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DOI： 10.1016/j.sandf.2020.09.004

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DOI： 10.11408/jsidre.89.I_181

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Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.sandf.2020.01.009

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DOI： 10.1016/j.sandf.2019.08.002

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

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

DOI： 10.11408/jsidre.87.II_29

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10333-019-00722-5

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Other Link： http://link.springer.com/article/10.1007/s10333-019-00722-5/fulltext.html

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DOI： 10.1016/j.sandf.2018.09.006

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

DOI： 10.2208/jscejam.75.1

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

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

DOI： 10.2208/jscejge.74.213

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

DOI： 10.2208/jscejam.74.i_95

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC CIVIL ENGINEERS  

The spatial distribution of the strength inside river dikes is generally identified through sounding tests. In this research, the electric Cone Penetration Test (CPT) is employed, and spatially long- and short-interval tests are mixed to efficiently evaluate the piping risk to a dike. The Indicator Simulation (IS) method is used as the geostatistical method to simulate the N value distribution and to predict the weak area inside the dike. The synthesized approach of the CPT and the Surface Wave Method (SWM), which is one of the geophysical methods, is proposed to compensate for the shortcoming of each approach when conducting the IS. Consequently, the correlation structure inside the dike can be identified accurately, the high resolution of the spatial distribution of the N values can be visualized, and the piping risk to the dike can be discussed based on the results of the investigation.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Ltd.  

The spatial distribution of the strength inside the earth-fill is identified by the sounding tests. In this research, the Swedish weight sounding (SWS) is employed, and the spatial high-density test is performed to identify the spatial correlation structure. Furthermore, the synthesised approach of the SWS and surface wave method, which is one of the geophysical method, is proposed to compensate the shortage of each approach. Consequently, the correlation structure of an earth-fill could be identified accurately, and the high resolution of the spatial distribution could be visualised based on the survey results.

DOI： 10.1080/17499518.2016.1197406

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Other Link： http://www.tandfonline.com/doi/pdf/10.1080/17499518.2016.1197406

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Ltd.  

ABSTRACT: This paper deals with a strategy for the maintenance of geotechnical structures such as earth-fill dams. Standard penetration test (SPT) N-values are frequently used to determine the soil parameters. For this purpose, a statistical model for the N-values is firstly determined from sounding test results. In this research, however, Swedish weight sounding (SWS) tests are employed as they are simpler than SPTs. The identification of spatial correlation of the soil parameters is very difficult, since the number of sampling points is very limited to model the spatial variability. SWS is advantageous, compared with other major sounding method to identify the spatial correlation structure inside the geotechnical structures, since it makes spatially short-interval exams possible due to its simplicity and compactness. Based on the statistical model for the N-values, the shear strength parameters are derived through the empirical relationships. Then, a reliability analysis of the embankments is conducted considering the variability of the internal friction angle and the seismic hazard. Consequently, the probability of damage to the earth-fill over the next 50 years is calculated, and the effect of improving the earth-fill is evaluated based on this probability.

DOI： 10.1080/17499518.2015.1124123

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

DOI： 10.2208/jscejam.72.i_97

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Language：Japanese   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

Floods due to dam breaches have the greatest influential effect on hydraulic structures for irrigation and drainage, and estimating the costs of damage to these structures is important for risk assessment and management in agricultural land improvement projects. Existing methods for estimating damage costs require many types of asset data and usually a long time because of complications, and is not applicable for the practice in estimation of the damage costs. To overcome the problems, the authors have proposed a surrogate model called response surface (RS). This study aimed to verify the accuracy of the proposed RS by applying the surrogate model to risk evaluation of dam breaches due to rainstorms. We compared the damage costs of four earth dams calculated by using RS and existing methods, and found that the variances between the results of RS and existing methods was smaller than the unbiased variance of the RS based on 21 results of flow analysis. Therefore, the proposed method can easily estimate the risks of dam breaches due to rainstorms.

DOI： 10.11408/jsidre.84.I_47

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Other Link： https://jlc.jst.go.jp/DN/JLC/20020753571?from=CiNii

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

DOI： 10.2208/jscejam.72.i_35

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

Recently, the evaluation of the failure potential of earth-filled dams has become important because of the increasing occurrence of storm rainfall. Although most instances of earth-filled dam failure are caused by overflow, in-depth knowledge of the mechanism of the erosion and failure process of embankments due to overflow is still lacking. This paper presents a numerical method for simulating an embankment erosion and failure process by the moving particle semi-implicit (MPS) method. To reasonably simulate the erosion and failure process of an embankment due to overflow, a simple erosion model whose parameters can be determined through erosion tests on embankment materials was newly incorporated into the original MPS method. An embankment erosion and failure process observed in a model test was simulated by the proposed MPS method to confirm its practicability. Although the simulation accuracy for the erosion rate is slightly low at the beginning of the erosion, the average simulated values of the erosion rate are almost the same as the experimental values. The proposed MPS method can be a useful tool in embankment design practices to simulate embankment erosion due to overflow and to discuss remedial measures against overflow.

DOI： 10.11408/jsidre.84.I_31

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

This study has investigated sensitivity of input parameters in stability analysis of earthen embankments to its factor of safety (F-s) using an experimental design approach. Computer experiments based on orthogonal designs were carried out to achieve efficient experiments, and a linear regression model was applied to analyze the results of the experiment. The Standardized Regression Coefficients (SRCs) obtained from the regression analysis was employed as indexes of the sensitivity of the input parameters to the F-s. The results of the sensitivity analysis showed that the parameters about the geometry of embankments such as height and slope gradient are more sensitive to F-s, although the parameters about hydraulic characteristics of embankment materials are less sensitive to the F-s. In addition, interaction effects between input parameters were also analyzed, and its sensitivity to F-s was discussed.

