DDA SIMULATION OF MOBILITY OF DAGUANGBAO LANDSLIDE WITH FRICTIONALLY WEAKENED SLIDING BED

Daguangbao landslide is the largest landslide triggered by Wenchuan earthquake. How did it reach high speed and long-runout?This question attracted wide attentions of scholars at home and abroad. This paper aims the explanation for the mechanism of high-speed and long-runout and adopts the velocity-depending frictional weakening of sliding bed due to thermal decomposition and dynamic crystallization. This paper modifies the input manner of the strength parameter in the Discontinuous deformation analysis(DDA)method. The constant strength parameter in original DDA is replaced by the velocity-depending strength parameter. The paper realizes the dynamic adjustment of the friction coefficient with the change of relative velocity between two blocks on a contact. The modified DDA is used to simulate the mobility of Daguangbao landslide. The results show that the mechanism of frictional weakening can be an important reason for the characteristic of high-speed and long-runout of Daguangbao landslide. Comparing to the original DDA,the mobility characteristics of high-speed and long-runout landslides can be simulated more reasonably by the modified DDA,where the frictional weakening of the sliding bed can be implemented. Daguangbao landslide was instable during the earthquake. Due to the frictional weakening of sliding bed,more energy was converted into kinetic energy. After the high-speed sliding mass crossing the Huangdongzi valley,the sliding mass was blocked by the opposite Pingliangzi slope,and then the sliding mass stopped. Comparing with the original DDA results,the modified DDA′s simulation is in good agreement with the result from post-earthquake field investigation. It also indirectly proves that the friction coefficient of Daguangbao landslide may be reduced due to the thermal decomposition and powder lubrication caused by friction flash heating between dolomites,which may be an important reason for the high-speed characteristics of Daguangbao landslide.