We studied the reinforcement effects of foamed mixture lightweight soil by mixing short fibers reutilized waste PET bottles. The conclusions obtained from this work are as follows: When the minimum flow value is 160mm, the additive rate of short fibers is affected by the diameter and length of the short fibers, as well as by the design unconfined compressive strength. We, therefore, propose an empirical formula of the additive rate in which these three elements are used as variables. On the other hand, it has been confirmed that the unconfined compressive strength, modulus of deformation and residual strength highly depend on the index value, sand cement ratio and the design unconfined compressive strength. We also suggest an empirical formula of the unconfined compressive strength that has above-mentioned indexes as variables.

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 It is confirmed that battered pile foundation viaduct has damping effects due to the reverse rocking movement and input loss by ground deformation in addition to the static rigidity increasing effect. However, the damping effects can not be evaluated quantitatively until now. In this study, we conducted vibration tests using the rigid frame viaduct models (about 1/10 scale) with vertical and battered piles (the angle is 5 degrees). As the results, aseismicity of the viaduct for the horizontal acceleration can be improved by using batter pile in all frequency ranges. And the earthquake resistance improvement of the batter pile viaduct by the effects of reverse rocking movement and input loss can be quantitatively obtained through numerical analysis.

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 In this study, in order to investigate the change of pore size distribution with progress of deterioration and consolidation characteristics of the lime-treated clay immersed in seawater, the measurement of pore size distribution by mercury intrusion porosimeter and consolidation test were performed for both deteriorated and non-deteriorated lime-treated clay specimens. The pore size distribution of lime-treated clay immersed in seawater gradually shifts to those of non-treated clay with maintaining total pore volume constant. Furthermore, it was found that the specimen deteriorated in seawater showed large compressibility compared with non-deteriorated specimen. The reason for this phenomenon is not only by disappearing of the cementation in the lime-treated clay due to calcium leaching but also by changing of pore size distribution.

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 Ground anchor technique has been widely used for stabilizing cut slopes and embankments in Japan for the last thirty years. As ground anchors are anticipated to be deteriorated by geological environments such as ground water and natural disasters such as earthquake and typhoon, it is necessary to evaluate appropriately the damage of anchors as well as the stability of slope reinforced by deteriorated ground anchors. This paper analyzed the reliability of soundness diagnosis based on the past regular surveys and lift-off tests statistically, proposed a deterioration model for a single ground anchor using the Weibull distribution and finally assessed the stability of reinforced slope with the proposed model.

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 The crack is generated in the soil structure by drying shrinkage, earthquake, creep deformation. In recent years, the observed rain intensity is greater than the past. However, it is not clear about the influence of the crack which provides the water level rises and rainfall infiltration into the soil structure. In this paper, the effect of crack on the model embankment was examined under rainfall. The tests showed that: as the number of cracks increase, the volumetric water content and the water level in the embankment increases. Furthermore, the water level per unit time is decreased with the repetition of rainfall. As one of the causes, we suggested the effect of adhesion of the crack.

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 Safety calculation methods of slope were presented more than 70 years ago and various methods have been presented in the past. Slip surface of the safety factor calculation method of slope practically adopted assumed to be circular. Because it has small number of parameters, simple algorithm, efficient and high computation stability. On the other hand, one of the safety factor calculation methods of slopes with non-circular slip surface is Spencer method, which has complex algorithm and low computation stability. In this research, factors of computation instability in the safety factor calculation of slope by Spencer method were revealed and improved algorithm of the safety factor calculation method with high computation stability was presented.

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 Dynamic load test of piles has been developed and increasingly conducted in recent years. Dynamic load test has the greater advantage that there is no need to prepare special machines for the test in case of the tested piles are planned to be driven by hammers. Therefore, it is easy to test a large number of piles at a single construction site. On the other hand, the procedures to utilize the obtained test results for design of structures are not described in Japanese design codes for port facilities, road bridges, and so on. This paper will introduce a series of dynamic load test results obtained at a single construction site, and evaluate the variance of it. The procedure to utilize the test results for design will be discussed based on the results of considerations.

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 Deformation characteristics of rock masses are often significantly anisotropic due to discontinuities e.g. sedimentary planes and joints. Anisotropic properties of rock masses are commonly obtained by several triaxial tests using rock cores sampled to different orientations, but which is costly and time consuming. In this study in-situ torsional shear test for rock masses is proposed by the authors. Anisotropic deformation properties can be obtained by fewer tests than the conventional testing method. In this paper, for developing testing methods, a method of determining constitutive parameters for transversely isotropic rock masses is proposed. In this proposed method, the directions of anisotropy are determined by the strain responses under isotropic consolidation and 5 elastic parameters of transversely isotropic rocks are determined by both strain responses during isotropic consolidation and the distributed stress responses during torsional shearing.

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 As for the low permeable layer, important functions are expected as an engineered barrier of radioactive waste disposal for low-level waste with comparatively high radiation levels. On examining the construction methods of this low permeable layer, it is important to confirm the possibility of the construction in the conditions similar to the actual constructed conditions with a true scale size. Therefore, the construction examination for the bottom part of the low permeable layer by bentonite and the performance check test of the buffer layer were carried out. The result of the construction examination showed that the possibility of the construction were confirmed, and the result of performance check test showed that it was possible to ensure the required performance of the low permeable layer, such as hydraulic conductivity.

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