Comprehensive analysis of hazardous rock mass and simulation of potential rockfall processes using 3D terrain model: A case studyof the high cut slope near damsite of a hydropower stationin southern China

The steep slopes on both sides of the hydropower station in the southwestern mountainous region develop a multitude of dangerous rock formations. The rolling, collapsing and falling of these hazardous rocks have profound implications on the normal operation of the dam, main buildings, factories, roadways, and slope support systems. At present, the prediction and protection measures against rockfall disasters are predominantly reply on the two-dimensional Rockfall method, which ignores the spatial geometry of these dangerous rocks. In reality, falling rockfalls exhibit three-dimensional motion, and their threat zone extends throughout a three-dimensional geographical space. In view of this, this study is based on the hazard assessment results of the hidden danger investigation in a specific hydropower station of Yunnan Province. It employs field investigations, airborne LiDAR remote sensing measurement technology, and unmanned aerial vehicle (UAV) oblique photography technology to obtain high-precision laser radar point cloud data for the study area. This data is used to constrct detailed rock mass models and authentic three-dimensional scene models. The analysis includes historical rockfall distribution characteristics, rock mass structural characteristics, characteristics of hazardous rock masses in collapse source areas, and unstable modes. Furthermore, the study utilizes Unity3D three-dimensional rockfall analysis methods to simulate the motion characteristics of dangerous falling rocks after collapse. This enables the determination of the trajectory of dangerous falling rocks, as well as parameters such as bounce height, impact energy, and rolling area at different locations. The results indicate that for the right bank dangerous rock area of the hydropower station, a typical dangerous rock mass can achieve a maximum bounce height of up to 7.92 meters, with an impact range of approximately 145 meters. Most of these rocks roll towards the dam, which has multiple levels of passive protection nets and does not pose a threat to important facilities within the power plant. In the case of the right bank dangerous rock area two, after the collapse of dangerous rocks masses, the impact range of the falling rocks is approximately 120 meters, and some of the falling rocks may roll along the road embankment onto the road, potentially posing a threat to the main traffic artery. On the left bank, dangerous rock area one has a massive and unstable typical rock mass, with a maximum bounce height of up to 9.02 meters, ultimately falling into the reservoir storage area. Hazardous rock area two on the left bank has a dense distribution of hazardous rock masses, with a significant quantity, and after collapse, the impact range is approximately 380 meters. However, due to the dense vegetation cover on the slope, most of the falling rocks accumulate on the slope surface, posing a certain threat to pedestrians and vehicles. The related research results can provide valuable insights for the identification of hazardous rock masses and simulation of rockfall events in similar hydropower facilities.