Faculty Profiles - NODA, Toshihiro

Papers - NODA, Toshihiro

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Elastoplastic finite element simulation of domino fault formation associated with tilting of highly structured ground Reviewed International journal

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

SOILS AND FOUNDATIONS Vol. 64 ( 5 ) 2024.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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Scopus

Soil-water-air coupled finite deformation analysis considering trapped air and continuous air phases Reviewed International journal

Yoshikawa, T. and Noda, T.

SOILS AND FOUNDATIONS Vol. 64 ( 5 ) 2024.10

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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Tsunami hazard evaluation of river embankment structures incorporating their vulnerability to seismic strong motion Reviewed International journal

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

EARTHQUAKE SPECTRA Vol. 40 ( 3 ) page： 2008 - 2037 2024.8

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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Super/sub-loading surface model for constitutive equation of friction Reviewed International journal

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

TRIBOLOGY INTERNATIONAL Vol. 191 page： 109080 2024.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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Comprehension of Seismic-Induced Groundwater Level Rise in Unsaturated Sandy Layer Based on Soil-Water-Air Coupled Finite Deformation Analysis Reviewed International journal

Yoshikawa, T. and Noda, T.

WATER Vol. 16 ( 3 ) 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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Unconditional convergence of theoretical solutions to u-p formulation Reviewed International journal

Toyoda T. and Noda T.

Soils and Foundations Vol. 64 ( 1 ) page： 101421 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Reviewed International journal

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

EARTHQUAKE SPECTRA Vol. 40 ( 1 ) page： 287 - 313 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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Experimental study on sand anisotropy using hollow cylinder apparatus Reviewed International journal

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

SOILS AND FOUNDATIONS Vol. 63 ( 3 ) 2023.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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Finite-Deformation Cam-Clay Model Considering Elastic Dilatancy and Soil Skeleton Structure Reviewed International journal

Yamada Shotaro and Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMECHANICS Vol. 23 ( 2 ) 2023.2

Language：English Publishing type：Research paper (scientific journal)

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

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Verification of a Macroelement Method with Water Absorption and Discharge Functions in Quasi-Static Problems Reviewed International journal

JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING Vol. 148 ( 7 ) 2022.7

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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Method to introduce the cementation effect into existing elastoplastic constitutive models for soils Reviewed International journal

Journal of Geotechnical and Geoenvironmental Engineering Vol. 148 ( 5 ) page： 04022013-1 - 04022013-14 2022.5

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：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

Proposal of a simple evaluation method for evaluating the seismic aftershock resistance of a spherical gas holder inclined by the main earthquake Reviewed

Mio KOBAYASHI, Hideyuki TAZUKE, Kentaro NAKAI and Toshihiro NODA

Vol. 77 ( 2 ) page： I_543 - I_550 2022.2

Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

It is desirable for spherical gas holders, which require a high level of safety, to be able to retain their functions during aftershocks even when the foundation is subjected to unequal settlement due to a largescale earthquake. For this purpose, it is necessary to develop a simple method to evaluate the seismic resistance of inclined gas holders under the assumption of maximum aftershocks, which will contribute to the decision on whether or not to use the holders after a large-scale earthquake. The analysis to evaluate each element of the holder must take into account the material and geometrical nonlinear response mechanism of the supporting structure and nonlinear dampers, and it is not realistic to conduct detailed evaluation by 3D analysis in a short period of time after an earthquake. Therefore, in this paper, the simple evaluation method using a single mass-spring analysis that reflects the nonlinear spring characteristics from the pushover analysis is proposed. This method shows good agreement with the dynamic response of a 3D framework model of an actual gas holder until the maximum response value, and after that, the response value is calculated on the safe side, which means that the aftershock seismic resistance of the holder can be evaluated.

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 Reviewed International journal

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

Computers and Geotechnics Vol. 141 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 International journal

Applied Sciences (Switzerland) Vol. 11 ( 23 ) 2021.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：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

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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 Reviewed International journal

Toyoda, T. and Noda, T.

Soils and Foundations Vol. 61 ( 2 ) page： 352 - 370 2021.4

Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Soils and Foundations

The theoretical and numerical solutions for the one-dimensional dynamic deformation of saturated ground were obtained using the u–w–p governing equation. The numerical analysis was performed based on the finite element method, and the occurrence of superficially peculiar phenomena, i.e., S-shaped settlement–time relation, non-harmonic oscillation in the settlement/pressure–time relation in highly permeable soil, and inconsistency in the vertical load and immediate pressure was identified heuristically. The theoretical solution of the damped wave equation was derived from the original governing equation expressed as the superposition of several modes with different eigenvalues, and this solution could successfully explain the phenomena observed heuristically. It was noted that the phenomena were induced by the presence of inertia, because the static solution and u–p analysis did not exhibit such phenomena. The verification of the analysis was conducted owing to the correspondence of the theoretical solutions of the damped wave equation and the u–w–p analysis results.

DOI： 10.1016/j.sandf.2020.12.007

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Importance of considering unsaturated triaxial tests including ceramic disk as initial and boundary value problems Reviewed International journal

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

Soils and Foundations 2021.3

Language：English Publishing type：Research paper (scientific journal)

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

LIQUEFACTION DAMAGE SUPPRESSION EFFECTS OF EXISTING SMALL SCALE STRUCTURE RECEIVING ECCENTRIC LOAD USING FLOATING GRID TYPE IMPROVEMENT Reviewed

Vol. 76 ( 2 ) page： I_279 - I_288 2021.2

Language：Japanese Publishing type：Research paper (scientific journal)

all over the world. If the existing small-scale structures such as houses are tilted due to liquefaction, they suffer more serious damage than they are subsided. In this paper, the effect of countermeasure against tilting damage due to liquefaction using floating grid-type improvement was investigated by 2D model tests under 1g condition using eccentric model structure, and non-linear FEM analyses. From the results, it was found that the floating grid-type improvement can significantly suppress the settlement damage of structure by suppressing the lateral flow of the liquefied ground even if the dead load of structure is eccentric. It was also found that lateral flow of the liquefied soil hardly occurs when the structure inclines due to liquefaction, and the effect of countermeasure against tilting damage due to liquefaction using floating grid-type improvement was not as high as the effect of suppressing subsidence damage. Therefore, it was found that desirable to use a floating grid-type improvement and drainage method to prevent tilting damage of structure.

