The Effect of Asperity Inclination and Orientation
on the Shear Behavior of Rock Joints

Ali Khosravi¹; Mohammad H. Sadaghiani²; Mohammad Khosravi³; Christopher L. Meehan⁴

¹Assistant Professor, Sharif University of Technology, Civil Engineering Department, Tehran, Iran
E-mail: khosravi@sharif.edu (corresponding author)
²Assistant Professor, Sharif University of Technology, Civil Engineering Department, Tehran, Iran
E-mail: mhsadagh@sharif.ac.edu
³Ph.D. Student, University of Delaware, Dept. of Civil and Environmental Engineering, 301 DuPont Hall, Newark, DE 19716, U.S.A.
E-mail: khosravi@udel.edu
⁴Bentley Systems Incorporated Chair of Civil Engineering & Associate Professor, University of Delaware, Dept. of Civil and Environmental Engineering,
301 DuPont Hall, Newark, DE 19716, U.S.A.
E-mail: cmeehan@udel.edu

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Geotechnical Testing Journal, 2013, Volume 36, Number 3, pp. 404-417

Abstract
This study investigates the effect of asperity inclination angle and asperity orientation on the shear behavior of rock joints under
constant normal loading conditions. The effects of these two rock joint characteristics were investigated by creating artificial rock joints having a regular pattern of triangular asperities that were oriented at different angles in the plane of shear. Large-scale direct shear tests were conducted over a range of normal stresses, on 0.30 x 0.30 m gypsum blocks containing well-mated joints with different asperity orientation and inclination angle characteristics. Experimental results illustrate the importance of considering both the asperity orientation with respect to the loading direction and the applied normal stress when predicting the shear behavior of rock joints. In general, higher normal stresses increased the stiffness of the rock joints in shearing, while a reduction in the shear strength of the rock joints was observed when increasing the asperity orientation angle. The dilation curves indicated the occurrence of both dilation and lateral displacement during shearing. Two different techniques are used to quantify the condition of the joint surfaces: the first approach utilizes the concept of fractal dimension, and the second utilizes the concept of potential contact area. These approaches can be applied in a useful fashion within the framework of existing shear failure criterion for oriented rock joints.

Keywords
Rock joint; Direct shear test; Asperity inclination angle; Asperity orientation angle; Fractal dimension

Reference
Khosravi, A., Sadaghiani, M. H., Khosravi, M., and Meehan, C. L. (2013). “The Effect of Asperity Inclination and Orientation on the Shear Behavior of Rock Joints.” Geotechnical Testing Journal, ASTM, 36(3), 404-417. (doi:10.1520/GTJ20120060)

DOI
10.1520/GTJ20120060