研究者詳細 - 野田　利弘

論文 - 野田　利弘

分割表示 >> ／全件表示 209 件中 1 - 209 件目

Elastoplastic finite element simulation of domino fault formation associated with tilting of highly structured ground 査読有り国際誌

Yamada, E., Noda, T. and Asaoka, A.

SOILS AND FOUNDATIONS 64 巻 ( 5 ) 2024年10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：Soils and Foundations

Ground deformation on the Earth's surface layer is strongly affected by the nonlinearity of geomaterials. However, the formation process of such deformation has yet to be described in a unified manner based on mechanics. The present study focuses on the normal faults in a submarine ground with highly developed soil skeleton structures and attempts to reproduce the process of normal fault formation associated with the tilting of a horizontally deposited submarine ground using an elastoplastic finite element simulation. The simulation was conducted using the soil–water coupled finite deformation analysis code GEOASIA, which incorporates an elastoplastic constitutive equation of the soil skeleton based on the modified Cam-clay model and the soil skeleton structure concept. The key findings are as follows: 1) Normal faults are formed from the ground surface to depth as shear bands, where shear strain is localized while exhibiting softening behavior with plastic volume compression. 2) Multiple normal faults are almost equally spaced and parallel to each other, with the inter-fault blocks rotating backward. The morphology of normal faults formed by the tilting of the ground shows domino-style characteristics. 3) The degree of the soil skeleton structure influences the formation of normal faults. This study demonstrates that elastoplastic geomechanics can explain the formation process of ground deformation, which has usually been interpreted from the perspectives of geomorphology and geology.

DOI： 10.1016/j.sandf.2024.101475

Web of Science

Scopus

Soil-water-air coupled finite deformation analysis considering trapped air and continuous air phases 査読有り国際誌

Yoshikawa, T. and Noda, T.

SOILS AND FOUNDATIONS 64 巻 ( 5 ) 2024年10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：Soils and Foundations

Since the soil–water characteristic model relates the matric suction and the water content, it cannot describe changes in the water content when the suction is zero and constant, i.e., all the pore air is trapped air. To reasonably describe changes in the water content due to air entrapment and the compressibility of trapped air, this paper presents a deformation analysis method based on the mixture theory for a four-phase mixture consisting of the soil skeleton, capillary water, trapped air, and continuous air, in which the pore air phase is divided into trapped air and continuous air phases. Specifically, considering the mass conservation equation and the equation of motion for each phase of trapped air and continuous air, and considering the mass exchange between the trapped air and continuous air phases, governing equations were derived for the initial and boundary value problems of the four-phase mixture in a finite deformation field using a rate-type equation of motion. Two examples are provided to validate the new method. Firstly, experiments and analyses of soil water retention tests were conducted under multiple drying-wetting cycles. A comparison shows that, even if hysteresis is not considered in the relationship between the effective degree of saturation and suction, the new method can successfully describe the gradual decrease in the degree of saturation at a suction of 0 kPa with multiple drying-wetting cycles, indicating that the pore air gradually becomes trapped in the pore water, by modelling the mass exchange between the trapped air and continuous air phases. Secondly, analyses of an unexhausted and undrained triaxial compression test under zero suction were conducted, comparing the new and previous soil–water-air coupling methods. The results show that the new method, unlike the previous method, can successfully simulate the experimental result. This is because the new method is able to describe the compressibility of trapped air as the change in the capillary water degree of saturation, which is a novel state variable defined as the ratio of the volume of capillary water to the total volume of capillary water and trapped air. The new method contributes to the simplification of the soil–water characteristic model and enables evaluations of the soil deformation behavior due to the compressibility of trapped air, such as a countermeasure against liquefaction caused by unsaturation.

DOI： 10.1016/j.sandf.2024.101480

Web of Science

Scopus

Tsunami hazard evaluation of river embankment structures incorporating their vulnerability to seismic strong motion 査読有り国際誌

Imai, K., Nakai, K., Hirai, T., Noda, T., Arai, N., Iwama, S., Iwase, H. and Baba, T

EARTHQUAKE SPECTRA 40 巻 ( 3 ) 頁： 2008 - 2037 2024年8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：Earthquake Spectra

Development of coastal areas in Japan for various land uses since the 1960s has contributed to industrial upgrades and improved the efficiency of transportation networks. However, there are concerns about the vulnerability of developments on alluvial plains and reclaimed lands to geological events, like ground subsidence due to liquefaction during large earthquakes. Realistic assessment of earthquake and tsunami hazards and evaluation of possible countermeasures require accurate estimation of the amount of subsidence that can be expected from liquefaction at coastal and riverside sites supporting various structures. In this study, to evaluate the amount a river embankment structure might be expected to settle as a result of strong motion from an assumed Nankai Trough great earthquake, we conducted a numerical simulation using the soil–water coupled finite deformation analysis code GEOASIA. We then investigated the effect of the estimated embankment subsidence on tsunami inundation, which was simulated by using nonlinear shallow-water equations and a grid spacing as fine as 3.3 m. The influence of urban structures on the inundated area was taken into account by using a structure-embedded elevation model (SEM). The results showed that subsidence of river embankments and the collapse of parapet walls on top of them would increase both the depth and area of inundation caused by a tsunami triggered by a Nankai Trough scenario earthquake. Our findings underscore the importance of evaluating not only earthquake resistance but also vulnerability of coastal and riverside structures to strong motion in tsunami hazard analyses. Furthermore, the importance of tsunami inundation analysis using a SEM for predicting the behavior of tsunami flotsam in urban areas was demonstrated.

DOI： 10.1177/87552930241237815

Web of Science

Scopus

Super/sub-loading surface model for constitutive equation of friction 査読有り国際誌

Toyoda, T., Yasuike, R. and Noda, T.

TRIBOLOGY INTERNATIONAL 191 巻頁： 109080 2024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：Tribology International

In this study, an elasto–plastic constitutive model of friction incorporating the superloading surface concept was formulated as an extension of the subloading friction model. The proposed model regards the state in which the static friction coefficient is larger than the kinetic friction coefficient as the “bulkiness” of structure and the smooth transition of friction was expressed by the evolution rule of structure.The positive definiteness of the plastic multiplier, the loading condition, and a condition equation for material parameters were clearly derived. The capability of the proposed model in accordance with the subloading-friction model was confirmed in the stick–slip simulation of a mass-spring system.

DOI： 10.1016/j.triboint.2023.109080

Web of Science

Scopus

Comprehension of Seismic-Induced Groundwater Level Rise in Unsaturated Sandy Layer Based on Soil-Water-Air Coupled Finite Deformation Analysis 査読有り国際誌

Yoshikawa, T. and Noda, T.

WATER 16 巻 ( 3 ) 2024年2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：Water (Switzerland)

Immense liquefaction damage was observed in the 2011 off the Pacific coast of Tohoku Earthquake. It was reported that, in Chiba Prefecture, Japan, the main shock oozed muddy water from the sandy ground and the aftershock which occurred 29 min after the main shock intensified the water spouting; thus, the aftershock expanded the liquefaction damage in the sandy ground. For comprehending such a phenomenon, using a soil–water–air coupled elastoplastic finite deformation analysis code, a rise in groundwater level induced by main shock is demonstrated, which may increase the potential of liquefaction damage during the aftershock. The authors wish to emphasize that these results cannot be obtained without soil–water–air coupled elastoplastic finite deformation analysis. This is because the rise in groundwater level is caused by the negative dilatancy behavior (plastic volume compression) of the saturated soil layer which supplies water to the upper unsaturated soil layer, and it is necessary to precisely calculate the settlement of ground and the amount of water drainage/absorption to investigate the groundwater level rise. This study provides insight into the mechanism of ground liquefaction during a series of earthquakes.

DOI： 10.3390/w16030452

Web of Science

Scopus

Unconditional convergence of theoretical solutions to u-p formulation 査読有り国際誌

Toyoda T. and Noda T.

Soils and Foundations 64 巻 ( 1 ) 頁： 101421 2024年2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：Soils and Foundations

Dynamic soil-water coupling analyses, based on the u-p formulation, are inapplicable to highly permeable soils, causing numerical instability. In this study, it is demonstrated that theoretical solutions to the u-p formulation itself certainly exhibit unconditional convergence regardless of the permeability coefficient. This suggests that the instability is only numerical and can be observed in a temporally discretized system. Firstly, the linearized governing equation for the u-p formulation was proven to be reduced to a damped wave equation under a one-dimensional condition, similar to the Full formulation. Secondly, theoretical solutions for the u-p formulation were derived and their unconditional convergence was confirmed. Then, the essential characteristics of the u-p theoretical solutions, that is, the underestimation of permeability, overestimation of compression wave celerity, and occurrence of negative pore water pressure against positive load application, were described and compared with theoretical solutions for the Full formulation.

DOI： 10.1016/j.sandf.2023.101421

Scopus

Severe and nonuniform liquefaction damage of reclaimed ground contributed by interference between body waves and stratigraphic irregularity-induced surface waves 査読有り国際誌

Nakai, K., Noda, T. and Asaoka, A.

EARTHQUAKE SPECTRA 40 巻 ( 1 ) 頁： 287 - 313 2024年2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：Earthquake Spectra

The 2011 off the Pacific Coast of Tohoku earthquake caused extensive liquefaction damage to reclaimed land along the Tokyo Bay coast, even though it was approximately 400 km from the epicenter. The characteristics of the liquefaction damage include the fact that liquefaction occurred in soils with a high percentage of fine particles and that the distribution of liquefied and nonliquefied areas was nonuniform. The factors contributing to such nonuniform liquefaction damage included the heterogeneity of the ground materials and their depositional conditions, and the effects of the long earthquake duration. Although these points are certainly valid as reasons for the occurrence of severe liquefaction damage, they do not fully explain the mechanisms of the liquefaction of the fine-grained soils, or the localized extent of the liquefaction. To elucidate the severe and nonuniform damage, seismic response analyses of a multi-layered ground were conducted focusing on the stratigraphic irregularities in the ground beneath Urayasu city. The results showed that the thicker and softer sedimentary layers amplify the slightly long-period component of the seismic motion and increase the shaking at the ground surface. Moreover, the wave propagation in the ground became very complicated owing to the focal effect caused by the refractions and reflections of body waves at the stratum boundary, surface wave excitation at the base of the slope, and amplified interference between body and surface waves. This complex wave propagation contributed to nonuniform surface ground shaking and severe liquefaction damage. In addition, surface waves, which consist primarily of slightly long-period components, can propagate far and wide; as such, they triggered extensive damage owing to delayed shaking phenomena that continue even after the earthquake. The analysis results suggested that multidimensional elasto-plastic seismic response analyses considering stratigraphic irregularities are important for detailed seismic evaluation.

DOI： 10.1177/87552930231220005

Web of Science

Scopus

Experimental study on sand anisotropy using hollow cylinder apparatus 査読有り国際誌

Yamada, S., Okada, M., Nakano, M. and Noda, T.

SOILS AND FOUNDATIONS 63 巻 ( 3 ) 2023年6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：Soils and Foundations

This study investigated sand anisotropy experimentally using a hollow cylinder apparatus. The effect of the initial anisotropy on the shear behavior of sand was illustrated by conducting experiments on specimens with bedding planes and systematically varying the density, principal stress direction, and intermediate principal stress. The change in induced anisotropy during shearing was experimentally captured by re-shearing the specimens subjected to prior shear history. The experimental results revealed the following: (a) Anisotropy in sand, whether initial anisotropy developing during specimen preparation or induced anisotropy developing due to shear history, causes pseudo-density changes in the mechanical behavior, in which sand of the same density behaves as if it has a different density depending on the direction of shear. (b) The changes in induced anisotropy, due to shearing in the same direction as that of the prior shear, make the soil behave similarly to dense sand, whereas shearing in a direction perpendicular to the prior shear makes the soil behave similarly to loose sand. (c) The larger the prior shear, the more pronounced the pseudo-density changes that appear in the subsequent behavior. Moreover, the significance of induced anisotropy in liquefaction and compaction phenomena was experimentally demonstrated through single and double swing cyclic shear tests. The results obtained from the study will be useful for validating models that incorporate induced anisotropy.

DOI： 10.1016/j.sandf.2023.101326

Web of Science

Scopus

Finite-Deformation Cam-Clay Model Considering Elastic Dilatancy and Soil Skeleton Structure 査読有り国際誌

Yamada Shotaro and Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMECHANICS 23 巻 ( 2 ) 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

Elastoplastic constitutive equations for soils often employ the nonlinear rate-type isotropic Hooke’s law, which is based on theadditive decomposition of strain rate and considers the pressure dependency in the elastic part. Hooke’s law has independent isotropic anddeviatoric components, and therefore, it cannot express elastic dilatancy as confirmed in experiments. In this model, although the elastic vol-ume change is path-independent, the shear strain exhibits a significant residual when subjected to an effective stress cycle. This study pro-poses a rate-type elastic constitutive equation for soil applicable to elastoplastic constitutive equations based onfinite deformation theoryusing an objective stress rate and additive decomposition of stretching; these equations cover these shortcomings of the rate-type Hooke’slaw. The proposed rate-type elasticity constitutive equation is based on the hyperelastic body in the infinitesimal deformation theory proposedby Einav and Puzrin or Houlsby et al. and has confining pressure dependence, path independence of elastic volume change, and elastic di-latancy. Further, the residual strain is considerably smaller than that of the rate-type Hooke’s law. Moreover, this study improves the elasto-plastic constitutive equation, SYS Cam-Clay model, based on the skeleton structure concept by introducing the proposed elastic constitutiveequation. The basic behavior of the elastoplastic constitutive equation for clay and sand is demonstrated to show that the newly acquiredelastic dilatancy improves the mean effective stress reduction behavior during shear stress unloading under undrained conditions and thestiffness recovery behavior during liquefaction, which is essential for describing cyclic mobility.

