Evolution of forces and deformations of flexible protective net system of a high slope under rockfall impacts
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摘要: 柔性防护网作为高边坡落石灾害的主要防护手段，具有施工快速、安装便捷、防护能力突出等优点。以某高速公路改扩建工程为实例，基于离散元方法，对柔性防护网、边坡及落石进行数值仿真建模，并对高边坡落石冲击防护网的全过程进行模拟，探究了落石从崩落到冲击防护网过程的运动轨迹和速度变化规律，并详细分析了落石冲击防护网过程的动力学响应。研究结果表明：柔性防护网通过耗能器逐步吸收落石动能，可以大幅降低落石速度，并有效拦截高速落石；落石冲击被动防护网时，有两个变形峰值区，对应落石首次冲击和落石从防护网中段落至底部的二次冲击，最大形变量发生在首次冲击；防护网锚绳受力分析表明，不同位置的锚绳受力不同，受冲击位置影响较大。本研究证实了柔性防护网在应对高边坡落石灾害中的关键作用，为高边坡落石防护提供了理论依据和实践指导。Abstract: Flexible protective nets are the primary means of protection against rockfall disasters on high slopes, characterized by rapid construction, easy installation, and outstanding protective capabilities. This paper takes a highway reconstruction project as an example and employs the discrete element method to numerically simulate the flexible protective net, slope, and falling rocks, simulating the entire process of high slope rockfall impacting the protective net. The study investigates the motion trajectory and velocity change patterns of rocks from detachment to impact with the protective net and provides a detailed analysis of the dynamic response during the rock impact on the protective net. The results show that flexible protective nets can significantly reduce the velocity of falling rocks and effectively intercept high-speed rocks by gradually absorbing their kinetic energy through energy dissipaters. The research finds that there are two deformation peak areas when rocks impact the passive protective net, corresponding to the first impact and the second impact when the rock falls from the net to the bottom. The maximum deformation occurs during the first impact. Analysis of the forces on the protective net’s anchor ropes indicates that the forces on anchor ropes at different positions vary, with significant influence from the impact location. This study confirms the key role of flexible protective nets in dealing with rockfall disasters on high slopes, providing important theoretical basis and practical guidance for high slope protection.
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Key words:
- discrete element simulation /
- rockfall protection /
- flexible protective net /
- high slope
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图 5 某高速公路改扩建工程典型边坡
Figure 5. Typical slope in a highway reconstruction and expansion project
图 9 防护网特征截面（A截面和B截面）及截面测点分布
Figure 9. Distribution of characteristic sections (section A and section B) and measurement points of the protective net
图 10 防护网特征截面及测点形变
Figure 10. Deformation of characteristic sections and measurement points of the protective net
图 11 防护网特征截面各测点应力时程曲线
Figure 11. Stress–time history curves of each measuring point on characteristic sections of the protective net
图 12 防护网各锚绳受力情况
Figure 12. Force conditions of each anchor cable in the protective net
表 1 防护网各部件接触模型参数表
Table 1. Contact model parameter table of each component of protective net
模型 参数类型 参数名称/单位 取值 落石 基本参数 颗粒半径/m 0.63 颗粒密度/(kg·m−3) 2500 时间步长/s 0.0001 线性接触模型 法向刚度/(kN·m−1) 5.0×103 切向刚度/(kN·m−1) 5.0×103 摩擦系数 0.3 防护网网面及锚绳 基本参数 颗粒半径/m 0.03 颗粒密度/(kg·m−3) 2000 摩擦系数 0.5 平行黏结模型 线性有效模量/MPa 5 黏结法向刚度/(kN·m−1) 4.8×105 黏结抗拉刚度/(kN·m−1) 4.8×105 黏聚力/MPa 31 耗能器 三阶段激活力/kN 0，50，80 各阶段刚度/(kN·m−1) 2.0×106
1.3×105
3.2×105边坡 线性接触参数 法向刚度/(kN·m−1) 5.0×103 切向刚度/(kN·m−1) 5.0×103 摩擦系数 0.3 
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