By using advantages of a semi-analytical approach and Laplace transform technique, a Laplace Transform Finite Layer (LTFL) method is presented for the problem of unsteady flow in leaky confined aquifer systems. The finite layer formulation for drawdown response is developed in the Laplace space. Based on the solution in Laplace space, the groundwater drawdown at a given time and an arbitrary point is obtained by using numerical inversion of Durbin algorithm. The validity of the LTFL scheme is verified based on the existing analytical solution and finite difference method, and the applicability for groundwater flow in modeling flow to partially penetrating wells (PPWs) in the anisotropic leaky confined aquifers is demonstrated.

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A three-dimensional numerical model is applied to the calculation of dynamic impedances of scoured pile groups embedded in layered soil deposits during earthquake. The pile group is modeled by means of beam finite elements and the soil is assumed to be a horizontally layered half space. The pile-soil-pile interaction and radiation damping are accounted for in the frequency domain by considering suitable Green’s functions expressing the dynamic force-displacement relationship at the nodes of pile elements. A parametric study to investigate the scour effect on dynamic impedances of 5×5 pile groups with various scour depths is discussed in this paper. It is found that the impedances decrease significantly as the scour depth increases.

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In this paper, the influence of shear deformation happened in the process of the oceanic plate subducting beneath into the continental plate, and the dynamic force from earthquake on the formation of the décollement zone, a special horizontal plate boundary fault, is investigated with a specific numerical tests. The numerical tests are conducted with a static/dynamic soil-water coupling finite element-finite difference method (FE-FD) based on a sophisticated constitutive model in finite-deformation scheme. Particular attention is paid to the change of volumetric strain of the geomaterials in the proto-décollement zone that would become the décollement zone during the plate collision process. It is found that, a significant compressive volumetric strain would happen if the seabed rock has subjected to periodic earthquake loadings during twenty thousand years with a re-occurring period of every two hundred years. Amazingly, in spite of the fact that more than 20% of the volumetric strain happened, the structure of the material within the proto-décollement zone remains undisturbed, which is quite similar to the mechanical behavior of the décollement zone observed in the field. In other words, the cyclic loading might be one of the main reasons to form a fault zone (e.g., the décollement zone) with a much-higher density but keeping the random fabric structure intact.

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Based on the rapid impact compaction (RIC) technique, the dynamic compaction process of gravel soil ground and dynamic interaction between the concrete bridge foundation and the soil were simulated using the particle flow discrete element method (DEM). The improvement effect and the influence depth of the dynamic compaction of the gravel soil foundation were analyzed based on the porosity variation of the foundation soil during the dynamic compaction process. The influence of the dynamic compaction on the bridge foundation was also analyzed in this study. The feasibility of the numerical simulation for the dynamic compaction process of the gravel soil ground and dynamic interaction of the soil-structure were discussed.

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This paper presents a new slope stability analysis regarding rainfall-induced landslides by coupling a saturated-unsaturated seepage analysis and a rigid plastic finite element method (RP-FEM). Currently, a more valid and reliable disaster prevention system detecting the risk of slope instability due to sudden intense rainfall is required in Japan. However, conventional slope stability methods often fail to predict this new type of landslides. There-fore, the aim of this study is to propose the new slope stability analysis method in the context of rainfall infiltra-tion. This method introduces the effect of seepage force, an increase of unit weight and a reduction of apparent cohesion due to the change in soil suction to obtain the slope stability load factors and collapse mechanisms. ###sConsequently, this method can provide the relatively accurate and valid analysis results, which can be well com-pared with experimental data. Moreover, it is ascertained that this method can evaluate the different type of slope failure mechanisms: an initial small failure at the toe of the slope caused by the seepage forces and a large-scale failure due to the degradation of the soil apparent cohesion.

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This paper presents a new approach for modelling moisture migration in unsaturated freezing soil, in which the evaporation and condensation processes of water vapor are taken into account. Comparing predicted date with the measured result of one-dimensional soil freezing test shows proposed model is capable of effectively simulating the freezing process of unsaturated soil. Parametric analysis is carried out to clarify the role of vapor in moisture migration during freezing, which shows that vapor largely contributes to ice formation, occupying around 10% - 60% of total water fluxes in an unsaturated and closed system. The result also shows that, total ice content and vapor flux percentage increases and decreases with the increase of initial water content, respectively. The higher the temperature gradient, the greater the vapor flux percentage, while the total ice content is insensitive to the temperature gradient. Peak values exist for the variations of total ice content and vapor flux against saturated hydraulic conductivity.

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