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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 6 | Copyright
Nat. Hazards Earth Syst. Sci., 18, 1811-1823, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 29 Jun 2018

Research article | 29 Jun 2018

The effects of gravel cushion particle size and thickness on the coefficient of restitution in rockfall impacts

Chun Zhu1,2,3, Dongsheng Wang2,3, Xing Xia2,3, Zhigang Tao2,3, Manchao He1,2,3, and Chen Cao1 Chun Zhu et al.
  • 1College of Construction Engineering, Jilin University, Changchun 130026, China
  • 2State Key Laboratory for Geomechanics & Deep Underground Engineering, Beijing 100083, China
  • 3School of Mechanics and Civil Engineering, China University of Mining & Technology, Beijing 100083, China

Abstract. Gravel cushions are widely used to absorb the impact energy of falling rocks in open-pit mines. A particularly important application is to enhance the energy-absorbing capacity of rockfall sheds. In this paper, we study how varying the thickness and particle size of a gravel cushion influences its energy-consumption and buffering effects. We performed a series of laboratory drop tests by dropping blocks from a fixed height onto cushions of different thicknesses and particle sizes. The results indicate that, for a given impact energy, the cushion thickness has a strong influence on the measured coefficient of restitution (COR) and therefore impact pressure. Additional tests were performed to study how the radius of the block and the height it is dropped from affect the measured COR. This showed that as the movement height of the block is increased the COR also increases, and blocks with larger radii exhibit a larger variability in measured COR. Finally, we investigated the influence of rockfall block radius, r, movement height, H, cushion thickness, h, and particle size, d, on the COR and the damage depth, L, of the cushion. The test results reveal that the cushion thickness is the primary design parameter, controlling not only COR, but also the stability of the cushion material. The results provide a theoretical and practical basis for the design of gravel cushions for rockfall protection.

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Short summary
Gravel cushions are widely used for rockfall prevention in open-pit mines to absorb energy; the energy-consumption and buffer mechanism of different thicknesses and particle sizes of gravel cushions under the impact effects are studied. A series of laboratory tests for different cushions are conducted, combining the blocks' volume and drop height. It provides a theoretical and practical basis for the wide application of cushion design to control rockfall.
Gravel cushions are widely used for rockfall prevention in open-pit mines to absorb energy; the...