Publishing type：Research paper (bulletin of university, research institution)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

There have been attempts to improve the operational efficiency of construction projects and plan response countermeasures for estimated damage following disasters through the utilization of accumulated electronic data, which constructs a digital twin that can reproduce a physical space in cyberspace and feedback the cyberspace simulation results to physical space. However, the application of such simulations is limited, unless numerical models can be automatically constructed from the data. In this study, we develop a program that utilizes a data processing platform to read, transform, and integrate data to create mediated data with a common data structure. This mediated data can be used to construct analytical models for various numerical analyses. Using the program developed, a grid model of 3-D ground surface as the mediated data was constructed based on borehole data obtained through a ground survey. Each grid point has basic material parameters of soil, and these parameters are estimated from borehole data and other investigation reports. Each grid point has general geotechnical parameters and can be easily converted to a 3-D finite-element model. When the borehole data is added or changed, the analytical model can be updated with almost no cost, whereas it would be very costly to create the model manually.

DOI： 10.1109/TMECH.2021.3105062

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Publishing type：Research paper (scientific journal)   Publisher：International Journal of Geomate  

DOI： 10.21660/2021.86.j2270

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

Recently, the occurrence of large earthquakes has become a concern in Japan, prompting the need for a numerical method that can accurately predict real phenomena, such as the elastoplastic soil-water coupled finite element method. Because the elastoplastic constitutive model requires many material parameters, various soil tests and specialized knowledge are needed to determine these material parameters. In this study, a new method was proposed to determine the material parameters from the limited ground information obtained by borehole inspections and the method was validated by comparing the numerical results with monitored seismic behavior. One-dimensional seismic analyses were conducted using the material parameters estimated from borehole data near the target sites. It was confirmed that the amplitude and predominant period obtained by numerical simulation were consistent with the monitored data. As a result, it was found that the dynamic numerical result was more consistent with the monitored data when the compression index was set to be larger than that in the static analysis.

DOI： 10.21660/2021.85.j2228

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

The pagoda of Wat Krasai, built in the 17th century on the outskirts of the Ayutthaya district in the Kingdom of Thailand, tilts approximately 2 degrees to the north and may continue to tilt further. The cause of this tilt is thought to be the uneven settlement of the foundation ground, but no supporting evidence has been presented. Three cohesive soil layers that may cause uneven settlement have been confirmed in the foundation ground around the pagoda, but soil tests are inadequate, leading to uncertainty in proving the cause of inclination. Hence, the cause of inclination was investigated in this study by calculating the inclination that can occur within the realistic ranges of the soil properties through numerical analysis using the finite element method. A method of correcting plane strain analysis, which has a low computational cost, with a three-dimensional effect coefficient, was utilized to assess over 500 cases considering ground material uncertainties, and the probability distribution of the possible inclinations was calculated. This method is useful as it considers fluctuations in the ground material parameters to address land settlement, which is largely influenced by the three-dimensional effects. This approach will also be applicable to future predictions aimed at pagoda preservation.

DOI： 10.21660/2021.82.j2108

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Publishing type：Research paper (international conference proceedings)   Publisher：Construction Materials & Environment  

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Publishing type：Research paper (conference, symposium, etc.)  

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Publishing type：Research paper (conference, symposium, etc.)   Publisher：日本原子力学会  

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Publishing type：Research paper (conference, symposium, etc.)   Publisher：九州橋梁・構造工学研究会  

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

DOI： 10.1016/j.sandf.2020.08.005

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

DOI： 10.21660/2020.73.96594

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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

DOI： 10.1016/j.sandf.2020.02.007

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

Although the soil, water and air coupling theory has been deductively derived from the three-phase mixture theory, assumptions and interpretations inherent in soil mechanics are also conveniently introduced in this theory. Mechanical properties of unsaturated soils are phenomenologically integrated into the constitutive equation for a deformation problem, with effective stress expressed as a combination of partial stresses acting on each phase of the mixture. The governing equations of two seepage problems describing the movements of pore water and pore air are formulated by a priori introduction of Darcy's law. Consequently, the coupling theory consists of a deformation problem and two seepage problems, in which the soil-water retention characteristics play the role of a mediator connecting these problems. If the theoretical structure is clarified in this way, an extension of this theory is easily made. In this paper, the extension of the theory to each of four examples and their performance is demonstrated. The features of settlement caused by absorption of soil water due to vegetation; dissolution, advection and diffusion of substances in groundwater; desaturation and state change due to vaporisation of dissolved gas from pore water; and the liquefaction potential of unsaturated soil are presented.

DOI： 10.1680/jgere.18.00004

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

In the wide area of the eastern part of Tokyo, the ground level is less than mean sea level. This area is more vulnerable to disasters than other areas. If large flood damage such as storm surge should occur in this area, the disaster would be a long-term catastrophe. On the coast of Tokyo Bay, countermeasures have been taken by tide embankments and floodgates. However, considering the damage scale when it occurs, an analysis in this area is very important. In this area, ground settlement occurred and groundwater head dropped because groundwater excessively withdrew by the industrial purpose during the period of economic growth. Currently, the groundwater head recovers and the ground settlement has been subsided. However, due to the groundwater head fluctuation, pore water pressure distribution had been different from hydrostatic pressure distribution. Therefore, in the analysis in this area, it is necessary to consider past groundwater head fluctuation. In this research, the ground settlement and the distribution of pore water pressure are simulated from groundwater level fluctuation over the past 100 years. Then, we conducted the seismic analysis by input the distribution of effective stress calculating from the simulated ground water pressure. The sites analyzed in this research are Tokyo Sea Life Park at the mouth of Arakawa River.

DOI： 10.32732/jcec.2019.8.2.41

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1093/gji/ggy499

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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

DOI： 10.32732/jcec.2019.8.1.13

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

DOI： 10.2208/jscejsp.75.31

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

The migration of contaminant through soil is usually modeled using the advection-dispersion equation and assumes that the porous media is stationary without introducing a constitutive equation to represent soil structure. Consequently, time-dependent deformation induced by soil consolidation or physical remediation is not considered, despite the need to consider these variables during planning for the remediation of contaminated ground, the prediction of contaminated groundwater movement, and the design of engineered landfills. This study focuses on the numerical modeling of solute transfer during consolidation as a first step to resolve some of these issues. We combine a coupling theory-based mass conservation law for soil-fluid-solute phases with finite element modeling to simulate solute transfer during deformation and groundwater convection. We also assessed the sensitivity of solute transfer to the initial boundary conditions. The modeling shows the migration of solute toward the ground surface as a result of ground settlement and the dissipation of excess pore water pressure. The form of solute transport is dependent on the ground conditions, including factors such as the loading schedule, contamination depth, and water content. The results indicate that an understanding of the interaction between coupling phases is essential in predicting solute transfer in ground deformation and could provide an appropriate approach to ground management for soil remediation.

