Quantification of joint roughness using various empirical relations between JRC and roughness parameters

Abstract

The mechanical and hydraulic properties of rock joints are significantly controlled by the joint surface roughness at low normal stresses. For this reason, it is necessary to accurately quantify joint roughness. The Joint Roughness Coefficient (JRC) has been widely used in engineering practice to quantify joint roughness and to estimate discontinuity shear strength over the years. However, several researchers have pointed out drawbacks of the JRC. This study presents a review of various attempts that have been made over the years to improve JRC and reduce its subjectivity. In addition, various empirical equations that are available in the literature between JRC and roughness parameters at 0.5 mm sampling interval have been assessed and compared using some widely accepted roughness parameters including the root mean square of the slope of the profile, Z 2 , structure function, SF, the maximum apparent dip angle in the shear direction/an empirical roughness parameter + 1, θ*Max/[C+1] 2D , and the standard deviation of the inclination angle of the profile, SD θ P . Using a one-meter square joint surface digitized at 0.5 mm sampling interval, over 1715 joint profiles in the X direction and 1,515 joint profiles in the Y direction have been used to calculate JRC values through the aforementioned roughness parameters and empirical equations at joint lengths of 1000 mm, 500 mm, 250 mm and 125 mm, and the roughness anisotropy has been studied. New empirical relations have also been suggested in this study between JRC and four roughness parameters based on Barton’s ten standard profiles digitized at 0.5 mm. The suggested empirical relations were successfully used to quantify the roughness of the studied rock joint surface.