Studies on flexible rockfall barriers for failure modes, mechanisms and design strategies: a case study of Western China

A field investigation on the actual protective performance of a flexible rockfall barrier along a mountain road in western China is presented in this paper. The total area of the flexible rockfall barrier under investigation was approximately 20,000 m2. Five typical failure modes of the flexible rockfall barrier were revealed, including steel post buckling, connection failure, ring net destruction, steel cable rope breakage and anchorage point failure. In addition, component rusting, which leads to decrease in durability, was noted. Furthermore, failure mechanisms were analysed, and the main factors that were found to induce flexible rockfall barrier failure included the sliding capacity of the cable ropes at the end post support positions, the boundary conditions of the steel posts and the compatibility between the energy dissipating devices and connected cable ropes. From these observations, corresponding design strategies were proposed. In addition, an improved flexible rockfall barrier system was constructed, and its effectiveness was verified by a full-scale impact test using 5000 kJ of impact energy. Finally, the impact deflection, impact force, cable force and energy dissipation of the improved flexible rockfall barrier system were studied in combination with a non-linear numerical simulation which could be a useful tool for design of flexible barrier systems.