Microcrack generation and propagation is an important phenomenon, which describes the long-term behavior of a crystalline rock. In this study, a progressive development of microcrack in granite and its proagation was observed using microscope under water-saturated triaxial compression. A series of triaxial relaxation tests was performed with fine and coarse grained granite. Results revealed that there exists a strong relationship between the stress relaxation and the microcrack propagation. Three stages of stress relxation rate were identified where stage one offers the maximum microcrack generation and propagation. The microcrack propagation in fine grain granite was found higher than the coarse grain granite because of higher number of contact points between the grain boundaries. Stress concentration occurs in these boundaries and microcracks are propagated through these contact points.

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Considerable generation of industrial waste is becoming a serious social problem. Under these circumstances it has therefore become necessary to develop effective strategies for the utilization of wastes. This study employed field trials to investigate the application granular waste for use as replacement material for frost prevention. A new method for dealing with such waste using soil bags filled with granular waste consisting of glass cullet and expanded poly-sterol to facilitate reduced volumes was used to backfill precast concrete L-type retaining walls. From November 2002 to May 2004, the frozen state of backfill soil and displacement of the walls were measured. These measurements revealed that granular waste is suitable for use as a frost heave prevention material.

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It is extremely important to evaluate the consolidation yield stress accurately in order to predict the settlement in the chohesive soils in which long-term large settlement due to a loading occurs in the neighborhood of the consolidation yield stress. Especially, in the soils where the compressibility is large after yielding, the influence of the decided consolidation yield stress value on the accuracy of settlement prediction of settlement is significant. Moreover, it is important to consider the strain rate dependency, because strain rate influences consolidation yield stress. In this study, various consolidation tests were carried out using clays of three areas (Osaka Bay, Amagasaki, Kyoto) with different consolidation history, and strain rate dependency of consolidation yield stress was studied in detail. As a result, it is shown that understanding of the strain rate dependency on the consolidation yield stress up to the level of ε=10^-11 s^-1 is very important for engineering.

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Liquefaction-induced flow occurred in the liquefied ground behind seawalls and river revetments during several past earthquakes. The authors considered that a countermeasure by installing piles between seawalls and pile foundations, would prevent the liquefaction-induced flow. As the preventing piles were not continuous, this method can be applid in the area where many buried structures are existing, such as oil plants, harbors and so on.
Then, shaking table tests and three dimensional residual analyses were conducted to demonstrate the effectiveness of the preventing piles. Two types of model countermeasures, preventing piles and a sheet pile, were placed between a seawall and a pile foundation. In the first countermeasure, preventing piles were constructed with square and triangular arrangements. Test and analyzed results showed that the installation of the two types of countermeasures was able to reduce displacement of the pile foundation. In the preventing piles, the trianglar arrangement was more effective than the square arrangement.

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The Chikugo plain locates on the left coast of the Chikugo river which is the longest in Kyushu. The subsidence in the Chikugo plain has occurred since as nearly same time or a little earlier time as that in Saga plain. The scale is nearly the same as or larger than that in Saga plain. In the paper, on the basis of the investigation in the previous reports and new data, the ground subsidence in the coast area of Ariake bay, Chikugo plain, the decrease in the ground water in the deep ground layer, the subsidence of Ariake bay's bottom and the mining coal under the bay bottom were mentioned. It is concluded that the ground subsidence and recent expansion were caused by the water pumping for the coal mining under the bay bottom and the recovery of ground water after the close of the mining respectively.

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A three-dimensional swelling deformation of bentonite-sand mixtures is investigated. It is confirmed that the magnitude of volumetric strain ε_v due to wetting depends mainly on mean principal stress p regardless of principal stress ratio R while the magnitude of deviator strain (ε_a-ε_r) induced by wetting depends on principal stress ratio R regardless of mean principal stress p. A linear relation exists between montmorillonite void ratio e_m (defined as a ratio of water volume to montmorillonite volume) and mean principal stress p in their log scales. This relation between montmorillonite void ratio e_m and mean principal stress p is independent of initial dry density, mixing rate of bentonite and sand, and principal stress ratio R. In addition, there is a linear relation exists between deviator strain log(ε_a-ε_r) and principal stress ratio R.

