Abstract: Taking the typical rainfall-induced landslides in the pilot test area of the Pearl River-Xijiang Economic Belt as the research object, we carried out three sets of physical model test on the whole process of rainfall-induced landslides by introducing the hydrodynamic similarity principle and taking the Weber number criterion as the rainfall similarity criterion. By analyzing the response law of slope to rainfall infiltration, the influence of infiltration process on slope deformation, the slope failure process and failure modes, we preliminarily obtained the formation mechanism of rainfall-induced landslide and the characteristics of disastrous rainfall in South China. (1) The high porosity caused by strong weathering of shallow rock and soil is the material basis of rainfall-induced landslides in the test area. The dissipation of matric suction of unsaturated rock and soil is the essential cause of rainfall-induced landslides in the test area. The specific matric potential (water content) distribution after rainfall infiltration lays the condition for rainfall-induced landslides. (2) The cumulative rainfall needed for totally weathered granite landslide disaster induced by rainfall is smaller than that of strongly weathered clastic rock landslide, but the sliding influence range of strongly weathered clastic rock landslide is larger than that of fully weathered granite landslide. (3) The cumulative rainfall required for landslide disaster induced by heavy rainfall is smaller than that induced by intermittent rainfall. Heavy rainfall is more likely to induce landslide, and the induced landslides are larger in scale.

Key words: rainfall, landslide, model test, fully and strongly weathered, unsaturated