Development of a new equation for joint roughness coefficient (JRC) with fractal dimension: a case study of Bakhtiary Dam site in Iran

The joint roughness has a significant effect on the shear behavior of rough joints, which control the shear strength of jointed rock mass. This index plays an important role in the mechanical and hydraulic properties of rock masses. There have been extensive studies in last a few decades. Joint roughness coefficient (JRC) and fractal dimension D are two well-studied and adopted parameters used in estimating the surface roughness of rock joints. This study proposed a new relation between JRC and D, and compared this relation with the previous studies by applying it on JRC profiles. This relation was also introduced into Barton’s empirical equation to assess the shear strength of rock joints, and its performance was estimated by applying it to more than 30 laboratory direct shear tests on natural rock joints from Bakhtiary Dam site. The advantage of this study, when compared to the previous works done by others, is using the results of more than 30 direct shear tests on natural rock joints for the evaluation of reliability of the proposed equation. Therefore, the new obtained relationship between JRC and D seems to capture well the roughness coefficient of natural rock joints.