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

PROGRESSIVE FAILURE OF UNSATURATED FILL SLOPE CAUSED BY CUMULATIVE DAMAGE UNDER SEEPAGE SURFACE Reviewed International journal

Murao Hidehiko, Nakai Kentaro, Yoshikawa Takahiro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE Vol. 20 ( 78 ) page： 1 - 8 2021.2

Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Journal of GEOMATE

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

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Triaxial test on water absorption compression of unsaturated soil and its soil-water-air coupled elastoplastic finite deformation analysis Reviewed International journal

Yoshikawa Takahiro, Noda Toshihiro

SOILS AND FOUNDATIONS Vol. 60 ( 5 ) page： 1151 - 1170 2020.10

Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Soils and Foundations

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

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

Noda, T. and Nakai, K.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) page： 4b-0040 2020.9

Localized/enormous seismic damage of subsurface ground induced by the stratum irregularity International journal

Nakai, K. and Noda, T.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) page： 1d-0092 2020.9

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

Yoshikawa, T. and Noda, T.

Proc. of the 17th World Conference on Earthquake Engineering (17WCEE) page： 4b-0051 2020.9

Validation of the applicability of a drainage method for reducing settlement and inclination of utility poles in liquefied ground Reviewed

ITO, H., ISHIMARU, M., NAKAI, K. and NODA, T.

Vol. 15 ( 3 ) page： 643 - 652 2020.9

Authorship：Last author Language：Japanese Publishing type：Research paper (scientific journal)

In the 2011 Earthquake off the Pacific coast of Tohoku, extensive liquefaction occurred in the Kanto region. This resulted in the settlement and inclination of thousands of utility poles. In urban areas, utility poles are often installed in narrow easements with limited clearance. Therefore, a simple and inexpensive countermeasure is desired. In this study, we attempted to reduce the settlement and inclination of utility poles in the liquefied ground by providing drain
holes in the utility pole. In the centrifugal model tests conducted using pole models with drain holes at the bottom and sides, settlement and inclination decreased in relation to the amount of drainage. Therefore, it was determined that the drainage method has a definite effect on the reduction of both settlement and inclination of utility poles in the
liquefied ground.

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 Vol. 57 ( 8 ) page： 1263 - 1263 2020.8

Soil-water-air coupled finite deformation simulation of model test on seepage failure of levee Reviewed

Vol. 75 ( 2 ) page： I_379 - I_388 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

Due to heavy rain in northern Kyushu in July 2012, failure of the Yabe River levee occurred, caused by local piping in highly permeable foundation ground, and it was a great shock when river engineers and researchers realized that levees can collapse without overflow. Regarding the Koyoshi River levee slope slip and the Kakehashi River levee slope failure that occurred in July 2013, it is also considered that the damage was the result of highly permeable foundation ground. In this paper, to clarify the seepage failure mechanism of river levee with highly permeable foundation ground, numerical simulations of model tests were conducted using a soil-water-air coupled finite deformation analysis code. As a result, the simulation was able to reproduce the difference between the case when the seepage failure occurred and the case when the seepage failure did not occur in the experiment. In addition, using this analysis code, case studies were conducted and the influence of introducing suction effect to elastoplastic constitutive model on seepage failure behavior was also discussed.

DOI： 10.2208/jscejam.75.2_I_379

Reduction effects of liquefaction damage using small scale floating grid-type improvement for existing small scale structure Reviewed

Vol. 75 ( 2 ) page： I_329 - I_339 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

Earthquake resistance of important structure have been promoted based on the lessons learned from the big Earthquake in Japan. However, liquefaction still causes serious damages to many detached houses in the world. Also, most soil improvement methods apply to original ground without structure, and countermeasure against liquefaction for existing small structure has not been sufficiently investigated. Therefore, we investigated reduction effects of liquefaction damage using small grid-type improvement as countermeasure against liquefaction for existing small structure. To this end, 2D model tests under 1g condition and non-linear FEM analyses have been carried out. From the model tests results, it was found that if the interval of improved wall is within 1.2 times of the base width, some degree of counter measure effect agaisnrt subsidence due to liquefaction can be obtained with a small grid-type improvement where the improvement depth is about twice the base width. The numerical simulation has shown a similar result as found in the observations.

DOI： 10.2208/jscejam.75.2_I_329

Influence of neighboring houses on liquefaction damage of detached houses Reviewed

Vol. 75 ( 2 ) page： I_401 - I_410 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

In the 2011 off the Pacific Coast of Tohoku Earthquake, the liquefaction damage in the residential area of Urayasu City was huge, and many detached houses suffered uneven settlement. In Japan, however, there has not been sufficient knowledge about liquefaction- induced damage of detached houses. Therefore, in this study, with regard to the liquefaction damage form of the detached houses constructed on the liquefiable ground, the following points were clarified focusing on the influence of the neighboring houses using soilwater coupled finite deformation analysis. 1) In the case of single structure evaluation, even if stability is maintained without tilting, tilting damage may occur when considering neighboring houses. 2) The direction of inclination of neighboring houses can be explained by using the computed direction of post-seismic displacement vector in the case of one house alone.

