Influence of rainfall infiltration on the stability of unsaturated coal gangue accumulated slope

The slope instability is associated with increasing rate of rainfall infiltration which cause shear strength reduction and suction loss and the slope tend to failure. The influences of rainfall infiltration on the stability of clayey and sandy slopes have been analyzed but the effect of rainfall infiltration on the stability of unsaturated coal gangue accumulated slope was needed to study. Therefore, a coal gangue accumulated slope prone to failure in Fuxin area of Northeast China was considered to evaluate its failure mechanism under different rainfall events. The effects after five different rainfall events on slope stability were physically analyzed, numerically investigated and the results from both uncoupled(hydraulic) and coupled(hydromechanical) responses were compared using finite element analysis. It was observed that the decisive soaking and leaching under different rainfall conditions caused maximum deformation at the crest of slope due to maximum value of permeability coefficient of coal gangue. The critical duration of moderate intensity(147 mm/day) of rainfall for the instability of coal gangue accumulated slope is declared as five days. The results from finite element analysis in this paper further clarifies that increase in duration of rainfall infiltration process cause hysteretic change in positive pore-water pressure causing decrease in factor of safety and increase in deformation. It is concluded that the stability of unsaturated coal gangue accumulated slope is greatly influence by the coupled effect of stress and porewater pressure in comparison of uncoupled(hydraulic) analysis as the obtained factor of safety values after five days of rainfall infiltration were 0.9 and 1.1 respectively.

Uncertainty assessment in hydro-mechanical-coupled analysis of saturated porous medium applying fuzzy finite element method

The purpose of the present study was to develop a fuzzy finite element method,for uncertainty quantification of saturated soil properties on dynamic response of porous media,and also to discrete the coupled dynamic equations known as u-p hydro-mechanical equations.Input parameters included fuzzy numbers of Poisson's ratio,Young's modulus,and permeability coefficient as uncertain material of soil properties.Triangular membership functions were applied to obtain the intervals of input parameters in five membership grades,followed up by a minute examination of the effects of input parameters uncertainty on dynamic behavior of porous media.Calculations were for the optimized combinations of upper and lower bounds of input parameters to reveal soil response including displacement and pore water pressure via fuzzy numbers.Fuzzy analysis procedure was verified,and several numerical examples were analyzed by the developed method,including a dynamic analysis of elastic soil column and elastic foundation under ramp loading.Results indicated that the range of calculated displacements and pore pressure were dependent upon the number of fuzzy parameters and uncertainty of parameters within equations.Moreover,it was revealed that for the input variations looser sands were more sensitive than dense ones.