| At 2:28 p.m. on May 28, 2008, Ms8.0 earthquake occurred in Wenchuan Sichuan,Because of high magnitude, long duration, large energy release, seismic zero vulnerability of the geological environment, the earthkuake induced a large number of fallings,landslides and other secondary geological disasters,in the ological disasters,Da guang bao landslide lying in An County Sichuan province is the largest and most complex mechanism body of geological disasters. the volume of landslide is preliminarily estimated about at 742 million m3.Detailed geological mapping by field survey and qualitative analysis, The use of 3D discrete element software is to reach the role of slope dynamic numerical simulation of the whole process of reproduction, Obtain the following basic conclusions and the knowledge:(1) In the earthquake process Daguangbao massive landslide is the one-time production after the shattering for high speed movement, there is no large-scale secondary or several level collapse or failure phenomena;(2) Da guangbao landslide has typical and unique geological phenomenon:they are :①The main landslide body after its'movement 1.2km is not fully disintegrated;②The front sliding body of incomplete disintegration reached to thrust deformation, rock drumlin formation and anti-Alice Produced a strong extrusion shear fractures and raised tension fracture;③The south slope plane of vegetation within a certain height and the shallow soil are "missing",the reason of Deformation and failure are perfect unique;④The back slope of the north failure surface develope a number of tension fracture, many see pull trapped deep groove width, but the back slope of landslide back scarp is intact.(3) Landslide dynamic formation mechanism and the movement characteristics has the following characteristics and stages:①Stage of slope shatering cracking and loosing, slightly open cracks starts to appear and to continue to produce more deep cracks extended;②Posterior fracture surface,south skid surface and north side of failure surface break through the border,Rock in the bottom of Sliding bed were crushed, after the overlying heavy mountain and seismic vertical stress produce repeated tension and compression, As the high temperature generated by friction,the rack have become a near carbon-like particles;③Slope from the static friction to dynamic friction state changes, at the start of the process of constantly being accelerated, When the slope is accelerated over the threshold,Daguangbao slope overally produced shattering-sliding rupture;④During the process of the landslide High-speedly crossing huangdongzi valley,"Air-cushion effect"occurred;⑤High speed front-end landslide body strongly collides the face of the mountain,the rock collapse jet and are broken up debris flow ; the overall stiffness suddenly reduce,because of the process the middle and back rock of landslide body produce thrust deformation, the buffer reduction speed, successfully realize "soft landing" to maintain the overall integrity.(4)Numerical simulation results show that:①Landslide formation and sporting characteristics and qualitative analysis and field geological phenomenon are actually in good agreement;②the displacement,speed and acceleration dynamic response curves of changes are basicly consistent in morphological characteristics and the tendency, which has demonstrated that a one-time landslide occurred;③In high elevation and slope position of special terrain,the rock have strong dynamic response ,especially in thin ridge bar ends ,the responses are more obvious;④At the large terrain and high-elevation position acceleration amplification factor significantly increased, no significant amplification in the valley.
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