Influence of Matric Suction on Slope Instability of Stratified Laterite Gravel Tableland Induced by Rainfall
Date Issued
2012
Date
2012
Author(s)
Cheng, Szu-Yuan
Abstract
Slope stability of laterite gravel tablelands margin is an important geotechnical issue, since the high and steep slopes composed of thick gravel layer could remain stable in normal conditions but become highly potential to collapse after rainfall events. To simulate the process of state change in laterite gravel slope induced by rainfall event, unsaturated finite element slope models were built with different hydrogeological conditions. The numerical material parameters were summarized from previous domestic researches and tests. In this study, Coupled stress-stain and seepage analysis was used to calculate the changes of pore-water pressure, unsaturated shear strength, stress state and cumulative shear strain during rainfall event. Parameter sensitivity analyses, which are about slope angle, position of aquitard, pre-infiltration condition and the thickness of laterite layer, could explain the most critical factors that affect the failure potential and slip surface.
According to the analysis results, the most critical factor of slope failure mechanisms of laterite gravel tablelands is slope angle. The main effects of others factors are changing the location of potential slip surface and the failure potential. Sinc the wetting zone of steep slopes during rainfall event could not deep in internal slope, the potential slip surface is more shallow than gentle slope, but the area of unstable stress state is larger. Failure surface in gentle slope is significantly affected by the position of wetting front and aquitards. According to the result of analysis with different pre-infiltration, less amount of infiltration would due to shallower potential failure surface but greater deformation.
Subjects
laterite gravel
infiltration
unsaturated soil
heterogeneity
matric suction
wetting zone
Type
thesis
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