DOI： 10.2208/jscejam.75.2_I_401

Undrained cyclic shear behavior of clay under drastically changed loading rate International journal

Khan Imran, Nakai Kentaro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE Vol. 18 ( 66 ) page： 16 - 23 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

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

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Experimental research on development/diminishing of anisotropy and its effect on mechanical behavior of clay Reviewed International journal

Khan Imran, Nakai Kentaro, Noda Toshihiro

INTERNATIONAL JOURNAL OF GEOMATE Vol. 18 ( 65 ) page： 9 - 14 2020.1

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

Proc. of 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019 2020

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) International journal

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

Canadian Geotechnical Journal Vol. 57 ( 8 ) 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：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 International journal

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

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

Language：English Publishing type：Research paper (scientific journal) Publisher：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 International journal

Toyoda Tomohiro, Noda Toshihiro

Proc. of the 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering (16ARC) page： JGS-064 2019.10

Language：English

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

Yoshikawa Takahiro, Noda Toshihiro

Proc. of the 7th Asia-Pacific Conference on Unsaturated Soils (AP-UNSAT2019) page： EA56 2019.8

Language：English

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 International journal

Noda Toshihiro, Yoshikawa Takahiro

Proc. of the 7th Asia-Pacific Conference on Unsaturated Soils (AP-UNSAT2019) page： EA59 2019.8

Authorship：Lead author Language：English

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.

Development and verification of a soil-water coupled finite deformation analysis based on u-w-p formulation with fluid convective nonlinearity Reviewed International journal

Noda Toshihiro, Toyoda Tomohiro

SOILS AND FOUNDATIONS Vol. 59 ( 4 ) page： 888 - 904 2019.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Soils and Foundations

Most soil–water coupled analyses of saturated soil are based on the u–p formulation, where a set of equations is reduced by assuming that the acceleration of the fluid phase relative to that of the solid phase is less than that of the solid phase. Therefore, this analysis cannot be used for a coupled analysis with dynamic water flow in highly permeable soil. This study aims to present a soil–water coupled finite deformation analysis method based on full formulation, or u–w–p formulation. This method differs from conventional methods in the following ways: (1) the governing equations explicitly include the equation of motion for the fluid phase, (2) a relative convective term is used to describe a change in the relative configuration between the two phases, and (3) the moving/inclined discharge boundary is directly implemented to the discretized governing equations. Herein, one/two dimensional seepage and plane-strain deformation analysis results are reported. In the seepage analysis, accelerating permeation of pore water is obtained and the undrained constraint condition is verified. In the deformation analysis, dynamic migration in a high permeable soil specimen, i.e., wave propagation and rotational flow of pore water, is observed.

DOI： 10.1016/j.sandf.2019.03.008

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Validation for the effectiveness of vacuum consolidation method including the one with air-water separation system using a numerical simulation approach Reviewed

Vol. 75 ( 5 ) page： 303 - 315 2019.7

Language：Japanese Publishing type：Research paper (scientific journal)

In the vacuum consolidation method, the pressure under the air-tight sheet increases according to ground surface settlement. An air-water separation system for the vacuum consolidation method (VCM) was developed to improve this issue and enhance the vacuum effect. Although it has been demonstrated up to today that the system can obtain a higher vacuum pressure, the suppression effect of the new type VCM against deformation has never been discussed. In this study, therefore, mainly to reveal the suppression effect of the new method against deformation, several numerical simulations were conducted by using a soil-water coupled analysis code, GEOASIA, which mounts the macro-element method with discharge and drainage functions of vertical drains. The main findings of this study are as follows: 1) The air-water separation system has a high efficiency against deformation. Especially, the method remarkably restricts settlement that occurs after stopping vacuum pumps because it has a high preloading effect. 2) The conventional VCM also restricts deformations including a lateral deformation even if large settlement occurs. This is because the vacuum loading effect is maintained even though the pressure under the airtight sheet increases according to ground surface settlement. 3) Short-term constructions that have never been attempted can be performed in both the type VCMs. The above discussions demonstrated that the
numerical simulation method used in this study allows the selection of effective countermeasures and
economical construction conditions.

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

Non-contact estimation of strain parameter-triggering liquefaction Reviewed International journal

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

INTERNATIONAL JOURNAL OF GEOMATE Vol. 16 ( 57 ) page： 82 - 88 2019.5

Language：Japanese Publishing type：Research paper (scientific journal)

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

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

Noda Toshihiro, Yamori Katsuya, Harada Kenji

JOURNAL OF DISASTER RESEARCH Vol. 14 ( 2 ) page： 375 - 386 2019.3

Soil-water-air coupled finite deformation simulation of model test on seepage failure of levee Reviewed

Vol. 75 ( 2 ) page： I_379 - I_388 2019.2

Language：Japanese Publishing type：Research paper (scientific journal)

Due to heavy rain in northern Kyushu in July 2012, failure of the Yabe River levee occurred, caused by local piping in highly permeable foundation ground, and it was a great shock when river engineers and researchers realized that levees can collapse without overflow. Regarding the Koyoshi River levee slope slip and the Kakehashi River levee slope failure that occurred in July 2013, it is also considered that the damage was the result of highly permeable foundation ground. In this paper, to clarify the seepage failure mechanism of river levee with highly permeable foundation ground, numerical simulations of model tests
were conducted using a soil-water-air coupled finite deformation analysis code. As a result, the simulation
was able to reproduce the difference between the case when the seepage failure occurred and the case when the seepage failure did not occur in the experiment. In addition, using this analysis code, case studies were conducted and the influence of introducing suction effect to elastoplastic constitutive model on seepage failure behavior was also discussed.