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Language：Japanese   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

Earth-dam breaches arise from earthquakes and severe rainstorms and sometimes cause downstream floods. Floods have the greatest influential effect on hydraulic structures for irrigation and drainage, and estimating the costs of damage to these structures is important for risk assessment and management in agricultural land improvement projects. Although some methods for estimating damage costs have been proposed, most of these methods require many types of asset data and usually a long time because of complications. This paper proposes a simplified method for estimating damage costs in flood zones due to breach of earth-dams. The proposed method is based on asset data that are freely available, economical and easier to apply to practices in land improvement projects. Flood analyses of three actual earth-fill dams were performed, and the costs of damage in their flood zones estimated based on the results of the flood analyses using the proposed method. The proposed method estimated damage costs with ease, and accuracy was almost the same as other existing methods. Therefore, the proposed method can be a useful tool in agricultural land improvement projects.

DOI： 10.11408/jsidre.83.39

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10422689

Language：Japanese   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

Most of small earth dams in Japan were constructed at least 100 years ago and need to be improved because Japan is constantly at risk of severe earthquakes and heavy rainstorms. When improvements of earth dams are planned, small earth dams that have a higher risk of dam breaches should be given priority for improvement. Although a risk is defined as the product of occurrence probability and damage costs, estimating the damage costs using existing methods is very difficult and complicated. Therefore, simplified methods are necessary to select earth dams that must be preferentially improved. In order to overcome the difficulties in estimating damage costs, this study proposed a simplified estimation method for damage costs of floods due to earth dam breaches using a response surface method (RSM). RSM is a methodology that produces regression equations, called response surface, that quantitatively express the relationships between responses (output) and factors (input) by regression analyses based on experimental designs. Although many factors need to be considered to estimate damage costs of floods due to dam breaches, this study focused on four factors that largely affect the damage costs as based on results from a sensitivity analysis. Then a response surface that can estimate damage costs of floods was created by using the four parameters and its applicability was examined. As a result, the determination coefficient of the response surface R² was 0.84 and the proposed response surface can be easily applied to estimate damage costs of floods due to dam breaches.

DOI： 10.11408/jsidre.83.I_147

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

This research deals with a strategy for the maintenance of geotechnical structures such as earth-fill dams. Standard PenetrationTest (SPT) N-values are frequently used to determine the soil parameters. Firstly, a statistical model for the N-values is determined from sounding test results. In this research, however, Swedish Weight Sounding (SWS) tests are employed as they are simpler than SPT. Secondly, an indicator simulation is conducted to interpolate the spatial distribution of the N-values, and the results are utilized to find degraded areas inside the embankments and to maintain the embankments. Based on the statistical model for the N-values, the shear strength parameters are derived through the empirical relationships. Then, a reliability analysis of the embankments is conducted considering the variability of the internal friction angle and the seismic hazard.

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

This study presents an eco-friendly design method for infrastructures based on contingent valuation method (CVM). First, a questionnaire survey based on the CVM was conducted to estimate monetary values of stream habitat which can be damaged by river improvement works such as flood prevention works. Second, a design method which can quantitatively evaluate impacts on stream habitat due to flood prevention works was proposed by combining computation of non-uniform flow with a method of stream habitat estimation called physical habitat simulation model (PHABSIM). Finally, monetary value of environmental loss due to flood prevention works was estimated by using results of CVM, and the effectiveness of the eco-friendly design method was discussed through a numerical example.

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

Strong nonlinear behavior such as slope failure involves large uncertainties. Even if we conduct model tests on slope failure under the same test conditions, we cannot reproduce the same results although the linear behavior can be reproduced with relative ease. This kind of uncertainties is well known as "aleatory uncertainty" and they should be distinguished clearly from the epistemic uncertainty in reliability-based design. However, characteristics of aleatory uncertainty have not been studied very well so far. This study quantitatively investigates the aleatory uncertainties involved in failure behavior of slopes thorough centrifuge model tests. The centrifuge model tests were conducted under the same test conditions twenty times to quantitatively investigate the variability of slip lines.

DOI： 10.3233/978-1-61499-580-7-353

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

The spatial distribution of the strength inside an earth-fill dam is identified by sounding tests. In this research, the Swedish Weight Sounding (SWS) test is employed, and the spatially high-density test is possible to identify the spatial correlation structure by the SWS. The correlation structure of an earth-fill could be identified accurately based on the sounding results, and the high resolution of the spatial distribution could be visualized by using the indicator simulation. Consequently, it has been verified the practical use of the spatial distribution of the probability that the N-value is lower than the threshold value, may be used for the maintenance of an earth-fill dam.

DOI： 10.3233/978-1-61499-580-7-334

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

This research deals with a strategy for the maintenance of geotechnical structures such as earth fill dams. Standard penetration test (SPT) N-values are frequently used to determine the soil parameters. Firstly, based on the statistical model for the N-values, the shear strength parameters are derived through the empirical relationships. Secondly, a reliability analysis of the embankments is conducted considering the variability of the internal friction angle and the seismic hazard. Thirdly, the probability of overflow of earth fills during heavy rains is evaluated. The rainfall intensity is dealt with as a probabilistic parameter, and the various rainfall patterns are tested by the Monte Carlo method.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  

This study has investigated sensitivities of input parameters in stability analysis of embankments to safety factor Fs based on experimental deign. In addition to the geotechnical parameters, parameters about geometry such as height, width, and slope gradient of embankments were also considered in the analysis. This study applied regression analysis based on orthogonal design to the sensitivity analysis. The geotechnical parameters required for the stability analysis were used in the sensitivity analysis, and the sensitivity of these parameters to Fs was investigated. The results of the sensitivity analysis showed that the parameters about geometry of embankments such as height and slope gradient are more sensitive to Fs, although the parameters about hydraulic characteristics of embankment material are less sensitive to the Fs.