DOI： 10.1061/IJGNAI.GMENG-7117

Web of Science

Verification of a Macroelement Method with Water Absorption and Discharge Functions in Quasi-Static Problems 査読有り国際誌

JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING 148 巻 ( 7 ) 2022年7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：ASCE

When simulating the vertical drain method using a soil–water coupled finite-element analysis, we the macroelement method can be adopted to provide the water absorption function of drains to individual elements approximately. A previous study added the discharge function of vertical drains to the technique so that the occurrence of well resistance can be considered in accordance with its mechanism. This paper verified the approximation accuracy of this new macroelement method in quasi-static problems. The macroelement method was derived under the assumption that the axisymmetric pore water pressure distribution is equal Barron’s solution, but the first numerical example demonstrated that the technique has high approximation accuracy even for nonaxisymmetric problems by appropriately converting the permeability of a drain. The second calculation example included a number of drains and applied the vacuum consolidation method to clayey ground containing a middle sand layer. In this calculation, there was remarkable well resistance, and pore water flowed from the unimproved region to the improved region or between the effective areas of each drain. The calculation results indicated the superiority of the new macroelement method in terms of accurate approximations even for such a complex problem. Moreover, this study demonstrated the effectiveness of waterproof sealing, a countermeasure for sucking pore water from the middle sand layer, using the new macroelement method.

DOI： 10.1061/(ASCE)GT.1943-5606.0002803

Web of Science

Method to introduce the cementation effect into existing elastoplastic constitutive models for soils 査読有り国際誌

Journal of Geotechnical and Geoenvironmental Engineering 148 巻 ( 5 ) 頁： 04022013-1 - 04022013-14 2022年5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）出版者・発行元：ASCE

This study proposes a new method to introduce the cementation effect into existing elastoplastic constitutive models for soils. The mechanical properties of cement-treated soil are evaluated via element tests and compared with those of naturally deposited clay. The similarities and differences between cement-treated soils and naturally deposited clays are studied, focusing on two states, the undisturbed and remolded states. The effective stress for cement-treated soils incorporating an internal state variable representing the cementation effect is newly defined to describe the mechanical properties of cement-treated soils. Moreover, by applying this extended effective stress to the super-subloading yield surface (SYS) Cam-clay model, which is an elastoplastic model for soils based on the skeleton structure concept, the scope of this constitutive model is extended to include cement-treated soils. The cementation effect introduced by the proposed method allows reproducing the mechanical behavior of the cement-treated soil. Finally, a brittle behavior not described at the element level can be obtained, leading to a soil–water coupled finite deformation analysis incorporating the proposed constitutive model.

DOI： https://doi.org/10.1061/(ASCE)GT.1943-5606.0002727

本震による傾斜を想定したガスホルダーの余震耐震性の簡易評価手法査読有り

小林実央，田附英幸，中井健太郎，野田利弘

土木学会論文集 A2(応用力学) 77 巻 ( 2 ) 頁： I_543 - I_550 2022年2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：土木学会

高度な安全性が要求される球形ガスホルダーは，大規模地震により基礎に不等沈下が生じた場合であっても余震時に供給機能を保持できることが望ましく，地震後の使用可否判断に資する，最大余震を想定した傾斜ガスホルダーの耐震性評価手法が必要である．その評価では支持構造部の材料・幾何学的非線形性や非線形ダンパーを考慮しなければならず，3 次元解析による詳細な評価は地震発生後短期間で実施することは現実的でない．このため本論文ではPushover解析から非線形ばね特性を反映した1 質点ばねモデル計算を用いた簡易な評価手法を提案した．本手法は，実機を対象にした3次元骨組モデルの動的応答との比較から最大応答値までは良い一致を示し，それ以降は安全側に応答値を算出するため，ホルダーの余震耐震性を評価できることを明らかにした．

DOI： https://doi.org/10.2208/jscejam.77.2_I_543

Combined-loading elastoplastic constitutive model for a unified description of the mechanical behavior of the soil skeleton 査読有り国際誌

Yamada S., Noda T., Nakano M., Asaoka A.

Computers and Geotechnics 141 巻 2022年1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：Computers and Geotechnics

This paper proposes a combined-loading elastoplastic constitutive model (CL model) for a unified description of the mechanical behavior of soil materials, including clay, sand, and intermediate soil. This mathematical model combines the super-subloading yield surface Cam-clay model and the non-associated Drucker–Prager (DP) model. The first model introduces the skeleton soil structure concept into the Cam-clay model based on critical-state soil mechanics. It describes the mechanical behavior of naturally deposited clay more accurately than the existing model does. The non-associated DP model considers the frictional properties of granular materials and is widely used to describe the undrained shear behavior, particularly that of sandy soil. The newly proposed model is one in which these two independently existing models simultaneously or independently work in loading states according to the loading criterion, which can be derived as a natural result from plastic multipliers. This framework allows for a unified description of a wide range of soil materials, including naturally deposited clayey soils and sandy soils.

DOI： 10.1016/j.compgeo.2021.104521

Scopus

Effects of Strong Ground Motion with Identical Response Spectra and Different Duration on Pile Support Mechanism and Seismic Resistance of Spherical Gas Holders on Soft Ground 国際誌

Kobayashi Mio, Noda Toshihiro, Nakai Kentaro, Takaine Toshihiro, Asaoka Akira

APPLIED SCIENCES-BASEL 11 巻 ( 23 ) 2021年12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：Applied Sciences (Switzerland)

Safety measures are required for spherical gas holders to prevent them from malfunctioning even after a large earthquake. In this study, considering the strong nonlinearity of the ground and damage to the pile during an earthquake, a three-dimensional seismic response analysis of the holder-pile-ground interaction system was conducted for an actual gas holder on the soft ground consisting of alternating layers of sand and clay. In the analysis, the seismic response of the structure to strong ground motions of different durations with the same acceleration response spectrum was verified. The results show that the piles were relatively effective in controlling the settlement when the duration of the earthquake motion was long. This is because the axial force acting on the pile increased due to the redistribution of the holder load caused by the lowering of the effective confining pressure of the sand and clay layers during the earthquake, which increased the bearing capacity of the pile. In contrast, when the duration of the seismic motion was short, the piles had little effect on the reduction in the settlement because the maximum acceleration was higher than that in the former case, and the piles immediately lost their support function.

DOI： 10.3390/app112311152

Web of Science

Scopus

Numerical simulation based heuristic investigation of inertia-induced phenomena and theoretical solution based verification by the damped wave equation for the dynamic deformation of saturated soil based on the u-w-p governing equation 査読有り国際誌

Toyoda Tomohiro, Noda Toshihiro

61 巻 ( 2 ) 頁： 352 - 370 2021年4月

Importance of considering unsaturated triaxial tests including ceramic disk as initial and boundary value problems 査読有り国際誌

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

Soils and Foundations 2021年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

Considering unsaturated triaxial tests including a ceramic disk as initial and boundary value problems, a series of suction change, isotropic consolidation, and drained shearing processes was simulated using a soil-water-air coupled elastoplastic finite deformation analysis code. As a result, it was demonstrated that the delayed behavior of a wetting-induced collapse during the suction change and isotropic consolidation processes, as well as water-absorption behavior during the subsequent drained shearing process, were attributed not to the characteristics of the soil specimen, but to the permeability of the disk. Thus, it is important to take the ceramic disk into account in unsaturated triaxial tests regarded as initial and boundary value problems in order to understand the temporal change behavior of unsaturated soil specimens. Otherwise, there is a risk that the behavior appearing as the solution of an initial and boundary value problem may be modeled as a constitutive relation.

DOI： 10.1016/j.sandf.2020.12.009

Scopus

浮き型格子状地盤改良による偏心荷重が作用した既設小規模構造物の液状化被害抑制効果査読有り

中谷一貴，森河由紀弘，中井健太郎，前田健一，野田利弘

土木学会論文集 A2(応用力学) 76 巻 ( 2 ) 頁： I_279 - I_288 2021年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）

近年，多発している大規模な地震に伴う液状化によって多くの戸建住宅で深刻な被害が発生している．ここで，液状化被害の中でも構造物が傾斜する場合には構造物自体にも重大な損傷が発生するため，構造物が沈下する場合より被害はさらに深刻になる．そこで，本稿では接地圧が偏心し，傾斜被害が発生しやすい模型構造物を対象にした重力場での二次元模型実験や水～土骨格連成有限変形解析から浮き型格子状地盤改良による液状化被害の抑制効果について検討した．検討の結果，側方流動を抑制することを目的とした浮き型格子状地盤改良により，偏心荷重が作用した構造物においても液状化時における沈下被害を大きく抑制可能であることが分かった．一方で，浮き型格子状地盤改良で得られる傾斜被害抑制効果は沈下被害抑制効果ほど大きくないことが確認された．

DOI： https://doi.org/10.2208/jscejam.76.2_I_279

PROGRESSIVE FAILURE OF UNSATURATED FILL SLOPE CAUSED BY CUMULATIVE DAMAGE UNDER SEEPAGE SURFACE 査読有り国際誌

Murao Hidehiko, Nakai Kentaro, Yoshikawa Takahiro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE 20 巻 ( 78 ) 頁： 1 - 8 2021年2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）

Seepage surface position of fill slope can fluctuate owing to rainfall and groundwater supply from behind the slope. Therefore, in this study, shaking-table tests of an unsaturated fill slope were conducted to examine the influence of the seepage surface position on the fill slope stability by comparing with previous results in the fully saturated condition. An acceleration amplification factor was used to evaluate the stability. If the embankment was in an unsaturated condition, a slip plane was formed along the seepage surface. With ongoing increase of input acceleration, the slip progressed to behind the slope. Comparison of the unsaturated and saturated results showed that although the failure mechanism in which the slip surface was formed by the reduction in rigidity was common, the input acceleration at failure and deformation mode were different. When the slip surface was formed and failure occurred, the input acceleration in the unsaturated fill slope was more massive, and the deformation at the same excitation stage was small. These results imply that the unsaturated fill slope has a higher earthquake resistance than the saturated fill slope. Moreover, it is shown that the progress of plastic deformation inside the embankment and the formation process of the slip plane can be estimated from the change in the acceleration amplification factor regardless of seepage surface position.

DOI： 10.21660/2020.78.j2036

Web of Science

Scopus

Triaxial test on water absorption compression of unsaturated soil and its soil-water-air-coupled elastoplastic finite deformation analysis 査読有り国際誌

Yoshikawa Takahiro, Noda Toshihiro

SOILS AND FOUNDATIONS 60 巻 ( 5 ) 頁： 1151 - 1170 2020年10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）

Triaxial tests and numerical simulations were conducted to determine the water absorption compression of unsaturated soil. In the triaxial tests, unsaturated silt specimens under the same initial condition were prepared and the processes of different suction reduction, isotropic consolidation, and exhausted-drained shearing were applied to the specimens. The numerical simulations used a soil-water-air coupled finite deformation analysis code with a newly incorporated elastoplastic constitutive model. The degree of saturation was introduced to the internal state variables of the yield function of the SYS Cam-clay model and a soil-water characteristic model with void ratio dependency. Then, the triaxial test was treated as an initial and boundary value problem, and the series of processes in the experiments were simulated using a single set of material constants and initial values. The new findings are as follows: 1) The loading criterion and the classification of loading conditions considering change in saturation degree can be specified in the elastoplastic constitutive model for unsaturated soil. 2) Water absorption compression behavior was observed in the experiments not only under suction reduction but also under constant suction condition. This water absorption compression under constant suction condition was explained as a saturation-increase behavior due to volume compression using the soil-water characteristic model with void ratio dependency. 3) By considering the triaxial test as an initial and boundary value problem, the temporal change in the volume and the amount of water absorption/drainage were able to be reproduced.

DOI： 10.1016/j.sandf.2020.06.010

Web of Science

Scopus

Seismic damage of soft clay layer directly under the river levee that becomes prominent by L2 earthquake 国際誌

Noda, T. and Nakai, K.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) 頁： 4b-0040 2020年9月

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

鋼矢板せん断壁を用いた岸壁の液状化・側方流動抑止工法の提案とその解析的検討査読有り

伊勢典央，妙中真治，野田利弘，中井健太郎，高稲敏浩

土木学会論文集 A2(応用力学) 74 巻 ( 2 ) 頁： I_615 - I_625 2019年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

岸壁背後地盤の液状化および側方流動化の両方の抑止工法として，既往研究において有効性が示されている抑止杭を参考にするとともに，狭隘地での施工可能性も考慮して，岸壁背後に法線直角方向に鋼矢板せん断壁を配置する工法を提案した．この提案した工法について，2次元/3次元・水～土骨格連成有限変形解析コードGEOASIAを用いて検討を行い，液状化および側方流動化の抑止効果を確認した．具体的には隣り合う鋼矢板せん断壁の間隔を狭くする，形状に凹凸が多いほど効果が大きいことを明らかにし，新たな岸壁耐震補強工法の可能性を示した．

DOI： https://doi.org/10.2208/jscejam.74.I_615

最大級の地震による激甚シナリオを想定した砂地盤上の球形ガスホルダーの3次元地震応答解析査読有り

小林実央，野田利弘，中井健太郎，高稲敏浩，浅岡顕

土木学会論文集 A2(応用力学) 74 巻 ( 2 ) 頁： I_693 - I_703 2019年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

録
レベル2地震動に対する高度な安全性が要求される球形ガスホルダーについて，上部基礎一体かつ3次元形状にてモデル化し，地盤の地震前～中～後までの力学挙動を一貫して扱うことができる水～土連成有限変形解析コードを用いて，3次元地震応答解析を行った．その結果，最大級の地震想定では，(1)地震発生直後にすべての杭が「塑性化」して支持機能をほぼ完全に失うため，杭を想定しない場合の挙動とほぼ同一になること，(2)ゆえに，最大限の地盤の不等沈下によるホルダーの傾斜を想定した終局状態は相当程度安全側の評価になること，また，(3)今回の解析条件下であれば，終局状態の評価は2次元解析で十分に可能であること，さらには，(4)ホルダーの構造安定性を一体的に評価する必要性があることを示した．

DOI： https://doi.org/10.2208/jscejam.74.I_693

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

Noda T., Yoshikawa T.