DOI： 10.1002/nag.2787

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

In view of the need to utilize ocean space and to develop seabed resources, the assessment of the stability of deep seabed soil has emerged as an important challenge in the field of geomechanics. To study seabed stability, the strength and stiffness of the natural ground must be ascertained. Accordingly, it is necessary either to conduct laboratory testing on soil specimens sampled from the seabed or to estimate the strength and stiffness by in-situ tests. While in the future it may be reasonable to conduct in-situ tests to estimate the stiffness and strength of seabed soil, it will still be necessary to compare the physical properties measured by in-situ testing with those measured by laboratory testing in advance of these determinations. In short, soil specimens must be sampled from the actual deep seabed, and laboratory mechanical tests must be conducted on the sampled soil specimens. However, soil sampled from the ocean bottom is subject to effects that differ from those exerted on soil sampled from the earth. More specifically, the non-negligible effects of disturbance are expected with soil sampled from the ocean bottom. The effects of disturbance occur during the sampling process due to the vaporization of dissolved gases, as these soil specimens are under relatively higher pressure and contain pore water with a high amount of dissolved gases. Therefore, numerical simulations were conducted in the present study to investigate the effects of vaporized dissolved gases on the mechanical behavior of soil specimens during sampling and on the undrained shear strength as determined by laboratory tests. The analyses revealed that the combination of the decreasing effective stress caused by the sampling and factors such as overconsolidation and unsaturation is attributable to the difference between the soil strength ascertained by laboratory testing and the in-situ soil strength.

DOI： 10.1016/j.sandf.2018.02.026

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Language：English   Publishing type：Research paper (international conference proceedings)  

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

Currently, finite element codes for small-strain have been widely applied in geotechnical engineering problems. However, the limitations of these codes are recognized, especially when the strain is large. To overthrow such limitations, finite-strain finite element code for porous media is needed. Therefore, this study aims to implement the finite element code for coupled solid-fluid at finite strain for static and dynamic problems. Firstly, the governing equation for porous media at finite-strain was introduced. Then, the mixed formulation of both phases with respect to the reference coordinates by deriving the governing equations with respect to the reference or current coordinates and by considering the solid and fluid as separate, was given. At present, the code is developed only for elastic regime as its preliminary step. In this study, the proposed code has been verified with the static and dynamic problem. And, the result of the finite-strain finite element code is then compared with the result of the analytical solution and small-strain finite element code within the small-strain regime. Thereafter, the proposed code was used to estimate the response of the earthen dam when subjected to a dynamic load. Finally, the results, discussion, and comparison between small- and finite-strain finite element analyses were presented.

DOI： 10.21660/2018.51.86896

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

The impermeability of bentonite is dependent on montmorillonite microstructures and varies with chemical alteration caused by related changes. The Kozeny-Carman equation is viewed as a rational hydraulic model for bentonite because it incorporates microstructure parameters such as specific surface area in addition to macrostructure parameters such as the void ratio. In the study reported here, a technique for measuring the specific surface area of compacted bentonite under constant volume conditions using X-ray diffraction was developed, and the hydraulic conductivity of various bentonite materials was evaluated based on the measurements thus obtained. The applicability of the Kozeny-Carman hydraulic model for evaluation of impermeability of bentonite was clarified. (C) 2017 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.

DOI： 10.1016/j.sandf.2017.08.001

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

Bentonite materials have been considered as a candidate material for engineered barriers in transuranium (TRU) waste disposal facilities due to their physical and chemical characteristics. Bentonite materials will be initially compacted and unsaturated. After closing the cavern, the bentonite material will become saturated through exposure to a percolating groundwater. It is therefore important to understand the behaviour of bentonite during saturation, which provides an initial condition of the disposal facilities. This paper explains a mathematical model which can express the saturation process. Subsequently, a series of numerical simulations were carried out. First, the swelling pressure of buffer and backfill was examined to verify the numerical model. It was confirmed that the simulated swelling pressure rises with water absorption, and swelling pressure test results from the literature are shown to be satisfactorily predicted by the numerical model, although these were slightly overestimated. Next, the mechanical behaviour of bentonite materials in a TRU waste disposal facility during the saturation process was examined using soil/ water/ air coupled finite-element method. Although it is difficult to examine the validity of analysis results because of the difficulty of an extremely long-term measurement, the qualitative behaviour of the saturation process could be inferred.

DOI： 10.1680/jenge.14.00041

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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

Bentonite has remarkable swelling characteristics and low permeability that enhance the stability of the buffer materials in repositories for the geological disposal of radioactive waste. It is necessary to apply reliable numerical simulation techniques to assess the safety and mechanical stability of repositories over a long period of time. Having a constitutive model that can describe the mechanical behavior of bentonite is key to such numerical simulations. This paper proposes an elasto-plastic constitutive model to describe the changes in the mechanical properties of bentonite due to saturation in the progress of a repository becoming submerged under groundwater. In the proposed model, the swelling index is formulated as a function of the degree-of-saturation to express not only the swelling behavior, but also the dependency of the degree-of-saturation on the dilatancy characteristics. The montmorillonite content is used as a material parameter to determine the normal consolidation line. The experimental results of swelling volume and swelling pressure tests in previous literature are shown to have been satisfactorily predicted by the proposed model. (C) 2017 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.

DOI： 10.1016/j.sandf.2017.01.006

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：地盤工学会  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：地盤工学会  

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

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.5445/KSP/1000068889

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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

The B-value, measured after setting up a specimen for triaxial testing, is used for evaluating the degree of saturation of a specimen. However, the stress conditions used when measuring the B-value have not been standardized. Although some experimental approaches have been pursued, no detailed analyses have evaluated the effects of the measurement conditions on the B-value results. In this study, the B-values of nearly saturated specimens under various stress conditions were investigated, using a smart triaxial test apparatus capable of elaborate stress control, and comparisons among measurement results were conducted. Moreover, by applying Henry's law, which governs the dissolution of the gas phase into the liquid phase, to an existing constitutive model for unsaturated soil, a new soil model was proposed. This new model accurately represents the behaviors of pore air even under nearly saturated conditions. In addition, the effects of the stress conditions on the B-values were investigated through numerical simulations of B-value measurements. (C) 2016 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V.

DOI： 10.1016/j.sandf.2016.08.009

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

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Geotechnical Society  

In this study, the generation process of the phreatic surface within a river levee is investigated through soil/water/air coupled simulation. Here, the effects of river level fluctuation and rainfall on changes in soil moisture distribution within a river levee are considered. The constitutive model proposed by Ohno et al.1) is formulated to the initial and boundary value problems in accordance with Borja's multi phases' concept and is used for simulation. Consequently, it is first found that high groundwater level is maintained for ground consisting of low permeability and high soil water retentivity. Moreover, it is found that the fluctuation of river level directly influences the phreatic surface, and that, in contrast, the effect of rainfall appears after a time lag.

DOI： 10.3208/jgssp.JPN-078

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

Most onshore earth structures, such as earthen dams, embankment, and river levees, are constructed by compaction. Transportation geotechnics also includes construction of compacted earth structures, such as road and railway embankment. Optimum compaction can increase shear strength, while decreasing compressibility and permeability of earth structures. For this reason, compaction has been used for earthworks since the dawn of times. Generally, a series of lab compaction tests is conducted to obtain a compaction curve before constructing these structures. The shape of the compaction curve, which determines the maximum dry density at the optimum water content, is very important in the design and construction of structures. However, it is difficult to control compaction quality on the basis of lab tests alone, as soil materials are inhomogeneous. Furthermore, there are differences in the compaction methods used in lab tests and at construction sites. Therefore, it is necessary to explain the mechanisms of compaction in the framework of soil mechanics. In this study, compaction of earthworks is simulated in a similar way. The effect of compaction layer thickness and the number of compaction layers on the distribution of dry densities in an earth structure was investigated through soil/water/air coupled simulation. Consequently, it was found that multi-layered compaction can create a gap in the dry density between two layers and that this gap can be reduced by thinner layer compaction. On the other hand, though the average dry density in a compacted earth structure can be increased by increasing the number of compacted layers, some gap between compaction layers was inevitable. Through these findings, this study contributes to the performance design of compacted earth structures.