DOI： 10.3208/jgssp.JPN-034

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Language：Japanese   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

This study was performed to clarify the soil characteristics of 40 damaged and 45 undamaged small embankment dams for irrigation (tame-ike in Japanese) in Northern Awaji Island, due to the 1995 Hyogo-ken Nanbu earthquake. With reference to the results of multivariate statistical analyses, pairs of damaged and undamaged dams were selected so that the conditions such as distance to epicenter, embankment volume (=dam height)×(crest length)(m²) and distance to Nojima Fault might become almost the same. Soil properties of damaged dams such as D₅₀ (0.514mm), moisture content (9.4%) and the cone penetration resistance (223kPa) are smaller than those of undamaged dams by 45 point, 30 point and more 30 point, respectively. But both specific gravities are the same. The damage rate (DR) of sandy soil is almost twice of that of gravelly soil. DR decreases as the moisture content or the cone penetration resistance increases.

DOI： 10.11408/jsidre.82.1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Civil Engineers (ASCE)  

This study presents a reliability-based design method for geotechnical structures based on the observational method, which can be used as a methodology for the performance verification of geotechnical structures. In the proposed method, the soil-water coupled finite element analysis is utilized as a performance-verification method, and stochastic uncertainties inherent in the geotechnical parameters are evaluated by a Monte Carlo simulation. The proposed method can select the optimum design/construction method from several design alternatives, from the viewpoint of Life Cycle Cost, and the predictions at the initial design stage are sequentially updated by the particle filter. The proposed method is applied to a numerical example of the construction problem of embankment specified quantitative performance criteria, such as allowable settlements and the probability of their exceedance, and the feasibility of the method is examined in this example.

DOI： 10.1061/9780784413609.246

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Civil Engineers (ASCE)  

This research deals with a strategy for the maintenance of geotechnical structures such as earth-fill dams. Standard penetration test (SPT) N-values are frequently used to determine the soil parameters. Firstly, a statistical model for the N-values is determined from sounding test results. In this research, however, Swedish weight sounding (SWS) tests are employed as they are simpler than SPT. Secondly, an indicator simulation is conducted to interpolate the spatial distribution of the N-values, and the results are utilized to find degraded areas inside the embankments and to maintain the embankments. Based on the statistical model for the N-values, the shear strength parameters are derived through the empirical relationships. Then, a reliability analysis of the embankments is conducted considering the variability of the internal friction angle and the seismic hazard.

DOI： 10.1061/9780784413609.236

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

A computational method, incorporating the finite element model (FEM) into data assimilation using the particle filter, is presented for identifying elasto-plastic material properties based on sequential measurements under the known changing traction boundary conditions to overcome some difficulties in identifying the parameters for elasto-plastic problems from which the existing inverse analysis strategies have suffered. A soil-water coupled problem, which uses the elasto-plastic constitutive model, is dealt with as the geotechnical application. Measured data on the settlement and the pore pressure are obtained from a synthetic FEM computation as the forward problem under the known parameters to be identified for both the element tests and the ground behavior during the embankment construction sequence. Parameter identification for elasto-plastic problems, such as soil behavior, should be made by considering the measurements of deformation and/or pore pressure step by step from the initial stage of construction and throughout the deformation history under the changing traction boundary conditions because of the embankment or the excavation because the ground behavior is highly dependent on the loading history. Thus, it appears that sequential data assimilation techniques, such as the particle filter, are the preferable tools that can provide estimates of the state variables, that is, deformation, pore pressure, and unknown parameters, for the constitutive model in geotechnical practice. The present paper discusses the priority of the particle filter in its application to initial/boundary value problems for elasto-plastic materials and demonstrates a couple of numerical examples. © 2012 John Wiley &amp
Sons, Ltd.

DOI： 10.1002/nag.2125

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DOI： 10.2208/jscejam.69.I_29

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

Data assimilation is a versatile methodology, developed in the earth sciences, such as geophysics, meteorology, and oceanography, for estimating the state of a dynamic system of interest by merging sparse observation data into a numerical model for the system. In particular, the data assimilation method referred to as the particle filter (PF) can be applied to nonlinear and non-Gaussian problems, and it holds the greatest potential for application to geotechnical problems. The objective of this study is to demonstrate the theoretical and the practical effectiveness of the PF for a geotechnical problem, i.e., applying the methodology to numerical experiments and actual model tests to identify the parameters of elasto-plastic geomaterials. Since the mechanical behavior of soils depends on both the current stress and the recent stress history of the soil, the sampling method called SIS, which can take into account the stress history experienced by soils, identifies the parameters of elasto-plastic geomaterials remarkably well. The results of the numerical tests have shown that the parameters identified by the PF based on the SIS have converged into their true values, and the approach presented in this study has shown great promise as an accurate parameter identification method for elasto-plastic geomaterials. Moreover, the simulation results using the identified parameters were close to the actual measurement data, and long-term predictions with high accuracy could be achieved, even though short-term measurement data were used. The PF approach produces more information about the parameters of interest than simple estimated values obtained from optimization methods. Namely, the identification comes in the form of probability density functions. (c) 2012 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sandf.2012.02.006

