DEM investigation of rock/bolt mechanical behaviour in pull-out tests--颗粒学报PARTICUOLOGY

Che, N., Wang, H., & Jiang, M. (2020). DEM investigation of rock/bolt mechanical behaviour in pull-out tests. Particuology, 52, 10-27. https://doi.org/10.1016/j.partic.2019.12.006

DEM investigation of rock/bolt mechanical behaviour in pull-out tests

Na Che ^a, Huaning Wang ^{a b *}, Mingjing Jiang ^{b c}

a School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China
b State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
c Department of Civil Engineering, Tianjin University, Tianjin 300072, China

10.1016/j.partic.2019.12.006

Volume 52, October 2020, Pages 10-27

Received 11 September 2019, Revised 20 November 2019, Accepted 9 December 2019, Available online 3 February 2020, Version of Record 24 June 2020.

E-mail: wanghn@tongji.edu.cn

Highlights

• Bolt pull-out tests are performed using the distinct element method (DEM).

• Contact model considers bond size to capture the main rock mechanical behaviour.

• The minimum sample width and height values are taken into account.

• Influence of bolt embedment length and confining pressure on mechanical behaviours is studied.

• Influence of bolt–grout interface bond strength on peak load and failure mode is discussed.

Abstract

Rock bolt anchorage performance is crucial for tunnel support safety. We investigate the mechanical behaviour of reinforced rock and the bolts that reinforce it from the micro-scale to the macro-scale. Bolt pull-out tests were performed on soft rock using the distinct element method, in which a new contact model that considers bond size, is employed to constrain the main rock mechanical behaviour. The minimum sample width and height values for which the boundary effect can be neglected are first proposed through numerous tests on the influence of sample size on peak load and bond breakage. The influence of sample width is substantially greater than that of sample height. We then select an appropriate sample size to study the influence of bolt embedment length and confining pressure on the mechanical behaviours of the rock and bolt. The results show that increased rock bolt embedment length and confining pressure can increase the peak load; however, the bolt length effect is limited when exceeding the critical anchorage length. In cases without confining pressure, bond breakage occurs in the rock around the grout-rock interface and the breakage zone is rectangular, whereas in cases under confining pressure, the breakage zone presents an inverted cone shape. We use our results to discuss the influence of bond strength at the bolt–grout interface on the peak load and failure mode. The failure mode changes gradually from complex failure to single failure along the bolt–grout interface with decreasing interfacial bond strength.

Graphical abstract

Keywords

Pull-out test; Rock bolt; Distinct element method; Bolt embedment length; Confining pressure

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