Combined Tension-Shear Experimental Study of Rock Failure

Abstract

This paper deals with experimental study of rock failure under combined tension-shear condition. Combined tension-shear stress state was achieved using self-developed apparatus. Tension-shear tests were conducted on brittle granite sample to investigate the characteristics of tension-shear failure. The failure criterion for whole stress state was obtained, a modified Mohr-Coulomb criterion, with consideration of tension-shear stress state, was proposed by analyzing the experimental results. The obtained failure envelope presents continuous double-lined variation, with relatively steeper slope in tension-shear zone. To quantitatively characterize failure surfaces under tension-shear conditions, fractal dimension (FD) was introduced to represent the roughness of failure surfaces, the technique of scanning electron microscopy (SEM) and 3D laser scanning technique were utilized to observe failure surfaces morphology. Analytical results suggested the variation of FD values calculated from the two methods coincide with each other, and that the roughness of failure surfaces increase with tensile stress. Different from the situation in compression-shear stress condition, under combined tension-shear stress condition, when applying a constant tensile load, the strength decreases with the increment of shearing rates.