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DOI： 10.2208/jscejam.68.I_317

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DOI： 10.2208/jscejam.68.I_103

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DOI： 10.2208/jscejam.68.I_89

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Language：Japanese   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

Thus far, the focus of studies on seepage failure, known as sand boiling or the piping phenomenon, has been to determine the critical hydraulic gradient or the critical seepage flow velocity. However, the transport of soil after seepage failure also needs to be well investigated in order to estimate the damage to soil structures or the ground. This study has experimentally investigated the behavior of sand and seepage water during sand boiling induced by upward seepage flow. In the experiments, the discharge of sand particles and seepage water were measured separately during sand boiling, and their migration velocities were obtained with the measurement of the hydraulic gradient. The results have revealed that the equilibrium of the forces exerted on the sand particles, i.e., gravity, buoyancy and fluid-particle interaction, can be used to estimate the velocity of the sand particles subjected to upward seepage flow regardless of the sand type.

DOI： 10.11408/jsidre.80.409

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

The limit state design method has been introduced into the design criteria for geotechnical structures.The current paper attempts to apply the reliability-based design method, at Level II, to the bearing capacity of the foundations of open channels from the viewpoint of the limit state design.To examine the applicability of the proposed procedure for practical structures, the reliability index is computed for evaluating the stability of the foundations of existing open channels designed by the conventional method.The conventional design procedure makes excessively safe side design.We applied the first order reliability methods (FORM) to the existing open channels designed by the conventional design procedure, and consequently, large values of reliability index, 3 and 5 were obtained for clayey and sandy soils, respectively.Finally, the partial factors for the soil parameters have been determined, corresponding to the target reliability indices β&lt
inf&gt
t&lt
/inf&gt
=1, 3 and 4. © 2011 Taylor &amp
Francis.

DOI： 10.1080/17499518.2011.558417

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

In this research, the spatial distribution of the strength parameters of decrepit earth-fill dams and an identification method are discussed. Swedish Weight Sounding (SWS) tests are conducted to determine the statistical model to represent the spatial distribution of the N-values. The spatial distribution model can be determined with high resolution from the sounding test results, since point estimations for the N-values are available. The Surface Wave Method (SWM), a geophysical exploration method, is also employed here. It can present the averaged image of the N-value distribution. In this research, these two sets of results are synthesized with the indicator simulation method.

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DOI： 10.11408/jsidre.79.195

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DOI： 10.3208/jgs.6.415

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Language：Japanese   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

The main purpose of this research is to develop a calculation method to assess the probability of liquefaction and a reliability-based design method to mitigate the liquefaction in sandy grounds. The probability of liquefaction is evaluated with the proposed model by considering the spatial variability of soil parameters. The liquefaction resistance is calculated from the SPT N-value, and the fines content, F_c, through the empirical relationship. The statistical models for these two soil parameters are determined with the maximum likelihood method. In this study, the probability of liquefaction is evaluated multi-dimensionally using the conditional simulation method. Finally, the reliability-based design method is discussed in order to determine the optimum design for ground improvement using sand compaction piles (SCP) based on the calculated probability of liquefaction.

DOI： 10.11408/jsidre.79.329

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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)  

Piping, as the result of internal erosion of embankments, is a primary cause of embankment breaks. Moreover, hollows or cavities of soil structures have been occasionally reported due to erosion within soils. The inner states of embankments are needed to be estimated to take appropriate measures for the prevention of the accidents of soil structures. In this study, simultaneous modeling of the internal erosion and the deformation of soils is carried out. As for the internal erosion, the equations governing the erosion and the transport of fine particles within a soil mass are derived with the concept of erosion rates of soils. Additionally, the constitutive model which can describe the deformation of soils caused by the internal erosion is proposed in this paper. © 2010 ASCE.

DOI： 10.1061/41105(378)11

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

About 50% of dam failures in the world have been triggered by piping, which is a primary cause of embankment breaks. The phenomenon of piping results from the erosion of soil particles and their transport within the soil mass. In this paper, a numerical method to analyze erosion within soils and transport of eroded soil particles is proposed. For the analysis, the saturated-unsaturated seepage flow of the pore liquid, the detachment of soil particles from the soil fabric and the migration of the eroded particles are needed to be considered. As the results of this numerical simulation, the temporal alteration and the spatial distribution of the porosity, the particle size distribution and the concentration of the detached soil particle in the pore liquid, as well as the pore liquid pressure, can be obtained. The results of this analysis have revealed that the method qualitatively predicts the development of piping inside soil structures, such as embankments, as the solutions of the initial and boundary value problem.

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In this study, a reliability-based design for the improvement of earth-fill dams is presented and the effect of improvement of the embankment for safety against earthquakes is evaluated.An inclined core is considered as the means of improvement for the earth-fill embankment.First, the spatial distribution of the strength of the earthfill materials is discussed, following which the damage level of earth-fill dams is evaluated, using the elastoviscoplastic finite element method (EVP-FEM).By averaging the resulting damage level with the Monte Carlo method, the expected failure costs are calculated.Finally, the effect of this improvement is evaluated by comparing the expected total costs for the original and the restored states of the embankment. © 2010 Taylor &amp
Francis.

