Study on the Effect of Negative Temperature Change on the Fracture Morphology of Granite under Impact

Abstract

SHPB test system was used to conduct dynamic impact experiments on frozen granite under different negative temperatures. The fracture surface of granite under impact load was found via scanning electron microscope (SEM). The micromorphological characteristics of rock fracture under negative temperature are analyzed to explore the influence of negative temperature on the rock fracture morphology, and a practicable explanation is given for the mechanical property changes of rock under different temperatures. Research results showed that low temperatures (<-20°C) caused “frostbite” in granite, leading to a sharp decrease in the rock dynamic mechanical strength under a high strain. Fracture morphology analysis indicated that the lower negative temperatures resulted in the formation of cracks among the mineral particles in the granite. These cracks have poor plastic deformation ability and are easy to destabilize and expand under a high strain rate. Moreover, the coupling effect of impact and negative temperature will cause the cleavage of some crystalline minerals, eventually resulting in the low-stress brittle failure of granite. It is considered that the nucleation of cracks in negative temperature rock under impact load is mainly caused by crystal deformation, which can be divided into three types: the nucleation of cracks resulted from elastic incompatibility between the grains, the nucleation of cracks caused by interface slip, and the nucleation of cracks caused by plastic deformation in crystalline solid.