7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019 2019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：7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019

Scopus

Influence of development/diminishing of anisotropy on the mechanical behavior of clayey specimen 国際誌

Khan, I., Nakai, K., Noda, T. and Mizukami, K.

4th International Conference on Science, Engineering and Environment (SEE) 頁： 593-598 2018年11月

記述言語：英語

Anisotropy refers to the directional dependence of material properties. In order to know the true behavior of naturally deposited soil, the knowledge of development/diminishing of anisotropy are very important. 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 and silty clay, isotopically consolidated for 24 hours 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 as compared to clay materials. 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 become constant as confining pressure increases.

堤体基礎の地震動脆弱性が津波氾濫解析に与える影響に関する検討査読有り

今井健太郎, 中井健太郎, 野田利弘, 新井伸夫, 岩間俊二, 馬場俊孝

土木学会論文集B2（海岸工学） 74 巻 ( 2 ) 頁： I_247 - I_252 2018年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）

本研究では，愛知県の巨大産業を支えるサプライチェーンを擁する地域のひとつである碧南市を対象として，南海トラフ巨大地震による地震動に対する堤体基礎の沈下量を数値解析によって評価した．この解析結果を津波氾濫解析に組み込むことで，堤体基礎の脆弱性が氾濫過程や浸水域に与える影響について検討を行った．堤体基礎の沈下や直立堤の崩壊を考慮することにより津波浸水域は大きく拡大することを定量的に示すことができた．このことは，沿岸構造物の耐震化の重要性を示していることはもちろんのこと，強震動による海岸・河岸構造物や堤体基礎部の脆弱性が津波ハザード評価に与える影響を無視できないことを示している．

DOI： 10.2208/kaigan.74.I_247

Deformation-failure mechanism of saturated fill slopes due to resonance phenomena based on 1g shaking-table tests 査読有り国際誌

Murao Hidehiko, Nakai Kentaro, Noda Toshihiro, Yoshikawa Takahiro

CANADIAN GEOTECHNICAL JOURNAL 55 巻 ( 11 ) 頁： 1668 - 1681 2018年11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：Canadian Geotechnical Journal

Earthquake motions include waves of various frequency bands ranging from low to high frequency. Notably, the dominant frequency affects the seismic stability of fill slopes. Hence, to analyze the deformation–failure mechanism during an earthquake, 1g shaking-table tests were conducted in this study on saturated fill slopes considering the resonance phenomenon. Results show that the deformation–failure mechanism of a fill slope cannot be defined by only one sliding surface. Multiple sliding surfaces are formed progressively depending on the ground and external conditions. Moreover, evaluating the seismic stability of fill slopes depends not only on the magnitude of the acceleration, but also on the relationship between the natural frequency of the fill slope and the input frequency. These phenomena cannot be considered in the seismic-intensity method nor in the Newmark’s method used in conventional design. When implementing seismic countermeasures, it is important to determine the frequency characteristics of fill slopes and design the countermeasures considering the predominant frequency of the seismic wave anticipated at the site.

DOI： 10.1139/cgj-2017-0385

Web of Science

Scopus

MONITORING THE TRIGGERING OF LIQUEFACTION USING IMAGE PROCESSING 査読有り国際誌

Uy Erica Elice Saloma, Noda Toshihiro, Nakai Kentaro, Dungca Jonathan Rivera

INTERNATIONAL JOURNAL OF GEOMATE 15 巻 ( 51 ) 頁： 180 - 187 2018年11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

Inrecent studies triggering or initiation of liquefaction is usually performed to characterize the potential of the soil to liquefy. Its behavior before, during and after liquefaction in a laboratory test needs to be understood. Image processing was implemented to monitor the triggering of liquefaction and estimate the cyclic shear strain that would trigger liquefaction. Lucas and Kanade pyramidal optical flow algorithm were used to track the movement of the soil. A mirrorless camera was the instrument used. The strain-controlled consolidated undrained cyclic triaxial test was performed. The loose condition was tested 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, the estimated values for the cyclic shear strain that would trigger liquefaction had a range of values due to the occurrence of non-homogeneous deformation. The minimum values were in agreement with the typical values while the maximum values were larger. For the behavior of the soil before, during and after liquefaction had occurred, the deformation behavior was different. More deformations were observed after the triggering of liquefaction.

DOI： 10.21660/2018.51.02150

Web of Science

Scopus

Seismic Response Analysis of Ground/Geo-structures using Geo-Analysis Integration Code 招待有り

Asaoka, A., Noda, T.

International Press-in Association Newsletter 3 巻 ( 3 ) 頁： 3-10 2018年9月

Full-field estimation of cyclic threshold shear strain 国際誌

Uy, E. E. S., Noda, T., Nakai, K. and Dungca, J. R.

Proceedings of the 20th International Conference on Soil Mechanics and Geotechnical Engineering, Osaka 頁： 3062-3066 2018年3月

記述言語：英語

Cyclic threshold shear strain is the cyclic shear strain amplitude that serves as the indicator of the development of pore water pressure. The parameter can be obtained by performing either cyclic triaxial test, shaking table test, cyclic simple shear or resonant column. In a cyclic triaxial test, other researchers install measuring devices in close proximity of the soil to measure the parameter. This method can cause sample disturbance which can affect the result of the experiment. Although there are already existing methods for determining the parameter, the movement and behavior of the soil before and after reaching this parameter needs to be understood. A method that can be used is by applying full-field measurement technique. The technique uses a camera to monitor and measure the movement of the soil. This study is an attempt to estimate the cyclic threshold shear strain parameter. The applied technique has the capacity to monitor the behavior of the particles at cyclic loading. For this study, the technique was incorporated in a strain-controlled consolidated undrained cyclic triaxial test. Two-dimensional image processing was implemented. Lucas and Kanade optical flow algorithm were applied to track the movement of the soil particles. Results from the full-field measurement technique were compared with the results from the linear variable displacement transducer. A range of values were determined from the estimation. The minimum values were in the order of 10-2% in some areas of the specimen. Nonhomogeneous movement was also observed.

Non-contact measurement of soil deformation in a cyclic triaxial test 国際誌

Uy, E. E. S., Noda, T., Nakai, K. and Dungca, J. R.

Proceedings of the 20th International Conference on Geotechnical Earthquake Engineering and Dynamic Soil Properties, Singapore 頁： 2318-2327 2018年3月

記述言語：英語

Deformation in a conventional cyclic triaxial test is normally measured by using a point-wise measuring device. In this study, non-contact measurement technique was applied to be able to monitor and measure the occurrence of the non-homogeneous behavior of the soil under cyclic loading. Non-contact measurement is executed through image processing. Two-dimensional measurements were performed using Lucas and Kanade optical flow algorithm and it was implemented Labview. In this technique, the non-homogeneous deformation was monitored using a mirrorless camera. A mirrorless camera was used because it is economical and it has the capacity to take pictures at a fast rate. The camera was first calibrated to remove the distortion brought about the lens and the testing environment as well. Calibration was divided into 2 phases. The first phase was the calibration of the camera parameters and distortion caused by the lens. The second phase was for eliminating the distortion brought about by the triaxial plexiglass. A correction factor was established during this phase. A series of consolidated undrained cyclic triaxial test was performed using a coarse soil. The results from the non-contact measurement technique were compared to the measured deformation from the linear variable displacement transducer. It was observed that deformation was higher in the area where failure occurs.

埋立高さの異なる名古屋港ポートアイランドの南海トラフ巨大地震時の耐震性評価査読有り

酒井崇之, 野田利弘, 中野正樹, 浅岡顕

土木学会論文集 A2(応用力学) 73 巻 ( 2 ) 頁： I_233-I_244 2018年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

名古屋港ポートアイランド(以下，PI)には，名古屋港の機能維持のため，毎年多くの浚渫土が仮置きされている．地震によりPIの護岸が被害を受けると，浚渫土の流出等により，名古屋港の機能低下に直結する恐れがある．本研究では，PIを対象に南海トラフ巨大地震を想定した地震動を用い，地震応答解析を実施し，浚渫土砂埋立高さがPIの地震時の挙動に及ぼす影響を調べた．結果は以下の通りである．現状の埋立高さであれば，浚渫土が護岸を乗り越えて港湾へ流出するまでには至らない．しかし，現状から4mの嵩上げを行うと，護岸部の変状が大きくなり浚渫土が港湾へ流出する危険性が高くなる．一方，埋立天高さを下げることにより，埋立地盤や護岸の側方流動を軽減できる．つまり，PIの埋立高さを少しでも低くすることが，地震被害を低減する上で重要である．

水～土連成有限変形解析による自然堆積粘土地盤に打設された杭に作用する地盤反力の検討査読有り

中井健太郎, 野田利弘, 河村精一, 白鳥洋平

土木学会論文集 A2(応用力学) 73 巻 ( 2 ) 頁： I_535-I_544 2018年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

地盤に長尺の杭が打設されている場合，地盤変位が大きく生じる大地震時には，杭の損傷が懸念される．これまでに，地盤の降伏および杭周面地盤の回り込みの影響を確認するために，土層内に配置された杭に強制変位を与える模型実験が実施され，杭に作用する地盤反力と粘性土のせん断強度の関係を把握している．本報では，模型実験のシミュレーションを行い，数値解析コードのValidationを行うとともに，自然堆積粘土地盤を想定した数値実験を実施した．その結果，1）間隙水のマイグレーションの影響で，地盤反力は，ある載荷速度領域内で急変すること，2）鋭敏比が大きく軟弱な自然堆積粘土地盤を想定した場合，再構成地盤に比べて地盤反力が小さくなるとともに，地盤内で局所的なせん断帯が次々と発生し，せん断ひずみの発生領域が広がることを示した．

名古屋大学減災館を活用した振動工学教育査読有り

岡本正吾, 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

工学教育（日本工学教育協会） 66 巻 ( 2 ) 頁： 64-68 2018年

Delayed deformation and progressive failure of slopes by soil-water coupled analysis

Asaoka A., Nakano M., Noda T., Mizuno K.

ISRM International Symposium 2000, IS 2000 2018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：ISRM International Symposium 2000, IS 2000

Delayed deformation and progressive failure of a cut slope in an overconsolidated clays is examined through a series of soil-water coupled finite deformation analysis using the subloading surface Cam-clay model for overconsolidated soils. In this present problem analyzed, the slope exhibits progressive failure after a long time period (90 years), associated with the fluctuation of nodal velocities on the slope. High shear strains occur initially at the toe of slope and subsequently propagate towards the top of slope with time forming a clear “circular slip surface”. The overconsolidation ratio (OCR) in this highly sheared zone is almost equal to 1.0 due to softening with swelling. Time to failure depends on the soil permeability that comes to the soil-water coupled analysis with Darcy's law. For either high initial OCR or low heights of the slope, no failure is observed due to lesser porewater migration within the slope that results low shear strain.

Scopus

Soil-water coupled analysis of pore water pressure dissipation method targeting even the case where excess pore water pressure exceeds the permissible value specified in the current design - examinations of effectiveness in reclaimed ground - 査読有り

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

Geotechnical Engineering Journal of the SEAGS & AGSSEA 48 巻 ( 3 ) 頁： 19-31 2017年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Japan has a large number of reclaimed regions unimproved against liquefaction and countermeasures in such regions are necessary to prepare for a great earthquake. A new macro-element method has been proposed that involves applying the soil-water-coupled finite deformation analysis code GEOASIA with an inertial term, and a numerical-analysis technique has been designed that quantitatively evaluates the improvement effect of the pore water pressure dissipation method (PWPDM). In this study, PWPDM effectiveness was examined for a reclaimed ground using the proposed method. Detailed examinations were conducted with the intention of developing a more advanced performance design, without being limited to the concept of the current design code. The main findings are as follows: 1) the proposed analysis code enables quantitative evaluation of the improved effectiveness of PWPDM in a reclaimed ground; 2) more advanced PWPDM designs are possible by not only suppressing the maximum excess pore water pressure to the permissible range of the current design code, but also evaluating the ground deformation adequately; and 3) the new macro-element method, capable of reproducing the phenomenon of well resistance, can evaluate the reduction in the improvement effect because of the degradation of drainage capability, thus making it useful for maintenance purposes such as drain clogging.

