Identification and numerical simulation analysis of unstable rock mass based on UAV tilt photography

Rockfall occurring on high and steep slopes is a major geological disaster in canyon area, which is characterized as high altitude distribution and strong emergency, seriously affecting the safety of project construction in the area.In this paper, the high altitude unstable rock mass at the entrance of Sangda Tunnel on the Yulin-Xinduqiao Expressway in western Sichuan Province was taken as an example.The 3D model and digital terrain model were generated based on the oblique photography technology.The geological and terrain spatial information of high-altitude unstable rock mass were obtained and the zoning evaluation as well as instability mode analysis were carried out.The motion process, motion trajectory and impact energy of unstable rock mass were simulated and analyzed through numerical simulation.The results indicated that the unstable rock mass in the research site could be divided into three zones, namely, strong developed zone, medium developed zone and high rock accumulation area.The failure types of rock mass were mainly split-dumping type and shear-slipping type.The unstable rock mass mainly moved down along the slope groove.The maximum velocity of particles was close to 40 m/s, which seriously threatened the highway structure below.The comprehensive analysis indicated that the zone II was affected least by high-altitude unstable rock mass and collapse of loose rock in the accumulation area, so it was suggested as a route scheme.The research results can provide references for identification and evaluation of high and steep collapse in the construction of highway and hydropower stations in canyons and mountainous areas.