Quantitative hazard assessment of rockfall and optimization strategy for protection systems of the Huashiya cliff, southwest China

Abstract

Frequent rockfall events at the Huashiya cliff near the dam site of Jinsha Hydropower Station poses great threats to construction projects along the Jinsha River. In order to protect the construction area, a comprehensive analysis of rockfall hazard was carried out including field survey, numerical simulation, quantitative assessment and mitigation strategy. High resolution Digital Terrain Model (DTM) was created by Terrestrial Laser Scanning (TLS), then used for the identification of rockfall sources and simulation of rockfall run-out behaviours. Approximately 60 rockfall simulations were conducted to analyze the interaction between rockfall block and protection nets. Quantitative assessment of rockfall hazard was then made to visualize the distribution and hazard of rockfall. The difference between the 60 rockfall simulations was quantified through Rockfall Interception Ratio (RIR) and the Energy Ratio of Overflying Rockfall (EROR). By integrating RIR, EROR and cost, the performance of protection measures were quantitatively assessed. Then, an optimization strategy was proposed to improve the cost-efficiency of the protection system. At the end of this paper, some problems that can be encountered when creating DTM and hazard maps were discussed, and some advices for designing passive protection system were introduced.