Soil-Water Coupled Analysis of Pore Water Pressure Dissipation in Performance Design-Examinations of Effectiveness in Reclaimed Ground 査読有り

Nonaka Toshihiro, Yamada Shotaro, Noda Toshihiro

GEOTECHNICAL ENGINEERING 48 巻 ( 4 ) 頁： 19-31 2017年12月

2011年東北地方太平洋沖震の余震時の補強土壁におけるにおける補強材の支圧抵抗と摩擦の動態観測査読有り

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

土木学会論文集C（地圏工学） 73 巻 ( 4 ) 頁： 311-329 2017年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）

補強土壁構造物は，これまでの地震時の実績より抗土圧構造物よりも高い耐震性が示されている．また，多くの機関で実施された実験により，その耐震性能の高さが証明されている．しかしながら，既往の研究はジオテキスタイルを用いた室内実験や模型実験が多く，全体安定などの挙動は示されているが，補強材軸力の効果や挙動については十分に把握されていない．本研究では，支圧抵抗と摩擦抵抗を組み合わせたアンカー式の補強材を用いた補強土壁において，2011年東北地方太平洋沖地震の余震時の補強材軸力を計測することができた．その結果，地震時には支圧補強体と摩擦補強体のそれぞれが抵抗力を発揮し，その抵抗力は補強材の土被りが小さい位置では支圧補強体，土被りが大きい位置では摩擦補強体が効果的に抵抗力を発揮することが示された．

DOI： 10.2208/jscejge.73.311

Seismic assessment of sheet pile reinforcement effect on river embankments constructed on a soft foundation ground including soft estuarine clay

Nakai Kentaro, Noda Toshihiro, Kato Kenta

CANADIAN GEOTECHNICAL JOURNAL 54 巻 ( 10 ) 頁： 1375 - 1396 2017年10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：Canadian Geotechnical Journal

Conventional seismic assessments of river embankments have focused on liquefaction damage of sandy ground. However, following the 2011 earthquake centered off the Pacific Coast of Tohoku, extensive damage of river embankments built on a clayey foundation has garnered greater attention. This paper presents seismic response analyses of river embankments constructed on soft and sensitive estuarine clay, as well as analyses of countermeasures implemented with sheet piles with a succession of penetration depth and placement. River embankments have kept stable if the clayey ground was assumed to be a nonsensitive condition. However, if a strong shake impacts actual sensitive clay, there is a risk of slippage generated from the clayey layer. If the penetration depth of piles is shallow in the clayey layer, the clay is strongly disturbed by the tip of the pile, generating extensive damage; if the penetration depth is sufficiently deep in the supporting layer, significant deformation control may be obtained at the reinforced side, although there is a risk of promoting deformation at the opposite side. These results indicate the importance of the specific inspection of pile penetration depth; otherwise, not only is it not possible to obtain a sufficient countermeasure effect, but also an adverse effect may be generated.

DOI： 10.1139/cgj-2016-0019

Web of Science

Scopus

A Full Formulation-based Soil-Water Coupled Finite Deformation Analysis on Undrained Compression Tests on Highly Permeable Soil Specimen 査読有り

Toyoda, T. and Noda, T.

Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, Seoul 2017 頁： 863-866 2017年9月

記述言語：英語

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.

Verification of a macro-element method in the numerical simulation of the pore water pressure dissipation method - A case study on a liquefaction countermeasure with vertical drains under an embankment

Nonaka Toshihiro, Yamada Shotaro, Noda Toshihiro

SOILS AND FOUNDATIONS 57 巻 ( 3 ) 頁： 472 - 487 2017年6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：Soils and Foundations

In the simulation of the vertical drain method using a soil-water coupled finite element analysis, a macro-element method has often been used as an approximate method to introduce the water absorption functions of drains into individual elements. In order to extend the function of this method, the authors modified the formula of the flow coefficient from soil to drains and introduced the discharge function of vertical drains to the method by treating the water pressure in the drains as an unknown and adding a continuity equation for the drains to the governing equations. The first attempt made it possible to divide a finite element mesh independently of the drain arrangement and the drain spacing, and the second attempt enabled the well resistance to be automatically generated by a series of calculations depending on the given conditions. Furthermore, although the macro-element method has been applied to quasi-static problems in most cases, the authors applied the expanded one to dynamic problems by equipping it with the soil-water coupled finite deformation analysis code GEOASIA with the inertial term. In this paper, in order to verify the new macro-element method in a dynamic problem, the results of a 2D approximate model using the new macro-element method were compared with those of a 3D exact model where vertical drains were exactly represented by finely dividing the finite element mesh in the case of a sand ground improved by the pore water pressure dissipation method under the embankment. The findings of this study are as follows: (1) 2D mesh-based analyses under plane strain conditions, using the new macro-element method, can accurately approximate 3D mesh-based analyses with a fine mesh in dynamic problems in terms of changes in the excess pore water pressure and ground deformation; (2) the new macro-element method can adequately evaluate the influence of drain spacing on a countermeasure for liquefaction in the quantitative sense, while using a single mesh; and (3) the new macro-element method improves the calculation efficiency in the simulation of the pore water pressure dissipation method by laborsaving in mesh-dividing and dramatically reducing the calculation time.

DOI： 10.1016/j.sandf.2017.05.012

Web of Science

Scopus

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

*Soil-water-air coupled finite deformation analysis based on a rate-type equation of motion incorporating the SYS Cam-clay model 査読有り

Noda, T. and Yoshikawa, T.

Soils and Foundations 55 巻 ( 1 ) 頁： 45-62 2015年2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）

With the aim of expanding the soil skeleton-water coupled finite deformation analysis code mounted with the SYS Cam-clay model and capable of accommodating inertia forces to deal seamlessly with soils from the unsaturated to the saturated states, a new soil skeleton-water-air coupled finite deformation analysis method (u-pw-pa-sw formulation) based on the three-phase mixture theory was proposed. The following are the main observations obtained through computations performed under simple conditions using this new method. (1)Simulation of constant cell pressure undrained (and unexhausted) triaxial tests on dense sand specimens with a degree of saturation of 99.9%, which in reality could be considered to be 'saturated soil,' was carried out. It was shown that when the back pressure was not sufficiently large, the existence of air causes desaturation to take place due to the effect of volumetric expansion and no increase in the deviator stress is observed. It was confirmed that the results of this simulation agreed with experimental results. (2)Unlike the conventional method of analysis in which the degree of saturation is not explicitly made an unknown, the current method of analysis, in which the degree of saturation is explicitly made an unknown (u -pw -pa -sw formulation), was shown to be capable of expressing the increase in the degree of saturation even in the case of insular air saturation when the suction is 0.

DOI： http://dx.doi.org/10.1016/j.sandf.2014.12.004

Resilient breakwater foundation against level II earthquake and tsunami

Hazarika, H., Chaudhary, B., Monji, N., Ishikura, R., Kasama, K., Hara, T., Yamazaki, N, Noda, T. and Yamada, S.

The 6th International Geotechnical Symposium on Disaster Mitigation in Special Geoenvironmental Conditions 頁： 35-46 2015年1月

浅層盤状改良工法による戸建て住宅の液状化被害軽減効果の検証と経済性評価査読有り

谷　和夫，松下克也，橋本隆雄，山本彰，竹内秀克，野田利弘，規矩大義，大林淳，清田隆

地盤工学ジャーナル 9 巻 ( 4 ) 頁： 533-553 2014年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）

2011年東北地方太平洋沖地震により発生した地盤の液状化により、数多くの戸建て住宅が被害を受けた。本研究では、戸建て住宅を対象とした経済的な液状化対策として、浅層盤状改良工法の適用の可能性について検討した。既往の研究と同地震による戸建て住宅の液状化被害を調査し、液状化に対する戸建て住宅に要求される性能として、その傾斜角を、中地震では10/1,000（めり込み沈下量10cmに相当）以下、大地震では16.7/1,000（めり込み沈下量15cmに相当）以下とすることが適切であることを示した。また、被害調査と遠心模型実験を通じて、浅層盤状改良工法による液状化対策の効果を明らかにした。そして、一連の数値解析により、表層地盤の固化工法による地盤改良層厚を3m以上とすることで、液状化に対する戸建て住宅の要求性能を満足することを示した。さらに、浅層盤状改良工法の種類と改良深度、改良面積をパラメータとした経済性評価を行い、同工法の設計に有益な情報を提供した。

DOI： http://dx.doi.org/10.3208/jgs.9.533

Numerical analysis of improvement effect on peaty ground by vertical drain/ vacuum consolidation based on a new macro-element method 査読有り

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

The 14th International Conference of the International Association for Computer Methods and Advances in Geomechanics (14IACMAG) 頁： 1145-1150 2014年9月

Seismic response analysis of river embankments constructed on alternatively layered soft ground 査読有り

Noda, T., Nakai, K. and Kato, K.

The 14th International Conference of the International Association for Computer Methods and Advances in Geomechanics (14IACMAG) 頁： 761-766 2014年9月

Evaluation of seismic behavior of model earth dams in the geotechnical centrifuge 査読有り

Kawai, T., Ishimaru, M. and Noda, T.

The 14th International Conference of the International Association for Computer Methods and Advances in Geomechanics (14IACMAG) 頁： 767-772 2014年9月

Soil-water coupled finite deformation analysis on subgrade reaction force acting on the underground pile 査読有り

Nakai, K., Noda, T., Komura, S. and Shiratori, Y.

The 14th International Conference of the International Association for Computer Methods and Advances in Geomechanics (14IACMAG) 頁： 997-1000 2014年9月

Verification of a new soil-water-air coupled analysis based on a rate-type equation of motion through realization of uniform deformation of an unsaturated soil specimen 査読有り

Noda, T. and Yoshikawa, T.

UNSAT2014: Unsaturated Soils: Research & Applications 頁： 613-619 2014年7月

Numerical simulation of mechanical behavior of a triaxial silty soil under undrained and various controlled air boundary conditions 査読有り

Yoshikawa, T. and Noda, T.

UNSAT2014: Unsaturated Soils: Research & Applications 頁： 589-595 2014年7月

Simulation of well resistance of vertical drains using new macro element method

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

COMPSAFE: Computational Engineering and Science for Safety and Environmental Problems 頁： 164-167 2014年4月

Seismic response analysis of river embankments constructed on the alternatively layered soft ground

Nakai, K., Noda, T. and Kato, K.

COMPSAFE: Computational Engineering and Science for Safety and Environmental Problems 頁： 140-143 2014年4月

Seismic and postseismic behavior of river levee on soft clay ground 招待有り

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

COMPSAFE: Computational Engineering and Science for Safety and Environmental Problems 頁： 138-139 2014年4月

A 3D soil-water coupled FE analysis of hollow cylinder test concerning non-uniform deformation 査読有り

Xu, B., Nakai, K., Noda, T. and Takaine, T.

Soils and Foundations 53 巻 ( 6 ) 頁： 923-936 2013年12月

Realization of uniform deformation of soil specimen under undrained plane strain condition based on soil-water coupled finite deformation analysis considering inertia forces 査読有り

Noda, T., Xu, B. and Asaoka, A.

Soils and Foundations 53 巻 ( 6 ) 頁： 937-950 2013年12月

Acceleration generation due to strain localization of saturated clay specimen based on dynamic soil-water coupled finite deformation analysis 査読有り

Noda, T., Xu, B. and Asaoka, A.

Soils and Foundations 53 巻 ( 5 ) 頁： 653-670 2013年10月

Simulation of delayed failure in naturally deposited clay ground by soil-water coupled finite deformation analysis taking inertial forces into consideration 査読有り

Yamada, S. and Noda, T.

Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013 頁： 841-844 2013年9月

Influence of brittle property of cement treated soil on undrained bearing capacity characteristics of the ground 査読有り

Yamada, S., Noda, T., Asaoka, A. and Shiina. T.

Geotechnical Engineering Journal of the SEAGS & AGSSEA 44 巻 ( 3 ) 頁： 84-93 2013年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

In this study, the influence of brittle property of geomaterials on the failure behavior of the ground in an undrained bearing capacity problem was investigated numerically from the standpoint of taking the brittle behavior of cement treated soil as softening behavior of the soil element. The numerical analyses were performed using the soil-water coupled finite deformation analysis code GEOASIA mounted with the SYS Cam-clay model, which describes the soil skeleton structure at work. Cement treated ground and naturally deposited clay ground were modelled and compared, and it was found that they showed widely differing failure processes depending on differing initial conditions. Especially, it was found that when progressive failure in which strain localization region develops due to propagation of material failure occurs, even though the ground is composed of brittle materials such as cement treated soil, those brittle properties do not directly manifest in the load-settlement relationship. Additionally, the investigation revealed that, since every soil element on the slip lines does not reach its peak strength simultaneously when progressive failure occurs, post-peak material properties, i.e. the ratio of residual strength to peak strength and softening rate from peak to residual state, affect the bearing capacity of the ground.

Oscillation of acceleration accompanying shear band and subsequent time-dependent behavior in overconsolidated clay under undrained plane-strain conditions 査読有り

Noda, T. and Xu, B.

Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013 頁： 403-406 2013年9月

SPH法による地盤の掘削解析査読有り

野々山栄人，中野正樹，野田利弘

土木学会論文集 A2(応用力学) 16 巻頁： I_341-I_350 2013年9月

ゆるい砂地盤における砂圧入締固めによる周辺地盤への3次元影響評価解析査読有り

竹内秀克，河村精一，野田利弘，浅岡顕

地盤工学ジャーナル 8 巻 ( 2 ) 頁： 239-249 2013年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）

「砂圧入式静的締固め工法」は，地盤中に流動化砂を圧入・押し広げることにより，周辺地盤に強制的に圧縮・せん断を与え，締固め効果を期待する工法である。工法の性格上，地盤に変位や応力を与えることに伴い，近接の既設構造物に少なからず影響を及ぼす。この影響の程度を予測／評価するためには，土要素の平均有効応力変化に伴う圧縮挙動だけでなく，せん断応力に伴うダイレイタンシー挙動もより精度よく評価する必要がある。本研究では，自然粘土～中間土～砂を一貫して説明することが可能な弾塑性構成式(SYSカムクレイモデル)を搭載する水～土連成有限変形解析を用い，3次元条件で砂圧入締固めの過程を再現して解析を実施した。この結果，砂圧入式静的締固め施工時の，周辺砂地盤の地表面および地中発生変位の距離に伴う減衰(距離減衰)や，近接構造物に与える地盤反力(側圧)分布は施工位置からの距離に応じて減少することがわかった。

Damage statistics (Summary of the 2011 off the Pacific Coast of Tohoku Earthquake Damage) 査読有り

Kazama, M. and Noda, T.

Soils and Foundations 52 巻 ( 5 ) 頁： 780-792 2012年10月

An attempt to replicate the so-called 'trampoline effect' in computational geomechanics

Asaoka, A., Sawada, Y., Noda, T., Yamada, S. and Shimizu, R.