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

Proposal of new countermeasure method and analytical study on the prevention of liquefied ground flow behind the quay with sheet-pile Reviewed

Vol. 74 ( 2 ) page： I_615 - I_625 2019.1

Language：Japanese Publishing type：Research paper (scientific journal)

As a construction method that can be constructed in even narrow space to suppress both liquefaction and lateral defomation of the ground behind the quay, referring to the previous study which was con-firmed effectiveness, we proposed a method for arranging steel sheet-pile shear walls in the direction per-pendicular to the quay wall. By analyzing using a soil-water coupled finite deformation analysis code, GEOASIA, we confirmed that the proposed method was useful in terms of suppressing liquefaction and lateral defomation. Furthemore, we showed the effectiveness of a new countermeasure method by reveal-ing that the reinforcement effect was proportional to the distance between the sheet-piles and shape of steel sheet-pile. This is a result that can be derived by finite deformation analysis.

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

3D SEISMIC RESPONSE ANALYSIS OF A SPHERICAL GAS HOLDER ON A SANDY GROUND CONSIDERING A SERIOUS SCENARIO BY THE GREATEST POSSIBLE EARTHQUAKE Reviewed

Vol. 74 ( 2 ) page： I_693 - I_703 2019.1

Language：Japanese Publishing type：Research paper (scientific journal)

This paper reports seismic response analyses about the spherical gas holder which requires higher safety focusing on the ultimate limit state of the level 2 earthquake. In the analysis, a gas holder and pile
foundation are modeled in 3D condition to evaluate their interactive behavior more realistically using a soil-water coupled finite deformation analysis code GEOASIA.
As a result, in the holder to be analyzed this time, all the piles lose the bearing function, and the piles have an insignificant effect on the response of the holder. Therefore, the ultimate limit state, which we have considered the maximum unequal settlement in the past examination, is assumed considerably safe. Also, under the greatest possible earthquake condition with this holder, it is possible to almost fully evaluate the seismic performance of the ultimate limit state by 2D analysis. On another front, 3D analysis should be applied for non-uniform condition such as a substandard earthquake input and irregular surface layers. Furthermore, by using this analysis method, it is possible to evaluate the structural stability of the
gas holder integrally.

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

Language：English Publishing type：Research paper (scientific journal) Publisher：7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT 2019

Scopus

Influence of development/diminishing of anisotropy on the mechanical behavior of clayey specimen International journal

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

4th International Conference on Science, Engineering and Environment (SEE) page： 593-598 2018.11

Language：English

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 Reviewed

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） Vol. 74 ( 2 ) page： I_247 - I_252 2018.11

Language：Japanese Publishing type：Research paper (scientific journal)

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 Reviewed International journal

Murao Hidehiko, Nakai Kentaro, Noda Toshihiro, Yoshikawa Takahiro

CANADIAN GEOTECHNICAL JOURNAL Vol. 55 ( 11 ) page： 1668 - 1681 2018.11

Monitoring the triggering of liquefaction using image processing Reviewed International journal

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

INTERNATIONAL JOURNAL OF GEOMATE Vol. 15 ( 51 ) page： 180 - 187 2018.11

Language：Japanese Publishing type：Research paper (scientific journal)

In recent 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

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Seismic Response Analysis of Ground/Geo-structures using Geo-Analysis Integration Code Invited

Asaoka, A., Noda, T.

International Press-in Association Newsletter Vol. 3 ( 3 ) page： 3-10 2018.9

Full-field estimation of cyclic threshold shear strain International journal

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 page： 3062-3066 2018.3

Language：English

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 International journal

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 page： 2318-2327 2018.3

Language：English

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 Reviewed

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) Vol. 73 ( 2 ) page： I_233-I_244 2018.1

Language：Japanese Publishing type：Research paper (scientific journal)

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 Reviewed

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) Vol. 73 ( 2 ) page： I_535-I_544 2018.1

Language：Japanese Publishing type：Research paper (scientific journal)

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 Reviewed

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） Vol. 66 ( 2 ) page： 64-68 2018

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

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：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 - Reviewed

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

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 48 ( 3 ) page： 19-31 2017.12

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

Nonaka Toshihiro, Yamada Shotaro, Noda Toshihiro

GEOTECHNICAL ENGINEERING Vol. 48 ( 4 ) page： 19-31 2017.12

Field Observation of Reinforced Soil Wall of Reinforced Member Using Bearing Resistance and Friction to Aftershocks of 2011 Off The Pacific Coast of Tohoku Earthquake Reviewed

Muto, H., Kamiya, T., Naganuma, A., Kodaka, T., Ying, C.,Nakano, M. and Noda, T.

Vol. 73 ( 4 ) page： 311-329 2017.10

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

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

Canadian Geotechnical Journal Vol. 54 ( 10 ) page： 1375 - 1396 2017.10

Language：Japanese Publishing type：Research paper (scientific 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 Reviewed

Toyoda, T. and Noda, T.

Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, Seoul 2017 page： 863-866 2017.9

Language：English

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

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

Soils and Foundations Vol. 57 ( 3 ) page： 472 - 487 2017.6

Language：Japanese Publishing type：Research paper (scientific journal)

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 - Invited Reviewed

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

Journal of JSCE Vol. 5 ( 1 ) page： 133-144 2017.3

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

中井健太郎，野田利弘

土木学会論文集 A2(応用力学) Vol. 73 ( 2 ) page： I_409-I_418 2017.1

Language：Japanese Publishing type：Research paper (scientific journal)

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

An attempt on experience-based vibration engineering program building to perform a lecture vibrated freely Reviewed

Vol. 53 ( 1 ) page： 99-101 2017.1

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 Vol. 2017-September page： 863 - 866 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：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 Invited

酒井崇之，野田利弘，中野正樹

基礎工 Vol. 44 ( 11 ) page： 84-87 2016.11

Application of numerical analysis for long-term settlement prediction of an embankment on soft ground and its ex-post evaluation

Vol. 64 ( 10 ) page： 14-15 2016.10

Construction Experiment of Reinfoced Soil Wall Using Reinforcement Member Incorprating Both Friction Resistance and Bearing Resistance Reviewed

Muto, H., Kamiya, T., Naganuma, A., Kodaka, T., Ying, C.,Nakano, M. and Noda, T.

