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

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

<p> In this study, based on the in-situ measurement results on the fill slope where macro-pores were developed, the influence of preferential flow due to heterogeneous pore distribution on rainfall infiltration and drainage characteristics was discussed. As a result, the following possibilities are shown.</p><p> First, in the slope where macro-pores have been developed, when pore-water pressure and volumetric water content increase rapidly due to rainfall, a preferential flow occurs as the permeability of soil containing macro-pores increases by several orders. And since the preferential flow forms a pseudo-saturated region in a short time, the pore-water pressure increased almost coincident with the rainfall peak due to the subsequent high-intensity rainfall. Accordingly, it is considered that since this pore-water pressure transmission occurs in a short time, the occurrence time of the shallow slope failure may be much faster than the result estimated by the conventional seepage flow analysis same as the past slope failure incidents.</p>

DOI： 10.2208/jscejge.76.2_122

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

© 2018 Elsevier Ltd Stress discontinuity plays an important role in both planar and conical heaps of granular materials. The aim of this study is to reveal the numerical solutions for the stress distribution in fully plastic conical sand heaps that obey the Mohr-Coulomb yield criterion under both passive and active conditions. Levy's circumferential stress assumption was added to the system of equilibrium equations to formulate a pair of ordinary differential equations that were integrated by the 5th order adaptive Runge–Kutta method. Moreover, the numerical perturbations of the initial conditions were put in place to overcome the singularities of the integrations. Trial-and-error iterations were implemented under the passive condition to indicate the location of the stress discontinuity in conjunction with the application of the stress jump condition. Meanwhile, the shooting technique was employed to facilitate the integration under the active condition. The results of the passive conical sand heaps exhibit a local minimum pressure at the center, thus initiating arch action. In addition, the trajectories of principal stresses visually elucidate the mechanisms of load transfer in the conical sand heaps. The linear-fitting relationship between the location of the stress discontinuity and the repose angle in a conical sand heap under the passive condition was also elaborated.

DOI： 10.1016/j.ijsolstr.2018.04.001

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS & MATERIALS  

DOI： 10.2320/matertrans.z-m2019809

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

<p>Under the situation that the frequency of rainfall-induced shallow landslide and debris flow, which may be attributed to climate change is increasing, the electrical prospecting has been applying for landslide risk assessment by focusing on fine particle distribution and soil water characteristic change of subsoil extensively. In this study, both the distribution of electric resistivity and the volumetric moisture content measured at the fill slope comprising weathered granite residual soil in Chiang Mai, Thailand were presented. Consequently, the comparison of electric resistivity and volumetric moisture content measured at the slope has revealed the characteristics on the significant change of electric resistivity during rainy season and dry season, which is limited to shallow area. Furthermore, based on findings obtained through this study, the applicability of electrical prospecting for landslide risk assessment for slopes at different geotechnical condition and different weather condition has been discussed.</p>

DOI： 10.3208/jgs.14.241

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

<p>Slope failures occasionally happened due to unstable masses during excavation of the toe of undercut slopes or weakening basal support after backfilling process can cause delay in open-pit mining. As one of countermeasures against slope failure in mining stage, a temporary slope reinforcement with stabilizing piles which is delaying a slope failure are undertaken at Mae Moh lignite mine in Thailand. In order to improve the efficiency and safety in mining, alignment of stabilized piles for mitigating undercut slope failure remains a challenging to study. In this study, reinforcement effects and failure mechanisms were investigated using a series of physical model of undercut slope with different alignments of shear pins by image analysis. It was found that the basic characteristics of shear pins have effects on a critical width of undercut slope and triggering mechanisms of slope instability.</p>

DOI： 10.3208/jgs.14.31

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

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

© 2018 The Society of Materials Science, Japan. In this study, fine particle distribution in artificial slopes comprising weathered granite, which may affect rainfall-triggered landslide, was investigated comprehensively, based on electrical resistivity, soil composition and unsaturated soil properties. The results showed that while degree of saturation plays a key factor on electrical resistivity in unsaturated soil, it has close correlation to pore-size distribution. Therefore, it can be considered that electrical prospecting is an effective method to investigate distribution of both coarse particle and fine particle. In addition, it was also pointed out that there is possibility that fine particle fraction involved in soil poorly compacted in artificial slopes may be eroded due to rainfall infiltration.

DOI： 10.2472/jsms.67.346

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本材料学会  

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Publishing type：Research paper (international conference proceedings)  

© 2018 ISRM & SRMEG (Singapore). Recent studies of undercut slope using physical models have indicated that the failure of undercut slope during the excavation of the base part involves the stress transition from active condition to passive condition. This study aims to further investigate the factor by which the stress condition and its transition in undercut slope are influenced. The stability of undercut slopes under the groundwater seepage was studied by geotechnical centrifuge modelling. Edosaki sand with 10% water content was selected as the modeling material. The humid sand was compacted layer by layer using rigid wooden frames on the inclined plane covered by a low-friction Teflon sheet. A set of pressure gauges and pore pressure transducers were embedded at the designed locations in order to observe the changes of earth pressure and pore water pressure during centrifugal acceleration and seepage flow. In addition, slope movements were monitored by laser sensors installed along the top of slope model. The seepage water was supplied by setting up a water tank on the side of the soil chamber with a remote controller of inlet valve. Influences of seepage pressure and groundwater flow to the critical undercut width of slope models were examined. The experimental results confirmed that the higher the seepage, the lower the undercut width. Nevertheless, it was found that destabilization due to seepage water causes the subsequent arching failure instead of the collapse of a whole slope.