Proceedings of l5th World Conference on Earthquake Engineering 頁： 1817 2012年9月

記述言語：英語

In this research, we reproduced the vertical asymmetrical acceleration response observed at the ground surface at KiK-net measurement station IWTH25 (West Ichinoseki) during the 2008 Iwate-Miyagi earthquake using the finite deformation analysis code GEOASIA, which employs an elasto-plastic constitutive equation, the SYSCam-clay model, that incorporates the concept of soil skeleton structure. Also, it was found that the asymmetrical acceleration motions in the vertical direction measured at the ground surface at this location can be caused by a ground uplift phenomenon associated with loosening of heavily overconsolidated soils.

Overview of the geotechnical damages and the technical problems posed after the 2011 off the Pacific Coast of Tohoku Earthquake 査読有り

Kazama, M., Noda, T., Mori, T. and Kim, T.

Geotechnical Engineering Journal of the SEAGS & AGSSEA 43 巻 ( 2 ) 頁： 49-56 2012年6月

SPH method with an elasto-plastic constitutive model taking account of soil skeleton structure at work

Nonoyama, H., Masaki, N. and Noda, T.

Proceedings of 6th International Workshop on New Frontiers in Computational Geomechanics 頁： 45-48 2012年5月

The effect of stratigraphic composition and dip of deeper layer on the occurrence of subsurface liquefaction

Nakai, K., Noda, T. and Asaoka, A.

Proceedings of 6th International Workshop on New Frontiers in Computational Geomechanics 頁： 173-176 2012年5月

A three-dimensional analysis of gas-governor located on a liquefiable soft ground

Takaine, T., Xu, B., Nakai, K. and Noda, T.

Proceedings of 6th International Workshop on New Frontiers in Computational Geomechanics 頁： 177-182 2012年5月

A preliminary simulation of undrained hollow cylinder torsional test on saturated overconsolidated clay

Xu, B., Nakai, K., Noda, T. and Asaoka, A.

Proceedings of 6th International Workshop on New Frontiers in Computational Geomechanics 頁： 177-182 2012年5月

Inertia effect on deformation and subsequent triggered acceleration during shear band in overconsolidated clay

Noda, T., Xu, B. Nakai, K. and Asaoka, A.

Proceedings of 6th International Workshop on New Frontiers in Computational Geomechanics 頁： 39-44 2012年5月

Numerical simulation of failure behavior of naturally deposited clay soil with dynamic motion

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

Proceedings of 6th International Workshop on New Frontiers in Computational Geomechanics 頁： 165-168 2012年5月

Anti-seismic mechanism of a sandy ground improved by SCP method 査読有り

Noda, T., Asaoka, A., and Takeuchi, H.

Proc. of 14th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (14th ARC) 頁： 273 2011年5月

担当区分：筆頭著者記述言語：英語

Anti-seismic mechanism of typical loose sandy ground improved by the sand compaction pile (SCP) method was investigated using the geo-analysis code GEOASIA, which is a dynamic/static soil-water coupled finite element deformation analysis code incorporating the SYS-Cam clay model as a constitutive model of the soil skeleton. The mechanism was evaluated on the two types of earthquakes, i.e., the so-called Level 1 (L1) and Level 2 (L2) earthquake motions under 2-dimensional plane strain conditions. The main conclusions are drawn as follows. (1)Compared with untreated grounds, the deformation caused by earthquakes is suppressed in the SCP-improved grounds, both L1 and L2 earthquake motions. (2)Stress concentration occurs at the sand piles because the sand element at the piles exhibits hardening behavior due to plastic expansion.

Numerical study on the seismic assessment of coastal reclaimed ground 査読有り

Nakai, K., Noda, T. and Asaoka, A.

Proc. of 14th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (14th ARC) 頁： 278 2011年5月

記述言語：英語

Seismic behavior of a coastal artificial reclaimed ground within the Port of Nagoya and antiseismic effects of two types of ground strengthening techniques were evaluated through numerical analysis. Use of the program GEOASIA for the numerical analysis enabled precise modeling of the targeted ground and consistent analyses of the pre-seismic, co-seismic, and post-seismic behaviors. Main findings are as follows. 1)Loose sand layers were subjected to large amount of lateral flow due to liquefaction during the earthquake, which led in turn to extensive damage to the revetment constructed on the reclaimed ground. 2) Steel pipe sheet pile cofferdam method is unlikely to be effective because the bending moment loaded on the steel pipes will exceed the yield stress during the earthquake. 3) Ground improvement using a jet grouting method will not contribute to damage reduction in the revetment area, but should drastically reduce the ground deformation around the improvement area.

Prediction of Settlement in Natural Deposited Clay Ground with Risk of Large Residual Settlement due to Embankment Loading 査読有り

Tashiro, M., Noda, T., Inagaki, M., Nakano, M. and Asaoka, A.

Soils and Foundations ５１巻 ( １ ) 頁： 133-149 2011年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

This study endeavors to predict the settlement that could occur in the future at a site where settlement due to embankment loading is already occurring at present. In the site studied here, large residual settlement of as much as 70 cm has already occurred in the 4 years since it entered into service. It is believed that settlement will also continue in the future because excess pore pressure is still present within the clay layers. Furthermore, according to the method of evaluation proposed previously by the authors, which is based on the sensitivity and compression index ratios, it can be judged that the ground includes clays that are sensitive to disturbance and have a strong possibility of large residual settlement. In this paper, simulation of the settlement observed up to now at the site as well as prediction of the settlement that could occur in the future was carried out by deducing the higher compressibilities possessed by the in-situ clays compared with the undisturbed clay specimens in the laboratory. The soil-water coupled finite deformation analysis was employed using the analysis program GEOASIA, in which the constitutive equation for the soil skeleton is mounted with the SYS Cam-clay model. In addition, the effect of modifying the vertical section of the embankment by overlaying in order to counter the settlement was also investigated by numerical analysis. The results showed that such a countermeasure cannot be expected to lead to faster consolidation and that it may require massive funding over a long period of time to cover the maintenance and management costs involved.

DOI： 10.3208/sandf.51.133

総説：巨大地震に備えるための現代地盤力学の役割招待有り

野田利弘

電力土木 ( 356 ) 頁： 6-11 2011年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

人工島・海上人工埋立地に生活・経済基盤を依拠する我が国にとって，切迫する巨大地震に対する人工地盤の耐震性再評価や耐震強化は喫緊の課題である。しかし，人工地盤の大半が粘土でも砂でもない細粒分を多く含んだ中間土からなるが，このことだけを取りあげても，砂だけ，粘土だけを対象にするような要素研究の細分化が進んだ近代土質力学的視野では対応できない。要素を統合的・俯瞰的視野で捉える新しい現代地盤力学の進展とその成果の工学への還元こそが必要となる。本稿では，この観点から近代土質力学の課題と現代地盤力学の役割について述べる。

軟弱地盤上に設置した仮設構造物の地震時安定性評価と転倒防止対策の一検討査読有り

中井健太郎, 野田利弘

地盤工学ジャーナル 5 巻 ( 3 ) 頁： 499-510 2010年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）

比較的簡単に設置・撤去ができる仮設構造物は，設置期間が短いものの，杭の設置や地盤改良など特段の対策が施されないため，施工・設置中に地震が発生した場合，転倒による人身被害等が懸念される。本論文では，2 種類の軟弱地盤（砂質地盤および粘性土地盤）上に建設された仮設構造物の地震時安定性を数値解析的に検討した。その結果，仮設構造物転倒の主たる原因は，単に加速度の増幅（最大加速度）ではなく，①仮設構造物の固有振動数と地盤の卓越振動数の一致に伴う揺れの増幅と，②表層地盤の液状化による支持力低下とそれに伴う構造物の不同沈下にあることがわかった。転倒防止対策としては，仮設構造物の幅と高さを変えることによって，構造物の固有振動数と地盤の卓越周波数を一致させないことも重要であるが，仮設構造物直下に敷設板を用いて構造物と地盤との設置面積を大きくすることが，簡単で効果的な対策となることがわかった。

部分的に固化改良したゆるい砂地盤の地震時／地震後応答解析査読有り

竹内秀克, 中井健太郎, 野田利弘

応用力学論文集，土木学会 13 巻頁： 443-452 2010年8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，薬液注入・高圧噴射等のセメント固化改良工法等により，部分的あるいは離散的に改良固化が施された砂質地盤を想定して，地震を受ける場合の変形抑止効果を数値解析的に調べた．解析は土骨格の弾塑性構成式にSYSカムクレイモデル3)4)を用いた水～土連成動的／静的有限変形計算コード（GEOASIA）5)6)により行い，改良砂質地盤の地震中および地震後の挙動を調べた．また定性的ではあるが，系統的な結果を得るために規則的に改良体を配置し，実スケールにて解析を実施して，改良部が周辺地盤に与える影響も調べた．

Seismic response analysis of a coastal artificial reclaimed ground containing a soft layer 査読有り

Noda, T., Nakai, K. and Asaoka, A.

IOP Conference Series: Materials Science and Engineering, Vol.10, Proceedings of 9th World Congress on Computational Mechanics and 4th Asian Pacific Congress on Computational Mechanics CD, No.012107 巻頁： 19-23 2010年7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 seismic resistance of a coastal artificial ground situated within the Port of Nagoya against the Tokai-Tonankai-Nankai triple-segment earthquake was assessed. The analysis was carried out using the elasto-plastic constitutive equation for soils (SYS-Cam clay model) mounted on the soil-water coupled finite element deformation analysis program The model focuses attention on the action of the soil skeleton structure, and the analysis allows description of the mechanical behavior of a wide range of soils without distinguishing between static and dynamic behavior. When considering earthquake damage, attention usually tends to focus only on the phenomenon of liquefaction in sandy grounds. In this paper, finite element analysis was employed to simulate the phenomenon of liquefaction of soft sand and, in addition, to show that because of disturbance of the soil during the earthquake, there is a danger of large settlement occurring over a long period after the earthquake in the soft clay layer directly beneath the area that is under the action of vertical loads.

Different failure modes of a clay foundation-embankment system corresponding to different incident seismic waves 査読有り

Nakai, K., Noda, T., and Asaoka, A.

Geotechnical Special Publication No.201, Soil Dynamics and Earthquake Engineering, ASCE 頁： 125-130 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

In recent years, damage to embankments from earthquakes has been frequently reported. In this paper, the deformation and failure behavior of an embankment constructed on a weak clay foundation during and after an earthquake is investigated using numerical analysis, GEOASIA, assuming a 40 g centrifugal field. The main conclusions obtained were as follows. 1) Although the embankment remained stable without large deformation during the earthquake, a slip plane subsequently penetrated through the embankment, resulting in delayed failure (circular arc slip). 2) The deformation behavior (failure mode) of the foundation and embankment varies greatly depending on the characteristics of the incident seismic motions.

Modeling and seismic response analysis of a reclaimed artificial ground 査読有り

Noda, T., Asaoka, A. and Nakai, K.

Geotechnical Special Publication No.201, Soil Dynamics and Earthquake Engineering, ASCE 頁： 294-299 2010年6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）

Compared with natural grounds formed by sedimentation over many years, reclaimed artificial grounds are often weak. In this work, modeling of a reclaimed offshore artificial ground and its seismic response analysis were carried out, and the vulnerability of the weak reclaimed layers to seismic activity is pointed out. This study was carried out using a soil-water coupled finite deformation analysis program GEOASIA incorporating an elasto-plastic constitutive model (the SYS Cam-clay model). This model is capable of describing, within a single framework, the behaviors of sands, clays, and intermediate soils consisting of sand/clay mixtures through their soil skeleton structures (structure, overconsolidation, anisotropy) and its works. In reclaimed sand, lateral flow and upward lifting of lightweight underground structures occur because of liquefaction during an earthquake. In reclaimed clay, long-term settlement, which continues for several years after the earthquake, occurs.

Numerical analysis on co- and postseismic behavior of sandy/clayey soil ground improved by sand compaction pile method 査読有り

Takeuchi, H., Noda, T., and Asaoka, A.

Geotechnical Special Publication No.201, Soil Dynamics and Earthquake Engineering, ASCE 頁： 218-224 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

The co- and postseismic behaviors of typical loose sandy ground and soft clayey ground improved by the sand compaction pile (SCP) method were investigated using a soil-water coupled finite element deformation analysis program incorporating the SYS-Cam clay model. The results indicated that the deformation caused by earthquakes was suppressed in the SCP improved grounds, irrespective of whether they were sandy or clayey. Although the surrounding ground was liquefied in the case of SCP-improved sandy ground, the confining pressure was maintained in the SCP interpile zone because of the compaction effect produced by the cavity expansion of the sand piles. In the case of the SCP-improved clayey ground, negative excess pore pressures appeared in the SCP sand piles because of the hardening that results from plastic expansion and stress was concentrated on them.

Soil-water coupled finite deformation analysis of seismic deformation and failure of embankment on horizontal and inclined ground 査読有り

Nakano, M., Sakai, T., Noda, T., and Asaoka, A.

Geotechnical Special Publication No.201, Soil Dynamics and Earthquake Engineering, ASCE 頁： 139-144 2010年6月

Seismic stability assessment of a steel plate built-up column sited on a liquefiable soft ground

Nakai, K., Noda, T., Xu, B. and Asaoka, A.

Proceedings of 5th International Workshop on New Frontiers in Computational Geomechanics, IWS-Brisbane 頁： 69-74 2010年5月

Seismic stability assessment of a lightweight structure on sandy/clayey foundations 査読有り

Nakai, K. and Noda, T.

Recent Developments of Geotechnical Engineering, Proc. of the 4th Japan-China Geotechnical Symposium 頁： 564-571 2010年4月

記述言語：英語

For a temporary structure, which is comparatively easy to placement and withdrawal, special countermeasures such as pile penetration or ground improvement are not taken into considerations. As a consequence, when an earthquake occurs during the placement/construction, personal injury might be caused by overturning of the temporary structure. In this paper, co- and post-seismic responses of interactive systems consisting of a temporary structure - alternately layered sandy/clayey foundations were numerically investigated by using a soil-water coupled elasto-plastic finite deformation analysis. The findings are mainly as follows. 1) An unstable structure such as temporary structure become at high risk of overturning by means of liquefaction of sand layer. 2) Although it is possible to consider countermeasure against overturning by widen the breadth and lower the height of the temporary structure, it turned out that installation of a construction board is very effective.

