摘要:
常用抗落石冲击被动柔性防护网防护能级和国内标准检验能级均不高于5000kJ，而山区桥梁等重要交通基础设施面临更高冲击能级落石灾害的威胁，本文采用数值仿真方法开展8000kJ能级被动柔性防护网的抗落石冲击分析与设计工作。首先基于显式动力学有限元软件ANSYS/LS-DYNA对典型被动柔性防护网单环和三环环链拉伸试验、网片顶破试验以及2000kJ能级落石冲击足尺防护网试验进行数值仿真复现，通过与网环最大破断力、破断位移和破坏特征、落石冲击全过程以及防护网钢丝绳内力时程等试验数据对比，充分验证了所采用数值仿真方法的可靠性。进一步分析了钢柱倾角、跨距、高度以及消能装置规格等参数对落石冲击下防护网动力行为的影响。结果表明：消能装置规格是控制防护网内力与位移的关键参数；钢柱倾角建议取10°；钢柱跨距增加会减小结构的面内刚度，而对横向锚固力影响较小；钢柱高度增加会显著提升柱底支反力；钢柱高度和跨距改变需同时合理调整各钢丝绳的锚固位置。最后，通过调整防护网几何尺寸、消能装置规格和添加横向辅助支撑绳等措施给出了两种8000kJ能级防护网设计方案，均通过EAD 340059-00-0106标准检验。
Abstract:
The protection level and domestic standard test level of commonly used passive flexible barrier against rockfall impact are not higher than 5000 kJ, while bridges in mountains and other important transportation infrastructures are facing rockfall disaster threat with higher impact energy level. The analysis and design of 8000kJ-level passive flexible barrier against rockfall impact were carried out at present based on the numerical simulation method. Firstly, by adopting the explicit dynamic software ANSYS/LS-DYNA, quasi-static tests including the tensile test on single wire ring and three-ring chain, net puncturing test, and the dynamic impact test, i.e., 2000 kJ rockfall impacting the full-scale passive flexible barrier, were numerically reproduced, and the reliability of the numerical simulation method was fully verified by comparing with the experimental data, i.e., the maximum breaking force and breaking displacement of the wire ring and its failure characteristics, the whole impact process of rockfall and the cable force-time history curves. The influencing factors, i.e., the inclining angle, span, height of the steel post, and different specifications of energy dissipating devices ranging from 50 kJ to 70 kJ on the dynamic behavior of the passive flexible barrier were further analyzed. The results showed that: the specification of energy dissipating device is the most critical parameter controlling the internal force and displacement of the passive flexible barrier; the inclining angle of the steel post is recommended to be taken as 10°; the increase of the post spacing can reduce the in-plane stiffness of the structure, while having less effect on the transverse anchorage; the increase of the post height will cause a significant increase in the support reaction force at the post bottom; the reasonable adjustment of the anchorage position of each wire rope is required when the post height and spacing are changed. Finally, based on the results of parameter analysis, two design schemes for passive flexible barrier against 8000 kJ rockfall impact were given by adjusting the geometry of the structure, the specification of the energy dissipating device, and the addition of transmission support ropes, and both of them passed the test of the European standard EAD 340059-00-0106.
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