The Failure and River Blocking Mechanism of Large-Scale Anti-dip Rock Landslide Induced by Earthquake

Landslide and river blocking induced by earthquakes have occurred widely in nature. The topography and geological structure of slopes have a considerable influence on the geotechnical structure of the formed landslide dam. In the Hongshiyan valley (Niulan river, Yunnan province, China), a large-scale anti-dip rock landslide was triggered by Ludian earthquake in 2014 with more than 1.36 × 10⁷ m³ of displaced rock, which formed a barrier lake with an estimated volume of 2.6 × 10⁸ m³. In relation to this example, the whole process from triggering, failure, disintegration, to landslide dam formation blocking a river is simulated using the discrete element method (DEM). For this, a 3D DEM modeling methodology of the complex landslide is proposed that includes an inversion strategy which uses laboratory tests of rock samples from the landslide to obtain the numerical parameters for the DEM. Initial investigations indicate that the weak slope base is an important internal factor resulting in the failure of the slope. During the earthquake, this part of the slope is the first to disintegrate and flow out under the upper rock mass pressure. This exposes the upper rock mass to large domains of tensile stress that eventually leads to the failure and disintegration of the upper hard rock mass. The anti-dip bedding of the slope results in a landslide dam consisting of "fine particles at the lower elevations and coarse rock blocks deposit at the higher elevations". Our model also suggests that the triggering and failure mode of the landslide may mostly depend on the external factors (such as earthquake, rainfall, and river erosion and so on), while the subsequent dynamic process of the landslide and the engineering geological structure of the landslide dam mainly depend on the geological structure of the slope, sliding distance and topography of the valley.