Publication: Physical and numerical modelling of unsaturated slope stability behavior under the influence of rainfall
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Date
2022-10-01
Authors
Mohd Yusoff, Siti Aimi Nadia
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Abstract
Rainfall has been identified as one of the main causes of slope failures in areas where high annual rainfall is experienced. The prediction and mitigation of slope failure are consequently major challenges due to the complexity of the unsaturated behavior of soil subjected to heavy rainfall. The mechanism of slope failure and process, particularly within the soil movement and the behavior of pore water pressure during failure are poorly understood in the current knowledge. Therefore, it is important to characterize the hydraulic and mechanical properties of unsaturated soil with the appropriate apparatuses. The aim of this research is to study the effects of pore water pressure and to understand the initiation processes of rainfall-triggered landslide under heavy rainfall and eventually possible mass movements. The pore water pressure (PWP) and Volumetric water content (VMC) is considered as an important parameter in studying the behavior of landslide where the increase of PWP and VMC was resulting the loss of shear strength of the soil. Six laboratory testing and numerical analysis via Seep/W and Slope/W were carried out involving with three different rainfall intensity (40,60, and 80 mm/hr) and two different slope geomorphologies (40° and 60°) to investigate the responses of the slope. As soon as rainfall started, PWP of the soil quickly increased and reached the saturated condition where TSM4 and TSM3 recorded 0 to -0.1kPa during less than 1 hour of the rainfall event. Meanwhile for TSM1 and TSM2 for all cases shown that after rainfall started the maximum PWP recorded is in arrange -0.4 and -0.5 kPa. Meanwhile as predicted by Seep/w, the behavior of PWP and VMC shown a good agreement with the obtained results from the laboratory modelling. Most of the cases shown the translational failure pattern. In addition, the changes in the factor of safety shows that cases with 60°of slope and higher rainfall intensity (80 and 60mm/hr) shows the FOS below than 1. Finally, it is concluded that the rainfall intensity, duration of rainfall event, slope geomorphology and soil properties really effecting pore water pressure, slope stability, and mass movement.