Experimental study on crack formation in sandstone during crater blasting under high geological stress

Crater blasting is widely used for rock excavation. In deep rock engineering projects, blasting is done in a high stress environment. To study the effects of high geological stresses on rock blasting, crater blasting tests on sandstone using an exploding electric wire were conducted under three different static load conditions. The evolution of the strain fields and the propagation of cracks on the surfaces of samples were recorded and subsequently analysed by digital image correlation. The rock fracturing mechanisms are discussed. The experimental results indicate that (1) the areas of major principal strain on the sample surfaces are circular under conditions of no static stress and symmetric biaxial stress loads, but the strain area is elliptical under a uniaxial load; (2) after blasting, the static stress state changes the crack initiation mode, crack propagation, and the distribution of the cracks in the crack network; and (3) static stress can increase the size of the blasting crater.