Predictive simulation of deformation and failure of peat-calcareous soil layered ground due to multistage test embankment loading

Takaine, T., Tashiro, M., Shiina, T., Noda, T., and Asaoka, A.

Soils and Foundations 50 巻 ( 2 ) 頁： 245-260 2010年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

The continuous behaviour of a ground-embankment system from the stage of deformation up to failure was predicted with respect to an actual test embankment that had been constructed in stages on a soft ground made up of peat and calcareous soil. The behaviour prediction was carried out by employing soil-water coupled finite deformation analysis, which also included simulation of the embankment construction process. The information used in the analysis was limited to such things as the results of soil tests on soil materials (peat and calcareous soil) sampled from the ground, including their sensitivity ratios, and the embankment's construction history. The SYS Cam-clay model was used in the constitutive equations of the soils to determine the material constants of the soils and the initial conditions of the ground, and the computations were performed under plane strain conditions. As a result, the computed profiles of W-type ground settlement and of slip surfaces running through the embankment were found to be in good overall agreement with the actual profiles measured at the site. Furthermore, we found that this slippage is attributable to the undrained shear response of the soil elements in the calcareous soil layer, where slippage begins to occur during embankment loading. In other words, the slippage is caused by the rapid softening behaviour caused by the degradation of structure after the effective stress ratio reaches the vicinity of the critical state line.

Reproduction of a reclaimed ground considering its construction history and evaluation of its seismic behavior by using a soil-water coupled analysis 査読有り

Noda, T., Yamada, E., Nakano, M., Asaoka, A. and Sun, K.

Recent Developments of Geotechnical Engineering, Proc. of the 4th Japan-China Geotechnical Symposium 頁： 174-179 2010年4月

担当区分：筆頭著者記述言語：英語

The Nagoya port has reclaimed grounds of about 4500ha now, and has supported the economic activity of the postwar period of Japan. In the Chubu area including this Nagoya port, it is said that a trench type big earthquake occurs in high probability. In this paper, first, a reclaimed ground in the Nagoya port was reproduced numerically by using the geo-analysis code GEOASIA according to the construction history from the reclamation-by-drainage performed about 200 years ago to the present. In this calculation, the influence of the Tonankai earthquake which occurred in 1944 was also taken into consideration. Next, the Tonankai and Tokai linked-type earthquake assumed here from now on was inputted into this reclaimed ground by using the same analysis code in order to evaluate the co- and post-seismic behavior of the ground. The main findings from the results of the analysis were as follows. (1) In the linked-type earthquake assumed, liquefaction may occur even in diluvial sand layer whose N-values are comparatively large, and consolidation settlement of the layer may occur after the earthquake as well as the clay layer. (2) Quay wall may move about 3.5m horizontally to the sea side.

剛な構造物近傍の埋戻し地盤の地震時沈下挙動に関する遠心力模型実験とその数値シミュレーション査読有り

河井正，石丸真，野田利弘，浅岡顕

地盤工学ジャーナル 5 巻 ( 1 ) 頁： 45-59 2010年3月

記述言語：日本語掲載種別：研究論文（学術雑誌）

2007年新潟県中越沖地震の際，東京電力柏崎刈羽原子力発電所では，底面が岩着された原子炉建屋近傍で局所的に大きな埋戻し土の沈下が生じたことが報告されている。本研究では，剛な構造物近傍において，地震時にこのような大きな沈下が確認された例が少ないことを踏まえ，地盤の拘束圧を実物に近づけることが可能な遠心力模型実験によって現象を再現し，近傍地盤では，構造物から離れた地盤と同様の土の圧縮による沈下に加えて，壁面から地盤が離れる際に主働すべりによる沈下が生じていることを把握した。さらに，遠心力模型実験を対象にGEOASIA によるFE 解析を実施し，沈下現象の再現を試みた。その結果，解析結果において，地盤のダイレイタンシーに伴う土の圧縮による地盤の沈下が再現されており，構造物の近傍における上述の主働すべりによる大きな沈下も概ね再現可能であった。

練返し試料の圧縮曲線に及ぼす試料作製時の含水比の影響査読有り

田代むつみ，稲垣太浩，中野正樹，野田利弘，浅岡顕

地盤工学ジャーナル 5 巻 ( 1 ) 頁： 81-87 2010年3月

記述言語：日本語掲載種別：研究論文（学術雑誌）

自然堆積粘土の力学特性を把握するためには骨格構造概念が重要であり，骨格構造の働きを定量的・定性的に記述するためには，土台となる練返し試料による試験が必要不可欠である．本論文では，練返し試料の圧縮曲線に着目し，練返し時の含水比が及ぼす影響について検討した結果，以下の結論を得た．(1)液性限界よりも低い含水比で練り返した試料は，試料が固く練返しに大きな力を必要とするため過圧密土的な挙動を示す．(2)液性限界よりも高い含水比で練り返した試料は，構造が残存し嵩張った挙動を示す．(3)骨格構造を完全に喪失した練返し試料の作製に最も適した含水比は，液性限界である．

Proposal of a simple method for assessing the susceptibility of naturally deposited clay grounds to large long-term settlement due to embankment loading 査読有り

Inagaki, M., Nakano, M., Noda, T., Tashiro, A. and Asaoka, A.

Soils and Foundations 50 巻 ( 1 ) 頁： 109-122 2010年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

A simple method that utilizes the results of laboratory tests has been proposed for judging soft clay grounds that are susceptible to large residual consolidation settlement due to embankment loading. It was found that there is a possibility of large long-term settlement if the sensitivity and compression index ratios of the clay material that constitutes the ground are equal to or more than 8.0 and 1.5, respectively. The compression index ratio is defined in this paper as the ratio (Cc/Ccr) of the steepest gradient of the compression curve of an undisturbed sample to that of a remolded sample. Through the SYS Cam-clay model, an elasto-plastic constitutive model that describes the actions of the soil skeleton structure, it was found that clays with large sensitivity and compression index ratios are characterized by initially highly structured soils initially and that decay/upgradation of the structure can occur easily due to plastic deformation. In addition, by following Schmertmann's graphic method for the compression curves of in-situ compression curve(1953), this paper proposes a method of deducing the in-situ initial conditions from the results of laboratory consolidation tests on undisturbed samples. These investigations revealed not only that large delayed settlement is facilitated in clays that have high levels of structure and fast rates of structural decay, but also that the Δe method and other simple methods of predicting settlement may underestimate the amount of settlement.

*Co-seismic and post-seismic behavior of an alternately layered sand-clay ground and embankment system accompanied by soil disturbance 査読有り

Noda, T, Takeuchi, H., Nakai, K. and Asaoka, A.

Soils and Foundations 49 巻 ( 5 ) 頁： 739-756 2009年10月

Aiming at all soils all states all round geo-analysis integration 招待有り

Asaoka, A. and Noda, T.

International Symposium on Urban Geotechnics, Incheon, Korea 頁： 3-26 2009年9月

過圧密地盤の排水支持力解析査読有り

山田正太郎，野田利弘，浅岡顕

応用力学論文集，土木学会 12 巻頁： 247-254 2009年8月

飽和地盤に埋設されたダクト構造物の地震時挙動に関する数値シミュレーション査読有り

河井正，野田利弘，浅岡顕

応用力学論文集，土木学会 12 巻頁： 1021-1028 2009年8月

Evaluation of seismic performance of a box culvert buried in saturated sand with centrifuge and its numerical simulation 査読有り

Kawai, T., Noda, T. and Asaoka, A.

Proc. Int, Conf. on Performance-Based Design in Earthquake Geotechnical Engineering — from case history to practice —, IS-Tokyo 頁： 1087-1093 2009年6月

Coseismic and postseismic behavior of intermediate soil ground improved by sand compaction pile method 査読有り

Takeuchi, H., Noda, T. and Asaoka, A.

Proc. Int, Conf. on Performance-Based Design in Earthquake Geotechnical Engineering — from case history to practice —, IS-Tokyo 頁： 1199-1205 2009年6月

Numerical analysis on deformation/failure patterns on embankments observed in 2004 Chuetsu earthquake 査読有り

Noda, T., Nakano, M., Asaoka, A., Yamada, E., Itabashia, K. and Inagaki, M.

Proc. Int. Symp. on Prediction and Simulation Methods for Geohazard mitigation, IS-Kyoto 2009 頁： 103-109 2009年5月

*Soil-water coupled finite deformation analysis based on a rate-type equation of motion incorporating the SYS Cam-clay model 査読有り

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

Soils and Foundations 48 巻 ( 6 ) 頁： 771-790 2008年12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）

This paper presents a new method of soil-water coupled finite deformation analysis of saturated soils that considers inertial forces. This method allows changes in the geometric shape of the soil to be taken into account and is capable of dealing with all types of external forces irrespective of whether they are static or dynamic. To be more specific, the paper describes the following points, which differ from the conventional methods: 1) the governing equations for saturated soil including the rate-type equation of motion containing a jerk term of the soil skeleton conforming to u-p formulation and updated Lagrangian, 2) derivation of a weak form of the rate-type equation of motion and discretization of the finite elements, and 3) use of the implicit time integration method for application of the conventional linear acceleration method (which assumes linear variation of acceleration) to the jerk term.
By mounting the elasto-plastic constitutive equation (SYS Cam-clay model), which can cover a wide range of soils and soil conditions, onto the above method of analysis, examples of simulation of dynamic/static triaxial laboratory testing of saturated soil specimens are described. The soil specimens were assumed to be medium dense sand under conditions of small-amplitude cyclic loading, partial drainage, and constant cell pressure. The simulation yielded the following results. (1) In the case of low frequencies, compaction occurs during loading and compression progresses over the entire specimen. (2) In the case of high frequencies, during loading and in the period in which wave propagation continues within the specimen after the end of loading, compaction occurs at the drained end of the specimen, whereas liquefaction occurs in its interior. After this stage, massive compression takes place within the specimen, leading to consolidation (consolidation after liquefaction).

Delayed failure of a clay foundation-embankment system after the occurrence of an earthquake 査読有り

Noda, T., Nakai, K. and Asaoka, A.

Theoretical and applied mechanics JAPAN 57 巻頁： 41-47 2008年12月

Ground improvement of intermediate reclaimed land by compaction through cavity expansion of sand piles 査読有り

Nakano, M., Yamada, E. and Noda, T.

Soils and Foundations 48 巻 ( 5 ) 頁： 653-671 2008年10月

Numerical simulation of centrifugal model tests on seismic response of embankment-foundation systems

Nakai, K., Noda, T. and Asaoka, A.

Proc. of 4th International Workshop on New Frontiers in Computational Geomechanics(IWS-Pittsburgh) 頁： 29-32 2008年10月

Post-seismic consolidation settlement of clayey soil due to the co-seismic disturbance

Noda, T., Takeuchi, H., Nakai, K., Nakano, M. and Asaoka, A.

Proc. of 4th International Workshop on New Frontiers in Computational Geomechanics(IWS-Pittsburgh) 頁： 57-60 2008年10月

Delayed failure of a clay foundation-embankment system after the occurrence of an earthquake

Noda, T., Nakai, K. and Asaoka, A.

Proc. of 57th Japan national congress for theoretical and applied mechanics (Ed. Murakami,.A.) 頁： 41-47 2008年6月

担当区分：筆頭著者記述言語：英語

By using a soil-water coupled finite element method, deformation/failure behavior during and after the occurrence of an earthquake in a clay foundation-embankment system was numerically examined. The elasto-plastic constitutive model for the soil skeleton is the Super/subloading Yield Surface Cam-clay model. The embankment was calculated as a saturated soil. The results showed that the embankment maintained stability without any significant large deformation during the earthquake, while slip failure penetrating to the crest was suddenly generated a few hours after the earthquake.

Effects of embankment rigidity on behavior of naturally deposited soils during/after earthquakes

Noda, T., Asaoka, A, Nakano, M. Nakai, K. and Takeuchi, H.

Proc. of International Workshop on Earthquake Hazards and Mitigations 頁： 249-256 2007年12月

記述言語：英語

The effects of the rigidity of earth structures such as embankments on the deformation behavior of sand-clay laminated soil (top layer of sand, under-layer of clay) and embankment coupled systems during and after earthquakes were investigated. The investigation was carried out through static and/or dynamic soil-water coupled finite deformation analysis using the SYS Cam-clay model as the constitutive equation of soils. The results showed that the large-scale deformation behavior of the top sand layer during and after seismic activity is different from that of the clay under-layer depending on the rigidity of the embankment. If the embankment is made up of soft soil, the occurrence of liquefaction of the top sand layer during an earthquake is accompanied by large-scale deformation of the embankment itself, but the clay under-layer remains almost unaffected even after the earthquake. In contrast, if the embankment is rigid, while the sand layer is again subjected to liquefaction during the earthquake, the embankment load is transferred to the lower clay layer, leading to large-scale ground (clay layer) settlement after the earthquake has passed.

Elasto-plastic description of various soils having distinct skeleton structure 招待有り

Noda, T.

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) Post conference volume 巻頁： 364-373 2007年12月

記述言語：英語

Naturally deposited clay and loose sand are generally said to have a highly developed soil skeleton structure. Of the three skeletal determinants (structure, overconsolidation, anisotropoy), this paper focuses particularly on structure and argues that alongside structural degradation there is also an opposite process of upgradation. This upgradation process is then introduced as a new extension into the authors' existing SYS Cam-clay model, which incorporates the soil skeleton mechanisms into the original Cam-clay model as a base. Using this extended model, observations are made on the role of the upgradation process in leading to a ductility behavior in the naturally deposited clay and to a cyclic mobility behavior in the sand.