DOI： 10.1016/j.proeng.2016.06.035

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：地盤工学会  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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

As for the low permeable layer, important functions are expected as an engineered barrier of radioactive waste disposal for low-level waste with comparatively high radiation levels. On examining the construction methods of this low permeable layer, it is important to confirm the possibility of the construction in the conditions similar to the actual constructed conditions with a true scale size. Therefore, the construction examination for the bottom part of the low permeable layer by bentonite and the performance check test of the buffer layer were carried out. The result of the construction examination showed that the possibility of the construction were confirmed, and the result of performance check test showed that it was possible to ensure the required performance of the low permeable layer, such as hydraulic conductivity.

DOI： 10.2208/jscejge.71.147

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Other Link： https://jlc.jst.go.jp/DN/JLC/20013233950?from=CiNii

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 土木学会  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 土木学会  

DOI： 10.2208/jscejam.71.I_171

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

&nbsp;In recent years, enormous damage has been caused by natural disasters. Disaster Medical Assistance Team (DMAT) play an important role in minimizing human suffering. However, since factual information is intermingled with disinformation in the event of a disaster, it is difficult to obtain correct information, such as where and to what extent medical care is required, in order to dispatch DMAT appropriately. In this study, using a victims estimation formula empirically derived from the cumulative death toll data with the passage of time in past seismic hazard, an optimization problem was addressed to minimize the number of deaths.<br>&nbsp;Consequently, it was found that early dispatch of DMAT would be effective, and DMAT should be dispatched according to the circumstances (number of DMAT, conditions of affected areas) in order to minimize the cumulative death toll. And, by setting the conditions of the affected area, it was possible to consider the way of reasonable DMAT dispatch. Thus, it has become possible to suggest the way of effective dispatch of finite DMAT, to use limited DMAT resources efficiently, and to help make decisions.

DOI： 10.2208/jscejsp.71.32

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

&nbsp;Decision makers must decide the disaster correspondence by using uncertain information. When the decision maker makes this decision, they have the dilemma to prioritize which of &ldquo;the rapidity of correspondence&rdquo; and &ldquo;the accuracy of information&rdquo;. The result for disaster varies according to the difference in priority.<br>&nbsp;This study approximate the change of cumulative number of death with time lapse by using the Weibull distribution and proposed the Bayesian estimation model to predict the total number of deaths by utilizing the change of cumulative number of deaths. By considering the estimated total number of deaths with past earthquakes cases, it was possible to estimate the time period to make the disaster response decision. Therefore, this would be a judgment material to reduce the dilemma of decision makers.

DOI： 10.2208/jscejsp.71.46

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

DOI： 10.2208/jscejam.71.i_429

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CRC PRESS-TAYLOR & FRANCIS GROUP  

Undrained shear strength is used for estimating the bearing resistance of foundations and the safety factor of a slope. For this test, the pore-pressure coefficients, namely A and B as proposed by Skempton, are available. These coefficients can be obtained from the undrained triaxial test. According to Terzaghi's effective stress theory, the B-value must be 1.0 in a saturated soil. Therefore, a B-value of 1.0 is used as the target for saturating a specimen. However, it is difficult to achieve a B-value of 1.0 in the triaxial test. Because of this, a specimen with a B-value greater than 0.95 is regarded as saturated. The relationship between saturation and the B-value is still not clear. In this study, the factors influencing the B-value were numerically investigated with a soil/water/air coupled model that considers the solvability of pore-air to pore-water. Consequently, the pore-water pressure behavior, which depends on the initial degree of saturation and initial stress conditions, could be expressed.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CRC PRESS-TAYLOR & FRANCIS GROUP  

Due to its low permeability and excellent expansion characteristics, bentonite materials are considered to be the engineered barrier in Trans-Uranium (TRU) disposal facility. It is necessity to predict the mechanical behavior of bentonite using numerical simulation to evaluate the long-term performance of TRU disposal facility. In this paper, we simulated the saturation process of bentonite materials in TRU disposal facility from an initially unsaturated state. And we examined the mechanical behavior of bentonite buffer during the saturation process. This simulation result shows that Disposal waste is moved upward due to the difference of swelling pressure between buffer and backfill. And the facility existed in unsaturated state even under steady state conditions due to the entrapped air.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CRC PRESS-TAYLOR & FRANCIS GROUP  

In order to study the triggering factors for shallow landslides during rainfall, sandy soil slopes were prepared in laboratory angles of 30 and 45 degrees and those slopes were poured with rainfall intensities of 30 and 60 mm/hours through a specially developed rain simulator. Moreover, the rainfall on slope was simulated with using unsaturated soil/water/air coupled F.E. code, and the numerically calculated depth of water front and values of suction at different location in the slopes at various angles of inclinations matched well with the experimentally observed values. The combined results obtained with the numerical and experimental studies were utilized to predict the variation in the depth of water and values of suction at different intensities of rainfall as well as deformation of slopes during rainfall.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CRC PRESS-TAYLOR & FRANCIS GROUP  

In this study, we use conservation laws to construct a method for describing the movement of dissolved material. This is then applied to a mathematical model. Recently, soil pollution, induced by toxic materials in the ground water, is spreading. The mobility modes for this dissolved material can be divided into advection, induced by distribution of fluid head, and dispersion, induced by distribution of concentration content. First, Darcy's law is derived from the momentum conservation law using Bear's theory. Secondly, the concept of total fluid head is extended for application to various fluids. Additionally, an infiltration equation and an advection-dispersion equation are derived from mass conservation laws. Coupling the two equations, we construct a mass transfer model for unsaturated/saturated ground. Using the model, the effect of density flow is considered assuming basic one-dimensional areas. The results show that mobility of the dissolved material depends on its density. We concluded that density flow dominates along the vertical rather than the horizontal direction and mobility of the fluid is dulled in the unsaturated area.

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Language：English   Publishing type：Part of collection (book)   Publisher：CRC Press  

DOI： 10.1201/b17034-76

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Language：English   Publishing type：Part of collection (book)   Publisher：CRC Press  

DOI： 10.1201/b17034-91

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

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011440

CiNii Books

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011442

CiNii Books

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011441

CiNii Books

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011439

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：BGR  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOLOGICAL SOC PUBLISHING HOUSE  

Recently, the hydraulic/mechanical/chemical (HMC) analytical method has been studied with the aim of evaluating the long-term performance of Trans-Uranium (TRU) geological repositories. In this particular research, the hydraulic/mechanical modelling of bentonite materials for HMC analyses has been studied, with bentonite materials considered as the engineered barrier. It is said that the bentonite material in the TRU disposal facilities is altered chemically by cement leachate. Moreover, there is a concern that chemical alteration changes the expansion characteristics and water permeability of the bentonite material. In this paper, using past test results, the influence of montmorillonite content and the exchange of sodium and calcium ions on mechanical and hydraulics behaviour is examined. Hydraulic/mechanical mathematical modelling is also presented, describing the mechanical behaviour of bentonite from an initially unsaturated state while also taking into account the hydraulic and mechanical characteristics of bentonite mentioned above. We also simulate the saturation process from an initially unsaturated state in a TRU disposal facility, which is modelled one-dimensionally.

