Transient Analysis of Slope Stability Responding to Rain Infiltration Based on Poroelasticity Theory

Abstract

Landslide is a natural geomorphic erosion process on hillslopes and can be threat to people's life and property This paper aims to investigate shallow landslide triggering on hillslopes response to rainfalls We discuss the mechanism of water movement advancing through an unsaturated soil profile during rainfall by hillslopes hydrology monitoring in the Rivendell study site and propose a hydrologic response function combining the analysis of slope stability to clarify how does rainfall trigger landslide Instrumental records of soil moisture dynamics show very fast response to rain infiltration that suggests pressure wave propagation predominates leading to the release of old soil water downward into deep zones before new infiltrating water arrival Based on poroelsticity theory we propose two reference time tk and tep that can represent the arriving time at a certain depth of wave propagation and dissipation respectively Form ground surface to a depth of 1 m tk has ten-fold differences under nearly unsaturated conditions for diverse soil properties; however no significant variations in tk can be observed under nearly saturated conditions which just varies from 0 sec to 5 sec Values of tep for coarse sand is much greater but decreases to the smallest one (within 1 day) than those for other soil properties under a nearly saturated condition Results indicates that transient pore pressure transmission is mainly dominated by dynamic wave propagation but the effect of dissipation could become more important with increase in water saturation Analysis of slope stability for hypothetical sandy and silty soils with the function of pressure head evolution induced by rain infiltration derived from poroelasticity theory indicate that positive pressure heads concentrates on soil bedrock boundary leading to the generation of shear zone at this boundary Slope failures always occur with positive pressure heads Results also show that soil properties play an important role on shallow landsliding triggered by rainfall Use of those response function in conjunction with topographic data soil properties rainfall intensity and duration information and an infinite-slope failure criterion can evaluate the timing and depth of shallow rainfall-triggered landslide hereby refining hazard prevention and mitigation

Date of Award	2017 Mar 13
Original language	English
Supervisor	Chyan-Deng Jan (Supervisor)