Failure probability simulation of passive protection net for collapses and rockfalls in typical karst area

Guizhou Province is located in Southwest of China, with many mountains and hills, and is a typical karst topography and geomorphology area with frequent geological disasters such as collapses and landslides. The existing dangerous rock mass in the Xiaotunyan collapse zone in Sinan County has large range and volume, and fissures, concave cavities, and solution caves have developed. Objective In order to study the failure probability of passive protection nets for rockfalls in typical karst areas. Methods A three-dimensional model of the collapse zone through high-precision realistic modeling technology was constructed, by which the movement process of collapsed falling rocks was simulated. According to the results of the field investigation, aerial photography of the unmanned aerial vehicle and numerical simulation, an appropriate rockfall location layout for the passive protection net was selected. And based on the identification of the rockfall particle size, the different rockfall particle sizes were selected to simulate the interception effect of the passive protection net, then the failure probability of the passive protective net can be calculated. Results The results show that the rockfall breakthrough rates of 13 particle sizes vary: the interception effect of small to medium sized falling rocks with particle sizes ranging from 0.25 m to 2.25 m is effective, but the interception rate of passive protection net cannot reach 100%. When the particle size is larger than 2.25 m, the passive protection net fails, that is the upper limit of the design of the passive protection net under the Xiaotunyan collapse zone is the 2.25 m particle size of rockfall. According to the calculation, the failure probability of all rockfall particle sizes intercepted by the passive protection net is less than 5%, which is within the acceptable scope. Conclusion The research results provide a reference for rockfall protection measures in the Xiaotunyan collapse zone and are of great significance for the protection of life and property safety for people in karst mountainous areas.