Dangerous Rockfall Protection Technology Research on High Slopes of Large-Scale Underground Cavern Group Outlets of a Hydropower Station

Abstract

In the construction of hydropower projects in southwestern China, the powerhouse, diversion tunnel, tailrace tunnel, access tunnel, and other structures are often located underground in cavern groups. The high slopes of the outlets of these large cavern groups are often characterized by steep terrain, high elevation, and frequent rockfalls, which seriously threaten the safety of construction and operation personnel. Therefore, it is urgent to carry out research on protection technology for dangerous rockfalls on underground excavation outlet slopes. In this paper, Uncrewed Aerial Vehicle (UAV) survey technology is applied. First, large-scale three-dimensional (3D) terrain data is collected by a UAV, then a Digital Orthophoto Map (DOM) and Digital Elevation Model (DEM) of the slope are obtained, and a 3D visualization is constructed. Meanwhile, an orthophoto image for detailed UAV route planning is generated. Second, according to the 3D visualization, a preliminary judgment of potentially dangerous rockfall areas is made by the engineers, and the UAV track planning for these areas is carried out. Third, refined low-altitude aerial photography is carried out on the dangerous areas according to the results of the UAV trajectory planning, and high-precision pictures are obtained. Based on the rock joints, fissures, and configurations displayed in these pictures, the areas with the most likely rockfall risks are further determined. Finally, 3D rockfall simulation software is used for rockfall simulation analysis. Comparing the rockfall interception rates and the distribution probability of rockfalls in each area under different protective net schemes, the final protective net plan is determined. The research results are applied to the design of a dangerous rockfall protection scheme on a natural slope at the outlet of a large underground hydropower station on the Dadu River, which provide a scientific basis for the setting of the protective net. The researches results can be used as reference for similar projects and provide a new idea for the design of dangerous rockfall protection measures on high slope tunnel outlets.