DOI： 10.1080/17499511003676655

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

About 50z of the world's dam failures are triggered by piping, which is a primary cause of embankment breaks. The phenomenon of piping results from the erosion of soil particles and their transport within a soil mass. In this paper, a numerical method is proposed to analyze the erosion within soils and the transport of eroded soil particles by adopting the concept of the erosion rate of soils. In such an analysis, the saturated-unsaturated seepage flow of the pore liquid, the detachment of the soil particles from the soil fabric, and the migration of the eroded particles are taken into consideration, and the equations related to the conservation of the pore liquid and the eroded soil particles are numerically solved. This numerical simulation allows for the procurement of the temporal alteration and the spatial distribution of the porosity, the particle size distribution, and the concentration of the detached soil particles in the pore liquid, as well as the distribution of pore liquid pressure. The results have revealed that the method can reproduce the experimental data from previous studies on the internal erosion of soils and that it qualitatively predicts, from the numerical experiments, the typical development of piping within soils, such as soil blocks and embankments, as the solutions to the initial and the boundary value problems of the governing equations.

DOI： 10.3208/sandf.50.471

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：農業農村工学会  

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

Internal Erosion caused within soil structures, such as earth dams and irrigation ponds, lead to the piping failures of the structures. Most of studies on the internal erosion of soils have been experimental and the computational method to analyze the phenomenon is currently limited. The purpose of this study is to propose the numerical method for solving the internal erosion and the transport of eroded soil particles and to verify the applicability of the method. In this paper, three equations concerning the seepage flow, the change of porosity due to internal erosion and the transport of the eroded soil particles are introduced and computationally solved. The equation of the seepage flow is solved with Finite Element Method, and Finite Volume Method is applied to the equation of the transport of the soil particles. It is shown that the numerical approach can reproduce the experimental date of the previous study.

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DOI： 10.11408/jsidre.77.71

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DOI： 10.11408/jsidre.77.175

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DOI： 10.11408/jsidre.77.191

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

A reliability-based design for the improvement of earth-fill dams is discussed in this study, and the effect of improving of the embankment is evaluated in relation to the safety of the embankment against earthquakes. An inclined core is considered here as the means of improvement for the earth-fill embankment. To evaluate the stability of earth-fill dams, the elasto-viscoplastic finite element method (EVP-FEM) is used. Then, combining the Monte Carlo method with the EVP-FEM, the expected damage costs are calculated. Finally, the effect of this improvement is evaluated by comparing the total costs before and after the restoration of the embankment.

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DOI： 10.11408/jsidre.77.501

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The main purpose of this research is to develop a calculation method to assess the probability of liquefaction and a reliability-based design method to mitigate the liquefaction in sandy grounds. The probability of liquefaction is evaluated with the proposed model by considering the spatial variability of the soil parameters and the statistical characteristics related to the occurrence of earthquakes. The liquefaction resistance is calculated from the SPT N-value, the median grain size, D50, and the fines content, Fc, through the empirical relationship [Iwasaki T, Arakawa A, Tokida, K. Simplified procedure for assessing soil liquefaction during earthquakes. Proc Soil Dyn Earthquake Eng Conf 1982
925-39]. The statistical models for these three soil parameters are determined with the maximum likelihood method. The occurrences of earthquakes is modeled based on the maximum annual acceleration found in historical earthquake data records. In this study, the probability of liquefaction is evaluated multi-dimensionally using the cokriging method. Finally, the reliability-based design method is discussed in order to determine the optimum design for ground improvement using sand compaction piles (SCP) based on the calculated probability of liquefaction. © 2006.

DOI： 10.1016/j.strusafe.2006.11.002

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DOI： 10.11408/jsidre2007.2007.679

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DOI： 10.11408/jsidre1965.2007.201

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DOI： 10.11408/jsidre2007.2007.601

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DOI： 10.11408/jsidre1965.2006.97

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Language：Japanese   Publisher：日本コンクリート工学協会  

著しい鉄筋腐食やはつりだし補修過程に伴う鉄筋とコンクリート間の部分的な付着損失を想定し,これに着目した部材のせん断耐力実験を行った。着目した要因は,引張り鉄筋の付着損失本数比および付着損失の範囲の2種類である。実験の結果,これらの部材の耐力は付着の健全なRC部材のせん断耐力値といわゆるアンボンドRC部材の耐力値の概ね間にあった。その特徴について議論した。

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10640283

Language：Japanese   Publisher：The Japanese Society of Irrigation, Drainage and Rural Engineering  

DOI： 10.11408/jjsidre1965.73.7_626

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This study was performed to clarify which factors affected damage to tame-ike (small embankment dams for irrigation in Japanese) of northern Awaji Island in western Japan due to Hyogoken-Nambu earthquake. Multivariate and ordinary statistical analyses were carried out for 1788 dams (350 damaged and 1438 undamaged dams which identified using various documents). The model for analysis was created with 11 items and 136 or 100 categories for 4 groups (Location, Geology, Structure, and History of Dam). As a result of analysis, the factors causing to damage for dam in order are (1) distance to the epicenter (9 to 15km, which almost agree to the location of seismic intensity 7 JMA), (2) nearest fault (Nojima, Mizukoshi and D2), (3) embankment volume (the larger the more), (4) angle of crest axis to epicenter (normal or vertical), (5) angle of crest axis to nearest fault (normal or vertical), especially reservoir located backward dam, (6) distance to the nearest fault (less than 750m), (7) elevation of dam site, (8) plan view of dam axis (complicate), (9) surface geology of dam site (soil foundation), (10) leakage, (11) repair. Analysis in this way might be possible to notice the distribution of intensity of seismic force and prediction for damage of embankment.

