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Effect of joint microcharacteristics on macroshear behavior of single-bolted rock joints by the numerical modelling with PFC

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Abstract

Joint properties play a controlling role in the strength of rock mass. In response to the situation that existing researches on bolting mechanism of bolted rock joints principally concentrate on the macroelements, such as rock properties, bolting angle and joint morphology, the direct shear tests on unbolted and single-bolted rock joints under the conditions of different normal stress and different joint microproperties by numerical calculation method of particle flow (PFC) were carried out in this paper to reveal the microbolting mechanism and study the influences of joint properties. Subsequently, a comprehensive comparison of microfailure characteristics between unbolted and single-bolted rock joint demonstrated that during the shearing process, a triangle extrusion reinforcement area emerges around the bolt, where microcracks are extremely developed and rock blocks are considerably fractured, but it also improves the anti-shearing efficacy of rock joint. Meanwhile, both the macroshear behavior and microfailure characteristics of single-bolted rock joints with different joint microproperties was analyzed by comparing the shear stress–shear displacement curves and crack development. Specifically, the shear stiffness of single-bolted rock joints enhances with the increase of joint tangential stiffness, and the augmentation of joint tangential stiffness or friction coefficient intensifies the shearing resistance of single-bolted rock joints, whereas the joint normal stiffness was proven to share a negative correlation with the shear strength of single-bolted rock joints. Besides, the shear stiffness of single-bolted rock joints decreases approximately linearly with the increasing joint thickness. In addition, the thicker the joint, the lower the peak shear stress of single-bolted rock joints. With the increase of joint thickness, the crack number of single-bolted rock joint failure decreases, and the particle confinement of bolt is enhanced.

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Data availability

The data used to support the findings of this study are available from the corresponding author upon request.

Abbreviations

τ :

Shear stress, MPa

u :

Shear displacement, mm

σ :

Compressive stress, MPa

ε :

Compressive strain

UCS:

Uniaxial compressive strength, MPa

c :

Rock cohesion, MPa

φ :

Rock internal friction angle, °

E :

Elasticity modulus, MPa

Sj_kn:

Joint normal stiffness, GPa

Sj_ks:

Joint tangential stiffness, GPa

Sj_μ :

Joint friction coefficient

Sj_d w :

Joint thickness, mm

σ n :

Normal stress, MPa

τ p :

Peak shear stress, MPa

τ s :

Shear stiffness, MPa/m

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Acknowledgements

The anonymous reviewers are gratefully acknowledged for his valuable comments on the manuscript.

Funding

This paper gets its funding from project (51774322) supported by National Natural Science Foundation of China; Project (2018JJ2500) supported by Hunan Provincial Natural Science Foundation of China; Scientific research innovation project for graduate students of Central South University (2019zzts303). The authors wish to acknowledge these supports.

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Correspondence to Hang Lin.

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Chen, Y., Lin, H., Xie, S. et al. Effect of joint microcharacteristics on macroshear behavior of single-bolted rock joints by the numerical modelling with PFC. Environ Earth Sci 81, 276 (2022). https://doi.org/10.1007/s12665-022-10411-y

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  • DOI: https://doi.org/10.1007/s12665-022-10411-y

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