A modified I-D method was proposed for the purpose of improving an accuracy of slope failure risk prediction. This method was added the results of on-site measurement by a tensiometer to the concept of rainfall index. Since the formation of a saturated zone in a slope could lead to slope instability, it is important to estimate the time (𝑡_sat) of formation of saturated zones. In this study, a new estimation index for 𝑡_sat using rainfall index was proposed. As a result, the relationship between the average rainfall intensity and the duration between the beginning of rainfall and the formation of the saturation zone was shown the best result. Furthermore, by incorporating this result into a modified I-D method, the number of correct estimations increased significantly compared to the existing rainfall index. Therefore, by the proposed rainfall index of 𝑡_sat, it was confirmed that the slope collapse can be predicted only by the rainfall data, and the accuracy was improved.

 A capillary barrier system is the control technique of water flow adopted in waste landfills. A capillary barrier system constitutes a finer soil overlying a coarser one. The infiltration water is retained by the suction of the upper fine soil layer, and the infiltration water into the lower layer is halted. When the amount of infiltration water increases, the water across the interface between the finer soil layer and the coarser one infiltrates. When the constituent materials for the capillary barrier structure are selected, they are empirically selected based on their grain size characteristics, and their hydraulic properties are not considered. In particular, the performance of capillary barriers is dominated by the hydraulic property of the fine-grained soil that is the constituent material, and research has been conducted focusing on those characteristics.

 This study focused on the hydraulic properties of the constituent materials for the capillary barrier, and the diversion capacity with different combinations of earth materials is evaluated. From the experimental results, the breakthrough mechanism of the capillary barrier known from the previous studies is verified. The diversion capacities are evaluated using the index that considers the hydraulic properties of the constituent materials, and these results imply that the smaller the index, the greater the diversion capacities.

 When triaxial compression (TC) tests are performed for the design of fills of sandy soil, the specimens are usually prepared by uniform compaction in the laboratory. On the other hand, in field compaction, the dry density, ρ_d, noticeably decreases with depth in each compaction layer, while the surface layer of fill may be considerably disturbed due to local shear failure at the contact with a rigid steel roller. In this study, full-scale compaction tests were performed at various compaction energy levels in a wide range of ρ_d and water content, w, and the strength and deformation characteristics of field-compacted sandy soil were evaluated by TC tests on undisturbed samples from the test fills and those compacted in the laboratory. Empirical equations expressing the strength and stiffness of compacted soil were derived, which consists of an increasing function of ρ_d multiplied by a decreasing function of the degree of saturation, S_r. The equations take into account the effects of compaction disturbance and wetting/saturation while not including the compaction energy and compaction method as variables. It is shown that, when compacted at S_r equal to, or around, the optimum degree of saturation, (S_r)_opt, the effects of these factors are negligible, so, results of TC tests on unsaturated specimens compacted in the laboratory are applicable to the design field conditions.

 This study aims to analyse the relationships between rock shapes and distribution characteristics of rockfall run-out. A series of rockfall simulations is performed using the Discrete Element Method (DEM). 36 rock models with different shapes were defined by changing the geometrical parameters that were aspect ratio, oblateness, and cut ratio. A total of 200 simulations are carried out for each rock model to obtain the distribution of the final run-out position. The sphericity was employed for analysing the contributions of rock shape, and the relation between the sphericity and the distribution characteristics of rockfall run-out was analysed. According to the result, it was found that the effect of rock shapes on distribution characteristics of rockfall run-out can be expressed in a unified manner using two types of sphericity.

 In principle, the Japanese Industrial Standards call for soil compaction tests to be performed using a manual compactor. However, the use of an automatic compactor is also allowed if it can reproduce similar movements, and there are models that use various mechanisms to reproduce the lifting and rotational movements of rammers. Although automatic compactors are widely used, there is no way to evaluate their similarity to manual compactors, and the performance of various models is not known. Therefore, in this paper, we evaluate the performance of automatic compactors owned by 11 institutions and discuss their impact on soil dry density and the California Bearing Ratio (CBR). Although we find that the manual compactor provides uniform, ideal soil compaction, some automatic compactor models show large amounts of impact irregularity, greatly affecting density and CBR. Those effects can be summarized by the impact area, so we propose a simple method for measuring that area.

 Ground improved by penetration grouting method to prevent liquefaction of sandy ground has spatial variability in shear strength compared to naturally deposited ground due to non-uniformity of chemical penetration and spatial variability of soil properties. In this paper, the deformation behavior due to the dissipation of excess pore water pressure after liquefaction is stochastically and statistically investigated for a runway of an airport which was improved by penetration grouting method, by expressing the spatial variability of the shear strength by random field theory and modeling the existence of liquefaction of the ground during an earthquake. A novel performance-based evaluation method for bearing capacity and flatness is proposed, which are the performance index values required for runways after an earthquake by using the obtained results.

 This paper presents a soil-water coupled finite deformation analysis method based on mixture theory. We adopt the 𝒖-𝑝 formulation, which takes the displacement of the solid phase and the pressure of the liquid phase as unknowns, and applied finite element discretization to both displacement and pressure. The Cam-clay model based on the multiplicative decomposition theory of the deformation gradient is applied to the constitutive model of the solid phase. We simulate triaxial compression tests with a both drained and undrained conditions to verify the proposed formulation.