答解析を実施し，地盤－構造物相互作用系における耐震性評価を行った．その結果，地震波が構造物の固有周期帯を多く含んでいると，共振によって構造物の揺れが大きくなることに加えて，液状化によって剛性を失った地盤が煙突を支えることができず傾倒してしまうことを示した．つまり，地盤の上に建つ構造物の地震時挙動は，加速度の大きさのみで評価できるのではなく，構造物の固有周期と入射される地震動の卓越周期との関係性が極めて重要であることを意味する．また，地盤の不整形性および周辺構造物の影響評価を行ったところ，深部地層の傾斜や周辺構造物による引きずり込み沈下によって，上部構造物の地震時安定性が低下することを示した．

DOI： http://doi.org/10.2208/jscejam.72.I_409

講義を行う建物ごと自由振動させる体験型振動工学授業の試み査読有り

原進，福和伸夫，野田利弘，田代喬，飛田潤，長江拓也，倉田和己，井上剛志

計測自動制御学会論文集 53 巻 ( 1 ) 頁： 99-101 2017年1月

A full formulation-based soil-water coupled finite deformation analysis on undrained compression tests on highly permeable soil specimen

Toyoda T., Noda T.

ICSMGE 2017 - 19th International Conference on Soil Mechanics and Geotechnical Engineering 2017-September 巻頁： 863 - 866 2017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：ICSMGE 2017 - 19th International Conference on Soil Mechanics and Geotechnical Engineering

In the mechanics of saturated soil based on the theory of mixtures, the pore water pressure p and the displacements u and U of the solid and liquid phases, respectively, are assumed to be independent variables that are unknowns of the field when solving the equation of motion of each phase by coupling with the law of conservation of mass. This is called full formulation. In many analysis codes for saturated soil, this strict formulation is modified to reduce the number of equations by assuming that the acceleration of the liquid phase relative to the solid phase is much smaller than that of the solid phase (u-p formulation). As this assumption neglects the dynamic permeation of pore water, it has not been possible to apply u-p formulation to soils with very high permeability. This paper demonstrates that by utilizing the finite element method, the finite volume method, etc., it is possible to carry out deformation analysis of soils with very high permeability by solving the strict governing equations based on full formulation for finite deformation fields of soil-water coupled systems.

Scopus

名古屋港ポートアイランドの埋立地盤・基礎地盤の土質性状の把握と想定南海トラフ巨大地震に対する耐震性評価招待有り

酒井崇之，野田利弘，中野正樹

基礎工 44 巻 ( 11 ) 頁： 84-87 2016年11月

軟弱地盤上盛土の長期圧密沈下予測に対する数値解析の適用と事後評価

稲垣太浩，田代むつみ，野田利弘

地盤工学会誌 64 巻 ( 10 ) 頁： 14-15 2016年10月

摩擦抵抗と支圧抵抗を併用した補強材を用いた補強土壁の施工実験査読有り

武藤裕久，神谷隆，長沼明彦，小高猛司，崔瑛，中野正樹，野田利弘

地盤工学ジャーナル 11 巻 ( 3 ) 頁： 201-214 2016年9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，特に阪神大震災以降，補強盛土壁が普及してきている。それら補強土盛土壁では，国産を含む様々な種類の補強材が用いられている。著者らは，補強効率の向上を目的として，支圧抵抗と摩擦抵抗を組み合わせた補強材を新たに開発してきた。本論文では，その補強効果を確認するために，摩擦板と支圧板を有する棒鋼でできた補強材の小型引抜き試験を行った。その結果，奥行き方向に長い摩擦板の方が大きな引抜き抵抗力を発揮することが示された。また，支圧板の影響範囲外になるように離して摩擦板を設置することによって引抜き抵抗力が向上することが確認できた。さらに，摩擦板による引抜き力の負担割合は，引抜きの初期段階に60～70%程度発揮し，その後引抜き変位が増大するのに伴い負担割合は低下し，最終的に40～50%に収束することが確認できた。

DOI： 10.3208/jgs.11.201

Seismic response analysis of centrifugal model test on embankment foundation systems

Nakai, K. and Noda, T.

Proc. of the 12th World Congress on Computational Mechanics 頁： [MS983-5] (151147) 2016年7月

Analysis of the effect of groundwater level on the seismic behavior of an unsaturated embankment on clayey ground 査読有り国際誌

Yoshikawa, T., Noda, T., Kodaka, T. and Takaine, T.

