Current state of art is summarized for the geological and geomorphological principle and techniques necessary to locate potential landslide sites. For shallow landslides, precise mapping of potential sites is difficult at present because of spatial variability of soil structure and properties. Areal susceptibility evaluation of landslides on the basis of previous landslides would be feasible and more practical. Previous landslide scars can be well identified by using airborne laser scanner. Large landslides with volumes more than 100,000 m³ are preceded by precursory landforms in many cases induced by rainstorms or earthquakes, which would be important criteria for the mapping of potential landslide sites. However, landslides of pyroclastic fall deposits induced by earthquakes do not accompany precursory deformation of mountain slopes, so detecting the materials themselves would be important for site prediction.

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Earthquake-induced slope stability has been evaluated by force-equilibrium of soil mass, although it cannot evaluate how large the deformation will develop and how far the effect reaches down-slope. The present study aims the development of evaluation method for residual displacement of slope during earthquakes by energy approach. We conducted innovative model tests on a shaking table, in which energy balance in a sliding slope is quantified. Based on theoretical considerations on a rigid block model and model test results, a possibility of energy based design for slope displacements during earthquakes has been found.

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An optimal design method of rock bolting is proposed utilizing a topology optimization scheme, which has been developed on the basis of the mathematical homogenization theory. The installation spacings and angles of rockbolts are adopted as design parameters, and the reinforcing effect of the rock bolts, such as to increase the stiffness and strenght of rock mass, can be quantitatively evaluated by the homogenization analysis and expressed as functions of the design parameters. By use of them three kinds of objective functionals, which represent the global compliance and the stability against collapse of the reinforced rock mass, are defined. Optimization problems to minimize o these objective functionals are then formulated and solved by the optimal criteria method, then the optimal spacings and angles of rock bolts are designed. A standard patten of rock bolts for road tunnel is optimized as example, and the effectiveness of the proposed method is shown.

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Objective of this study is to compare the volumetric change of liquefied sand with that of dry sand under the same cyclic shear histories. To do this, multiple series of strain-controlled cyclic shear triaxial tests were conducted under both undrained and drained conditions. Under the same cyclic shear strain loading histories, the laboratory test results illustrated that the volumetric strain of drained cyclic test of dry sand was the same as that of post-cyclic drained test of saturated sand. The volumetric change under cyclic loading depends only on the strain histories and does not on the stress paths. In addition, it is found that the lower limit value of volumetric compression under cyclic shear can be noted. Under large shear exist, the void ratio converged at a particular value of the sandy material.

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At present, a safety factor obtained from the equilibrium equation of acting forces is used to estimate seismic stability of a retaining wall. It isn’t, however practical to apply it to huge earthquakes which seldom occur. Therefore, rational design method based on the prediction of the displacements of the retaining wall subjected to such earthquakes is required.
In this research, a series of dynamic centrifuge tests on the reinforced retaining walls with anchors has been conducted to examine the influence of the wall rigidity on the seismic stability of the retaining wall. In addition, the analysis using sliding blocks has been done to predict the deformation of the walls. As a result, it was concluded that the deformation modes of the wall was influenced by the wall rigidity and the results of the analysis corresponded well to those of the experiments.

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Thick deposits of Pleistocene strata are found at deeper depths below the seabed at Kobe Airport which was constructed offshore of Kobe Port. The Pleistocene Clays at the Osaka Bay are quasi-over-consolidated and their consolidation properties have not been well understood. Moreover, the drainage capacity of gravel or sand strata that interlay between the Pleistocene Clays was not clearly understood. In order to examine the settlement behavior of the Clays, a special precise measurement system over a unit depth of 1 or 3 m intervals was installed to measure both the compressions as well as the excess pore water pressures over the entire depths of the Upper Pleistocene Clays. The measurements covered the compressions of Upper Pleistocene Sand and Gravel layers, and those of Ma12 and uppermost Ma11 Clays that are to be brought into a normally consolidated state due to the airport fill load. Based on the measurements, it was found that the pre-consolidation pressure, p_c, of Ma12 is function of the strain rate that is highest near the upper drainage boundary and also that the field p_c value is smaller than that of the laboratory result because of the low strain rate in the field. The drainage capacity of sand and gravel layers was also found to be good.