DOI： 10.1144/SP400.13

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：地盤工学会  

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

The pore pressure coefficient B, which is measured on triaxial test, is useful for evaluating degree of saturation of specimen. However, the influential factors on this B value other than degree of saturation have not been investigated in detail up to now. In this study, first, Henry's law that indicates dissolved air in pore water was applied to the existing constitutive model for unsaturated soil in order to express the behavior of pore air on unsaturated soil extremely close to fully saturated state. Next, the influential factors, such as degree of saturation, confining stress and back pressure, were investigated through numerical simulations with using newly obtained model. Consequently, it was found out that B value depends on not only degree of saturation but also stress state.

DOI： 10.2208/jscejam.70.I_145

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：地盤工学会  

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

The East Japan Earthquake and Tsunami caused serious damages in the coastal area of eastern Japan. Many houses and cars on the road were swept away by the tsunami. Also, industrial facilities such as chemical plants in the coastal area were completely destroyed. Damage from saline seawater was not limited only to the rice field areas, and there were also serious anxieties regarding the possibility of ground contamination as a result of harmful heavy metals that leaked from destroyed chemical plants. In light of this scenario, we carried out a quantitative survey to examine these areas. This paper reports on the results of our survey. It was found that high salt concentrations were detected on the ground surface but predictions state that these concentrations can be diluted with rainfall. It was also revealed that serious ground contamination due to the harmful heavy metals was not detected.

DOI： 10.11345/nctam.62.141

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

In order to evaluate the long-term behaviour of the engineered barriers in geological disposal sites for transuranic element-bearing (TRU) waste, an evaluation by numerical analysis is required. Although chemical and hydraulic/mechanical analyses have been conducted independently until now, essentially both type of phenomena occur simultaneously and produce synergistic effects. Therefore, we focused attention on the buffer (bentonite) engineered barrier and conducted a study of which involved incorporating hydraulic/mechanical phenomena into the chemical analysis of bentonite alteration.
The simulations employed weakly-coupled chemical and hydraulic/mechanical effects to study the behaviour in one dimension. The results showed that the dissolution of the montmorillonite is suppressed in the buffer section nearest the cement material. Moreover, in order to achieve a fully coupled analysis in future, the present study also identifies issues that need to be resolved.

DOI： 10.1180/claymin.2013.048.2.13

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011407

CiNii Books

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011406

CiNii Books

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011408

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)  

Results obtained in a lab compaction test are difficult to apply to the design and compaction control at an actual geotechnical engineering site. This is attributed to the fact that the mechanism for compaction has not been explained using the principles of soil mechanics. The main theme of this study is interpretation of the compaction mechanism with unsaturated soil mechanics. Here, static compaction tests were simulated with soil/water/air coupled finite element analysis code DACSAR-MP. Consequently, the shape of the compaction curve was successfully expressed. Moreover, the effects of compaction on compressibility and permeability of compacted soil could be reasonably explained. Additionally, shear deformation was applied to the specimen obtained from static compaction simulations in soil/water/air coupled analysis. The relationships between shear strength and compaction curve showed good agreement with the actual behavior.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Chapter of International Geosynthetics Society  

DOI： 10.5030/jcigsjournal.28.109

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© Springer Science+Business Media Dordrecht 2013. In this chapter, the stress–strain relationship on the singular point of the yield surface of the original Cam clay model and the Sekiguchi-Ohta’s model is derived in order to compute the volume change correctly. Metastable space, the range of increment of strain in which effective stress does not get away from the singular point of yield surface, was theoretically derived. In metastable space, the increment of volumetric strain is larger than the increment of deviatoric strain.

DOI： 10.1007/978-94-007-5675-5_15

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© Springer Science+Business Media Dordrecht 2013. An elasto-plastic constitutive model for unsaturated soils is improved to realize numerical stability of computations at the singular point on the yield surface and an accurate prediction of the mechanical behavior of overconsolidated (or elastic state) soils in this chapter. The authors introduce the exponential contractancy model (EC model) by Ohno et al. (J Appl Mech JSCE 9:407–414, 2006) and the subloading surface model by Hashiguchi and Chen (Int J Numer Anal Method Geomech 22:197–227, 1998) to the elasto-plastic constitutive model for unsaturated soils by Ohno et al. (J JSCE 63(4):1132–1141, 2007). The applicability of the constitutive model is verified by simulating triaxial shear tests under constant net stress undrained conditions.

DOI： 10.1007/978-94-007-5675-5_14

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

In order to express time dependence actions, such as secondary consolidation, creep, and strain rate dependence, much elasto-viscoplastic constitutive models are proposed until now. However, in these constitutive models based on a viscoplasticity theory, the time dependence action from an overconsolidation domain to a normal consolidation domain cannot be expressed continuously. Moreover, Pc-effect by secondary consolidation cannot be evaluated quantitatively, either.<br> In this paper, the elasto-viscoplastic model in consideration of Pc-effect by secondary consolidation is proposed. Moreover, the simulations of shear test and consolidation test were carried out and the validity and applicability of this constitutive model were examined.

DOI： 10.2208/jscejge.69.404

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Other Link： https://jlc.jst.go.jp/DN/JALC/10024601176?from=CiNii

Language：English   Publishing type：Research paper (international conference proceedings)  

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

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011370

CiNii Books

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011372

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011371

CiNii Books

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011374

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This study presents a new constitutive model for expansive soils. Under any arbitrary state of degree-of-saturation, the mechanical void ratio predicted by the elasto-plastic constitutive models, i.e. EC model and Se-hardening model are combined with the additional void ratio in order to characterize the typical swelling behavior of expansive soil. Herein, the fully saturation curve which derived from compaction and consolidation experimental tests are taken into consideration. The proposed model is examined by simulating the typical experimental test on expansive soil, i.e. normally consolidation and swelling pressure tests. © 2012 IEEE.

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

DOI： 10.2208/jscejam.68.i_345

J-GLOBAL

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

Compacted soil is widely used for earth structures. However, the mechanism of compaction has not been explained, so it is difficult to grasp distributions of stress, void ration, and soil moisture within compacted earth structure. Therefore, estimation of safety and stability of compacted earth structures exposed to natural disaster is complicated. Compaction is decreasing void ratio by applying stress under certain water content and pushing air out of soil mass. Thus, the mechanics of unsaturated soil, which includes air within void, is needed for understanding of compaction. In this study, we regarded compaction as compression and expansion phenomenon of unsaturated soil under drained air and undrained water conditions and formulated it in initial-boundary-value problem. Here, the influences of permeability and soil water retention characteristics on compaction were considered and static compaction tests were simulated. Moreover, multi-layered compaction was examined.