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

© 2018 The Society of Materials Science, Japan. In this study, fine particle distribution in artificial slopes comprising weathered granite, which may affect rainfall-triggered landslide, was investigated comprehensively, based on electrical resistivity, soil composition and unsaturated soil properties. The results showed that while degree of saturation plays a key factor on electrical resistivity in unsaturated soil, it has close correlation to pore-size distribution. Therefore, it can be considered that electrical prospecting is an effective method to investigate distribution of both coarse particle and fine particle. In addition, it was also pointed out that there is possibility that fine particle fraction involved in soil poorly compacted in artificial slopes may be eroded due to rainfall infiltration.

DOI： 10.2320/matertrans.Z-M2018839

Scopus

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

The local minimum pressure in embankment initiated by the base deflection is revisited by an elastic model; whereby, the effect of elastic input parameters such as Young's modulus, Poisson's ratio, and basal roughness conditions on the pronounced local minimum pressure is also disclosed by mean of the elastic model. On the other hand, the characteristic of stress dip from the elastic solution was evaluated by comparing with that of an elasto-plastic solution. Finally, the effect of the geometric features such as the height of the embankment as well as the inclination angle of the slope on the pronounced local minimum pressure was also considered. The method of IsoGemetric Analysis (IGA) was implemented for discretizing the spatial domain instead of Finite Element Method; therefore, the superiority of IGA over FEM in terms of computational cost was also demonstrated.

DOI： 10.2208/jscejam.74.I_349

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Society for Rock Mechanics  

The frequency of rainfall-induced slope failure has been drastically increasing in Asian countries. The most plausible reason for it is considered that it may be attributed to Climate Change. According to historical landslide records in Asian countries, it is well-known that weathered granite is one of the most landslide-susceptive geological condition since engineering properties of granite significantly varies in accordance with the extent of mechanical/chemical weathering. Specially, it is pointed out that decomposed granite in shallow area behaves as soil. Therefore, it is inevitable to grasp characteristics of both absorption and desorption in unsaturated decomposed granite, in order to investigate slope stability against rainfall. The characteristics of unsaturated soil material have been traditionally discussed based on Laboratory Soil Water Characteristic Curves (hereafter, called “Lab-SWCCs”). However, many research works have recently revealed that the correlation of suction with moisture content measured in field (hereafter, called “Field SWCCs”) are different from Lab-SWCCs. From such a viewpoint, authors have conducted field monitoring to measure suction, volumetric moisture content and water bearing zone from electrical resistivity measurement, which are affected by engineering properties for unsaturated residual soil such as porosity, degree of saturation and so on, in slopes comprising weathered granite in Thailand. In this study, first it is revealed that the difference on both SWCCs is mainly attributed to in-situ stress condition and pore size distribution of materials. Furthermore, combining the above findings on SWCCs and measured electrical resistivity, the study comprehensively discusses an applicability of electrical prospecting for investigation on the correlation of geological profile and the possibility of rainfall-induced slope failure in unsaturated condition.

Scopus

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

Rainfall-induced landslides frequently occur in humid temperate regions worldwide. Research activity in understanding the mechanism of rainfall-induced landslides has recently focused on the probability of slope failure involving non-homogeneous soil profiles. This paper presents probabilistic analyses to assess the stability of unsaturated soil slope under rainfall. The influence of the spatial variability of shear strength parameters on the probability of rainfall-induced slope failure is conducted by means of a series of seepage and stability analyses of an infinite slope based on random fields. A case study of shallow failure located on sandstone slopes in Japan is used to verify the analysis framework. The results confirm that a probabilistic analysis can be efficiently used to qualify various locations of failure surface caused by spatial variability of soil shear strength for a shallow infinite slope failure due to rainfall.

DOI： 10.1007/s12517-017-3158-y

Web of Science

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 地盤工学会  

DOI： 10.3208/jgs.11.103

J-GLOBAL

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

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Geotechnical Society  

DOI： 10.3208/jgs.8.361

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Engineering Geology  

The purpose of our research is chiefly to study on-site estimates of groundwater level measurements and analysis of shallow layer at Fushimi region. Fushimi region is located in the southern part of Kyoto city. Kyoto city has various traditional cultures and industries. One of them is the production of Japanese sake, for which Fushimi region is famous. The object area, which is 4 km2 and overcrowded with 50 wells, uses underground water. First, we measured the groundwater level at 27 monitoring wells. We analyzed the tendency about the groundwater level to change and also, there are factors that affect the fluctuation of water level in each layer. Next, we performed the 3D simulation of groundwater flow while using those data. As a result of our study, having arranged the bore data, we constructed an accurate stratum model necessary for analyzing. We are able to estimates the groundwater level at this area.

