Assessment of conventional methodologies for joint roughness coefficient determination

Abstract

A numerical description of rock joint toughness is necessary to model the pseudostatic and dynamic rock joint behavior. The commonly used measure of joint roughness in rock engineering practice is the joint roughness coefficient (JRC), proposed by Barton and adopted by the International Society for Rock Mechanics. Barton and Choubey proposed an estimation method for determining JRC by visually matching joint surface profiles with ten standard profiles whose JRC ranges from 0 to 20. This approach is highly subjective and may introduce large estimation errors for the shear strength of rock joints, especially when the normal stress is low. To minimize this subjectivity, three alternate methods have been proposed for the estimation of JRC. One involves the use of an average deviation from the centerline about which roughness is measured, another uses the theory of fractal geometry, and the third uses the tilt test on rock joints as proposed by Barton and Choubey. In this paper, several methods are evaluated to determine their appropriateness for use in the assessment of the behavior of Apache Leap tuff joints by comparing the JRC values estimated using these methods to the JRC values back-calculated from laboratory direct shear test results. (A) This paper was presented at the 34th U.S. Symposium on rock mechanics, 27-30 June 1993, University of Wisconsin-Madison. For the covering abstract see IRRD 863389.