Vol. 11 ( 3 ) page： 201-214 2016.9

Language：Japanese Publishing type：Research paper (scientific journal)

The reinforced earth wall have come into wide use in Japan after the Great Hanshin Earthquake in particular. Various types of reinforcing members are applied in that reinforced earth walls, e.g. metal strips, geosynthetics, steel bars with a bearing plate, and so on. Some of them have been developed in Japan. The authors have newly developed a reinforcing member incorporating both bearing resistance and friction resistance. In the present paper, a series of the small-scale pull-out test of the reinforcing members consisting of a steel bar with friction plate and bearing plate are performed to confirm the effectiveness of the reinforcement. From the test results, as to the cross-sectional shape of the friction plate, the friction plate of long shape in depth direction performed large pull-out resistance compared with the plate of short shape of the same sectional area. Enough resistance of the friction plate was demonstrated by setting it apart from a bearing plate in order to cut off the influence of the bearing plate. Furthermore, in the beginning of the pull-out, a ratio of contribution of the friction resistance to the bearing resistance was 60 to 70%. The contribution ratio of the friction resistance decreased to 40 to 50 % in a final stage of pull-out.

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 page： [MS983-5] (151147) 2016.7

Analysis of the effect of groundwater level on the seismic behavior of an unsaturated embankment on clayey ground Reviewed International journal

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

Soil Dynamics and Earthquake Engineering Vol. 85 page： 217-230 2016.6

Language：English Publishing type：Research paper (scientific journal)

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

Investigation of soil properties and estimation of upward wave in foundation ground of Urayasu area during the Great East Japan Earthquake using K-NET record motions Reviewed

KANEDA Kazuhiro, NAKAI Kentaro, NODA Toshihiro, ASAOKA Akira and SAWADA Yoshihiro

Vol. 16 ( 4 ) page： 4_155-4_166 2016.3

Language：Japanese Publishing type：Research paper (scientific journal)

The widespread liquefaction disaster that occurred in the reclaimed land around Tokyo bay area during the Great East Japan Earthquake was alarming. Validating this disaster by simulation is needed to prevent any liquefaction that may occur during likely huge future earthquakes. To this end, accurate soil properties and appropriate input wave as well as the finite deformation analysis that simulates the reappearance of liquefaction should be comprehended. In this study, soil-water coupled analysis code GEOASIA with SYS Cam-clay model, which can reproduce the function of soil structure, was used. Firstly, elasto-plastic properties of Urayasu soils were identified from the results of boring survey and laboratory testing. Then, by means of transfer method, both NS and EW upward waves at the foundation ground were simultaneously estimated from K-NET recorded motions at Urayasu.

DOI： 10.5610/jaee.16.4_155

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

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

Soils and Foundations Vol. 55 ( 6 ) page： 1372–1387 2015.12

Language：English Publishing type：Research paper (scientific journal)

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.

Evaluation of mechanical behavior of a large river levee during seepage and during/after earthquake based on soil-water-air coupled finite deformation analysis Reviewed

Vol. 71 ( 2 ) page： I_621-I_632 2015.12

Language：Japanese Publishing type：Research paper (scientific journal)

In this study, seepage/seismic behavior of a large river levee on alternately layered ground of sandy and
clayey soil was evaluated by a soil-water-air coupled finite deformation analysis code. The main findings
are as follows: 1) Focusing on the river level, the analysis during seepage and during/after an earthquake
was performed. The higher the river level, the larger the deformation in a direction toward the landside. 2)
If the water permeability of the sandy soil layer is as high as 'gravel', 8 hours after the river level rose, ground heaving which will lead to piping occurred near the landside toe. This is because the permeability of covering clayey soil layer is low and much water was supplied from the river to the sandy soil layer. 3)In the case of high permeability in the sandy soil layer as 2), during an earthquake, even when the river level is low, pore water is able to migrate in the sandy soil layer underlying clayey soil layer with low permeability. This results in liquefaction of the top of the sandy soil layer though the permeability is as high as gravel.

Effects of initial imperfection on the Riedel shear bands in surface ground due to strike-slip fault Reviewed

Vol. 71 ( 2 ) page： I_463-I_474 2015.12

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

A slip on the strike-slip fault causes flower structures and Riedel shear band within the overlying cover. This paper simulates the formation of these structures, employing the dynamic elasto-plastic finite defor-mation analysis code GEOASIA®.
The main conclusions are as follows: (1) A set of Riedel shear structures accompanies the plastic ex-pansion of the material, (2) A pattern of the initial material imperfections dominantly influence the for-mation process of Riedel shear structures and (3) Riedel shear bands don't appear in larger models, whose bottoms have more lightly overconsolidated by higher overburden pressure.

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

Vol. 63 ( 10 ) page： 16-19 2015.10

Application of seismic response analysis under level 2 earthquake for an existing river embankment

Vol. 63 ( 10 ) page： 28-31 2015.10

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 Reviewed

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

Soils and Foundations Vol. 55 ( 5 ) page： 1130–1139 2015.10

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 Reviewed International journal

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

Soils and Foundations Vol. 55 ( 5 ) page： 1114–1129 2015.10

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed International journal

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

Soils and Foundations Vol. 55 ( 5 ) page： 1045 - 1058 2015.10

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

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 Reviewed International journal

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

Soil Dynamics and Earthquake Engineering Vol. 79 ( Part B ) page： 401–414 2015.8

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Soils and Foundations Vol. 55 ( 2 ) page： 343-358 2015.4

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

Noda, T. and Yoshikawa, T.

