Dynamic Response Analysis of Passive Flexible Protection System under Impact of Rockfalls
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摘要: 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.Abstract: 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.
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Key words:
- protection system /
- explicit analysis /
- impact loads /
- dynamic response
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图 2 被动柔性防护体系及构件编号
Figure 2. Number diagram of passive flexible protection system and components
图 4 多块落石冲击被动柔性防护体系过程分解
Figure 4. Process decomposition of rockfalls impact passive flexible protection system
图 5 落石初始动能与防护网的最大位移之间的关系
Figure 5. Relationship between initial kinetic energy of rockfalls and maximum displacement of protective net
图 6 不同初始冲击动能下冲击力时程曲线
Figure 6. Impact time history curve under different initial impact kinetic energy
图 7 滚动状态下落石冲击被动柔性防护体系的能量时程曲线
Figure 7. Energy history curve of rockfalls impact passive flexible protection system in the rolling state
图 8 弹跳状态下落石冲击被动柔性防护体系的能量时程曲线
Figure 8. Energy history curve of rockfalls impact passive flexible protection system in the bouncing state
图 9 被动柔性防护体系部分部件能量与速度曲线
Figure 9. Relationship between energy and velocity of parts of passive flexible protection system
表 1 有限元模型中的材料特性
Table 1. Material characteristics in finite element models
材料 弹性模
量/GPa密度/
（kg•m−3）泊松比 屈服强
度/MPa落石 33 2 840 0.3 钢丝绳、支撑绳、拉锚绳 177 7 850 0.3 1 780 钢柱 206 7 850 0.3 235 
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表 2 防护网达到最大位移所需时间
Table 2. Time required for the protective net to reach maximum displacement
s 初始动能/kJ 运动模式 滚动 弹跳 500 0.132 0.133 600 0.123 0.122 700 0.117 0.120 750 0.117 0.120
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表 3 冲击速度与防护系统变形情况
Table 3. Relationship between impact velocity and deformation of protection system
冲击速度 变形情况 接近初始值 仅接触点附近发生网片滑移 下降值接近 10 m/s 钢柱发生明显摆动 接近 10 m/s 防护网与中间落石开始分离 接近 0 落石开始反弹
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