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Multi-scale modeling based on the mathematical homogenization theory explains to us that the micro-scale problem in multi-scale modeling provide a constitutive (stress-strain) relationship for the macro-scale problem of a overall structure. We focus on this explanation to evaluate the macroscopic loading surfaces, and carry out three-dimensional micro-scale analysis of a granular material. At first, we give an overview of a multi-scale model to show that the micro-scale problem provides a constitutive relationship for the macro-scale problem. Next, we apply three-dimensional micro-scale analysis of idealized granular materials to evaluate and examine loading surfaces and the flow rule which is relevant to the loading surface. By the numerical experiments, we obtained the following main conclusions: Loading surfaces of granular materials are curved surfaces containing inflection points and exhibit kinematic and rotational hardening in p-q plane; plastic strain increments exhibit incremental nonlinearity near the inflection point; in π plane, it is difficult to uniquely define loading surfaces, because the incremental nonlinearity of plastic strain increments is conspicuous.

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This paper describes characteristics of air permeability of unsaturated soils. The method of air permeability test which is able to control the suction repetitively to adjust the degree of saturation of an unsaturated soil sample is proposed. The relationships among air permeability coefficient, degree of saturation and suction are evaluated. As a result, it made clear that air permeability coefficient in the range from 10^-3cm/s to 10⁰cm/s was able to be measured by the proposed method. And then, it was recognized that the relationships between air permeability coefficient, degree of saturation and suction showed hysteresis in drying and wetting processes, and that the air permeability coefficient in wetting process was larger than the one in drying process.

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Accurate prediction of the settlements for quasi-overconsolidated clay beds with structures is required. Various consolidation tests were carried out on natural clays with different levels of structures by various factors in order to investigate their consolidation characteristics. Based on the experimental results, a new index is introduced to evaluate the level of structure quantitatively. It is shown that the conditions for creep yielding and compression yielding are identical, and then compressibility of natural clays depends on the soil structure index at yielding. In addition, it is demonstrated that strain rate dependency of compression curves and secondary compression index can be evaluated from plastic chart quantitatively.

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Rockfall behaviour should vary with changes in various conditions, such as inclination of slope, slope materials, the shape and size of falling rocks. Thus it is not easy to predict its behaviour. On the other hand, a lot of numerical methods of rockfall are developed to conduct a plan of disaster prevention. However some probrems of characteristics of input parameters are not solved. Forthermore, under the present situation, rockfall simulations are restricted to perform back analysis method. In this study, the properties of normal velocity ratio(R_n) and velocity energy ratio(E_v) at impact, which are dependence on the incident angle through observations, are discussed. To use improved DDA considering these properties, we verified that the motion of rockfall by DDA simulation shows good agreements with the observations through the trajectory and the velocity of falling rocks.

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This paper presents analytical studies on effective countermeasures against actual piled bridge abutment constructed on thick soft clay ground. After 13 years from the construction, unloading of embankment with the use of EPS (Expanded Poly-Styrol) was unavoidable to prevent further damage to surroundings. The effects of unloading timing was varied in the first stage of the analyses, then the applicability of FCB was studied by varying the unloading timing and area. Based on the assumed scenario of each countermeasure, effective countermeasures in terms of cost performance were discussed.

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In the JRA Specifications for Highway Bridges a static analysis method using rigid frame and subgrade reaction models is recommended as a verification procedure of pile foundations for the level 2 (higher) level seismic motions. This paper investigates reasonable simple methods for analyzing dynamic behaviors of pile foundations embedded into liquefiable soils, with emphasis on evaluation of input conditions assumed in the verification procedure.
First, it presents the results of effective-stress analyses for overall soil-pile-structure systems, and then compares the analytical results with the results of parametric static rigid frame analyses considering ground deformations.
From this investigation it is concluded that dynamic behaviors of pile foundations at liquefiable sites can be simply analyzed, by assuming that ground displacements from the effective-stress response analysis of soil layers and structural inertia forces from the acceleration spectra analysis are taken as input conditions in the static rigid frame analysis.

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In the geological disposal facility of high-level radioactive wastes, it is important to grasp the hydraulic conductivity characteristic of bentonite. The purpose of this study is the advancement of the examination method for the measurement of a more reliable hydraulic conductivity using high-pressure consolidation test apparatus (maximum consolidation pressure 10MPa). Consequently, it succeeded in improving the reliability of data by raising the resolution of displacement used for an examination, increasing to 80 the number of measurement data for 20 minutes after making each consolidation pressure act on the occasion of measurement and adopting the data of a high consolidation pressure (more than 5.88MPa) stage.

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