Soils and Foundations Vol. 55 ( 1 ) page： 45-62 2015.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 page： 35-46 2015.1

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 Reviewed

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 Vol. 9 ( 4 ) page： 533-553 2014.12

Language：Japanese Publishing type：Research paper (scientific journal)

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 Reviewed

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) page： 1145-1150 2014.9

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

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

The 14th International Conference of the International Association for Computer Methods and Advances in Geomechanics (14IACMAG) page： 761-766 2014.9

Evaluation of seismic behavior of model earth dams in the geotechnical centrifuge Reviewed

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

The 14th International Conference of the International Association for Computer Methods and Advances in Geomechanics (14IACMAG) page： 767-772 2014.9

Soil-water coupled finite deformation analysis on subgrade reaction force acting on the underground pile Reviewed

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) page： 997-1000 2014.9

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 Reviewed

Noda, T. and Yoshikawa, T.

UNSAT2014: Unsaturated Soils: Research & Applications page： 613-619 2014.7

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

Yoshikawa, T. and Noda, T.

UNSAT2014: Unsaturated Soils: Research & Applications page： 589-595 2014.7

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 page： 164-167 2014.4

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 page： 140-143 2014.4

Seismic and postseismic behavior of river levee on soft clay ground Invited

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

COMPSAFE: Computational Engineering and Science for Safety and Environmental Problems page： 138-139 2014.4

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

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

Soils and Foundations Vol. 53 ( 6 ) page： 923-936 2013.12

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

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

Soils and Foundations Vol. 53 ( 6 ) page： 937-950 2013.12

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

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

Soils and Foundations Vol. 53 ( 5 ) page： 653-670 2013.10

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

Yamada, S. and Noda, T.

Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013 page： 841-844 2013.9

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

Noda, T. and Xu, B.

Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013 page： 403-406 2013.9

Excavation analysis of ground using SPH method Reviewed

Vol. 16 page： I_341-I_350 2013.9

Language：Japanese Publishing type：Research paper (scientific journal)

In order to solve large deformation problem of geomaterials, the SPH method is used which is
a kind of particle method based on the meshless Lagrangian scheme. The method can solve large deformation problems without mesh distortion. Moreover, it can handle the governing equations and existing constitutive models for geomaterials based on a continuum mechanics. To express various states of the soil, the elasto-plastic constitutive model taking account of soil skeleton structure is introduced into the method. In this paper, in order to verify the numerical scheme, a simulation of simple shear test is carried out. The obtained results are compared with theoretical solutions. Furthermore, the excavation problems for loose and dense sand ground are solved. From a series of the numerical results, the effectiveness of the method with the constitutive model of high performance is demonstrated.

Influence of brittle property of cement treated soil on undrained bearing capacity characteristics of the ground Reviewed

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

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 44 ( 3 ) page： 84-93 2013.9

Language：English Publishing type：Research paper (scientific journal)

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.

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 Reviewed

竹内秀克，河村精一，野田利弘，浅岡顕

地盤工学ジャーナル Vol. 8 ( 2 ) page： 239-249 2013.6

Language：Japanese Publishing type：Research paper (scientific journal)

「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) Reviewed

Kazama, M. and Noda, T.

Soils and Foundations Vol. 52 ( 5 ) page： 780-792 2012.10

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 page： 1817 2012.9

Language：English

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 Reviewed

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

Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 43 ( 2 ) page： 49-56 2012.6

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 page： 45-48 2012.5

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 page： 173-176 2012.5

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 page： 177-182 2012.5

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 page： 177-182 2012.5

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 page： 39-44 2012.5

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 page： 165-168 2012.5

Anti-seismic mechanism of a sandy ground improved by SCP method Reviewed

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

Proc. of 14th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (14th ARC) page： 273 2011.5

Authorship：Lead author Language：English

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 Reviewed

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

Proc. of 14th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (14th ARC) page： 278 2011.5

Language：English

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 Reviewed

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

Soils and Foundations Vol. ５１ ( １ ) page： 133-149 2011.2

Language：English Publishing type：Research paper (scientific journal)

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 Invited

野田利弘

電力土木 ( 356 ) page： 6-11 2011.1

Language：Japanese Publishing type：Research paper (scientific journal)

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。

A means for assessing the seismic stability of a temporary structure sited on soft ground and preventing its collapse Reviewed

Kentaro NAKAI and Toshihiro NODA

Vol. 5 ( 3 ) page： 499-510 2010.9

Language：Japanese Publishing type：Research paper (scientific journal)

While a temporary structure is relatively simple to erect and remove, the fact that no particular measures such as pile installations or soil improvements are taken for its protection can mean that there is a risk of it collapsing in the event of an earthquake. This paper reports a numerical analysis of the seismic stability of a temporary structure erected on a foundation of alternating clay and sand layers in a case where the surface layer is sandy and clayey. It finds that the main cause for the structure's collapse lies in 1) the increase in the amplitude of the tremors resulting from a coincidence of the predominant ground wave motion with the specific vibration of the structure, and 2) the decline in
the bearing force and the consequent unevenness in the settlement of the structure as a result of liquefaction in the surface sand layer. One important prevention measure is to ensure that the specific vibration does not coincide with the predominant ground motion by making appropriate changes in the height and width of the structure; but another
cheap but effective safeguard is to increase the area of contact between the structure and its foundation by laying a base immediately below the temporary structure.