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Quality of building stone is mainly evaluated by the color and tone for a dressing material in Japanese architecture. The color of stone is measured and evaluated by visual observation and/or a trichromatic colorimeter. However, the former has the demerit such as lacking of reproducibility of evaluation because evaluated result depends on an observer's experience and sensitivity. The demerit of the latter is that it confounds colors of two or more of composed minerals. To solve these problems, this study proposed new color measuring method by using a digital camera with high accuracy. Moreover, new quantitative indexes concerning color and tone were proposed from the results obtained with the proposed method. It was clarified that these indexes are effective for color evaluation of stone.

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Bentonite has been examined recently in some countries as candidates for buffer materials in highlevel radioactive waste repositories. Granular bentonites are anticipated as the raw materials for constructing bentonite-based buffer materials by in-situ compaction methods. For that reason, it is important to understand the influence of grain size distribution and physicochemical properties of bentonite ore on compaction and hydraulic properties of granular bentonites. In this study, compaction and hydraulic conductivity tests of some kinds of granular bentonite with different sources and grain size range were performed. As a conclusion, compaction and hydraulic properties of granular bentonites can be evaluated by plastic limit and montmorillonite content of bentonite ore used as raw materials.

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The objective of this paper is to evaluate tunnel face failure using model test apparatus with X-ray CT scanning. First of all, a three dimensional face failure was visualized using the results of CT scanning and the failure mechanism in three dimensions was quantified. Then, in order to discuss on the scale effect of model test on 1G condition, a series of centrifuge model test were conducted. Based on the comparison of the results of centrifugal testing with those of CT scanning, it was convinced that the failure mechanism obtained from CT scanning was fairly acceptable to model the failure mechanism for the purpose of stability analysis. Then, a three dimensional model on tunnel face failure was proposed based on the CT results and the stability analysis on the tunnel face failure was conducted using the proposed model. Finally, it was a first time that the stability analysis was done based on a true three dimensional failure mechanism and it was convinced that the effectiveness of the proposed model was validated.

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A new in-situ permeability test of determining field-saturated hydraulic conductivity k_fs and unsaturated hydraulic conductivity k_unsat in the near surface of unsaturated sandy soils is proposed. A ponded singlering infiltrometer technique, such as the Guelph Pressure Infiltrometer method was performed to determine k_fs. The Instantaneous Profile method with the unit hydraulic gradient assumption was applied to determine k_unsat during drainage period. The advantage of our proposed method is to measure k_fs and k_unsat continuously by simple permeability tests with soil moisture profile. The utility of our proposed method is demonstrated by using a numerical model and experimental data of unsaturated dune sands.

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To study the pollution of the ground by electrolytes, their adsorption to and desorption from soil particles need to be understood. In this study, batch tests were conducted to elucidate the mechanisms of adsorption and desorption; and the adsorption, desorption and exchange reactions of electrolytes were investigated using an electric diffuse double layer model proposed by Stern. The study revealed the concentration dependency of the adsorption and desorption mechanisms, factors that caused chemical hysteresis, and effects of soil acidity on adsorption and desorption properties. The authors formulated an equation for calculating the amounts of electrolytes adsorbed and desorbed based on the concentration dependency of the adsorption and desorption mechanisms, which was shown to almost perfectly reproduce the adsorption isothermal curve during increments and drops of electrolyte concentration.

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Since GBFS (Granulated Blast Furnace Slag) has hydraulic properties, the control of the property is one of the most important problems for the effective usage in the ground improvement. In this paper, authors verified the factors which affect the hardening property, by the laboratory and field tests. As a result, it is observed that the number of contact points of particles correlates with the unconfined shear strength, and when applying GBFS to the SCP-method the shear strength increased and the permeability decreased remarkably after 3 months by particle crushing due to the compaction.

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In order to investigate the behavior of dense sandy soils under high confining pressure, high-pressure triaxial tests were performed on three types of undisturbed specimens. As a result, it is confirmed that consolidation and shear characteristics of undisturbed dense sandy soils are similar to those of clayey soils. Under high confining pressure, the yielding stress of consolidation exists influencing the shear characteristics at the point. Through grain-size analysis, it was found that particle crushing increased with consolidation stress and was remarkable when the stress exceeded the yielding stress.

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