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| Study on the initiation mechanism of bedding rock landslide under seismic load |
| ZHAO Yuanping1，XU Ming1，2，LIU Xianshan1，2，LUO Bin3 |
| (1. School of Civil Engineering，Chongqing University，Chongqing 400045，China；2. National Joint Engineering Research Center of Geologic Hazards Prevention in the Reservoir Areas，Chongqing 400045，China；3. China Merchants Chongqing Communications Technology Research Design Institute Co.，Ltd.，Chongqing 400067，China) |
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Abstract To seek the initiation mechanism of bedding rock landslide under seismic load，the geometry and stress conditions of landslide′s initial crack propagation are analyzed and the calculating formula of the most dangerous initial crack angle is deduced by theory of fracture mechanics. Furthermore，based on completely cut-through of landslide′s back fault zone，the starting speed of landslide under the composite effect of elastic impulse，peak-residual strength drop and wave oscillation is derived. The results prove that if initial crack angle starts to break along the secondary joint structural plane，the initial crack of landslides whose dip angle of secondary joint′s structural plane is 39.5°will crack more easily；the landslide′s initiation has experienced a process of cumulative fracture of initial crack，cut-through of landslide′s back fault zone，instantaneous fracture of the locking segment，release of elastic impulse strain energy and peak-residual strength drop strain energy into starting kinetic energy of the slip mass，further accelerated by wave oscillation，and finally being thrown from landslide shear outlet. Based on the analysis of the Qingchuan Donghekou landslide happened in the 5?12 Wenchuan Earthquake，it is concluded that the starting speed of landslide is significantly affected by the elastic impulse effect and decisively controlled by the height of elastic impulse area′s slices and length of locking segment under instantaneous fracture of locking segment，if the internal relationship between height of the slices and length of the locking segment is not considered，the upper limit of landslide′s starting speed will be 12.5 m/s when energy conversion rate reaches 100%.
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2021, Vol. 40 
