Experimental study on the shear mechanical behaviour of rock-like materials containing one embedded flaw under unloading normal stress conditions

Abstract

It is difficult to cut internal defects, and capture the initiation and propagation of internal defects by direct observation in actual rocks. This article presents a new method to create internal defect samples by volatilisation of camphor. Then, in order to better understand the influence of unloading normal stress on shear mechanical behaviour, laboratory tests are carried out on rock-like samples containing one embedded penny shape flaw with constant shear stress and unloading normal stress under different stress paths and shear directions conditions. The failure pattern and fracture morphologies of rock-like samples with different shear paths, flaw inclination and shear direction are analyzed. The strength and deformation behaviour are investigated also. Results show that the degree of fracture surface of direct shear tests and linear normal unloading shear tests are smaller than that of the complex normal unloading shear tests. The normal unloading amount determines the failure mode of rock-like samples. The failure pattern transforms from tensile failure to shear failure when the normal unloading amount gradually decreases. Although normal unloading deformation plays an important role in rock failure, shear deformation has little effect on fracture mode.