Initiation mechanism and quantitative mass movement analysis of the 2019 Shuicheng catastrophic landslide

The Shuicheng landslide is a typical failure occurred in the slope deposits that has a close correlation with the antecedent rainfall. By using field investigation, laboratory tests and numerical simulations, the initiation mechanism was analyzed and the mass movement characteristic was quantitatively assessed. The numerical results indicated that the rainfall infiltration decreased the shear resistance of the slope and increased pore water pressure and soil weight, resulting in large deformation of the slope and gradual deterioration of its stability. After saturated, as the pore water pressure coefficient (ru) approached to 0.3, the overall safety factor dropped down to 1, and the failure eventually occurred. Quantitative mass assessment demonstrated that the unique terrain aggravated the erosion and entrainment effect, the inclusion of loose material and water promoted the moving state of the debris avalanche by transiting it into a fluidized state, resulting in a much larger landslide volume with a long runout distance. As a result, the volume of the failed mass which was calculated to be about 4.7×105 m3 at source area based on unmanned aerial vehicle (UAV) and terrestrial laser scanning (TLS) modeling techniques almost quadrupled eventually to more than 2.0×106 m3.