A new tool to quantify the failure probability of rockfall net fences

Rockfall is a high-energy natural hazard that poses significant threats to inhabited areas and infrastructure in mountainous regions. Rockfall net fences are widely used passive structural systems designed to mitigate this hazard by intercepting and stopping falling rocks through energy dissipation. Despite their widespread use, the design of these systems is not fully codified. Current European guidelines suggest ensuring that the system's capacity exceeds the expected load, expressed through unique values, but this approach neglects the system's failure probability. The authors propose a mathematical framework to compute the failure probability of rockfall net fences based on reliability considerations. This method accounts for all potential block volumes, recognizing that smaller blocks are more frequent. The framework provides design characteristics for a given failure probability or quantifies the failure probability of an existing net fence. The calculations use data on block velocity and trajectory from the site. Previously, this approach was limited to academia due to its complexity. The paper introduces a new tool that integrates with RocFall software, facilitating the reliability-based assessment of protection structures. This tool optimizes the design and performance of barriers, leading to better management of rockfall risks. Examples of applications demonstrate that this method can result in more informed management of hazardous areas, improving safety and effectiveness in mitigating rockfall hazards.