Direct shear tests of artificial jointed rock specimens with parallel joints

Abstract

The shear behavior of artificial jointed rock samples with parallel joints is studied using direct shear tests. The effects of the number (N) of parallel joints, the angle (β) between the parallel joints and the horizontal loading direction, and the length (l) of the parallel joints on the shear characteristics and the damage morphologies of artificial jointed rock specimens were studied. The test results indicate that (1) under forward shearing (β 90°), the entire shear process of parallel joints can be mainly represented by the following stages: the linear elastic stage, the crack initiation and expansion stage of the intermittent joints, the fracture and failure stage of the rock bridges, the frictional sliding stage of the fractured section, and the residual friction stage of the fractured section. The frictional sliding force of the fractured section under reverse shearing is less than that under forward shearing. (2) When l = 20 mm and β is fixed (15° < β < 165°), as N increases from 2 to 5, the total lengths of the rock bridges between the joints increase, the coalescence path of the cracks increases, the frictional sliding force between the crack surfaces increases, and the shear strength and cohesion c of the specimen increase. (3) When N = 2 and β is fixed (15° < β < 165°), as l increases from 20 to 50 mm, both shear strength and cohesion c of the specimen increase.