DOI： 10.2208/jscejam.68.I_299

J-GLOBAL

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

DOI： 10.2208/jscejam.68.i_291

J-GLOBAL

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

DOI： 10.2208/jscejam.68.i_307

J-GLOBAL

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer Berlin Heidelberg  

DOI： 10.1007/978-3-642-31343-1_23

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Language：English   Publishing type：Research paper (international conference proceedings)  

Thermal power plants burn oil and coal to generate electricity. Coal fly-ash is a product of the coal-burning process. Coal fly-ash has a self-hardening property and becomes extremely stiff over time. For this reason, it is being reused as a concrete aggregate in the production of concrete. Recently, coal-fly ash is being mixed with soil from construction waste for reclamation projects. To be able to reuse coal fly-ash in such a way, in the field of geotechnical engineering, the associated self-hardening properties must be incorporated in the framework of the constitutive model. It is generally known that cemented soil, such as fly-ash, behaves similar to unsaturated soil. In the constitutive model for unsaturated soil, hardening due to desaturation is expressed as the increase in yield stress. Here, changes in parameters used in the Cam-Clay model, generated by this self-hardening property, are studied by comparing the simulation results obtained from a soil/water coupled analysis with triaxial test results on two kinds of coal fly-ash. Consequently, the self-hardening property is expressed as an increase in the yield stress and an increase in the frictional angle, dependent on time. Differences between the two methods of producing fly-ash are reflected in the parameter set.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOS PRESS  

Static friction in granular wedges can stabilize own weight on a horizontal plane without lateral supports. This sort of problem provides fundamental knowledge about pressure distribution along the foundation of earth works which have a long triangular shape in particular. The present study reviews the authors' recent development on an analytic model of a sand heap which adopted Nadai's hypothesis on the major principal stress orientation and a framework of below-yielding limit. Because deformation analyses of many geotechnical engineering problems often require the magnitude of coefficient of lateral earth pressure at-rest K-0 to describe in situ lateral earth pressure, emphasis is placed on the evaluation of stress ratio under the apex of sand heap which represents Jaky's basic assumption on the derivation of K-0 in the prismatic sand heap sloped at an angle of repose. Comparison of the analytical stress ratio along the central plane of granular wedge with Jaky's expressions was reported.

DOI： 10.3233/978-1-60750-822-9-924

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

DOI： 10.2208/jscejam.67.i_231

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011336

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011340

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

DOI： 10.24546/81011337

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011338

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：神戸大学都市安全研究センター  

DOI： 10.24546/81011339

CiNii Books

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

An evaluation method for the mechanical behavior of unsaturated soils is studied in this paper. Although the mechanical behavior of unsaturated soils is complicated, a simple modeling is preferable in practice. This is because the soil properties are not homogeneous and ground data is limited when structures are being designed. In addition, in order to evaluate the reliability of the design, the physical meanings of the parameters applied in the prediction model should be clear. Firstly, the authors study the relationship between compaction curves and compression indexes in the unsaturated state that is used in the proposed constitutive model. Based on the constitutive model, the stress paths for constant volume shear tests are formulated under a constant void ratio condition and the stress paths for undrained shear tests are calculated under a constant water content condition. In the case of unsaturated specimens, the volume of these specimens changes with the shear deformation and the stress paths depend on the initial degree of saturation. The results of the calculation qualitatively describe the test results by considering the changes in effective confining pressure in the undrained condition and the water retention curves. © 2010 Springer Science+Business Media B.V.

DOI： 10.1007/s10706-010-9340-6

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Language：English   Publishing type：Research paper (international conference proceedings)  

Due to its low permeability and excellent expansion characteristics, bentonite is an excellent candidate with potential use as a buffer in the disposal of nuclear waste. Its expansion characteristics, activated by wetting, can be interpreted based on the full saturation line, depicted as a unique line on the density and the confining pressure relationship as proposed by Kobayashi et al. (2007). In addition, its elasto-plastic constitutive relation can also be formulated by introducing additional irreversible strain component describing the expansion of the montmorillonite present in the bentonite material. A constitutive model can consistently express the mechanical behavior of the compacted bentonite material from the unsaturated to the fully saturated state. This paper describes the density homogenization process that was conducted through a series of soil-water coupled elasto-plastic finite element simulations. Specifically, bentonite specimens, with different initial densities, were permeated with a constant water head. Stresses and strains developing in bentonite, particularly the density change, were carefully examined. A series of numerical simulations, performed on the two specimens, showed that specimens did not homogenize to a unique value of density upon reaching the fully saturated state. To confirm the simulation results, we carried out a series of experiments. The experimental results also support our simulation results. Copyright © 2011 by ASME.

DOI： 10.1115/ICEM2011-59153

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

In structural mechanics, Nadai's sand hill analogy is the interpretation of an ultimate torque applied to a given structural member with a magnitude that is analogously twice the volume of stable sand heap which can be accommodated on a transverse cross-section basis. Nadai's analogy is accompanied by his observation of a loose triangular embankment, based on the fact that gravitating loose earth is stable if inclined just under the angle of repose. However, Nadai's analysis of stress distribution in a planar sand heap was found to be inaccurate because the total pressure obtained from Nadai's solution is greater than the self-weight calculated from the heap geometry. This raises a question about the validity of his observation in relation to the analogy. To confirm his criterion, this article presents and corrects the error found in Nadai's solution by analyzing a radially symmetric stress field for a wedge-shaped sand heap with the purpose of satisfying both force balance and Nadai's closure. The fundamental equation was obtained by letting the friction state vary as a function of angular position and deduce it under the constraint that the principal stress orientation obeys Nadai's closure. The theoretical solution sufficiently agreed with the past experimental measurements. © 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jmps.2010.07.013

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Desertification due to salt damage has recently become a serious problem throughout the world. Salt damage is a phenomenon where salt in the groundwater gets concentrated at the ground surface and kills vegetation. In this study salt damage due to disequilibrium of water balance was simulated with unsaturated soil/water coupled simulation code, as applied the material transport equation. Evaporation and precipitation cycles were applied to a model of ground that contained salty groundwater in its deep region. This allowed the successful reproduction of the phenomenon of salt accumulation on the ground surface. Additionally, identical climatic conditions were applied to model grounds consisting of two types of soil, different in terms of their soil-water retention characteristics. It was found that two methods of overlay and insertion of a layer of coarse-grade material, known as 'mulching', are effective in the prevention of salt accumulation. © 2011 Taylor & Francis Group, London.

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Pressure distribution in sand heaps is affected by a particular arching action during the formation process. The closure of fixed principal axes successfully links arching criterion to capture the phenomenon of central stress minimum in conical sand heaps. However, it is insufficient to explain a negligible stress dip observed in planar sand heaps, which are of practical interest to civil engineers because many earthworks are triangular in shape. This study explains the closure of polarized principal axes and the stress distribution formulation, which was found to be agreeable with experimental data. The direction of major compression along a circle traced about the apex might provide a suitable arching criterion in the 2D space of sand heaps.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CRC PRESS-TAYLOR & FRANCIS GROUP  

To predict the long-term elasto-plastic behavior of unsaturated earth structures, a constitutive model, which can express the following typical mechanical behavior of unsaturated soil, is needed. This includes shrinkage and increase of stiffness upon drying (i.e. suction increase), collapse with reduction of stiffness upon wetting (i.e. suction decrease), and the influences of suction history related to the hysteresis of soil-water retention characteristics. In this study, a new constitutive model is proposed for unsaturated soil where the effective degree of saturation is used as a parameter relating to stiffness. The model shows good agreement with experimental results. In addition, a soil/water coupled finite element simulation code (simulator), as applied to this model, is introduced. The appropriateness of the simulator is demonstrated for the case of a virtual fill.

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

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CRC PRESS-TAYLOR & FRANCIS GROUP  

When troublesome sludge discharged from industries and purification plants are burnt by 1300 degree, they change to innocuous micro-porous ceramic materials. The authors are seeking for practical use of such micro-porous ceramic materials in the geotechnical engineering field, particularly for geohazard mitigation. Then, in order to grasp fundamental mechanical properties of the micro-porous ceramic particles, a series of laboratory tests, that is, triaxial compressive shear tests, permeability tests and water retention tests, were performed. It is found that the stress-strain characteristics and permeability of the micro-porous ceramic particles are very similar to those of standard sandy materials but they have very high water retention capability. Next, applicability of the unsaturated elasto-plastic constitutive model proposed by Ohno et al. (2007) to the mechanical behavior of micro-porous ceramic particles was examined in this paper.

