Experimental Method for Direct Shear Tests of Hard Rock under Both Normal Stress and Lateral Stress

Shear failure is a typical failure mode of rock masses in underground engineering. Conducting shear tests of rocks in the laboratory is an effective research method. In this paper, a shear box is presented that can be used for the direct shear test of hard rocks under three-dimensional stress conditions with a true triaxial compression testing apparatus. The new normal linear variable differential transformer (LVDT) sensor fixture is used to make the obtained normal deformation data more accurate. The lateral deformation measurement adopts a U-shaped sensor design, which solves the problem of the lateral deformation measurement. Under different lateral stresses, a series of direct shear tests were conducted on the sandstone specimens, and the test results verify the reliability and practicability of the novel laboratory shear box. With the increase of lateral stress, the peak shear strength and peak normal displacement of the sandstone specimens also increase, and the lateral deformation is restrained. The lateral splitting block can be effectively reduced by applying lateral stress.