Effect of Rainfall Induced Wetting Zone on the Shallow Slope Failure in Unsaturated Soils

• Main Authors: Andrea Milena SAAVEDRA REY, 宋安潔
• Other Authors: WU,YUAN-HSUN
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/42062228952105972653

碩士 === 中華大學 === 土木工程學系 === 105 === Rainfall infiltration has been considered the main cause of the majority of landslides in unsaturated soils that happened in countries with heavy seasonal rainfalls. These landslides are mostly triggered by the deepening of the wetting front (WF) as it generates an increase in pore water pressure, reduction in soil matric suction, and loss in soil shear strength. The main parameters that affect the slope stability include rainfall intensity (I), hydraulic conductivity or coefficient of permeability (k), shear strength, slope angle (α), and slope height (H). This study analyzes and compares the above parameters to evaluate their effects on the slope stability. The storm conditions used was defined by the Central Weather Bureau of Taiwan. For simplicity, the storm conditions and the shear strength were kept constant for all the cases. A series of finite element modeling experiments have been conducted on soils with different permeability values using Van Genuchten model to describe the hydraulic behavior of unsaturated soils (zones above the ground water table). These models were used to analyze the pattern of rain infiltration into the slope under different conditions, the development of WF, and the effects of soil permeability and slope geometry on wetting front characteristics. Also, as a resulted wetting front was located, its influence on the slope stability was analyzed. Research results indicate that the geometry of the slope is more important in considering the Factor of Safety (FOS). Also, in a slope with low permeability, the infiltration process takes more time, and the wetting front formation or changes in the ground water table cannot be observed. However, for a slope with a high soil permeability value (higher than rain intensity), the factor of safety is affected to trigger the slope failure, and changes of the ground water table by the wetting front can be easily observed.