Experimental study on granite weathered crust landslides with different residual layer thicknesses under heavy rainfall

Abstract. Granite weathered crust exhibits a dual structure, which affects the pattern of damage on slopes. This study designed three kinds of slope models with residual layer thicknesses against the background of a landslide cluster in Mibei Village, Longchuan County, Guangdong Province. The hydrological response and deformation damage characteristics of granite weathered crust slopes under heavy rainfall conditions were analyzed and the disaster-causing mechanism of landslides was studied through physical model tests. The results show that the three types of slopes exhibit distinct disaster mechanisms. For the slope with a residual layer of 10 cm thickness, rainfall rapidly infiltrates the soil-rock interface, resulting in the formation of a temporary water table at the interface. The residual layer is rapidly saturated and is susceptible to overall flow-slip damage under seepage, with no obvious sliding surface. For the slope with a residual layer of 20 cm thickness, it takes a long time for rainfall to penetrate into the soil-rock interface. Rainwater gathered at the interface significantly reduces the shear strength of the residual soil. Slope tends to slide along the soil-rock interface at the slope toe under the traction and drag of water flow, which can result in sudden slide. For the slope with a residual layer of 10 cm thickness, no evidence of strong seepage is observed within the slope. The slope gradually slides along the wetting front under hydrostatic pressure and self-sliding force, with the circular arc sliding surface.