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

The phenomenon of hydraulic fracturing is considered to be one of the causes of leakage in fill-type dams. In recent years, it has been found that an estimate of the fracture toughness of a given type of soil could be used as an indicator of the soil's resistance to hydraulic fracturing. One of the problems encountered in its estimation is the assumption that fracture toughness has been theoretically defined for samples of infinite sizes. In this study, laboratory tests were conducted to determine the fracture toughness of samples (of the same size) prepared with initial cracks of various lengths. The main objective was to investigate the relationship of the initial crack length to fracture toughness. The stress distribution around the crack tip for each laboratory test sample was estimated by FEM analysis and by a theoretical equation. These analytical results corresponded reasonably well to results from laboratory tests to determine the appropriate length of the initial crack for the test specimens.

DOI： 10.1007/s10333-004-0036-5

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DOI： 10.11408/jjsidre1965.72.5_377

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DOI： 10.11512/jiban.JGS39.0.205.0

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Publisher：The Japan Landslide Society  

DOI： 10.3313/jls.41.193

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Language：English   Publishing type：Part of collection (book)   Publisher：Elsevier Ltd.  

This chapter focuses on a multidimensional consolidation inverse analysis. The effects of the measured pore water pressure and the assumption of anisotropy are investigated. An elastoplastic hypothetical ground is analyzed to check the proposed analytical method. The hypothetical observation data are obtained based on the Sekiguchi-Ohtaelasto-plastic model. The effectiveness of the observed pore water pressure is proved
vertical and lateral displacements and pore water pressure are predicted well with the observed pore water pressure. The laboratory anisotropic consolidation tests are also analyzed, because accurate measurements are necessary for the development of the method. The measured deformation and pore pressure obtained in the tests are used for the inverse analysis. According to the results of this analysis
it is shown that the measured pore water pressure and assumption of anisotropy work well, to predict the future consolidation behavior. © 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/B978-008044268-6/50039-9

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DOI： 10.11408/jsidre1965.2003.559

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Language：Japanese   Publisher：農業土木学会  

DOI： 10.11408/jsidre1965.2003.815

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DOI： 10.11512/jiban.JGS38.0.277.0

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

One-dimensional consolidation inverse analysis based on the stochastic nonlinear consolidation model (SNCM) is discussed in this study. The model is determined from the standard consolidation test results, and represents the non-linearity and spatial variability of the coefficient of volume compressibility and the coefficient of permeability simultaneously. Furthermore, the inverse analysis method is proposed on the basis of the SNCM and the finite element method mixed with the Monte Carlo simulation. Measured settlement and pore water pressure are used as observation data in the inverse analysis. The method is applied to the consolidation test results of kaolin clay, and its applicability is confirmed firstly. Then the inverse analysis of an actual soft ground is performed. Future consolidation behavior of the ground is predicted, and the spatial variability and the non-linearity of the consolidation parameters are identified. It is clarified in this study that complicated spatial variability and non-linearity of the consolidation parameters could be considered appropriately in the proposed inverse analysis method, and the method gives accurate prediction of consolidation behavior.

DOI： 10.3208/sandf.42.3_45

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Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS37.0.311.0

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DOI： 10.11512/jiban.JGS37.0.965.0

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DOI： 10.11512/jiban.JGS37.0.337.0

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DOI： 10.11408/jsidre1965.2001.423

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DOI： 10.11408/jsidre1965.2001.777

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DOI： 10.11408/jsidre1965.2000.763

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This study was performed to clarify which factors affected damage to tame-ike (small embankment dams for irrigation) in Hokudan Town as a result of the January 17,1995 Hyogoken-Nambu earthquake. Factors were assumed to be : Location (e.g., Distance to Epicenter, etc.), Structure (e.g., Angle to Nearest Fault, Embankment Volume, etc.), Soil Properties of Embankment, Geology of Dam Site and History (Era of Construction, Repaired, etc.). Multivariate statistical analyses were performed for documentary data (damaged : 181,undamaged : 328). Ordinary statistical analyses were conducted for the data investigated in situ for soil properties of the embankment. The results show that the factors causing damage to dam are : (1) Nearest Fault (Nojima, Mizukoshi and D2), (2) Distance to Nearest Fault (less than 500 m), (3) Distance to Epicenter (approximately 8 to 14 km, which almost agrees with the location of seismic intensity 7 JMA), (4) Elevation of Dam Site (higher than 100 m), (5) Embankment Volume (the greater the volume the more damage was caused), (6) Direction of Dam Axis (normal or diagonal to the epicenter or to nearest the fault), (7) Plan View of Dam Axis (3 or 4 axes), (8) Surface Geology of Dam Site (non-cohesive soil type ground), (9) Era of Construction (prior to 1891) and (10) Soil Properties of Embankment (sand, not silty sand or gravel, penetration resistance that is 10% smaller than the undamaged dams).

DOI： 10.3208/sandf.40.6_117

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

This paper discusses the change of the normal stress due to the surface tension and the matric suction of the pore water in unsaturated assemblies of spheres, and also discusses the change of the shear strength of sandy soils with the matric suction. Theoretically derived are the relationships between the change of the normal stress and the matric suction in unsaturated assemblies of regularly/randomly packed equal-sized/non equal-sized spheres. Shear tests with poorly- and well-graded sandy soils were also carried out. Experimental results show the same tendency of the relationships between the change of the normal stress and the matric suction as that from theoretical considerations.

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

This paper discusses the applications of FEM on the basis of the elasto-viscoplastic model to landslide problems. Fluidity parameter gamma which governs the time dependent behavior of landslide, is determined from the comparison of the calculated displacement of landslide with the measured in the Site. Concluding remarks are as follows: 1)The fluidity parameter identified from five typical landslide Sites is within the range of 1*10(-5)similar to 7*10(-4)(day(-1)); 2)The effect of dewatering method was proved by the proposed method; 3)Using this model, it may be possible to make predictions on the future trend of deformation.