Structural upgradation in clay and sand accompanying plastic swelling 査読有り

Noda, T., Asaoka, A., Nakai, K. and Tashiro, M.

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) 頁： 23-26 2007年12月

記述言語：英語

Liquefaction-induced consolidation settlement of soil after earthquake 査読有り

Asaoka, A., Sawada, Y., Noda, T. and Nakai, K.

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) 頁： 602-605 2007年12月

記述言語：英語

A calculated case history concerning a soil of alternate layers of sand and clay is presented through a soil-water coupled computation employing the SYS Cam-clay model. Delayed consolidation settlement at this site has definitely been occurring as a result of embankment loading, and is in fact still continuing. In the computation, the delayed compression is due to a progressive breakdown in the clay skeleton structure. If there were to be an earthquake in the course of this delayed consolidation, even the medium-dense upper layer of sand would be certain to liquefy, resulting in considerable undrained shearing deformation in the clay layers beneath. Following the earthquake, the sand layer would consolidate within a few hours, but the underlying clay layers would remain subject to an additional consolidation settlement due to the earthquake for several tens of years.

Seismic/post-seismic response of a natural soil in delayed settlement

Asaoka, A. and Noda, T.

頁： 73-86 2007年11月

記述言語：英語

This paper is a natural extension of the former paper (Asaoka and Noda, 2007), published by the same authors in the international workshop on Constitutive Modelling held in Hong Kong. The behavior of a naturally deposited soil in a delayed consolidation phase during/after and earthquake is presented as a soil-water coupled calculation example. Emphasis is laid throughout on the importance of an analytic technique that copes consistently with all soils, clay or sand, in all states, consolidated or liquefied/compacted, and is sufficiently all-round to cover both static and dynamic problems. The soil in the example consists of an 8m top-layer of sand and a 13m under-layer of alluvial clay, and has undergone more than 20 years of continuous consolidation settlement since being loaded with a highway embankment. Settlement loss exceeds 3m, and no end to the process is yet in sight. After showing that delayed compression of this kind is due to a progressive breakdown in the clay skeleton structure, this paper makes clear what will happen at this site if the top-layer of sand is liquefied by being struck by an earthquake and sustained consolidation/shear deformation then continues in the clay under-layer for several tens of years.

Explanation of cyclic mobility of soils: approach by stress-induced anisotropy 査読有り

Zhang, F., Ye, B., Noda, T., Nakano, M. and Nakai, K.

Soils and Foundations 47 巻 ( 4 ) 頁： 635-648 2007年8月

*Some bearing capacity characteristics of a structured naturally deposited clay soil 査読有り

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

Soils and Foundations 47 巻 ( 2 ) 頁： 285-301 2007年2月

*All soils all states all round geo-analysis integration

Asaoka A. and Noda, T.

International Workshop on Constitutive Modelling - Development, Implementation, Evaluation, and Application 頁： 11-27 2007年1月

Some distinct characteristics of natural clay that yields large residual consolidation settlement

Nakano, M., Tashiro, M., Noda, T. and Inagaki, M.

Proc. of 3rd Int. Workshop on New Frontiers in Computational Geomechanics (IWS-XIAN 2006) 頁： 73-78 2006年10月

High ductility of structured clay and cyclic mobility of sand

Nakai, K., Noda, T., Nakano, M., Tashiro, M. and Asaoka, A.

Proc. of 3rd Int. Workshop on New Frontiers in Computational Geomechanics (IWS-XIAN 2006) 頁： 183-186 2006年10月

飽和粘土地盤の圧密変形に及ぼす幾何学的非線形性の効果査読有り

竹内秀克，高稲敏浩，野田利弘

応用力学論文集，土木学会 9 巻頁： 539-550 2006年9月

A super/subloading yield surface approach to compaction/liquefaction of sand and secondary consolidation of clay

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

Proc. of the 2nd China-Japan Geotechnical Symposium 頁： 24-33 2005年10月

Progressive consolidation settlement of naturally deposited clayey soil under embankment loading 査読有り

Noda, T., Asaoka A., Nakano, M., Yamada, E. and Tashiro, M.

Soils and Foundations 45 巻 ( 5 ) 頁： 39-52 2005年10月

Long-term consolidation settlement with progressive failure of soil skeleton structure

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

Proc. 2nd Int. Workshop on New Frontiers in Computational Geotechnics (IWS-Fortaleza) 頁： 83-88 2005年9月

Progressive consolidation of highly structured clay under embankment loading 査読有り

Asaoka A., Noda T., Yamada E. and Tashiro M.

Proc. the 16th Int. Conference on Soil Mechanics and Geotechnical Engineering 頁： 1831-1835 2005年9月

記述言語：英語

A long-term continuous consolidation settlement often observed in a natural soft clay foundation is numerically simulated using "super/subloading elasto-plastic constitutive model." The settlement behavior was found to exhibit accelerated rate of settlement several times during consolidation with a rise of excess pore water pressure under a constant applied load after the completion of the embankment. The likely causes of this lie in the progressive decay of soil skeleton structure of the clay which causes "compression accompanied by softening."

Soil-water coupled elasto-plastic analysis on bearing capacity of naturally deposited clay soil 査読有り

Noda, T. and Yamada S.

Proc. the 16th Int. Conference on Soil Mechanics and Geotechnical Engineering 頁： 933-937 2005年9月

担当区分：筆頭著者記述言語：英語

To investigate a problem of bearing capacity of a natural clay, a soil-water coupled finite deformation analysis is performed with the elasto-plastic constitutive model that describes the effect of the decay of soil skeleton structure due to plastic deformation. From the computational results the findings are as follows: (1) In a structured clay soil, a load peak phenomenon appears, accompanied by a local circular slip field. (2) In a clay soil possessing anisotropy, this area of failure is more confined, and the peak is lower.

沈下低減と荷重分担に着目したパイルドラフト敷設地盤の変形解析査読有り

野田利弘，田代むつみ，高稲敏浩，浅岡顕

土木学会論文集 799 巻 ( Ⅲ-72 ) 頁： 37-49 2005年9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）

パイルドラフトを弾性体，自然堆積地盤を水～土2相系の弾塑性体として，3次元有限変形解析を実施し，基礎形式（杭長・杭配置）・ラフト剛性等が，沈下量低減と杭の荷重分担率に及ぼす影響を調べた．杭が長い場合ほど高拘束で低圧縮性の地盤深部に荷重が伝達され，また杭が外側に均等配置された場合ほど地盤から受ける杭の摩擦抵抗が大きくなるため沈下抑制に効果的であるが，杭の荷重分担率が大きくなる,などを示した．

A soil-water coupled analysis on compaction of sandy ground

Noda, T., Yamada, E., Yamada, S. and Asaoka, A.

Geomechanics: Testing, Modeling, and Simulation, Geotechnical Special Publication No. 143 頁： 269-285 2005年6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 mechanism and characteristics of a static compaction pile method for sandy ground that is used as a measure against liquefaction, in which non-vibratory cavity expansion is gradually carried out from the bottom up, are numerically investigated using a soil-water coupled computation. The compaction procedure of the sandy ground is simulated employing a Super/subloading Yield Surface Cam-Clay model as an elasto-plastic constitutive model for sand. By introducing the concepts of soil structure, overconsolidation and stress-induced anisotropy and their evolutions, this model allows the description of a wide variety of sand behaviors using a single set of material parameters that are independent on density.
From the computational results, it is found that loose sandy ground is easily compacted/densificated because, in terms of sand elements, the soil structure of the sand is rapidly collapsed until the expansion takes place around the sand element and at the loading stages at which the casing pipe is driven in. Moreover, the shear characteristics of the ground are further improved because the overconsolidation ratio of the sand is increased cumulatively when the expansion is performed above the sand element and at the unloading stages at which the casing is pulled out.

Mechanical behaviour of structured clay and simulation

Shibuya, S. Li, D. Noda, T. and Nakano, M.

Geomechanics: Testing, Modeling, and Simulation, Geotechnical Special Publication No. 143 頁： 286-306 2005年6月

Elasto-plastic behavior of naturally deposited clay during/after sampling 査読有り

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

Soils and Foundations 45 巻 ( 1 ) 頁： 51-64 2005年2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）

Changes in soil structure and overconsolidation in highly structured natural deposited clay as a result of sampling and setting in laboratory tests, together with their effects on the subsequent mechanical behavior, are numerically investigated in terms of unconventional elasto-plastic mechanics. To describe the mechanical behavior, a Super/subloading Yield Surface Cam-Clay model is employed. This model allows a description of the decay of soil structure, loss/increase of overconsolidation and evolution of anisotropy with ongoing plastic deformation from the process of the soil sampling through the unloading with swelling up to the subsequent tests.
The clay sample, after being collected, mounted on the test apparatus, and subjected to isotropic unloading and/or one-dimensional unloading with swelling down to the first stage vertical loading level, displays a response to some degree different from that of the soil at the original sampling site, in the following respects. An overconsolidated sample subjected to isotropic unloading with swelling will display rewinding behavior in a subsequent undrained tri-axial compression test, and “secondary consolidation"/“delayed compression" in a one-dimensional consolidation test. In contrast, a sample subjected to one-dimensional unloading with swelling will not become heavily overconsolidated but will remain in a state of either slight overconsolidation or normal consolidation accompanied by destructuration, and will display unloading at the beginning of a subsequent one-dimensional compression test. The most important thing to note from the testing viewpoint is that one-dimensional unloading with swelling gives better results than isotropic unloading, in the sense that the subsequent compression test is better able to predict the in-situ “consolidation yield stress".
Artificially disturbed clay subjected to repeated undrained shearing after sampling suffers a significant loss of structure. This results in a drop in

Simulation of shear and one-dimensional compression behavior of naturally deposited clays by Super/subloading Yield Surface Cam-Clay Model 査読有り

Nakano, M., Nakai, K., Noda, T. and Asaoka, A.

Soils and Foundations 45 巻 ( 1 ) 頁： 141-151 2005年2月

Elasto-plastic description of undrained shear behavior of sand depending on confining stress

Nakano, M., Noda, T., Nakai, K. and Asaoka A.

Proc. of. Int. Symposium on Plasticity 2005 頁： 283-285 2005年1月

Description of "compaction" and "liquefaction" behavior of sand based on evolution of soil skeleton structure

Nakai, K, Nakano, M., Noda, T. and Asaoka, A.

Proc. 2nd International Workshop on New Frontiers in Computational Geotechnics (IWS-Fortaleza) 頁： 29-32 2004年9月

カムクレイモデルと骨格構造が発達した土の弾塑性モデル

野田利弘、山口栄輝、堤成一郎

土と基礎，地盤工学会 52 巻 ( 8 ) 頁： 10-12 2004年8月

土の骨格構造の働きに着目した「擬似過圧密効果」の一考察査読有り

田代むつみ, 野田利弘,中野正樹

応用力学論文集，土木学会 7 巻頁： 589-596 2004年8月

Mechanical behaviors of clay and sand in terms of active soil skeleton structure 査読有り

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

Proc. Int. Conference on Computational & Experimental Engineering and Sciences (ICCES'04), Madeira, Portugal. 頁： 772-777 2004年7月

Mechanical differences between sand and clay under monotonic and cyclic loading 査読有り

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

Proc. Int. Conference on Cyclic Behaviour of Soils and Liquefaction Phenomena (CBS04), Bochum, Germany. 頁： 77-84 2004年3月

Piled raft foundation behavior on a soft soil system 査読有り

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

Proc. Int. Symposium on Shallow Foundations (FONDSUP 2003), Paris. 頁： 209-212 2003年11月

Delayed settlement behavior of naturally deposited clayey soil due to the decay of soil structure 査読有り

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

Proc. Int. Workshop on Prediction and Simulation Methods in Geomechanics (IWS-Athens 2003) 頁： 173-176. 2003年10月

Delayed compression associated with low land subsidence due to dewatering 査読有り

Kaneda, K., Noda, T., Nakano, M., Asaoka A. and Yamada, S.

Proc. of Sino-Japanese Symposium on Geotechnical Engineering, Beijing. 頁： 25-32 2003年10月

Soil-water coupled analysis of upheaval behavior of soil after deep excavation 査読有り

Noda, T., Yamada, E., Asaoka, A. and Kuriyama, K.

Proc. of Sino-Japanese Symposium on Geotechnical Engineering, Beijing. 頁： 173-180 2003年10月

Compaction behavior of sand with degradation of structure and overconsolidation 査読有り

Nakano, M., Noda, T., Asaoka A. and Nakai, K.

Proc. of Sino-Japanese Symposium on Geotechnical Engineering, Beijing. 頁： 455-462 2003年10月

Compaction of sandy ground by "static" cavity expansion 査読有り

Noda, T., Yamada, E. and Yamada, S.

Proc. 12th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering 頁： 501-504 2003年8月

土の構造とメカニックス」-ミクロからマクロへ-　6. 土の微視的構造の変化と弾塑性モデル

浅岡顕、中野正樹、野田利弘

土と基礎，地盤工学会 51 巻 ( 2 ) 頁： 43-48 2003年2月

Elasto-plastic description of shear behavior after compaction of loose sand

Nakano, M., Noda, T., Yamada, E., Kaneda, K., Nakai, K. and Asaoka A.

Proc. 1st International Workshop on New Frontiers in Computational Geomechanics (IWS-CALGARY 2002) 頁： 27-32 2003年1月

*An elasto-plastic description of two distinct volume change mechanisms of soils 査読有り

Asaoka, A., Noda, T., Yamada, E., Kaneda, K. and Nakano, M.

