THE PUSACUN ROCKAVALANCHE ON AUGUST 28, 2017 IN ZHANGJIA-WAN NAYONGXIAN, GUIZHOU: CHARACTERISTICS AND FAILURE MECHANISM

A large scale of mountain rock avalanche occurred in Pusa village, Zhangjiawan town, Nayong county, Guizhou Province at about 10:30 on August 28, 2017. The rock mass with the volume of 49.1×10⁴ m³ moved down and scraped the original loose deposits and finally formed deposits of 82.3×10⁴ m³, which destroyed parts of Pusa village, resulted in the death of 26 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and ground based synthetic aperture radar(GBSAR)monitoring and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the rock avalanche. The preliminary study suggested that the rock masses of the source area were shattered due to the underground mining activities. The shattered rock masses suffered long-term effects of gravity, which eventually resulted the failure of the rock masses. The movement of the rock avalanche lasted for 7 minutes and 21 seconds in which the main rock masses failure lasted for only 26 seconds with the long runout of 788 m and the maximum speed of 43.83 m·s^-1, belonging to typical high speed and long runout rock avalanche. There will be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of rock masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China.