Immediately after the occurrance of the 1995 Hyogoken-Nanbu (Kobe) earthquake, the Japan Road Association revised the Specifications for Highway Bridges in late 1996. In the course, the author took a role to revise the simplified procedure for assessing liquefaction potential of soils. The main points to be revised were the extent of liquefiable soils, estimation of liquefaction strength of in-situ soils based on penetration blow counts and soil gradation data, and the simplified liquefaction potential assessment procedure. The intent of this paper is to present and interpret the background data, both field and laboratory, that were obtained by a comprehensive study. In particular, a large amount of laboratory liquefaction data are based on those of in-situ frozen samples. At the end of the paper, technical issues to be further studied are also mentioned.

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Analytical studies were carried out on the fractuations of the minimaum sliding safety factors of the the foundation ground and surrounding slope of nuclear power stations at various combinations of the horizontal and vertical earthquake motions. The range of the combinations were determined from the investigations on the phase deference between horizontal and vertical motions actually recorded at the rock sites. It was revealed that the fluctuations of the minimum sliding safety factors were not seriously affected by the phase differences between them.
Furthermore, fundamental studies on the damping and stiffness (bulk modulus) of the ground are conducted in order to more reasonably analyse the ground response by employing the equivalent linear analysis method with dynamic horizontal and vertical input motion.

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This paper deals with the liquefaction process of the inhomogeneous sand bed under the oscillating water pressure. The inhomogeneous sand bed treated in this study has a smaller porosity in upper zone and has a larger porosity in the lower zone. In our experiment, it is formed after the loosely deposited sand bed has been once liquefied, The study is carried out experimentally and numerically, by means of the vertical one-dimensional model of sand bed. The applicability of the analytical model proposed in our past study to the inhomogeneous sand bed is verified.

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In order to foresee collapse of rock slope, numerical method will be extremely useful. However, it will be difficult to simulate collapsed, considering difficulties of rock parameter, such as geology, fracture, fault and laboratory testing into numerical calculation. This paper deals with the relevance of numerical modeling with respect to mechanical properties of rock proposed by authors. The actual data of Amatoribashi west district is referred in this paper, which was the representative case of our field monitoring studies, 13 sites in Japan.

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In order to clarify the influence of pH on consolidation characteristics of cohesive soils, one-dimensional consolidation test with stage loading was performed on five soil samples in which pH values were artificially changed by adding sulfuric acid and sodium hydroxide solutions. The tests showed that the change in void ratio was influenced and not influenced by pH-value depending on the kind of soil sample. The coefficient of consolidation and the coefficient of permeability were changed with pH-value. The coefficient of volume compressibility hardly changed with the pH value but that the compression index did or did not change with the pH-value. The soil structures formed by the consolidation changed with pH-value and the kind of soil sample.

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Characterization of the deformation behavior of sands around a cone penetrometer was conducted using an X-ray fluoroscope technique in order to establish a clear understanding of the experimental penetration process. Further experiments to evaluate, quantitatively, the situation of particle breakage during the penetration process were also conducted. Model penetration tests were performed with the following parameters as the variables: the tip form, overburden pressure and relative density. From the results, it became clear that the deformation characteristics of the penetrometer in sand significantly depend upon the sand state (packing of the grains), while it is hardly affected by the tip form of the penetrometer when the tip angle is comparatively blunt.

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Centrifuge model tests were conducted to clarify the mechanism of the passive state at failure around ECL tunnels. The model ground movements were observed with controlling the pressure of the rubber balloon filled with de-aired water. The passive earth pressure derived from some calculation models were compared to the results of the centrifuge model tests. Following conclusions may be drawn by these studies. (1) The pressure when the ground surface started uplifting was higher than the initial vertical earth pressure, but the pressure became lower according to the shear resistance reduces. (2) The failure surface observed in the tests resembled the logarithmic spiral in appearance. (3) The calculation model that the shear plane was considered as a straight line could simulate the passive earth pressure and the shear plane observed in the centrifuge model tests as well as the logarithmic spiral.

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Bentonite-based buffer materials for high-level nuclear waste disposal are expected to fill up the space between buffer and a wall of the disposal pit, and/or between buffer and an overpack by its swelling deformation. That is called as self-sealing ability. This study performs the one-dimensional model tests simulated the relationship between buffer and space mentioned above. It also investigates the validity of the new equations for evaluating the swelling characteristics of bentonite-based buffer material, which were proposed the first and second authors, by comparing the calculations and the experimental results. The experimental works and calculations showed the filling-up of spaces by swelling of buffer, and the high applicability of authors' equations to evaluate self-sealing ability.

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Skirt-suction foundation consists of the cylindrical thin walls, which are sunk into the seabed by applying suction inside the skirt compartment. In this paper, a new method of predicting penetration resistance of skirts under various ground conditions is proposed by taking account of effective stress change of the inside and outside of the foundation ground. Appropriateness of the method is verified by comparing the calculation with the field observation of an actual skirt-suction foundation. Consequently, it is clarified that the proposed method can be successfully applied to predict the penetration resistance of skirt-suction foundations.

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The real scale coupled thermal, hydraulic and mechanical experiment (FEBEX in situ test) has been performed at Grimsel test site in Switzerland in order to evaluate the coupling processes on high-level radioactive waste disposal. The heaters as waste canisters were put horizontally based on the Spanish disposal strategy. In this paper, the existing coupling model which has been validated with the coupled experiment at Kamaishi mine was applied to FEBEX in situ test and the effects of the disposal strategy and bentonite materials were clarified. Especially, the identification of water diffusivity coefficient in non-isothermal unsaturated area is very important because it is based on the physical considerations.

