Abstract
Rock joint surface roughness, which influences the shear resistance of joints, dictates the stability of rock blocks. However, there is a weakening effect on the shear behavior of a rock joint as it becomes “un-matching” caused by external factors, such as vibration due to nearby blasting, excavation or earthquake. This paper presents an experimental investigation of the shear behavior of artificial rock joints under different matching conditions by direct shear test, modeled by imposing varying magnitude of horizontal dislocation along the shear direction between the upper and lower rock blocks. The peak shear strength decreases with increasing dislocation. However, the effect of dislocation on peak shear strength becomes less pronounced as the normal stress increases. With increasing dislocation, the peak shear displacement increases; the shear stiffness decreases and gradually approaches a constant. The influence of dislocation on shear stiffness is more prominent under a higher applied normal stress. The results also show that the peak shear strength of matching joints is influenced mostly by shear velocity.
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Abbreviations
- \( {\text{Ave}} \) :
-
Average value
- \( d \) :
-
Horizontal dislocation between the upper and lower rock blocks (mm)
- \( E \) :
-
Young’s modulus (GPa)
- \( I \) :
-
Positive integer, I = 1, 2, 3
- \( {\text{JMC}} \) :
-
Joint matching coefficient
- \( {\text{JRC}} \) :
-
Joint roughness coefficient
- \( {\text{JRC}}_{\text{Ave}} \) :
-
JRC value of joint surface
- \( {\text{JRC}}_{\text{i}} \) :
-
JRC value obtained from the three researchers
- \( {\text{JRC}}_{\text{j}} \) :
-
JRC value of the j-th profile along the shear direction
- \( j \) :
-
Positive integer, j = 1, 2, 3,…, 9
- \( {\text{K}}_{\text{s}} \) :
-
Shear stiffness (MPa/mm)
- \( {\text{L}} \) :
-
Specimen length along the shear direction (mm)
- \( {\text{Max}} \) :
-
Maximum value
- \( {\text{Min}} \) :
-
Minimum value
- \( {\text{SD}} \) :
-
Standard deviation
- \( \tau_{\text{p}} \) :
-
Peak shear strength (MPa)
- \( \varphi_{\text{b}} \) :
-
Basic friction angle of rock joint (°)
- \( \sigma_{\text{c}} \) :
-
Uniaxial compressive strength of model material (MPa)
- \( \sigma_{\text{n}} \) :
-
Normal stress (MPa)
- \( \sigma_{\text{t}} \) :
-
Tensile strength of the model material (MPa)
- \( \upsilon \) :
-
Poisson’s ratio
- \( \rho \) :
-
Density (kg/m3)
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Acknowledgments
The first author gratefully acknowledges the support from the Natural Science Foundation of China under project 41402247, the National Basic Research Program of China (973 Program) under project 2014CB046904, the opening fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection under project SKLGP2014K018 and the 55th China Postdoctoral Science Foundation under project 2014M550407. The direct shear tests were performed by the first author (supported by the Natural Science Foundation of China under project 40972178) at the Tongji University during the period of studying for his PhD degree, and thanks are given to Prof. Caichu Xia. The first author wishes to thank Mr Yinglong Song for preparing the model specimens and assisting the direct shear tests. The first and fourth authors acknowledge the support by the Singapore Academic Research Fund Tier 1 Grant (RG112/14). The authors would also like to express their appreciation for the helpful comments and suggestions from an anonymous reviewer.
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Louis Ngai Yuen Wong was formerly with School of Civil and Environmental Engineering, Nanyang Technological University.
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Tang, Z.C., Huang, R.Q., Liu, Q.S. et al. Effect of contact state on the shear behavior of artificial rock joint. Bull Eng Geol Environ 75, 761–769 (2016). https://doi.org/10.1007/s10064-015-0776-z
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DOI: https://doi.org/10.1007/s10064-015-0776-z