Collapse Mode and Mechanism of High Magmatite Rock Slope in Wenchuan Epicentral Area

Wenchuan earthquake of magnitude of 8.0 triggered a large amount of rock slope collapse. In Yingxiu, many high magmatite rock slopes collapsed when Wenchuan earthquake struck, which resulted in huge damage. So it is urgent to study the collapse mechanism. This study takes Laohuzui collapse, a typical high slope collapse located at Yingxiu, the Wenchuan earthquake epicenter, as the object of this research. The engineering geological condition was investigated and the physical and mechanical parameters of rockmass and structural plane was determined. With the stereographic projection method using the discontinuity network simulation results, the basic failure modes of the slope was obtained, which is dual-plane sliding mainly due to the interconnected three group joints. Re-establishing the Laohuzui high slope model before earthquake, the process of dynamic response on the rock slope under earthquake was simulated by using 2DUDEC, and the destruction and collapse mechanism was analyzed. The main conclusion is that the Laohuzui slope collapse is a progressive failure. At first, the tensile failure took place in the slope toe, then the slope top would be subject to tensile failure followed by the front surface failure along the cut-through plane by three group joints, which resulted in the whole slope collapse. The slinging failure took place at the slope top under the seismic and gravity action condition.