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In the earthquake-proof design of the road embankment by performance-based design, it is necessary to recognize quantitatively the amount of settlement due to the earthquake, since the earthquake-proof ability is estimated on the settlement at the top of embankment as an index. The seismic motion and the rank of the road are also considered in the design.
In this research, in order to investigate the seismic behavior of road embankment on the soft ground which is improved by Deep Mixing Method and Sand Compaction Pile method, dynamic centrifuge model test and dynamic FEM analysis were performed.

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Triaxial compression test was carried out to study effect of fine content on shear strength of coarse grained soil. Siliceous sand and wetted glass beads were used as coarse sand and fine content, and they were mixed in mould to make specimen. It is found that the increase of ratio of glass beads decreases the internal friction angle under constant void ratio of siliceous sand, and that the dependency of shear strength on confining pressure decreases with the increase of ratio of glass beads. The modified internal friction angle for dilatency at failure depends on the weight ratio of glass beads and siliceous sand. Finally, we propose a prediction method for the measured internal friction angle by using the relationship between confining pressure and the dilatency coefficient at failure.

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An image processing procedure of soil deformation behavior is presented by combining PIV (particle image velocimetry) and block-diagonalization method. Plane strain compression tests of sand specimens are conducted to observe localized deformation modes. The time variation of the velocity field of deformation is observed by PIV to make clear the formation of shear band at an early state. This verocity field is decomposed into a symmetric component and antisymmetric one, which corresponds to a bifurcation mode. The symmetric one is forming wedge (s) from the beginning to the end, while the antisymmetric one changes greatly to show the occurrence of bifurcation and the formation of shear bands.

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A geophysical prospecting technique using seismic signal while drilling has been applied to a relatively small-scale drilling in a civil engineering such for high level nuclear waste disposal repository. For the purpose of it, a small-size downhole three component seismic detector was developed for measuring drilling signal. Then, the performance of the measurement system was verified by a calibration test using an artificial seismic source. A data acquisition of in-situ drilling signal was conducted during a drilling at a granitic quarry, and subsurface structure were estimated by the triaxial drillbit VSP method. The distribution of underground reflection coefficients was obtained to a depth of about 300m by drilling signals from only 10m drilling, and the estimated image agrees well with other borehole observations.

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A numerical model based on results during pre-investigation phases was applied to the groundwater flow change caused by the construction of Äspö HRL. The drawdowns and chloride concentration during tunnel construction were simulated to validate the numerical model. The groundwater flow was induced by inflow from the Baltic Sea to the tunnel through the hydraulic conductor domain (HCD). The time series of tunnel progress and inflow, boundaries of the Baltic Sea, transmissivity and geometry of HCD are therefore important in representing the groundwater flow. The numerical model roughly represented the groundwater flow during tunnel construction. These simulations were effective in validating the numerical model for groundwater flow and solute transport.

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Performance of permeable reactive barriers for contaminated groundwater remediation was evaluated using FEM seepage analysis. The retention time and the capture width were calculated on the funnel-and-gate system having different geometries, in order to evaluate the effects of these geometries on the performance of funnel-and-gate system. Based on the calculated results, costs associated with the installation of funnel-and-gate system satisfying a certain performance were obtained to estimate the cost-effective geometry. Finally, optimum design flow for permeable reactive barriers was proposed.

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In order to reveal the mechanical characteristics for in-situ volcanic soils, triaxial tests for undisturbed and reconstituted specimens were carried out. SPT, CPT and SCP tests were also performed at the sampling sites. The test results showed that the effects of fabric anisotropy and welding on monotonic shear behavior are insignificant for crushable volcanic soils due to fabric change induced by particle crushing. Although the influences of grain size, fines content and welding on liquefaction strength for in-situ volcanic soils seem to be strong, liquefaction strength and its anisotropy effect for brittle pumice are reduced with the increase in confining pressure and fabric change. Moreover, since in dynamic penetration test the particle crushing of volcanic soil grounds occurs, it was found that the correlations between N-value and strength parameter are different from that of sandy grounds.

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Huge inland earthquakes often cause fault rupture hazards. The mechanism of surface fault rupturing is significantly affected by the features of fault movements at the basement and the characteristics of unconsolidated surface layers, and very little has been elucidated for the cases of strike-slip faults. In this study, a series of model tests of strike-slip faulting are conducted using X-ray CT technique to observe shear bands in the model ground. Typical development processes, shapes and sizes of shear bands forming typical flower structures are investigated.

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The bearing capacity of sandy ground with one-layer reinforcement was investigated based on the results of centrifuge model tests in the laboratory. The results agreed with those of the conventional model test in gravitational force field: 1) There exists an optimum depth for installing reinforcement at which the reinforcing effect is a maximum; this depth is approximately equal to the width of strip footing, and is independent of the reinforcement width. 2) The qualities of load-settlement and the failure modes vary with the optimum installed depth, and are independent of the reinforcement width. 3) When the reinforcement depth is shallower than the optimum installed depth, although the reinforcing effect increases with reinforcement width, when a certain reinforcement width exceeds, the increase in reinforcing effect lessens.

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