STUDY ON THE MECHANISM OF INITIAL DEPARTURE WITH HIGH-SPEED OF XINMO ROCKSLIDE, MAOXIAN, SICHUAN

On June 24,2017,a large rockslide occurred in Xinmo Village,Maoxian County,Sichuan Province. In approximate 2 minutes,the rockslide traveled with more than 2500 m horizontally. The field investigation indicates that the kinetic process of the Xinmo rockslide was divided into four stages: the initiation of ejection,flying,scraping,stopping and accumulating. To investigate the possible initiation mechanism,we carried out a physical model test. Monitoring data of rockslide acceleration showed that the sliding body was subjected to a shaking force in the direction normal to the rupture surface,and the value of acceleration was up to 0.94g when the locked segment is broken. The failure behaviours show that the strong vibration effects triggered by the release of strain energy at the same instant within the brittle locked segment. and a shaking force played an important role in the initial stage of Xinmo rockslide. Under the dynamic model,the rockslide ejected along the 15.5° direction to the horizontal plane. Considering the strong vibration effects,the software Rockfall was used to simulate and analyze the motion characteristics of the sliding rock by assuming a variety of initial velocities(at 0,10 20,30,40 and 50 m ·s^-1). It is observed that the rock avalanches arrived at the opposite side of the Songping gully,when the values of initial velocity were larger than 30 m ·s^-1. Furthermore,we estimated the total duration of the main sliding process and the mean value of the velocity of the mobile rock mass. The estimation results are about 60 s and 45 m ·s^-1,respectively.