Study on the Effect of Loading Method on Mechanical Behavior of Rockbolt Based on DEM Modeling
Publication: International Journal of Geomechanics
Volume 22, Issue 7
Abstract
Fully grouted rockbolt is a form of reinforcement commonly used in underground projects. Its mechanical behavior is of vital importance to enhancing the stability of surrounding rock masses. To investigate the effect of different loading methods on the mechanical behaviors of rockbolt, the distinct element code PFC2D was adopted to simulate the pullout test on rockbolt and a compression test on the bolted rock mass, with Hongtoushan Copper Mine as the engineering background. The stress distribution along rockbolt and the maximum pullout capacity were analyzed. The results indicated that the loading method has significant effects on the mechanical behaviors of rockbolt. In the pullout test, the peak stress in the rockbolt always occurs near the free face. As the rock mass is a passive load-bearing component, the cracks and weak intercalations in the rock mass have little effect on the mechanical behaviors of the rockbolt. Meanwhile, as the external load acts directly on the outer end of rockbolt, the effect of the bearing plate cannot be reflected. However, in the compression test on the bolted rock mass, the peak stress in the rockbolt gradually transfers to greater depth. The existence of cracks and weak intercalations have an impact on the mechanical behaviors of the rockbolt. In addition, with increasing size of the bearing plate, the maximum pullout capacity of the rockbolt gradually increases. Comparison of the simulation results showed that the maximum pullout capacity obtained by the pullout test on a rockbolt is higher than that obtained by the compression test on a bolted rock mass. Therefore, appropriate reduction of the maximum pullout capacity obtained by the pullout test is suggested for rockbolt design, and the reduction factor should be in the range of 0.7–0.8.
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Acknowledgments
This research was supported by the Guangdong Basic and Applied Basic Research Foundation of China (2020A1515011398).
Notation
The following symbols are used in this paper:
- A
- area of the measuring circle;
- Ft
- pullout capacity of rockbolt;
- Fy
- resultant force of the contact forces between particles within the measuring circle in the y-direction (axial direction of the rockbolt);
- σy
- average stress in the y-direction within the measuring circle;
- l
- rockbolt length; and
- Φ
- rockbolt diameter.
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Published In
International Journal of Geomechanics
Volume 22 • Issue 7 • July 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Aug 16, 2021
Accepted: Feb 8, 2022
Published online: May 10, 2022
Published in print: Jul 1, 2022
Discussion open until: Oct 10, 2022
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