Anisotropic Characteristics of Post Sheared Fracture Surface

Abstract

In this study, a novel servocontrolled direct shear test set-up is proposed for testing of both intact and jointed rocks, and direct shear tests under different conditions were applied on intact sandstone samples and artificial joint samples. A three-dimensional (3D) laser-scanning profilometer system was employed to detect fracture surfaces and obtain the data of point clouds. Also, the anisotropic characteristics of the fracture surfaces were discussed based on data in variograms. Results revealed that crack initiation and propagation were affected by normal stresses in terms of path and mode. Based on the morphology of sheared fracture surfaces, the processes of crack initiation and propagation during shear failures were investigated. Two parameters (C and a) in the variogram were employed to quantify the anisotropy of fracture surfaces: the sill (C) reflects the height of the fluctuation body in fracture surfaces and the range (a) reflects the single fluctuation body and its fluctuation frequency. Additionally, a novel peak shear strength criterion was developed based on anisotropy indexes and it exhibited improved accuracy. Hence, it is concluded that the proposed model is superior to various conventional models.