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This paper discusses the coincident effects of rainfall and earthquake on the slope stability. A numerical program for the analysis of the slope instability due to rainfall has been already developed. The program unites a finite element program for the infiltration analysis and a Rigid-Body-Spring-Model (RBSM) program for the slope stability analysis. The numerical results for a model slope show that the reduction of the shear strength of the slope surface soil due to rain infiltration causes the reduction of the safety factor of the slope. When the slope suffers from both rainfall and earthquake, its safety factor will decrease more and it must become more unstable. The effect of seismicity is taken into account by applying the additional horizontal seismic force in RBSM as the pseudo-static limit equilibrium procedure of the slope stability analysis. The calculation results show that the slope suffering from the rain infiltration becomes more unstable when the additional seismic force acts. The greater magnitude of the seismic intensity strongly reduces the safety factor of the model slope.

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

This paper discusses the effect of hysteresis in soil-water characteristic curves of decomposed granite soils on the instability of their unsaturated slopes due to rain infiltration, using the numerical analysis. Almost all soils exhibit hysteresis in soil-water characteristic curves, and the curves are ordinarily measured in the drying process because of the simplicity of measurement. However, the numerical results indicate that the curve measured in the drying process gives incorrect estimates for the slope instability due to rain infiltration. In conclusion, the soil-water characteristic curves of soils should be measured in the wetting process when applied to the slope stability analysis considering rain infiltration.

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DOI： 10.2208/jscej.1998.603_101

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Language：Japanese   Publisher：The Japan Landslide Society  

This paper discusses the applications of Finite Element Method on the basis of the elasto-viscoplastic model to landslide problems. Fluidity parameter "γ" is determined from the examinations of the analytical value in comparison with the observed data. Some results from this paper can be summed up as follows.<br>1) It can be inferred that the fluidity parameter "γ" of landslide area-A is 1×10^-5 (day^-1).<br>2) The effect of dewatering method in landslide area-C were proved by the above numerical method.<br>3) Using the above numerical model, it may be possible to make predictions on the future trend of deformation and time.

DOI： 10.3313/jls1964.31.4_1

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

The retention behavior of five 20-oxosteroids (pregnenolone, 3 beta - hydroxy- 5 alpha -pregnan-20-one, 3 beta -hydroxy- 5 beta - pregnan-20-one, 3 alpha -hydroxy- 5 alpha -pregnan-20-one, and 3 alpha - hydroxy-5 beta -pregnan-20-one) and their sulfates derivatized with 4-(N,N-dimethylaminosulfonyl)- 7-hydrazino-2,1,3-benzoxadiazole were examined using reversed-phase high-performance liquid chromatography with fluorescence detection. Inclusion chromatography using cyclodextrin as a mobile phase additive was also used for this purpose and found effective in separating the isomeric derivatized 20-oxosteroids and their sulfates.

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DOI： 10.11408/jjsidre1965.63.5_513

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Language：Japanese   Publisher：農業土木学会  

DOI： 10.11408/jsidre1965.1993.35

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DOI： 10.11408/jsidre1965.1992.45

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DOI： 10.11408/jsidre1965.1992.162_1

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Language：Japanese   Publisher：農業土木学会  

DOI： 10.11408/jsidre1965.1991.154_1

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DOI： 10.11408/jsidre1965.1991.154_9

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DOI： 10.11408/jsidre1965.1990.150_75

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Language：Japanese   Publisher：農業土木学会  

DOI： 10.11408/jsidre1965.1988.136_61

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DOI： 10.3850/978-981-18-5184-1_MS-13-067-cd

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DOI： 10.3850/978-981-18-5184-1_MS-13-050-cd

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This paper presents the numerical evaluation of the strength and stability of a ground improved via vacuum consolidation combined with a preloading embankment. To assess the stability of soft grounds, the undrained shear strength is definitely required. A numerical analysis is desirable for predicting the strength of the improved ground, and the elasto-plastic FEM for soil-water coupled problems, incorporating the SYS Cam-clay model, is adopted in two dimensions. The compression index of clay and the coefficient of permeability of organic soil, which are the primary factors for evaluating the ground behavior, are identified through an inverse analysis from the measured settlements. As the inverse approach, the particle filter is employed to account for the strong nonlinearity of the ground behavior. A stability analysis of the slip surface method is performed based on the evaluated undrained shear strength to assess the effect of the ground improvement on the construction of earth structures. The results show the validity of the ground improvement using vacuum consolidation with a preloading embankment.

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Language：English   Publisher：Asian Regional Conference on Soil Mechanics and Geotechnical Engineering  

To mitigate the disasters of decrepit earth-fill dams, improvement work is conducted. Since there is a recent demand for low-cost improvements, the development of a design method for optimum improvement work at a low cost is the final objective of this research. The reliability-based design approach is discussed as such a design method. Heavy rains are the most serious events for aged fill-dams, and sometimes overflows leading to breaching occur. From the estimated probability of overflow, the probability of submergence in the downstream is estimated for the reliability-based design. The remarkable point in this paper is that the probability of occurrences of heavy rains and the uncertainty of the soil properties are simultaneously considered for the design. Considering the disaster loss, the risk of submergence could be assessed.