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Discontinuity at the vertex of the Sekiguchi-Ohta model causes numerical troubles when associated flow rule is applied because the singularity encountered in the derivatives of yield function. Based on Koiter's associated (low rule, the numerical implementation to accommodate the vertex singularity had been generalized. The set of applied strains had been formulated and defined as the domain of metastability. This study is focused on validity of the domain of metastability by a regularized method. Infinitesimal vicinity adjacent to the vertex is considered to regularize all of plastic flow in outwards normal direction to the yield surface. It was confirmed that the metastable domain of the Sekiguchi-Ohta model is bounded by an elliptical cone in principal strain space.

DOI： 10.11345/nctam.57.89

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：JSCE  

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It is empirical knowledge that vegetation can influence the behavior of earth structure. It prevents surface failure and erosion due to rain and wind, and contributes to the stability of earth structure. Moreover, it encourages water circulation with transpiration, fixes atmospheric nitrogen and carbon via photosynthesis, and improves the environment. Therefore, surface seeding is purposely performed when an earth structure, such as an embankment or an earth dam, is constructed. Typically, vegetation grows on unsaturated soil. Consequently, a constitutive model for unsaturated soil is needed for understanding the effects of vegetation on the ground. In this study, we focus on the effect of vegetation-induced water uptake. The effect of water uptake due to evapo-transpiration can be regarded as reduction of water content within soil and appropriately represented in simulation studies. The constitutive model proposed by Ohno et al. (2007) is used for the simulation. In this model, the effective degree of saturation is treated as a parameter expressing hardening/softening. Moreover, the 'root element,' where the reduction of water content occurs, is applied to the soil/water coupled analysis with unsaturated soil mechanics. To verify the applicability of this model, the accident in Poland where non-uniform settlement and building damage were caused by water uptake of vegetation was simulated. The results show that water uptake increased suction and induced non-uniform settlement. This method is effective for understanding the effects of vegetation on the ground. © 2009 IOS Press.

DOI： 10.3233/978-1-60750-031-5-526

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

DOI： 10.2208/jscejeep.1.135

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Language：English   Publishing type：Part of collection (book)   Publisher：CRC Press  

DOI： 10.1201/9780203885949.ch52

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

The soil/water-coupled analysis for unsaturated soil mechanics with the finite element method is used to express the behavior of compacted earth structures exposed to rainfall. The constitutive model, which is proposed by Karube et al. (1996, 1997) and modified by Karube and Kawai (2001), is formulated for initial and boundary problems and coded as DACSAR-U (lizuka et al., 2000). A deep fill, which consists of compacted, unsaturated soil, was analyzed with DACSAR-U. Different patterns of rainfall were applied to deep fills in finite element simulations. As a result, non-uniform settlement of deep fill can be calculated and the magnitude of settlement of deep fills is dependent on the amount of collapse, namely, the compression due to the decrease in suction. Moreover, delayed settlement due to rainfall and an accumulation of an irreversible settlement due to cyclic rainfall was observed.

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A new constitutive model of swelling soil material is proposed to evaluate its mechanical characteristics. In the case of the compacted bentonite material, nonlinear behavior appears more dominantly than ordinary clay materials in the consolidation test. The original Cam-clay model cannot describe these characteristics observed in the compacted bentonite materials. Therefore, a new modeling that strain increment consists of linear summation of the swelling component and the elast-plastic component is introduced to describe the nonlinear behavior in the unloading stage. From the result of the simulation of the triaxial compression test, it is demonstrated that the stress pass and the stress and strain relationship are well simulated by the new model.

DOI： 10.2208/jsceseee.24.102s

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DOI： 10.2208/journalam.10.971

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：MILLPRESS SCIENCE PUBLISHERS  

In this paper, the authors focus on the confining effect brought by geosynthetic-reinforcement. The reinforcement effect is not brought by the geosynthtics itself but mobilized complexly as a composite material consisting of geosynthetics and compacted soils. If the geosynthetics and the compacted soils are unified more tightly, higher reinforcement effect may be expected. Then, in this paper, presented is an experiment, that is, making soil cantilevers with compacted soils wrapped by geosynthetics which are tightly unified by prestressed steel bars. Two types of soil cantilevers were constructed. The soil structures were, first, constructed and wrapped by geosynthetics on the bases of styrene forms and, next, prestressed through the steel bars penetrated from the top surface to the bottom of the geosynthetic-reinforced soil structures. The soil cantilever was formed by melting and removing the styrene forms in order from the edge with monitoring the vertical displacements. It was found that amazing reinforcement effect appears by tightly confining the dilative deformation of compacted soils with the geosynthetics and the prestressed steel bars. The reinforcement effect is numerically investigated. A series of elasto-plastic FE numerical simulation was carried out. The compacted soil was modelled to be elasto-plastic body and the geosynthetics was expressed by the elastic material.

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This paper discusses the volume change characteristics of compacted soil based on oedometer test results. After making specimens with different water contents and under different compaction loads, compression tests are conducted under both saturated and unsaturated conditions. The effects of the compaction conditions on the compression curves are discussed. It is confirmed that the yield stress and the water content are important factors when evaluating a compression curve, while dry density and suction are important factors when evaluating the yield stress. Copyright ASCE 2006.

DOI： 10.1061/40802(189)66

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：Kobe University  

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Changes in the instantaneous shear modulus associated with the non-coaxiality of NC clay materials are presented. A series of hollow cylindrical shear tests was performed to measure the changes in the instantaneous shear modulus with shear history. After each normally consolidated clay specimen was compressively sheared until a prescribed shear level, it was continuously torsionally sheared under a constant volume to measure the instantaneous shear modulus. Coaxial constitutive relations, such as these of the conventional Cam-clay type of models, predict that the instantaneous shear modulus obtained, does not change regardless of the compressive shear history. On the contrary, it is known that non-coaxial constitutive relations theoretically bring about changes in the instantaneous shear modulus in relation to the compressive shear history. The test results supported the predictions made by the non-coaxial constitutive models. Finally, the proper formulation for the non-coaxiality between the stress and the incremental plastic strain is discussed.

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10424246

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

Changes in the instantaneous shear modulus associated with the non-coaxiality of NC clay materials are presented. A series of hollow cylindrical shear tests was performed to measure the changes in the instantaneous shear modulus with shear history. After each normally consolidated clay specimen was compressively sheared until a prescribed shear level, it was continuously torsionally sheared under a constant volume to measure the instantaneous shear modulus. Coaxial constitutive relations, such as these of the conventional Cam-clay type of models, predict that the instantaneous shear modulus obtained, does not change regardless of the compressive shear history. On the contrary, it is known that non-coaxial constitutive relations theoretically bring about changes in the instantaneous shear modulus in relation to the compressive shear history. The test results supported the predictions made by the non-coaxial constitutive models. Finally, the proper formulation for the non-coaxiality between the stress and the incremental plastic strain is discussed.

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TAYLOR & FRANCIS LTD  

The prediction of back-fill settlement due to the excavation work is getting important, particularly in the urban area. The finite element simulation would be a suitable choice to answer it. However, it is less feasible in practice to carry it out because input parameters needed in the F.E. simulation are not sufficiently provided in advance at the stage of design work. In the past, some simple evaluation methods for predicting the back-fill settlement due to excavation works were presented by Peck, Long and Moormann et al. and so on. In this paper, a new method capable for predicting the back-fill settlement at the stage of design work is proposed, taking account of design parameters, i.e. soil parameters, retaining wall parameters and construction sequences. The proposed method is built up based on a lot of monitored records obtained from sites and the numerical results obtained from a series of F.E. simulations for imaginary excavation works. It is designed to be simple and useful at the stage of design work. This method consists of two parts, predictions of the maximum amount of back-fill settlement and the distance from the retaining wall. Finally, some case studies in which the proposed new method was applied to actual excavation sites in Japan are presented.

