Study on Prediction and Mechanism of Residual Soil Slope Failure due to Rainfall by Numerical Analysis

本研究的目的在于找出影响原状风化花岗岩土渗透特性的因素，以探讨边坡破坏的机制。通过试验研究了风化程度与渗透参数之间的关系，并对渗透参数的物理意义进行了分析，得出了渗透参数与风化程度之间的关系。各种风化花岗岩土的性质。从工程角度来看，烧失量和干密度都可以作为风化程度的标准，用中子辐射法可以准确地确定原状土样的渗透特性控制参数，湿陷性地基的特征是土水特征曲线的滞后性和主导孔隙尺寸采用不同的风化土层模型--饱和-非饱和渗流分析与弹塑性分析相结合的有限元分析方法进行数值分析。研究结果表明，孔隙水压力和土体变形特性都可以预测边坡渗水破坏模式。

The purpose of this study is to find out the factors controlling the seepage properties in the undisturbed decomposed granite soil in order to investigate the mechanism of the slope-failure, and to clarify the applicability of the seepage parameters to numerical analysis for the water permeation into the layered soils.It has done to examine experimentally the relationship between the degree of weathering and the seepage parameters evaluated by the physical properties of various kinds of the decomposed granite soil. From this research, both the values of ignition loss and the dry density of sample are useful as a criterion of the degree of weathering from the engineering points of view, and, also the parameters controlling the seepage characteristics of undisturbed sample can be determined accurately by means of neutron ray radiation method.The collapsible ground is characterized by the hysteresis of soil water characteristics curve and the dominant pore size distribution, and these factors give a large influence on the hydraulic conductivity.The numerical analysis was conducted by using a different weathered soil layer model-FEM analysis combining the saturated-unsaturated flow analysis and the elastic-plastic analysis. As a result, it has demonstrated that slope failure pattern due to water permeation can be predicted by both the properties of pore water pressure and soil deformation.