Effects of drought preceding rainfall on slaking-induced slope instability

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This study investigates the effects of wetting and drying on the strength and deformation characteristics of mudstone, known as slaking. When rainfall-induced landslides occur, the intensity-duration of precipitation is often examined, but the drought conditions preceding the landslide-inducing rainfalls are not usually considered. The author proposed a hypothesis that such drought and rainfall cycles would accelerate slaking on the geo-materials. First, we undertook to collect landslide data from various sources in order to identify slaking-induced landslides. Second, a series of direct shear tests was conducted by simulating cyclic drying and wetting (D/W) under different stress condition. Considerable creep deformations on crushed mudstones were found during both D/W phase, and a gradual decrease of friction angle was observed with the increasing number of D/W. Higher slaking index, lower water content before wetting and lower initial density accelerate the slaking of geo-materials.