DOI： 10.5110/jjseg.54.16

CiNii Books

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

In this research, we chiefly proceed on-site measurement and analysis to examine how the pumping wells influence groundwater properties. The examined region is surrounded by mountains formed by a bowl shaped depression in the Paleozoic strata and granite. The paleozoic strata basin rock is an impermeable bed upon which there is a permeable diluvium and then alluvium. It is estimated a lot of groundwater is saved. However, if an excessive pumping is continued, it can cause the exhaustions of the groundwater and the subsidence, and especially multiple wells which take a large amount of water in a small area are considered to have a great impact. We established a 3D model for groundwater and make suggestions for the adequate management of the groundwater by a pumping simulation analysis. This simulation was the subject of which was a pumping well for water service - water levels for one pump were large. As a result, it can be seen from this that the fluctuation of water level group wells cause accuracy by using our model made in the present study.

Web of Science

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

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Authorship：Corresponding author   Publishing type：Rapid communication, short report, research note, etc. (bulletin of university, research institution)  

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Language：English   Publisher：IOP Publishing  

<title>Abstract</title>
The Lower Central Plain of Thailand has a deep and highly irregular basement filled with complex layers of alluvial sandy soil and deltaic clay or silt. The Bangkok Metropolitan region with its high level of infrastructure development is located in this plain. With high population density, the problem of land subsidence is critical. This study uses borehole data and the Kriging method to interpolate the data. A detailed 3D stratigraphic model of the basin is presented and several cross sections along two directions. Seventeen layers and the points used for modelling each layer are presented. The model shows eight aquifers in the Bangkok basin, lying between eight layers of clay, and a bottom layer above the basement. The bottom of the lowest aquifer of the Bangkok aquifer system is 610 m deep. The basement extends down to a depth of more than 2000 m in some places. Our 3D model, which extends to the basement, is of interest for mining and site-specific seismic risk analysis. Moreover, our results can be very useful for groundwater and land subsidence studies.

DOI： 10.1088/1755-1315/851/1/012014

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Other Link： https://iopscience.iop.org/article/10.1088/1755-1315/851/1/012014/pdf

Language：Japanese  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese  

CiNii Books

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Language：English  

CiNii Books

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Language：Japanese   Publisher：[土木学会岩盤力学委員会]  

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Authorship：Lead author   Language：English   Publishing type：Article, review, commentary, editorial, etc. (international conference proceedings)  

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Authorship：Lead author   Language：English   Publishing type：Research paper, summary (international conference)  

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Language：Japanese  

CiNii Books

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Language：English   Publisher：Japanese Geotechnical Society  

<p>In order to increase the maximum width to which the slope can be undercut, slope stabilization shear pins is required. In this study, two layout patterns of pencil leads, 2 mm in diameter, were placed into physical models of undercut slope made of a confined block of humid silica sand No.6 resting a Teflon plate. The soil pressure and slope movement during which the slope was undercut from the center line until reaching the failure were monitored by a set of pressure gauges, digital camera and high-speed VDO camera. The experimental results revealed that for a given similar number of pencil leads, the layout in vertical row has a higher influence on the stability than that in horizontal row. </p>

DOI： 10.3208/jgssp.v04.j23

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Language：English   Publisher：The Japanese Geotechnical Society  

<p>This study expects to demonstrate that a) basal deformation and roughness have influence on stress distribution within embankments and b) implementing of Bézier Extraction in IsoGeometric Analysis (IGA) substantially improves the numerical robustness. Two-dimensional elastic solutions of embankment to which the prescribed basal deformation of either subsidence or uplift and different condition of either fully rough or fully smooth base has given were compared and discussed, focusing on the variation of pressure profiles. The numerical results obtained from IGA were validated with those of finite element method (FEM), revealing that the performance of IGA under Bézier extraction is superior to FEM by achieving the lower computational resources necessary to obtain the same accuracy.</p>

DOI： 10.3208/jgssp.v04.j17

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Authorship：Lead author   Language：English   Publishing type：Research paper, summary (international conference)  

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Authorship：Lead author   Language：English   Publishing type：Research paper, summary (international conference)  

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Authorship：Lead author   Language：English   Publishing type：Research paper, summary (international conference)  

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Authorship：Lead author   Language：English   Publishing type：Research paper, summary (international conference)  

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Authorship：Lead author   Language：English   Publishing type：Research paper, summary (international conference)  

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Authorship：Lead author   Language：Japanese  

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Authorship：Lead author   Language：English   Publishing type：Article, review, commentary, editorial, etc. (international conference proceedings)  

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Authorship：Lead author   Language：English   Publishing type：Article, review, commentary, editorial, etc. (international conference proceedings)  

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Authorship：Lead author   Language：Japanese  

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Authorship：Lead author   Language：English   Publishing type：Research paper, summary (international conference)  

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Authorship：Lead author   Language：English   Publishing type：Article, review, commentary, editorial, etc. (international conference proceedings)  

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Authorship：Lead author   Language：English   Publishing type：Research paper, summary (international conference)  

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Event date： 2020

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Event date： 2020

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Language：Japanese   Presentation type：Oral presentation (general)  

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