Soil Dynamics and Earthquake Engineering 85 巻頁： 217-230 2016年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

Numerous river levees on clayey soil grounds were damaged by the 2011 off the Pacific coast of Tohoku Earthquake. In order to investigate such damage, the behavior of an unsaturated embankment on clayey ground was simulated during its construction, during an earthquake and after the earthquake. The simulation was carried out using a soil-water-air coupled finite deformation analysis code, with attention being focused on the effect of groundwater level. The results indicated that if the groundwater level is high, a saturated area (settlement-induced saturation area) is formed at the base of the embankment due to penetrative settlement during/after construction. In addition, the mean skeleton stress is low compared with the low groundwater level. As a consequence, in the embankment on ground with the high groundwater level, the co-seismic deformation is greater and the mean skeleton stress decreases sharply, particularly in the settlement-induced saturation area during the earthquake. It was also shown that after the earthquake, the groundwater level rises because water flows toward the unsaturated embankment from the settlement-induced saturation area and/or the saturated clayey ground. If the groundwater level is high, in particular, a phreatic line is formed temporarily within the embankment.

DOI： 10.1016/j.soildyn.2016.02.008

浦安地区の地盤材料物性の把握と東北地方太平洋沖地震におけるK-NET浦安地震記録を用いた基盤上昇波の推定査読有り

金田一広，中井健太郎，野田利弘，浅岡顕，澤田義博

日本地震工学会論文集 16 巻 ( 4 ) 頁： 4_155-4_166 2016年3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東京湾沿岸域の埋立て地盤で広範囲な液状化被害が発生した。今後発生する巨大地震に対して液状化対策を行う上で、今回の地震被害について検証する必要がある。このような地盤変状について再現シミュレーションをするためには地盤情報と入力地震動の評価が重要であるとともに、複雑な現象を再現することのできる弾塑性有限変形解析が必要である。本研究では土骨格構造の働きを記述できる弾塑性構成式(SYS Cam-clay model)を用いて、まず、浦安地区で詳細な地盤調査を実施し、地盤物性の把握と共に弾塑性パラメータの同定を行った。次に、太平洋沖地震で観測された液状化の発生がみられず比較的非線形の影響が小さいと考えられるK-NET浦安の地表面加速度を取り上げ、この構成式を搭載した有効応力解析コードGEOASIAを用いて、EW、NS両方向の観測波を同時に再現するように基盤上昇波を伝達関数法によって推定した。

DOI： 10.5610/jaee.16.4_155

横ずれ断層に伴う表層地盤のリーデルせん断帯の形成に及ぼす材料的初期不整の影響査読有り

野田利弘、山田正太郎、豊田智大、浅岡顕

土木学会論文集 A2(応用力学) 71 巻 ( 2 ) 頁： I_463-I_474 2015年12月

担当区分：筆頭著者記述言語：日本語掲載種別：研究論文（学術雑誌）

横ずれ断層の活動時は，断層上部の地盤内部で深部から地表に向かって枝分れしたフラワー構造や地表面でリーデルせん断帯などが付随発生することが知られている．澤田・上田らが実施した大変形解析にならい，本研究では速度型の運動方程式を忠実に時間積分して土の運動を求める弾塑性有限変形解析コードGEOASIA®を用いて，横ずれ断層の運動に伴うせん断帯発生過程の再現を試みた．この結果，主として以下の事項が明らかとなった．1) フラワー構造・リーデルせん断帯が塑性膨張を伴って生成する．2) この生成には地盤に与える材料的初期不整の影響が大きい．3) 間隙比一定の地盤では，地盤の模型寸法が大きくなるほど地盤深部での正のダイレイタンシーの効果が薄れるため，せん断帯が出現しにくくなる．

空気～水～土連成有限変形解析による大規模河川堤防の浸透・地震時挙動の評価査読有り

吉川高広、野田利弘、加藤健太、小高猛司、李圭太、高稲敏浩

土木学会論文集 A2(応用力学) 71 巻 ( 2 ) 頁： I_621-I_632 2015年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）

本論文では，空気～水～土骨格連成有限変形解析コードを用いて，実在する砂質土・粘性土互層地盤上の大規模河川堤防の浸透・地震時挙動の評価を行った．まず，河川水位の差に注目した浸透と地震の複合時の解析を実施し，河川水位が高いほど堤内地への被害が大きくなることを示した．次に，基礎地盤の砂質土層が礫質土相当の透水性を有する場合を想定して，非定常浸透と地震時の応答を解析した．非定常浸透時には，砂質土層上部に難透水性の粘性土層があるために，河川から砂質土層に大量の水が供給されて，河川水位上昇後8時間経過時点からパイピング破壊に繋がり得るヒービングが発生することを示した．地震時には，礫質土相当の透水性であれば地震中に間隙水の移動が十分に生じて，難透水性の粘性土層で覆われた礫質土層上部に集水するため，礫質土相当の透水性であっても液状化が生じることを示した．

Air coupled effects on triaxial shearing behavior of unsaturated silty specimens under constant confining pressure and various drained and exhausted conditions 査読有り

Yoshikawa, T., Noda, T. and Kodaka, T.