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

This paper presents the modeling of the composite soil-geosynthetic structure and discusses the effect of the reinforcement arising from the confining of the deformation of the soil by geosynthetics. A series of compressive shear tests for compacted sandy soil specimens, wrapped in geosynthetics, is carried out for the purpose of quantitatively examining the effect of the geosynthetic reinforcement arising from the confining of the deformation of compacted soils during shearing. Furthermore, an elasto-plastic modeling for compacted soil and a rational determination procedure for input parameters, needed in the elasto-plastic modeling, are presented. In this paper, the subloading yielding Surface is introduced to the elasto-plastic modeling in order to describe the irreversible deformation characteristics of compacted soil during shearing. Since compacted soil is essentially unsaturated and its mechanical behavior is influenced by the suction working in the compacted soil media, the suction effect is taken into account in estimating of the degree of compaction. Finally, an elasto-plastic finite element simulation is conducted and the geosynthetic-reinforcement effect is presented. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.geotexmeml.2004.01.001

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

There are some constitutive models for unsaturated soil. However, their mathematical structures, particularly for expression of collapse phenomenon, are essentially the same. Therefore, it is possible to unify the constitutive models which were proposed in the past. In this paper, a generalized constitutive model for unsaturated soils is presented. First, we outline existing constitutive models for unsaturated soil and, next, we propose a comprehensive constitutive model for unsaturated soils in terms of the effective stress for unsaturated soils. To this new elasto-plastic model, it is easier to introduce sophisticated methods such as a rotational hardening, a subloading surface and so forth. This model is formulated in the form of incremental general stress and strain relationship and is incorporated into a finite element code, DACSAR-U, for unsaturated soils. The performance of the new constitutive model is demonstrated by comparing with the models proposed by Karube et at and by Honda et al

DOI： 10.2208/journalam.7.505

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

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS39.0.259.0

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Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS39.0.261.0

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Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS39.0.913.0

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

A highway embankment built in Akita prefecture using ground stabilization methods was constructed on very soft peat and clay deposits on a sloping base. This paper presents a case study of a soil/water coupled elasto-viscoplastic finite element simulation of an actual embankment construction, that is, the deformation analysis of a soft clayey foundation deposited on an inclined base with embankment loading. For execution of the numerical simulation, determining the input parameters needed in the analysis and evaluating the shape of sloping bedrock under the ground were problems. The former is discussed for a practical procedure of determining input parameters using unconfined compression strengths and the latter is accomplished by drawing a contour map of the top face of the bedrock under the ground, with reference to the geographical features of the area around the site and to a topographic map. The performance of the numerical simulation is discussed in comparison with in-situ monitored records. The effectiveness of ground stabilization methods employed at the site is also a topic of discussion.

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Language：English   Publishing type：Research paper (international conference proceedings)  

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

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

Experimental evidence suggests that a mutual relationship between anisotropy and structure of clays exists. It was hypothesized that development and decay of the structure of clays (called structuralizing and destructuralizing) can be regarded as development of anisotropy and decay of anisotropy (isotropization), respectively. Using this hypothesis, an anisotropic rotational hardening rule was incorporated in the Sekiguchi-Ohta elasto-plastic constitutive model. The subloading surface concept was also introduced to model the plastic deformation inside the yield surface more accurately.
The proposed model provided some rational as well as physical explanations for the experimental facts. Using the proposed model, it was possible to simulate the apparent softening behavior observed in anisotropically consolidated specimens. For isotropically consolidated specimens, no softening was observed, which is consistent with the experimental data. At the critical state, the undrained shear strength of the anisotropically consolidated specimens was the same as that of the isotropically consolidated specimens. This is due to both specimens having the same soil structure after large shearing. The shape of yield surface obtained from stress probe tests was investigated by simulating the tests with the proposed model. Typical data of the stress probe tests of natural clays shows that the yield surface generally has a smooth elliptical shape. By modeling the rotation of yield surface, the proposed model was capable of simulating this 'apparent' yield surface.

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Language：English   Publishing type：Part of collection (book)  

DOI： 10.1201/9781439833919.ch45

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Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS38.0.293.0

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Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS38.0.283.0

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Language：English   Publishing type：Research paper (international conference proceedings)  

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

DOI： 10.2208/journalam.5.785

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)  

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

The mechanical behavior of unsaturated soils strongly depends on the pore water distribution as well as the suction. The water characteristic curve (W. C. C) specifying the pore water content and the suction value plays a very important role in describing the mechanical modeling for unsaturated soils. However, the W. R. 0 shows the hysteresis loop in the wetting/drying processes. This paper emphasizes the importance of considering the hysteresis of W.C.C in the modeling. The accumulation of irreversible strains in the soil structures caused by rainfalls cannot be explained well without considering the hysteresis of W. C. C. An existing model of W. C. C is modified so as to express the accumulation of irreversible strains as the cyclic suction loading. Finally, it is shown that the modified model well explains the experimental results.

DOI： 10.2208/journalam.5.777

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

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

DOI： 10.24546/00317653

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

DOI： 10.2208/journalam.5.601

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Language：English   Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS37.0.761.0

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Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS37.0.327.0

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Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS37.0.325.0

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

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

The reinforcement technique using flexible materials such as geosynthetics has been widely employed in the current engineering practice. However, the reinforcement mechanism has not revealed sufficiently, i.e. the mechanical interaction between the reinforcements and soils, the confining effect induced by reinforcements and so forth, and then it has not yet led into a proposal of rational design procedure. This paper reports in-situ loading tests carried out on the compacted soil structure reinforced by flexible beltlike materials. Elasto-plastic finite element simulations were also performed considering dilatancy characteristics of compacted soils during shearing. Throughout comparison with the field records monitored in the site and the results obtained from the conventional elastic computation, discussed are the applicability of the elasto-plastic analysis and the role of dilatancy characteristics of compacted soils in the reinforcement mechanism.

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

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

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

This paper discusses the geosynthetic-reinforcement effect. The reinforcing effect arises from the equilibrium of inner forces between extension forces working to the geosynthetics and stresses induced in the soil media. In this paper, a series of model tests and their numerical simulations are carried out to examine this geosynthetics-soils mechanical interaction. The compacted soils are wrapped by geosynthetics and sheared in the newly developed loading test apparatus with monitoring the deformation and stresses. It is revealed that, throughout this paper, the geosynthetic-reinforcement effect is mobilized by confining the &lsquo;dilatancy characteristics&rsquo; of compacted soils. And also, a numerical simulation technique to rationally explain the observed facts obtained from model tests is proposed in this paper.

DOI： 10.2208/jscej.2001.680_15

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

DOI： 10.11345/japannctam.tam51.0.91.0

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

DOI： 10.2208/jscej.2001.694_67

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

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

Apart from following general outlines for input procedures and parameter findings when performing excavation analysis using FEM, some additional considerations should be taken. The influences of appropriate soil stiffness, pre-load efficiency, actual strut stiffness, soil/wall interface, crack in concrete retaining wall, and foundation piles installed before excavation have been investigated to weight the impact on analysis quality, enhancing acceptability in practice. Computed deformations and strut axial loads of a case study agreed quite well with field responses after applying these effects.

