ANALYSIS OF COLLAPSE EFFECT FACTORS AND FAILURE MECHANISM UNDER SEISMIC WAVE FUNCTION

The Wenchuan Earthquake triggered a large number of collapses,landslides and other secondary disasters which caused serious loss of life and property.Among them,the mountain collapse in the back of Panda Garden rearing sheds located in Wolong was a typical shock-triggered damage.Because the collapse region is relatively close to the focal point of the earthquake,the seismic action is a master external factor affecting collapse damage.The topography and rock mass structure are the most critical factors in the internal factors.Based on the field investigation and laboratory tests,the slope dynamic response characteristics is simulated using the calculation software of discrete element to obtain the collapse failure mechanism,advantage-shattering region and controlling factors.The simulation results are showed as follows: (1)the combined action of the tension,compression and shear which are caused by coupling of primary wave and secondary wave, is the direct driving force of the collapse damage.(2)in the early stage of seismic action,the first tensile failure generates in the group of tectonic joints with near steep dip angle and forms a wedge-shaped crack extending from the outside to the inside.Later stage,because the second tectonic group of joints and bedding plane trend to outside of slope,the collapse instability of the shattered and cracked rock blocks occurs in the ways of dumping and slippage outside.The slope looks like curved shape and produce overall instability.(3)Due to inertia effect of the earthquake,the collapse of the shattered and cracked rock in the surface starts with some initial velocity.This is one of the main reasons why earthquake-induced collapse has larger destructive influence scope.The prevention for the potential collapse damage of similar slope should be mainly based on reinforcement of steep structural plane,combining the strengthening of the slope shoulder support.