A quantitative optimization method for rockfall passive nets on high-steep slopes: case study of the Feishuiyan slope

Rockfall poses a formidable threat to the ongoing fast-paced construction of large-scale projects in uninhabited areas in high mountain valleys. In this study, an optimization method for arranging passive nets on high and steep slopes was presented to mitigate the threat from rockfalls. This method diverges from the conventional method of subjectively arranging passive nets along the perimeter of protected regions (due to its emphasis on cost considerations), in which the quantitative appraisal of rockfall movement characteristics and interception rates is frequently omitted, consequently failing to comprehensively ensure transportation routes and temporary construction sites. The methodology encompasses the acquisition of terrain data by unmanned aerial vehicles (UAVs), identification of rockfall sources based on UAV point clouds, quantitative assessment of rockfall hazards using a 3D probabilistic model, and optimization of the layout of passive nets based on the assessment results. The aim of the optimization of passive nets is to quantitatively assess the cost–effect relationship of passive nets, accounting for construction feasibility, interception potential, and likelihood of successful rockfall interception. We applied this method to the Feishuiyan slope in southwest China as an example, and the results demonstrated an enhanced interception rate of 99% and cost reduction by a factor of three relative to the original scheme. This innovative approach could enhance rockfall mitigation in high and steep areas, providing a viable strategy for future prevention efforts in these areas.