Laboratory study on the influencing factors and their control for the coefficient of restitution during rockfall impacts
Laboratory study on the influencing factors and their control for the coefficient of restitution during rockfall impacts
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DOI：
10.1007/s10346-019-01183-x
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发表时间：
2019-10
期刊：
影响因子：
6.7
通讯作者：
Z. Ji;Zhi-Jian Chen;Q. Niu;Tianxiao Wang;Hao Song;Tingjian Wang
中科院分区：
文献类型：
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作者：
Z. Ji;Zhi-Jian Chen;Q. Niu;Tianxiao Wang;Hao Song;Tingjian Wang
目前关于崩塌恢复系数的研究存在不同的观点，这些争论的根源在于崩塌灾害研究中对真实的冲击过程的还原程度不同。在前人研究成果的基础上，综合确定了影响COR的6个主要控制因素。本文通过实验研究了主要控制因素对COR的影响，利用专门设计的落石喷射器模拟了真实的落石冲击过程，得到了主要控制因素与COR的关系，并通过理论推导进行了验证。利用提出的碰撞接触点与质心投影的偏差理论，合理地解释了块体形状对COR值的影响。综合考虑表面积分布特征指标与具有正常COR（Rn）的几何形状之间的关系，提出了一种新的块体形状量化指标，形状因子的引入，表明分类与Rn具有显著的线性相关性。在落石冲击试验中，垂直冲击（VI）的COR值及其随冲击角的变化趋势并不等同于IH（斜向冲击）或II（斜向冲击）。COR值与撞击角并不完全呈线性关系，运动学COR（Rv）、切向COR（Rt）和Rn均随撞击角的增大而减小，并呈幂函数关系。块体的转速（ω）随Rt的增大而线性增大; ω和形状对Rn的影响是相伴的，非圆形块体的ω并不总是与Rn正相关，当ω较小时，可能与Rn正相关。回弹过程受多个影响因素综合控制，为后续研究多因素交互作用下的COR提供了必要的基础。
Different opinions exist in the current research on the COR (coefficient of restitution) of rockfall, and these controversies can be attributed to the difference in the reduction degree of the real impact process during research on rockfall disasters. According to the previous research results, six main controlling factors affecting the COR were comprehensively determined. In this paper, experiments about the effects of the main controlling factors on the COR were conducted; a specially designed rockfall ejector was able to simulate the real rockfall impact process, from which the correlations between the main controlling factors and COR were obtained and then validated by theoretical derivation. By means of the proposed deviation theory between the impact contact point and the projection of mass center, the effects of the block shape on COR values were reasonably explicated. Synthetically, considering the relationships between the characteristic index of surface area distribution and the geometry with normal COR (Rn), a new index for quantifying the block shape, i.e.,shape factor, was introduced, which shows a significant linear correlation of classification withRn. Not equated to IH (inclined impact on a horizontal slope) or II (inclined impact on an inclined slope) in impact experiments of rockfall, the COR values of VI (vertical impact on an incline slope) and its evolving trend with impact angle are varied. COR values are not linearly related to the impact angle completely; kinematic COR (Rv), tangential COR (Rt), andRndecrease with the increase of the impact angle and exhibit the power functions. The rotational speed (ω) of the block linearly increases with the increase ofRt; the effects ofωand shape onRnare concomitant, and theωof the non-round-shaped block is not always positively correlated withRn, which may be the opposite whenωis small. The bouncing process is synthetically controlled by multiple influencing factors, and this research will provide an essential foundation for the follow-up study on the COR affected by multiple factors of interaction.