Soils and Foundations 55 巻 ( 6 ) 頁： 1372–1387 2015年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

A simulation of triaxial shear tests on unsaturated silty specimens was performed under constant confining pressure and various drained and exhausted conditions starting from a single initial condition and passing through processes of suction variation and isotropic consolidation considering the triaxial test as an initial and boundary value problem. The simulation made use of a soil-water-air coupled finite deformation analysis code incorporating the SYS Cam-clay model as the constitutive equation of the soil skeleton and applying the average soil skeleton stress in the stress equation. The results showed that the coupling effect of the highly compressible air has a significant effect on the mechanical behavior. In addition, the results also explained other behaviors that would have been outside the capability of an analysis model that did not take account of factors other than air coupling such as suction. The authors wish to place special emphasis on the following findings:
(1) For simulation purposes, even using a soil water characteristic curve determined uniquely by the relationship between the degree of saturation and suction, it is still possible to calculate the increase in the degree of saturation for the drained and exhausted shear tests (under constant suction).
(2) A comparison of the experimental and calculated initial stiffnesses, volumetric strains, etc. showed that suction has an inhibiting effect on plastic deformation not only in drained and exhausted, but also in undrained and unexhausted conditions.
(3) For tests in which the volumetric restraint conditions of specimens were varied by controlling the air pressure under undrained conditions, results suggested that an introduction of gas leading to a rise in gas pressure within a highly structured ground may produce a risk of the ground displaying strain softening behavior. In the simulation, it was shown that this softening behavior can be represented in terms of structure decay as described by the SYS Cam-clay model.

地盤解析コードGEOASIA を用いた地盤・土構造物の地震応答解析

野田利弘，中野正樹，山田正太郎，中井健太郎，高稲敏浩，浅岡顕

地盤工学会誌 63 巻 ( 10 ) 頁： 16-19 2015年10月

実河川堤防へのレベル2地震応答解析の適用

小高猛司，李圭太，野田利弘，吉川高広

地盤工学会誌 63 巻 ( 10 ) 頁： 28-31 2015年10月

Study on the pore water pressure dissipation method as a liquefaction countermeasure using soil-water coupled finite deformation analysis equipped with a macro element method 査読有り

Noda, T., Yamada, S., Nonaka, T. and Tashiro M.

Soils and Foundations 55 巻 ( 5 ) 頁： 1130–1139 2015年10月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

Numerical simulation of the pore water pressure dissipation method was performed using the GEOASIA soil-water coupled finite deformation analysis code, which is capable of accounting for inertial forces, together with the elasto-plastic constitutive SYS Cam-clay model based on the soil skeleton structure concept, with the goal of quantitatively assessing the effects of this method as a liquefaction countermeasure. At the same time, an effort was made to improve/enhance the calculation efficiency of the GEOASIA analysis code by incorporating a macro element method, which up to this point has only been applied to consolidation problems. The main findings of this study are as follows: 1) the macro element method is capable of highly accurate approximation even for dynamic problems; 2) it is capable of reproducing the pore water pressure increase suppression effect associated with the pore water pressure dissipation method, even when a relatively coarse mesh is used; 3) it is capable of reproducing the suppression of the decrease in effective stress due to the pore water pressure dissipation method, along with the resulting reduction in shear stiffness and lateral ground movement and settlement; and 4), it is possible to efficiently design the pore water pressure dissipation method by first performing calculations using a 1-D mesh to determine the effective drain spacing prior to performing calculations using 2-D or 3-D meshes.

DOI： http://dx.doi.org/10.1016/j.sandf.2015.09.013

Macro element method with water absorption and discharge functions for vertical drains 査読有り国際誌

Yamada, S., Noda, T., Tashiro M. and Nguyen, H. S.

Soils and Foundations 55 巻 ( 5 ) 頁： 1114–1129 2015年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

When simulating the vertical drain method using a soil-water coupled finite element analysis, a macro-element method can be used as a means of approximately applying the water absorption function of drains to individual elements. In this paper, the discharge function of vertical drains was added to the method by treating the water pressure in the drain as an unknown and adding a continuity equation for the drains to the governing equations. By extending the method in this way, the analytical results came to exhibit the well-resistance phenomenon automatically, depending on the analytical conditions. Numerical analyses were conducted after incorporating the proposed macro-element method into aquasi-static soil-water coupled elasto-plastic finite element method based on the finite deformation theory. The main conclusions are as follows:(1)the proposed method enables highly accurate approximations for problems involving material and/or geometrical nonlinearity and multilayered grounds; (2)the proposed macro-element method is capable of reproducing various phenomena that occur when the vacuum consolidation method is applied to a clayey ground containing a middle sand layer;(3)by following the formulation used in this paper,it is unnecessary to match the mesh division width to the drain arrangement and spacing. In addition, it is possible to obtain solutions that are minimally affected by the meshsize.

