Study On Dynamic Responses And Failure Mechanism Of Steep Bedding Rock Slope Triggered By Strong Earthquake

Hundreds of earthquake collapse and landslide are triggered by"5.12"Wenchuan earthquake with its powerful of hazard -formative force, in Chaping town,An xian country. Ganmofang Landslide is a typical steep bedding rock landslide, which lies at the right bank of Jinxi river in the area of Qianfo mountains, and triggered by Wenchuan earthqua ke too. This text take Ganmofang Landslide as an example, study on dynamic responses and failure mechanism of steep bedding rock slope under the action of strong earthquake. Based on the conclusion of the engineering geological conditions of the landslide researched area, this paper summarizes basic characteristics factors, structural characteristics and signs of deformation and failure of landslide, and analyzes formation mechanism of the landslide. Using numerical simulation and large shaking table test to analyse the acceleration dynamic response, the dynamic soil pressure, and the evolution trend of plastic zone of the steep bedding rock slope. Finally, the dynamic failure process of Ganmofang landslide discussed in details used by three-dimensional discrete element numerical simulation software 3DEC. Though above the research summary, several main conclusions as follow:(1) When the Wenchuan earthquake occurred, the slope destroied induced by a long duration of strong earthquake force, and formed landslide. The main sliding direction of Ganmofang landslide is about 80°, the overall volume of landslide is approximately 8.2×10⁵m³, the relative elevation of the landslide is about 190～210m. Landslide occurred in the strongly weathered bedrock of Qiujiahe Group Simian-upper Paleozoic (Z_bq). The main lithology is Siliceous Slate, Carbon Shale and Siliceous Shale, and the strata occurrence is N10°W/NE∠51°. The geological formation movement produced two groups of structural planes. (2) After Ganmofang landslide instability, the landslide boundaries shall be clearly visible. A large and thick accumulation platform was formed in the landslide mid-lower. Many tensile cracks and trapped trough developed on the accumulation platform. Numerous of slip scratches which approximate the landslide sliding direction were also seen on the slide bed. Many groups of tensile cracks perpendicular to the slid direction of landslide are discovered on the platform of landslide rear edge.(3) On the basis of field investigation, formation mechanism of Ganmofang landslide was analyzed:①the slope shattering-cracking and relaxed induced by strong earthquake, joint fissures opened and run through;②with the rock stratum broken off, and the rock mass of landslide bottom hunched and bulged, potential slide surface was formed which combined with fracture plane in bottom rock mass and run through joint;③then in the end, the slope overall shattering-slided by the bedding plane.(4) Through large-scale shaking table model test, several conclusions as follow:①The horizontal and vertical acceleration significantly amplified on elevation, and dynamic response of acceleration amplification factor (PGA) shows increasing in the trend of nonlinear;②The amplification of vertical acceleration is more significant than the horizontal acceleration;③At the same level of elevation, and nearly in the slope surface range, magnifying effect on slope surface is more significant than it inside.④As the input seismic amplitude increases for model, the peak of the dynamic soil pressure occurs on the slope shoulder, then appears in the middle of the slope. Finally, before the model destructed, the peak of the dynamic soil pressure appears at the foot of the slope.(5) The result of acceleration dynamic response of numerical model simulation in accordance with that of large-scale shaking table model test. Plastic yield zone model slope correlates closely to seismic waves. First, tensile-failure of plastic yield zone appeared at the top of the model slope; then, shear-failure of the plastic yield zone occoured at the bottom of slope; plastic yield zone has connected though the modle slope body at the end, and model slope entirely destroyed.(6) Based on the discussed above, discussed the dynamic failure process of Ganmofang landslide in details used by three-dimensional discrete element numerical simulation software 3DEC. The landslide gradually developed from deformation stage to failure stages driven by the continuing seismic load. The resule of numerical simulation show that, slide surface was formed which combined with fracture plane in bottom rock mass and run through joint, a sliding surface was formed caused by the key rock broken, then in the end Ganmofang landslide shattered-slided with sliding-bending deformation along the bedding plane.