Experimental study on shear fracture of rock with cylindrical specimens

Shear fracture properties of rock are of importance for structure design and safety assessment in rock engineering. Shear-box test is adopted to determine the Mode II fracture toughness KIIC of sandstone with cylindrical specimens. The experiment and calculation results show that both the tensile and shear stresses exist at the crack tip and the ratio of maximum shear stress to maximum tensile stress, τmax/σmax, is about 2∼9. The Mode II fracture toughness is about 2∼4 times to the Mode I fracture toughness, i.e. KIIC/KIC=2∼4. Compared with cube specimen, cylindrical specimen has the advantage of convenience sampling, which can guarantee the accuracy of the specimen in situ