多落石冲击被动柔性防护体系的动力响应分析

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

应用有限元分析软件ANSYS/LS-DYNA对被动柔性防护体系在落石冲击作用下的变形和能量进行研究,采用ANSYS/LS-DYNA的显式分析方法,模拟了多块落石在不同运动模式下,其冲击荷载对被动柔性防护体系的动力响应,根据时程曲线,对比分析了多块落石在不同运动模式下的位移、冲击力、能量变化规律.分析结果表明:随着落石初始冲击动能的增加,防护网达到最大位移所需时间总体呈现减少趋势,且冲击时间在0.11~0.14 s之间;落石的最大冲击荷载出现在0.04~0.07 s,且随初始动能增加逐渐增大;在落石冲击过程中,被动柔性防护结构发生能量耗散,其中钢丝绳网在落石为滚动状态下的能量大于落石为弹跳状态下的能量,且钢柱在落石为滚动状态下的最大峰值能量大于落石在弹跳状态下的最大峰值能量;在钢丝绳网被冲破时落石在滚动状态下钢柱的能量发生急剧增大.

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.