DOI： 10.3208/jgssp.JPN-044

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DOI： 10.11345/japannctam.62.0.203.0

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DOI： 10.11345/japannctam.62.0.210.0

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DOI： 10.11345/japannctam.61.0.54.0

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DOI： 10.11345/japannctam.61.0.55.0

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DOI： 10.11345/japannctam.58.0.84.0

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Language：English   Publisher：Graduate School of Environmental and Life Science, Okayama University  

The disposal of large amounts of sludge, deposited in many farm/irrigation ponds in Japan, has recently become an important task to be resolved. To dredge sludge helps to maintain the capacity of the ponds and the quality of the water in the pond. In other words, it is vital that the deposited sludge should be effectively dredged. Since the water content of dredged sludge is very high, it must be reduced to enable the transport and the reuse of the sludge. The authors of the present paper have developed a procedure to dehydrate in-situ dredged sludge from farm ponds using a compact filter press machine. The purpose of this study is to investigate appropriate conditions for the efficient dehydration of dredged sludge with a compact filter press machine. Since the dehydration mechanism inside the filter press machine is based on the hydraulic consolidation, hydraulic consolidation tests are conducted to simulate the filter press consolidation in order to clarify the relationship between the conditions of the filter press dehydration and the water content of the consolidated sludge. Results of the tests show that the most important factor in controlling the efficiency of the actual filter press dehydration process is the thickness of the filtration chamber of the filter press machine. Sludge is expected to be more effectively dehydrated when a filtration chamber with a smaller thickness is adopted.

DOI： 10.3107/jesss.2.21

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Other Link： http://eprints.lib.okayama-u.ac.jp/11438

A calculation method for the probability of liquefaction is shown in this paper. The spatial variability of soil parameters for the liquefaction resistance and the statistical characteristics of earthquake occurrences are considered in the analysis. Furthermore, a reliability-based design of sand compaction piles for ground improvement is discussed.

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The dispersion behavior of a substance in the ground water flow depends on the random field characteristics of the permeability. In this study, we clarify how the Gaussian and the non-Gaussian random fields of permeability affect the dispersion behavior. The non-Gaussian random field simulation method is newly proposed in this study. The finite difference method (FDM), combined with the Monte Carlo method (MCM), is used in the analysis to solve the advection and dispersion equations. Firstly, a tracer mixed with water is analyzed as a single-phase problem. Then, the migration of the DNAPL pool in the ground water is treated as a two-phase problem.

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Language：English   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

In many cases, the sludge dredged from the bottom of lakes is dewatered, made into sludge cakes, and then broken into pieces. In this study, the mechanical properties of pieces of sludge cakes to be used as banking material are considered. In particular, their consolidation behavior is discussed here. The following specific problem exists in the consolidation of sludge cake pieces. Since the large voids between the pieces shrink and then the inner void in each piece shrinks due to compression, the conventional consolidation theory is not supposed to be applicable. To understand the consolidation characteristics, large-scale consolidation tests were performed. The applicability of the super-subloading Cam clay model, for the compression behavior, and the least squares method, to identify the coefficient of consolidation, were investigated in this study based on the test results.

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Language：English   Publisher：A A BALKEMA PUBLISHERS  

A two-dimensional consolidation inverse analysis model is discussed in this paper. The effects of the measured pore water pressure and the assumption of anisotropy are investigated. Firstly, an elasto-plastic hypothetical ground is analyzed to check the proposed analytical method. Secondly, the laboratory anisotropic consolidation tests are analyzed, since accurate measurements are necessary for the development of the method. The measured deformation and pore pressure obtained in the tests are used for the inverse analysis. Finally, the method is applied to an actual soft ground problem to verify the applicability of the method to actual problems.

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J-GLOBAL

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Language：Japanese  

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Language：Japanese   Publisher：農業土木学会  

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Language：Japanese   Publisher：岡山大学環境理工学部  

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Language：English   Publisher：A A BALKEMA PUBLISHERS  

The laboratory consolidation tests were performed to investigate the compression characteristics of the dewatered sludge as a construction material. The sludge is dredged from the bottom of a lake. After the dehydration, it is broken into fragments. The fragments shows different compression behavior from that of ordinary undisturbed clay. The remarkable point in our research is: The e similar to log p curves of fragments have two kinds of compression index in the normally consolidation region. The first compression index has linear relation with initial water content, while the second one is almost constant.

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Language：Japanese  

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Language：English   Publisher：A A BALKEMA PUBLISHERS  

The consolidation inverse analysis is carried out in this study by using not only settlement measurement but also pore pressure measurement. A stochastic nonlinear consolidation model (SNCM) is applied to the one-dimensional analysis. The SNCM represents the non-linearity and spatial variability of the coefficient of volume compressibility and the coefficient of permeability at the same time. The method is applied to a model test result, and the effect of pore pressure measurement on the prediction of consolidation behavior is verified. Furthermore, a two-dimensional consolidation inverse analysis is performed by using triaxial anisotropic consolidation test results.

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Language：English   Publisher：A A BALKEMA PUBLISHERS  

The calculation method of the probability of liquefaction is clarified in this paper. The spatial variability of soil parameters for the dynamic shear strength and the statistical characteristics of the earthquake occurrence are considered in the analysis. Secondly, the reliability design of the sand compaction piles for the ground improvement is discussed.

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DOI： 10.11408/jjsidre1965.63.5_513

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Language：English   Publisher：A A BALKEMA  

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Language：English   Publisher：A A BALKEMA  

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Language：English   Publisher：A A BALKEMA  

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Other Link： http://ousar.lib.okayama-u.ac.jp/938

Language：English   Publisher：A A BALKEMA  

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DOI： 10.11408/jsidre1965.1993.35

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DOI： 10.11408/jsidre1965.1992.45

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DOI： 10.11408/jsidre1965.1990.150_75

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DOI： 10.11408/jsidre1965.1988.136_61

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