Dynamic Response Analysis of Passive Flexible Protection System under Impact of Rockfalls

Finite element program ANSYS/LS-DYNA was applied to study the deformation and energy of passive flexible protection system under rockfalls impact. Using the ANSYS/LS-DYNA explicit analysis, dynamic responses of the passive flexible protection system to impact loads of rockfalls in different motion modes were simulated. According to the time history curves, the displacements, impact forces and energy change of rockfalls in different motion modes were contrasted. Results show that as the initial impact kinetic energy of rockfalls increases, the time required for the protective net to reach the maximum displacement decreases generally, and the impact time is between 0.11 s and 0.14 s. The maximum impact load of rockfalls occur at around 0.04−0.07 s, and increases with an increase in the initial kinetic energy. In the process of rockfall impact, energy dissipation occurs in the passive flexible protective structure, and the energy of steel wire mesh under rolling rocks is greater than that under bouncing rocks. Besides, the maximum peak energy of steel posts under rocks in the rolling state is greater than its counterpart under rocks in the bouncing state; the energy of steel posts increases sharply at the moment the steel wire mesh is broken under the impact of rolling rocks.