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 Reviewed

竹内秀克, 中井健太郎, 野田利弘

応用力学論文集，土木学会 Vol. 13 page： 443-452 2010.8

Language：Japanese Publishing type：Research paper (scientific journal)

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 Reviewed

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 Vol. CD, No.012107 page： 19-23 2010.7

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Geotechnical Special Publication No.201, Soil Dynamics and Earthquake Engineering, ASCE page： 125-130 2010.6

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Geotechnical Special Publication No.201, Soil Dynamics and Earthquake Engineering, ASCE page： 294-299 2010.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Geotechnical Special Publication No.201, Soil Dynamics and Earthquake Engineering, ASCE page： 218-224 2010.6

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Geotechnical Special Publication No.201, Soil Dynamics and Earthquake Engineering, ASCE page： 139-144 2010.6

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 page： 69-74 2010.5

Seismic stability assessment of a lightweight structure on sandy/clayey foundations Reviewed

Nakai, K. and Noda, T.

Recent Developments of Geotechnical Engineering, Proc. of the 4th Japan-China Geotechnical Symposium page： 564-571 2010.4

Language：English

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 Vol. 50 ( 2 ) page： 245-260 2010.4

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Recent Developments of Geotechnical Engineering, Proc. of the 4th Japan-China Geotechnical Symposium page： 174-179 2010.4

Authorship：Lead author Language：English

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 Reviewed

河井正，石丸真，野田利弘，浅岡顕

地盤工学ジャーナル Vol. 5 ( 1 ) page： 45-59 2010.3

Language：Japanese Publishing type：Research paper (scientific journal)

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 Reviewed

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 Vol. 5 ( 1 ) page： 81-87 2010.3

Language：Japanese Publishing type：Research paper (scientific journal)

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 Reviewed

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

Soils and Foundations Vol. 50 ( 1 ) page： 109-122 2010.2

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Soils and Foundations Vol. 49 ( 5 ) page： 739-756 2009.10

Aiming at all soils all states all round geo-analysis integration Invited

Asaoka, A. and Noda, T.

International Symposium on Urban Geotechnics, Incheon, Korea page： 3-26 2009.9

過圧密地盤の排水支持力解析 Reviewed

山田正太郎，野田利弘，浅岡顕

応用力学論文集，土木学会 Vol. 12 page： 247-254 2009.8

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 Reviewed

河井正，野田利弘，浅岡顕

応用力学論文集，土木学会 Vol. 12 page： 1021-1028 2009.8

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

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 page： 1087-1093 2009.6

Coseismic and postseismic behavior of intermediate soil ground improved by sand compaction pile method Reviewed

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 page： 1199-1205 2009.6

Numerical analysis on deformation/failure patterns on embankments observed in 2004 Chuetsu earthquake Reviewed

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 page： 103-109 2009.5

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

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

Soils and Foundations Vol. 48 ( 6 ) page： 771-790 2008.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Theoretical and applied mechanics JAPAN Vol. 57 page： 41-47 2008.12

Ground improvement of intermediate reclaimed land by compaction through cavity expansion of sand piles Reviewed

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

Soils and Foundations Vol. 48 ( 5 ) page： 653-671 2008.10

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) page： 29-32 2008.10

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) page： 57-60 2008.10

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.) page： 41-47 2008.6

Authorship：Lead author Language：English

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 page： 249-256 2007.12

Language：English

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 Invited

Noda, T.

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) Vol. Post conference volume page： 364-373 2007.12

Language：English

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 Reviewed

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

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) page： 23-26 2007.12

Language：English

Liquefaction-induced consolidation settlement of soil after earthquake Reviewed

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

Proc. of 13th Asian Regional Conf. on Soil Mechanics and Geotechnical Engineering (13th ARC) page： 602-605 2007.12

Language：English

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.

page： 73-86 2007.11

Language：English

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 Reviewed

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

Soils and Foundations Vol. 47 ( 4 ) page： 635-648 2007.8

*Some bearing capacity characteristics of a structured naturally deposited clay soil Reviewed

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

Soils and Foundations Vol. 47 ( 2 ) page： 285-301 2007.2

*All soils all states all round geo-analysis integration

Asaoka A. and Noda, T.

International Workshop on Constitutive Modelling - Development, Implementation, Evaluation, and Application page： 11-27 2007.1

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) page： 73-78 2006.10

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) page： 183-186 2006.10

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 Reviewed

竹内秀克，高稲敏浩，野田利弘

応用力学論文集，土木学会 Vol. 9 page： 539-550 2006.9

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 page： 24-33 2005.10

Progressive consolidation settlement of naturally deposited clayey soil under embankment loading Reviewed

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

Soils and Foundations Vol. 45 ( 5 ) page： 39-52 2005.10

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) page： 83-88 2005.9

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 Reviewed

野田利弘，田代むつみ，高稲敏浩，浅岡顕

土木学会論文集 Vol. 799 ( Ⅲ-72 ) page： 37-49 2005.9

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

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．

Progressive consolidation of highly structured clay under embankment loading Reviewed

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

Proc. the 16th Int. Conference on Soil Mechanics and Geotechnical Engineering page： 1831-1835 2005.9

Language：English

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 Reviewed

Noda, T. and Yamada S.

Proc. the 16th Int. Conference on Soil Mechanics and Geotechnical Engineering page： 933-937 2005.9

Authorship：Lead author Language：English

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.