Soils and Foundations 42 巻 ( 5 ) 頁： 47-57 2002年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

In critical state soil mechanics, the volume change behavior of soils has typically been analyzed based upon conventional "e-logp' relationships". However, compaction/densification of loose sand, for example, can sometimes occur even without any significant increase of mean effective stresses. This study presents a model which considers the fact that volume change can occur due to decay/collapse of the structure of soils. Taking into consideration the differences between clay and sand, this study models super-subloading surfaces together with rotational hardening using the modified Cam-clay model. The effects of decay of the soil structure, loss of overconsolidation and evolution of anisotropy are mutually discussed concerning their relationship with ongoing plastic deformation. Fundamental constitutive model responses are illustrated in the present study particularly for "compaction" of sand. Repeated application of low-level shear stress upon loose sand yields a huge amount of volume compression, which is due to the rapid collapse of the initial soil structure. Repetition of the loading also results in a rapid increase of the overconsolidation ratio. Drained and undrained shear behavior of the sand naturally changes remarkably along this densification/compaction procedure, which is also consistently predicted using a single set of soil parameters. Elasto-plastic behavior of the same sand at various densities is thus totally described in the present study in a single the-oretical framework based on soil parameters independent of density.

Effects of sampling on delayed compression of naturally deposited clay

Noda, T., Nakano, M., Kaneda, K., Asaoka, A. and Yamada S.

Proc. of 1st International Workshop on New Frontiers in Computational Geomechanics (IWS-CALGARY 2002) 頁： 83-90 2002年9月

浅い基礎の設計理論と実際～パイルド・ラフト基礎を中心にして～

三村衛，野田利弘，山田英司，高稲敏浩，小高猛司，島津多賀夫

土と基礎，地盤工学会 50 巻 ( 8 ) 頁： 15-17 2002年8月

水～土連成計算を用いた砂杭拡径による砂地盤の締固めメカニズムの一考察査読有り

野田利弘，高稲敏浩，高木健次，野津光夫

土木学会論文集 Ⅵ-46 巻 ( 679 ) 頁： 111-122 2001年6月

Decay of structure and loss of overconsolidation

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

Proc. Int. Workshop on Deformation of Earth Materials, TC34 of ISSFMGE, Sendai. 頁： 109-118 2001年5月

泥岩粒の粘土化が原因となる飽和した泥岩砕石集合体の時間依存的力学挙動査読有り

中野正樹，野田利弘，高木健次，浅岡顕

地盤工学論文報告集 41 巻 ( 2 ) 頁： 143-151 2001年4月

An elasto-plastic description of the difference between sand and clay 招待有り

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

Proc. 10th Int. Conf. IACMAG (Int. Association for Computer Methods and Advances in Geomechanics), Tucson, Arizona, U.S.A. 1 巻頁： 263-270 2001年4月

パイルド・ラフト基礎が設置された地盤の水～土連成弾塑性変形解析査読有り

山田英司，高稲敏浩，水野和憲，大野雅幸，野田利弘

土木学会論文集 659/Ⅲ-52 巻頁： 113-128 2000年9月

"Sensitivity Ratio" and "Sampling Disturbance" of natural soils in terms of degradation of soil structure

Noda, T., Nakano, M., Asaoka, A. and Mizuno, K.

Proc. Int. Sym. on Coastal Geotechnical Engineering in Practice (IS-YOKOHAMA 2000), Yokohama. 頁： 113-118 2000年9月

「構造」を持った過圧密土の弾塑性挙動査読有り

浅岡顕，中野正樹，野田利弘

土木学会応用力学論文集 3 巻頁： 335-342 2000年8月

Delayed compression/consolidation of naturally clay due to degradation of soil structure 査読有り

Asaoka, A., Nakano, M., Noda, T. and Kaneda, K.

Soils and Foundations 40 巻 ( 3 ) 頁： 75-85 2000年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

The superloading yield surface concept applied to the original Cam-clay model is examined for the application to the one-dimensional consolidation problems of highly structured soils. When the proposed elasto-plastic constitutive model is taken to be the case for a structured soil, the one-dimensional consolidation computation clarifies the following : (1) Delayed consolidation should occur even under one-dimensional compression condition with a considerably low stress ratio when softening of the soil occurs with volume compression. The delayed consolidation is the consolidation process that has sometimes been referred to as "secondary compression". (2) The structure is always degrading as plastic deformation proceeds even within the period of "secondary compression". (3) The decay of overconsolidation to normal consolidation also proceeds with plastic deformation. In this sense, the degradation of structure can not be independent of the decay of overconsolidation. However, since the decay of overconsolidation is much faster than the degradation of structure in clay, then softening becomes possible with volume compression even under a considerably low stress ratio. Recovery of structure with time due to chemical bonding effects etc. in soil particles is beyond the scope of this study.

Superloading yield surface concept for highly structured soil behavior 査読有り

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

Soils and Foundations 40 巻 ( 2 ) 頁： 99-110 2000年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

The superloading yield surface concept is newly introduced to the original Cam-clay model in order to describe some aspects of the mechanical behavior of highly structured soils, in which destructured soils are assumed to follow the original Cam-clay model. Following are typically those aspects: (a) structured soils are always "bulky" compared with destructured soils, and if they are in the normally consolidatcd state they always take their state variables outside the "Roscoe surface" of the Cam-clay model (b) when void ratios are the same, structured soils exhibit strengths higher than those of destructured soils; (c) for the same stresses, the void ratios of structured soils are greater than remolded soils. The structured state of a soil is simply defined as the size ratio of the original Cam-clay yield surface and the superloading yield surface that should lie above the Cam-clay yield surface. On the basis of "unconventional plasticity" theory the superloading yield surface concept, together with Hashiguchi's subloading yield surface concept, describes the degradation processes from both an overconsolidated state to a normally consolidated state and a structured state to a destructured state. These degradation processes continue gradually with ongoing plastic deformation. Since plastic deformation is irreversible, the decay of soil structure is also irreversible: The degraded state can not come back to the original state again through elasto-plastic mechanical operation alone. Chemical and/or thermal effects with "aging", that are said to newly generate both overconsolidated state and structured state without any change of stresses, are beyond the scope of this study.

Delayed failure in soft clay foundations 査読有り

Noda, T., Fernando, G.S.K. and Asaoka, A.

Soils and Foundations 40 巻 ( 1 ) 頁： 85-97 2000年2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）

Even in normally consolidated or lightly overconsolidated clay foundations failures can occur some days/weeks after the load application is completed. Such an event can sometimes be attributed to creep-like failure. In this paper, the time dependent failure of a homogeneous normally consolidated soft clay foundation has been investigated using soil-water coupled elasto-plastic finite deformation analysis. The inviscid subloading surface Cam-clay model, which can express smooth transition from overconsolidated states to normally consolidated states during reloading, was used for the soil. With drained boundaries a clay foundation can experience failure, instead of consolidation, with the elapse of time after the end of load application. The foundation stays apparently stable for some time until it experiences a sudden failure. The occurrence of such a delayed failure in an elasto-plastic soil foundation is triggered off by the predominant pore water migration over the drainage from the soil mass due to softening that results in the increase of excess pore water pressure under this constant load. With time, the region in the foundation under higher excess pore pressure expands outward progressively from the centerline until failure. The pore pressure increase under constant load is similar to observed cases that registered increase in piezometric heads. When the magnitude of load at the end of construction is comparatively low, i. e. comparatively below the stationary load, only the consolidation process proceeds.

飽和粘土の遅れ破壊現象の水～土連成解析

野田利弘，中野正樹

土と基礎，地盤工学会頁： 5-8. 1999年5月

Progressive Failure of Heavily Overconsolidated Clays

Asaoka, A., Nakano, M., Noda, T., Takaine, T., Kaneda, K. and Constantinescu Dan T.

Soils and Foundations 39 巻 ( 2 ) 頁： 105-117 1999年4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）

In this study, in order to comprehend the progressive failure of an overconsolidated clay, triaxial compression tests under constant load application for the overconsolidated Kawasaki clay are carried out. These tests show, after a certain period of time, axial strain rate fluctuations with marked peaks until the specimen reaches outright failure. The experimental procedure is then numerically simulated using the soil-water coupled finite element technique. While the numerical simulation for the triaxial compression test under axi-symmetric conditions did not exhibit the same behavior as in the triaxial test (shear band formation and fluctuation of axial strain rate in the axial strain rate vs. axial strain plot), under plane-strain conditions it properly described the fluctuation of axial strain rate as observed in the experiments. Such fluctuations in the axial strain rate are closely related to the progression of the localized shear zones within the specimen. This behavior is attibuted to the "non-local" characteristics of saturated clays. Since the pore water supply to the localized shear zone can not always be sufficient due to Darcy's law which limits the gradient of global seepage head in the soil, the specimen exhibits varying strain rates. Tertiary mudstone pebbles can be idealized as heavily overconsolidated clay. The progressive failure of a heavily overconsolidated clay suggests that the behavior of crushed Tertiary mudstone is due to slaking at the contact points between the pebbles.

水～土連成計算による土留めに作用する力の時間依存性挙動の解析査読有り

野田利弘，高稲敏浩，浅岡顕

土木学会論文集 617/Ⅲ-46 巻頁： 125-138 1999年3月

Displacement/Traction Boundary Conditions Represented by Constraint Conditions on Velocity Field of Soil

Soils and Foundations 38 巻 ( 4 ) 頁： 173-181 1998年12月

Superloading yield surface concept for the saturated structured soils 招待有り

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

Proc. 4th European Conf. on Numerical Methods in Geotechnical Engineering, Udine, Italy. 頁： 233-242 1998年10月

間隙水の移動を伴った過圧密土の遅れ破壊の解析

浅岡顕，野田利弘，高稲敏浩

応用力学論文集(土木学会) 1 巻頁： 449-460 1998年8月

Consolidation deformation behavior of lightly and heavily overconsolidated clay foundation

Asaoka, A., Noda, T. and Fernando, G. S. K.

Soils and Foundations 38 巻 ( 2 ) 頁： 75-91 1998年6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）

Non-linear consolidation deformation behavior of saturated clays under embankment loading (plane strain) has been investigated using numerical analysis. The governing equations are based on the finite deformation theory which considers both geometric non-linearity and material non-linearity and the finite element method is used for the solution procedure. The subloading surface Cam-clay model for finite deformation is employed for the non-linear material behavior of lightly/heavily overconsolidated clays. The clay foundation response to embankment construction under both the non-linearities is discussed within the Critical State Soil Mechanics framework. For overconsolidated soils, both the hardening and softening behavior above the critical state line (p'-q stress space) occur with plastic volume expansion. The area under the embankment slope reaches the normally consolidated state first during load application. In a lightly overconsolidated clay foundation, this area undergoes strong strain localization which can lead to physical failure of the structure. The embankment toe area of a heavily overconsolidated clay foundation exhibits a softening behavior with net volume dilatation at the end of the consolidation. The drained loading of a heavily overconsolidated clay foundation tends to give higher load bearing capacity than for undrained loading as in the case of lightly overconsolidated soils.

Undrained creep rupture of normally consolidated clay triggered by the "mode switching" during pore water migration

Asaoka, A. and Noda, T.

Proc. of. Intl. Symp. on Deformation and Progressive Failure in Geomechanics 1 巻頁： 21-26 1997年10月

Progressive failure of heavily overconsolidated clay under constant load application, an experiment and its application

Asaoka, A., Nakano, M., Noda, T., Takaine, T. and Kaneda, K.

Proc. of. Intl. Symp. on Deformation and Progressive Failure in Geomechanics 1 巻頁： 69-74 1997年10月

Effects of changes in geometry on the linear elastic consolidation deformation

Asaoka, A., Noda, T. and Fernando, G. S. K.

Soils and Foundations 35 巻 ( 1 ) 頁： 29-40 1997年9月

Slaking behavior of saturated mudstones

Asaoka, A., Nakano, M., Noda, T., Matsuo, M. and Kodaka, T.

Proc. of. 14th Intl. Conf. on Soil Mechanics and Foundation Engineering, Hamburg 1 巻頁： 25-28 1997年9月

Soil-water coupled behavior of heavily overconsolidated clay near/at critical state line

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

Soils and Foundations 35 巻 ( 1 ) 頁： 13-28 1997年3月

Annealable Behaviour of Saturated Clay, An Experiment and Simulation 査読有り

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

Soils and Foundations 35 巻 ( 4 ) 頁： 9-20 1995年12月

Effects of Pore Water Migration on the Ultimate Behaviour of Soils

Asaoka, A and Noda, T.

Proc. of the 5th International Symposium on Plasticity and Its Current Application 1 巻頁： 407-410 1995年7月

Imperfection-sensitive Bifurcation of Cam-clay under Plane Strain Compression with Undrained Boundaries

Asaoka, A. and Noda, T.

Soils and Foundations, Journal of JSSFME 35 巻 ( 1 ) 頁： 83-100 1995年3月

水～土連成場での粘土供試体の破壊挙動

浅岡顕、中野正樹、野田利弘

第44回応用力学連合講演頁： 201-202 1995年1月

Imperfection sensitivity on the post-peak behaviour of Cam clay

Asaoka, A., Tamura, T., Kodaka, T., Nakano, M., Noda, T.

Proc. Int. Conf. on Computational Methods in Structural and Geotechnical Engineering, Hong Kong 3 巻頁： 824-829 1994年12月

Soil-water Coupled Behavior of Saturated Clay near/at Critical State

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

Soils and Foundations, Journal of JSSFME 34 巻 ( 1 ) 頁： 91-106 1994年3月

限界状態にあるカムクレイの平面ひずみ計算

浅岡顕、田村武、小高猛司、野田利弘

「粒状体の力学」シンポジウム発表論文集頁： 89-92 1993年12月

均質一様場からの分岐後のカムクレイ水-土連成挙動

浅岡顕、野田利弘

「粒状体の力学」シンポジウム発表論文集頁： 85-88 1993年12月

限界状態近傍にある飽和土の弾塑性境界値問題の実験・解析とその応用招待有り査読有り

浅岡顕，野田利弘

土木学会構造工学論文集 39A 巻頁： 361－374 1993年3月

　前のページ - 次のページ　

<野田 利弘>

論文 - 野田 利弘

<野田　利弘>

論文 - 野田　利弘