An estimation model for the fragmentation properties of brittle rock block due to the impacts against an obstruction An estimation model for the fragmentation properties of brittle rock block due to the impacts against an obstruction

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Vol14 No.6: 1161-1173

Title】An estimation model for the fragmentation properties of brittle rock block due to the impacts against an obstruction

Author】HOU Tian-xing1; XU Qiang2; XIE Hong-qiang3; XU Nu-wen3; ZHOU Jia-wen1*

Addresses】1 State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China; 2 State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China; 3 College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China

Corresponding author】jwzhou@scu.edu.cn

Citation】Hou TX, Xu Q, Xie HQ, et al. (2017) An estimation model for the fragmentation properties of brittle rock block due to the impacts against an obstruction. Journal of Mountain Science 14(6). DOI: 10.1007/s11629-017-4398-8

DOI】10.1007/s11629-017-4398-8

Abstract】Mountain hazards with large masses of rock blocks in motion – such as rock falls, avalanches and landslides – threaten human lives and structures. Dynamic fragmentation is a common phenomenon during the movement process of rock blocks in rock avalanche, due to the high velocity and impacts against obstructions. In view of the energy consumption theory for brittle rock fragmentation proposed by Bond, which relates energy to size reduction, a theoretical model is proposed to estimate the average fragment size for a moving rock block when it impacts against an obstruction. Then, different forms of motion are studied, with various drop heights and slope angles for the moving rock block. The calculated results reveal that the average fragment size decreases as the drop height increases, whether for free-fall or for a sliding or rolling rock block, and the decline in size is rapid for low heights and slow for increasing heights in the corresponding curves. Moreover, the average fragment size also decreases as the slope angle increases for a sliding rock block. In addition, a rolling rock block has a higher degree of fragmentation than a sliding rock block, even for the same slope angle and block volume. Finally, to compare with others' results, the approximate number of fragments is estimated for each calculated example, and the results show that the proposed model is applicable to a relatively isotropic moving rock block.

Keywords】Rock block; Rock fragmentation; Rock movement process; Crushing work ratio; Average fragment size.