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 page： 269-285 2005.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 page： 286-306 2005.6

Elasto-plastic behavior of naturally deposited clay during/after sampling Reviewed

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

Soils and Foundations Vol. 45 ( 1 ) page： 51-64 2005.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Soils and Foundations Vol. 45 ( 1 ) page： 141-151 2005.2

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 page： 283-285 2005.1

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) page： 29-32 2004.9

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 Vol. 52 ( 8 ) page： 10-12 2004.8

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 Reviewed

田代むつみ, 野田利弘,中野正樹

応用力学論文集，土木学会 Vol. 7 page： 589-596 2004.8

Mechanical behaviors of clay and sand in terms of active soil skeleton structure Reviewed

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

Proc. Int. Conference on Computational & Experimental Engineering and Sciences (ICCES'04), Madeira, Portugal. page： 772-777 2004.7

Mechanical differences between sand and clay under monotonic and cyclic loading Reviewed

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

Proc. Int. Conference on Cyclic Behaviour of Soils and Liquefaction Phenomena (CBS04), Bochum, Germany. page： 77-84 2004.3

Piled raft foundation behavior on a soft soil system Reviewed

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

Proc. Int. Symposium on Shallow Foundations (FONDSUP 2003), Paris. page： 209-212 2003.11

Delayed settlement behavior of naturally deposited clayey soil due to the decay of soil structure Reviewed

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

Proc. Int. Workshop on Prediction and Simulation Methods in Geomechanics (IWS-Athens 2003) page： 173-176. 2003.10

Compaction behavior of sand with degradation of structure and overconsolidation Reviewed

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

Proc. of Sino-Japanese Symposium on Geotechnical Engineering, Beijing. page： 455-462 2003.10

Soil-water coupled analysis of upheaval behavior of soil after deep excavation Reviewed

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

Proc. of Sino-Japanese Symposium on Geotechnical Engineering, Beijing. page： 173-180 2003.10

Delayed compression associated with low land subsidence due to dewatering Reviewed

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

Proc. of Sino-Japanese Symposium on Geotechnical Engineering, Beijing. page： 25-32 2003.10

Compaction of sandy ground by "static" cavity expansion Reviewed

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

Proc. 12th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering page： 501-504 2003.8

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 Vol. 51 ( 2 ) page： 43-48 2003.2

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) page： 27-32 2003.1

*An elasto-plastic description of two distinct volume change mechanisms of soils Reviewed

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

Soils and Foundations Vol. 42 ( 5 ) page： 47-57 2002.10

Language：English Publishing type：Research paper (scientific journal)

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) page： 83-90 2002.9

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 Vol. 50 ( 8 ) page： 15-17 2002.8

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 Reviewed

野田利弘，高稲敏浩，高木健次，野津光夫

土木学会論文集 Vol. Ⅵ-46 ( 679 ) page： 111-122 2001.6

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. page： 109-118 2001.5

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 Reviewed

中野正樹，野田利弘，高木健次，浅岡顕

地盤工学論文報告集 Vol. 41 ( 2 ) page： 143-151 2001.4

An elasto-plastic description of the difference between sand and clay Invited

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. Vol. 1 page： 263-270 2001.4

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 Reviewed

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 Vol. 659/Ⅲ-52 page： 113-128 2000.9

"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. page： 113-118 2000.9

「構造」を持った過圧密土の弾塑性挙動 Reviewed

浅岡顕，中野正樹，野田利弘

土木学会応用力学論文集 Vol. 3 page： 335-342 2000.8

Delayed compression/consolidation of naturally clay due to degradation of soil structure Reviewed

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

Soils and Foundations Vol. 40 ( 3 ) page： 75-85 2000.6

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Soils and Foundations Vol. 40 ( 2 ) page： 99-110 2000.4

Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

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

Soils and Foundations Vol. 40 ( 1 ) page： 85-97 2000.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 page： 5-8. 1999.5

Progressive Failure of Heavily Overconsolidated Clays

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

Soils and Foundations Vol. 39 ( 2 ) page： 105-117 1999.4

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 Reviewed

野田利弘，高稲敏浩，浅岡顕

土木学会論文集 Vol. 617/Ⅲ-46 page： 125-138 1999.3

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

Soils and Foundations Vol. 38 ( 4 ) page： 173-181 1998.12

Superloading yield surface concept for the saturated structured soils Invited

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

Proc. 4th European Conf. on Numerical Methods in Geotechnical Engineering, Udine, Italy. page： 233-242 1998.10

Delayed Failure of Overconsolidated Soils due to Pore Water Migration

Vol. 1 page： 449-460 1998.8

Consolidation deformation behavior of lightly and heavily overconsolidated clay foundation

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

Soils and Foundations Vol. 38 ( 2 ) page： 75-91 1998.6

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

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 Vol. 1 page： 21-26 1997.10

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 Vol. 1 page： 69-74 1997.10

Effects of changes in geometry on the linear elastic consolidation deformation

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

Soils and Foundations Vol. 35 ( 1 ) page： 29-40 1997.9

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 Vol. 1 page： 25-28 1997.9

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

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

Soils and Foundations Vol. 35 ( 1 ) page： 13-28 1997.3

Annealable Behaviour of Saturated Clay, An Experiment and Simulation Reviewed

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

Soils and Foundations Vol. 35 ( 4 ) page： 9-20 1995.12

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 Vol. 1 page： 407-410 1995.7

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

Asaoka, A. and Noda, T.

Soils and Foundations, Journal of JSSFME Vol. 35 ( 1 ) page： 83-100 1995.3

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 page： 201-202 1995.1

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 Vol. 3 page： 824-829 1994.12

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

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

Soils and Foundations, Journal of JSSFME Vol. 34 ( 1 ) page： 91-106 1994.3

Plane Strain Deformation Analysis of Cam-Clay at Critical State

Proc. of Sym. Medranics of Granular Materials, JSSMFE page： 89-92 1993.12

Soil-Water Coupling Boundary Value Problem Approach to the Post Peak Behaviour of Cam-Clay

Proc. of Sym. Mechanics of Granular Materials, ISSMFE page： 85-88 1993.12

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 Invited Reviewed

浅岡顕，野田利弘

土木学会構造工学論文集 Vol. 39A page： 361－374 1993.3

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