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Discussion papers | Copyright
https://doi.org/10.5194/nhess-2018-108
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 24 Apr 2018

Research article | 24 Apr 2018

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Natural Hazards and Earth System Sciences (NHESS).

Effects of the impact angle on the coefficient of restitution based on a medium-scale laboratory test

Yanhai Wang1, Wei Jiang1,2, Shengguo Cheng2, Pengcheng Song2, and Cong Mao2 Yanhai Wang et al.
  • 1Hubei Key Laboratory of Disaster Prevention and Mitigation (China Three Gorges University), Yichang, Hubei, 443002, People's Republic of China
  • 2Department of Civil, Structural, and Environmental Engineering, University at Buffalo, Buffalo, NY, 14260, USA

Abstract. The reliability of a computer program simulating rockfall trajectory depends on the ascertainment of reasonable values for the coefficients of restitution, which typically vary with the kinematic parameters and terrain conditions. The effects of the impact angle on the coefficients of restitution have been identified and studied using laboratory experiments. However, the laboratory tests performed to date have largely been limited to a small scale. This paper presents the results of a medium-scale laboratory test on the coefficients of restitution for spherical polyhedrons impacting concrete slabs. The specimens were made of natural limestone, and the motion trajectories were recorded by a 3D motion capture system. The normal coefficient of restitution Rn and the impact angle α are highly correlated. Comparisons between the results of existing tests and our experiments demonstrate that certain general rules regarding the effect of the impact angle hold regardless of the test scales and conditions. Increasing the impact angle will induce reductions in the values of Rn and the energy coefficient of restitution RE, whereas it will have a significant impact on the tangential coefficient of restitution Rt. A small impact angle will likely cause the rebound angle to exceed the impact angle, which typically causes a higher Rn and lower RE. This phenomenon leads to extreme scatter in the measured data under the conditions of a small impact angle and hinders the prediction of the rockfall trajectory.

Yanhai Wang et al.
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Short summary
Certain general rules about the effect of impact angle on coefficients of restitution in rockfall simulation hold regardless of the laboratory test scales and conditions. Increasing impact angle will induce reductions in Rn and RE, whereas it will have a trivial impact on Rt. A small impact angle will likely cause the rebound angle to exceed the impact angle, which usually causes a higher Rn and lower RE. This leads to extreme scatter results of restitution and hinders the trajectory prediction.
Certain general rules about the effect of impact angle on coefficients of restitution in...
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