A New Method to Estimate the Joint Roughness Coefficient by Back Calculation of Shear Strength

Abstract

The joint roughness coefficient (JRC) is an important factor affecting the shear properties of rock joints, and its accurate estimation is a challenging task in rock engineering. Existing JRC evaluation approaches such as the empirical comparison method and the statistical parameter method have some unresolved defects. In this study, a new method is proposed for JRC estimation to overcome the deficiencies of existing approaches based on back calculation of shear strength. First, the 10 standard roughness joints are established in numerical rock samples generated by the bonded particle method (BPM). Secondly, the microscopic parameters of the intact rock and joints are calibrated, and a series of direct shear tests of joint samples are carried out under different normal stresses. Finally, the empirical relationships between shear strength and JRC are proposed under high correlation conditions. The results show that the modified smooth joint model (MSJM) is proved to better simulate the mechanical properties of rough joints than the smooth joint model (SJM). When the shear strength of target joint is substituted in the corresponding relationship, the JRC of joint along the shear direction can be conveniently obtained. In addition, the JRC values of 10 standard roughness joint profiles under shear direction of from right to left (FRTL) are obtained. By estimating the JRC of 9 target joints in the literature, it can be seen that the new method proposed in this paper can well reflect the directionality of roughness and it is convenient to apply.

An Investigation on Local Shearing Mechanisms of Irregular Dentate Rock Joints Using the PFC

“…Obviously, this procedure ignored the effect of the protrusion size on overall roughness. The distribution law of the external force borne by the joint protrusion was rarely mentioned in the existing literature, and there was no quantitative result for reference [34][35][36]. Moreover, the size of joint protrusion in rough joints is difficult to be clearly simulated, which leads to poor correlation of corresponding analysis results [37].…”

Study on Evolution Mechanism of Structure-Type Rockburst: Insights from Discrete Element Modeling

“…However, the study related to the effect of the structural plane roughness on the rockburst is still limited. Moreover, the results from previous studies showed that the shear strength increased with the increase in friction coefficient µ in the SJM [56,57], and the joint roughness coefficient (JCR) was positively correlated with the shear strength [58].…”

Suggested New Statistical Parameter for Estimating Joint Roughness Coefficient considering the Shear Direction

“…e average horizontal length of 10 standard roughness joint profiles was about 99 mm. According to the processing idea of Zheng and Qi [25] and Huan et al [35], the horizontal length of the 10 joint profiles Surface height (y) Figure 2: e diagram used to define geometric coordinates of a joint profile [12]. Advances in Civil Engineering was assumed to be 100 mm, and the JRC values of them were assumed to be unchanged.…”

“…In addition, the shear direction of rock joints periodically reversed under cyclic shear conditions. e shear strength values are usually not equal, although the joint morphology does not change much before the last shearing process [32][33][34][35]. In the JRC-JCS model proposed by Barton [10], JCS, normal stress, and basic friction angle are all parameters without direction property.…”