Seepage and slope stability modelling of rainfall-induced slope failures in topographic hollows

Abstract

This study focuses on topographic hollows, their flow direction and flow accumulation characteristics, and highlights discharge of hillslope seepage so as to understand porewater pressure development phenomena in relation with slope failure in topographic hollows. For this purpose, a small catchment in Niihama city of Shikoku Island in western Japan, with a record of seven slope failures triggered by typhoon-caused heavy rainfall on 19À20 October 2004, was selected. After extensive fieldwork and computation of hydro-mechanical parameters in unsaturated and saturated conditions through a series of laboratory experiments, seepage and slope stability modellings of these slope failures were done in GeoStudio environment using the precipitation data of 19À20 October 2004. The results of seepage modelling showed that the porewater pressure was rapid transient in silty sand, and the maximum porewater pressure measured in an area close to the base of topographic hollows was found to be higher with bigger topographic hollows. Furthermore, a threshold relationship between the topographic hollow area and maximum porewater pressure in this study indicates that a topographic hollow of 1000 sq. m area can develop maximum porewater pressure of 1.253 kPa. However, the porewater pressures required to initiate slope instability in the upper part of the topographic hollows is relatively smaller than those in the lower part of the topographic hollows.

Understanding shallow landslides in Campos do Jordão municipality – Brazil: disentangling the anthropic effects from natural causes in the disaster of 2000

“…Another slope stability model is the modular software package GeoStudio (2012), in which SEEP/W and SLOPE/W plugins are used to simulate the instability of slopes during extreme rainfall events. Although GEO-SLOPE is a simplified "single slope" model, it has been used in several previous studies to understand the effect of infiltration on rainfall-induced landslides (for instance Ng and Shi, 1998;Gasmo et al, 2000;Kim et al, 2004;Huat et al, 2006;Oh and Vanapalli, 2010;Acharya et al, 2016), producing very good results (Tofani et al, 2006).…”

Forecasting Landslides via Three-Dimensional Discrete Element Modeling: Helong Landslide Case Study

“…The buoyant effect and saturated shear strength could also be considered and incorporated in the calculation of FOS, which is based on statics. However, the effect of rainfall on the slope stability is much more complicated [34][35][36][37], especially for unsaturated soil. Dynamic processes, such as seepage and the variation in pore water pressure from rainfall, affect the slope stability.…”

Understanding shallow landslides in Campos do Jordão Municipality – Brazil: disentangle the anthropic effects from natural causes in the disaster of 2000

“…Several previous studies have studied the effect of infiltration on rainfall-induced landslides using those plugins (for instance Ng and Shi, 1998;Gasmo et al, 2000;Kim et al, 2004;Huat et al, 2006;Oh and Vanapalli, 2010;Acharya et al, 2016). In this study, the versatility of GeoStudio (2012) for handling boundary conditions allowed to simulate several scenarios involving natural conditions and anthropic factors separately.…”