DOI： https://doi.org/10.1016/j.sandf.2015.09.012

Simulation and evaluation of improvement effects by vertical drains/ vacuum consolidation on peat ground under embankment loading based on a macro-element method with water absorption and discharge functions 査読有り国際誌

Nguyen, H. S., Tashiro, M., Yamada, S. and Noda, T.

Soils and Foundations 55 巻 ( 5 ) 頁： 1045 - 1058 2015年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

The authors previously extended themacro-element method proposed by Sekiguchi to include water absorption and discharge function sand incorporated this into a soil-water coupled finite deformation analysis code capable of accounting for inertial forces. The primary objective of this study is to validate the ability of the proposed method to simulate actual ground behavior by comparing the simulation results with the actual measurements of the embankment loading of a soft peat ground improved with vertical drain sand vacuum consolidation. It was found that the proposed method is capable of comprehensively and closely simulating not only the magnitude of settlement, but also various ground behaviors,
including the deformation of the surrounding ground and porewater pressure distributions. Furthermore, additional simulations were performed to elucidate the effect of a continuous middle sand layer found to exist and to span the entire improved area at an actual embankment site.

DOI： https://doi.org/10.1016/j.sandf.2015.09.007

Liquefaction countermeasures by shallow ground improvement for houses and their cost analysis 査読有り国際誌

Tani, K., Kiyota, T., Matsushita, K., Hashimoto, K., Yamamoto, A., Takeuchi, H., Noda, T., Kiku, H. and Obayashi, J.

Soil Dynamics and Earthquake Engineering 79 巻 ( Part B ) 頁： 401–414 2015年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

A large number of houses suffered from liquefaction-induced damages in recent large earthquakes due to lack of economical countermeasures. In this study, the shallow ground improvement, up to several meters deep, was proposed as an economical liquefaction countermeasure for houses. Based on the case studies, the design criteria of allowable tilt angles and penetration settlements of houses were proposed for the required level of serviceability against moderate and large earthquakes. The results of questionnaire survey, airborne LiDAR survey, and centrifuge model tests demonstrated that even a few meters of non-liquefiable layers in shallow ground could greatly reduce settlements and tilting of houses. A series of numerical analyses indicated that non-liquefiable layer of three meters thick below ground water table improved by solidification methods can prevent significant damages of houses. Furthermore, cost analyses were carried out for different ground improvement methods for both new and existing houses.

DOI： https://doi.org/10.1016/j.soildyn.2015.08.016

Simulation of large-scale deformation of ultra-soft peaty ground under test embankment loading and investigation of effective countermeasures against residual settlement and failure 査読有り

Tashiro, M., Nguyen, H. S., Inagaki, M., Yamada S. and Noda, T.

Soils and Foundations 55 巻 ( 2 ) 頁： 343-358 2015年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

The construction of a test embankment on ultra-soft ground containing an approximately 50-m-deep soft peat layer with N-values of 0 to 1 did not result in catastrophic slip failure during construction but did cause substantial deformation of the adjacent ground. In addition, large-scale settlement in excess of 11 m occurred in the approximately 3 years following embankment construction. Based on field observations, it became evident that this large settlement was attributable to delayed compression of the deep peat layer, which was assumed at the design stage not to be subject to settlement. Based on laboratory tests and site investigations, it was deduced that due to depositions under continuous artesian conditions, this peat layer had an extremely low consolidation yield stress and was in a state such that even a slight increase in stress would result in large-scale compression. After confirming the ability of the analysis code based on soil-water coupled finite deformation theory, which included an elasto-plastic constitutive equation describing the behavior of the soil skeleton, to reproduce the observed ground behavior, the code was used to predict future settlement. These simulations were then used to evaluate the effectiveness of countermeasures aimed not only at improving stability during construction, but also at reducing residual settlement. The results of these analyses were applied in the planning of large-scale repair work performed on the test embankment. Also, when an embankment was subsequently constructed near the test embankment on similar ultra-soft ground, ground improvements were conducted prior to embankment construction as a countermeasure against residual settlement. In this paper, valuable field data related to these latter construction efforts is also presented.

DOI： http://dx.doi.org/10.1016/j.sandf.2015.02.010

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