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

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

The prediction of back-fill settlement due to the excavation work is getting important, particularly in the urban area. The finite element simulation would be a suitable choice to answer it. However, it is not feasible in practice to carry it out because input parameters needed in the F. E. simulation are not provided in advance in the stage of design work. This paper proposes a simple prediction method of the back-fill settlement due to the excavation work. The proposed method is built based on a lot of monitored data obtained from sites and the numerical results obtained from a series of F. E. simulations for imaginary excavation sites. It is designed to be simple and useful in the stage of design work. This method consists of two parts, prediction of the maximum amount of back-fill settlement and prospect of the distance from the retaining wall.

DOI： 10.2208/jscej.2000.652_217

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

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

The specification of strength parameters is an important task in the design work of slope stability. Usually laboratory shear tests are employed to determine the strength parameters. The specimen in the laboratory tests is intended and generally assumed to represent a single point in the in-situ soil medium. And, the strength parameters obtained are interpreted as material properties of the soil element. However, since the uniformity of stress/strain distribution within the specimen is hardly achieved during shearing, the strength parameters thus obtained cannot be essentially regarded as material properties. In this paper, the shear box test under the condition of constant volume is considered and the distribution of stress/strain within the specimen is rigorously examined through numerical simulations based on finite incremental deformation theory. The mobilization of strength is explained associated with the development of shear bands in the specimen during shear.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

The strain localization developing inside clay specimens during shear is examined through the experimental observation and numerical F.E. simulation. In the experiment, clay specimens of column and hollow-cylinder shapes are uniaxially sheared and the development of shear bands is observed. The numerical simulation of compression shear is carried out under the plane strain condition for normally consolidated clay specimens with impermeable boundaries by using the elasto-plastic soil/water coupled finite element computation technique based on the finite deformation theory. Although the geometric boundary conditions are different in the experiment and simulation, discussed are the development of shear bands on/in the specimen and the transition of the localization mode which are found commonly in the experiment and simulation.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

This paper presents evaluation of undrained strengths obtained from unconfined compression tests, constant volume shear box tests and field vane shear tests which were carried out in a site. Theoretical expressions of these undrained strengths derived from the elasto-plastic constitutive model are summarized. And discussed are the correction factors that help converting the undrained strengths obtained from tests to ideal undrained strengths comparable to the theoretical strengths. Throughout comparison of the measured strengths and the theoretical predictions, reliable specification of the constitutive parameters for the model from the measured strengths is examined.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

Mechanical properties of soft clays, such as deformability and strength, are estimated using data obtained from in-situ and laboratory tests. These test methods were developed through experience gained in the development of geotechnical engineering. The undrained strength, for instance, of a soft clay estimated by using any one of these in-situ or laboratory tests is not usually the same as that estimated by another one of these tests. There are many possible reasons for the apparently different response of the clay to each of these testing methods. The differences caused by factors such as disturbance, stress history, detailed testing procedures, are sometimes surprisingly influential. This paper shows examples of the above mentioned complications encountered in engineering practice. The paper also describes the interpretation of such complications by means of an elasto-plastic constitutive model which was proposed by Sekiguchi and Ohta in 1977.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

The seismic deamplifying effect of soft clay layers is described. This deamplifying effect of soft clay layers on the propagated waves due to an earthquake is significantly influenced by the degree of consolidation of the soft clay underlying the site. In this paper, two buildings on Rokko Island are analysed. First, the static soil/water coupled analyses are carried out to assess the initial equilibrium conditions of the site just before the earthquake and, secondly, the dynamic response analyses are performed based on the data obtained from the static analyses. The emphasis is placed on evaluating the factor of safety against liquefaction at the various stages of consolidation and at the completion of consolidation. The results seem to be consistent with the overall phenomena observed in Port island and Rokko Island.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA  

A full-scale model test was conducted to investigate the mechanism of soil reinforcement by geosynthetic materials, A beam shaped soil structure reinforced by geosynthetics was designed and the global momentum stiffness was examined. This paper presents a brief description of the theoretical estimate of the global momentum stiffness of the reinforced structure for the laboratory model test and the numerical simulation of the full scale model test. The numerical simulation and the field test indicate that the effect of soil confinement by the geosynthetic material was particularly significant. A comparison of the numerical and field results is also presented.

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA  

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

This paper describes the mobilization mechanism of vane shear strength revealed in the naturally consolidated clay deposits. The vane shear test has been successfully simulated by the 3-dimensional soil/water coupling finite element program, DACSAR, and through this numerical analysis the mobilization mechanism of vane shear strength has been explained. After verifying the finite element modelling, discussed are, mainly, the development of shear stresses along the blade of vane, their distribution, the effects of partial drainage and material viscosity. The in-situ vane shear test hardly escapes from much influence both of partial drainage and material viscosity. In particular, the partial drainage of pore water yields the difference between strengths at the top and/or bottom edges of a vane blade and at the side edge of a vane blade.

DOI： 10.2208/jscej.1994.487_227

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：THOMAS TELFORD SERVICES LTD  

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

This paper describes the effect of non-coaxiality arising from material anisotropy on bifurcation phenomena such as shear band formation. The elasto-plastic model originally proposed by Sekiguchi and Ohta [7] is one of the typical models which include anisotropy and it is used to examine the effect of anisotropy on shear band formation. First, we shall extend this elasto-plastic model for infinitesimal strain to a model for finite strain and discuss the mathematical structure of this model. The stress induced anisotropy is found to bring about a vertex-like effect, such as the non-coaxiality between the Cauchy stress tensor and a plastic stretching tensor, into the constitutive relation. Then, we shall examine the effect of this non-coaxiality on bifurcation conditions in relation to the material rigidity which changes with the angle of simple shear. Finally, it will be concluded that this non-coaxiality arising from the anisotropy does not contribute much to triggering instability by localization of the deformations which result in shear band formation, while on the other hand, the non-coaxiality due to the yield vertex effect is rather inclined towards instability by localization of the deformations.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：THOMAS TELFORD SERVICES LTD  

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

Coupled elasto-plastic deformation-flow finite element analysis has been frequently used for the prediction of displacements, stresses and pore water pressures in geotechnical problems. However, the analysis is not suitable for the stability problems since its numerical results often become unstable after the stress paths of elements arrive at the critical state.<br>The analytical method including &ldquo;imaginary viscosity method&rdquo; which is a usual viscoplasticity computation scheme is developed to analyse the behavior of soil from the initial stress stage to the failure one.<br>In order to assess the validity and the applicability of this method, a problem of bearing capacity and an actual embankment are examined.

DOI： 10.2208/jscej.1987.388_121

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

DOI： 10.3208/sandf1972.27.3_71

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

The finite element technique using the imaginary viscoplastic calculation scheme is employed to compute the perfect plasticity region such as failure state. And the calculation of bearing capacity of footing in anisotropic normally consolidated ground is performed by incorporating theoretical equation of anisotropic undrained shear strength into yield function. The influences of anisotropy of ground are analytically investigated with taking notice of stress distribution near and in the applied footing stress at collapse of ground.

DOI： 10.2208/jscej.1987.382_255

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Total pages：294   Responsible for pages：pp.231-251   Language：English   Book type：Scholarly book

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Responsible for pages：p.82 pp.128-137   Language：Japanese   Book type：Scholarly book

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Language：Japanese   Book type：Textbook, survey, introduction

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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