LAUSR

In this paper, a number of artificial rock specimens with two parallel (stepped and coplanar) non-persistent joints were subjected to direct shearing. The effects of bridge length (L), bridge angle (γ), joint roughness coefficient (JRC) and normal stress (σn) on shear strength and cracking process of non-persistent jointed rock were studied extensively. The experimental program was designed based on Taguchi method, and the validity of the resulting data was assessed using analysis of variance. The results revealed that σn and γ have the maximum and minimum effects on shear strength, respectively. Also, increase in L from 10 to 60 mm led to decrease in shear strength where high level of JRC profile and σn led to the initiation of tensile cracks due to asperity interlocking. Such tensile cracks are known as “interlocking cracks” which normally initiate from the asperity and then propagate toward the specimen boundaries. Finally, the cracking process of specimens was classified into three categories, namely tensile cracking, shear cracking and combination of tension and shear or mixed mode tensile–shear cracking.