Occurrence conditions of the reverse rotation of rockfall and its influence on the restitution coefficient
Occurrence conditions of the reverse rotation of rockfall and its influence on the restitution coefficient
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DOI：
10.3389/feart.2023.1257187
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发表时间：
2023-09
影响因子：
2.9
通讯作者：
Z. Ji;Tingjian Wang;Fa-Quan Wu;Dong-Po Wang;Zhen-Hua Li
中科院分区：
文献类型：
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作者：
Z. Ji;Tingjian Wang;Fa-Quan Wu;Dong-Po Wang;Zhen-Hua Li
当落石沿密集岩坡发生时，落石的旋转方向并不总是下坡。具体而言，落石在一定条件下撞击后可能会获得反向旋转速度（RRS），其对恢复系数（RC）的影响不可忽视。根据前期实验得到的块体反向旋转（RR）现象的统计结果，RR的发生与块体形状、入射角和接触姿态有关。在本研究中，考虑到典型形状的立方体块，初步推导了RR的临界条件。根据结果，使用定制设备检查了 RRS 对四个典型形状块的 RC 的影响。结果表明，各区块的切向RC（Rt）值对RRS的变化不敏感，分布相对集中且数值较高。而且，正态RC（Rn）值对RRS不敏感，分布相对离散。 RRS影响Rn；然而，很难直接建立它们之间的关系。为此，考虑到块体的接触姿态和形状，提出了积分变量冲击系数（Ic）来确定RRS对Rn的影响。此外，还对块体的冲击弹跳行为进行了分类和分析。对于单次冲击后的块体回弹，当块体的质心（MC）位于接触点（CP）之前和之后时，Ic和Rn分别呈正相关和负相关。对于连续两次冲击后的块体回弹，随着 Ic 的增加，Rn 增加。这些结论有助于阐明RRS对RC的影响机制，为精确预测落石轨迹的程序开发和优化提供重要信息和思路。
When rockfall occurs along dense rock slopes, the rotation direction of rockfall is not always downhill. Specifically, the rockfall may obtain a reverse rotation speed (RRS) after impact under certain conditions, the effect of which on the restitution coefficient (RC) cannot be ignored. According to the statistical results of the reverse rotation (RR) phenomena of blocks obtained from previous experiments, the occurrence of RR is correlated to the block shape, incident angle, and contact attitude. In this study, considering a typically shaped cubic block, the critical condition for the RR is preliminarily deduced. Based on the results, the influence of the RRS on the RC for four typically shaped blocks is examined using a customized device. Results show that the tangential RC (Rt) values of each block are not sensitive to the change in the RRS, the distribution is relatively concentrated and the values are high. Moreover, the normal RC (Rn) values are not sensitive to the RRS, and the distribution is relatively discrete. The RRS influences Rn; however, it is difficult to directly establish the relationship between them. To this end, considering the contact attitude and shape of the block, an integral variable, the impact coefficient (Ic), is proposed to determine the influence of RRS on Rn. Moreover, the impact-bounce behaviours of the block are categorized and analysed. For the block rebound following a single impact, Ic and Rn are positively and negatively correlated when the mass centre of the block (MC) is in front and behind the contact point (CP), respectively. For the block rebound following two successive impacts, with the increase in Ic, the Rn increases. These conclusions help clarify the mechanism of the influence of the RRS on RC and provide vital information and ideas for the development and optimization of a program to accurately predict rockfall trajectories.