Characteristics of rockfall trajectory and hazard assessment in western Hubei Province: A case study of the Wapo collapse area in Yuan’an County

Taking the Wapo collapse area in Yuan’an County as an example, a three-dimensional model was established by drone aerial photography, geological survey and field mapping. Based on Rockfall Analyst (RA) analysis software, a large number of three-dimensional rockfalls in the Wapo collapse area were studied. The motion path, height, energy and other factors in the space were simulated to explore the three-dimensional motion characteristics of rockfalls. The risk assessment of rockfalls in the collapsed area was carried out to guide the prevention and control of the rockfalls. The research results showed that the main failure form of the dangerous rock was the toppling, and it was in an under-stable state at present; the three-dimensional motion trajectory of the simulated rockfall basically coincided with the existing rockfall point which indicating the simulation results were in good agreement with the actual situation; The mode of motion of the rocks were collision, bounce and free fall. Rockfalls were mainly concentrated in the gullies and roads but a few rocks reached residential areas. Therefore, the roads, gullies and the right side of the collapse area were in high risk area; Dangerous rock mass and boulders removal and passive protective nets were adopt as the prevention engineering,two passive protection nets which were 5 m high and 3 m high respectively were set on the inner side of the road and below the slope, and a net with an impact resistance of 2 000 kJ could effectively intercept falling rocks.