Pre-treatment influence of liquid nitrogen and microwave on the mode I fracture characteristics of granite

Microwave and liquid nitrogen have shown great potential applications in the mining, geological, petroleum, and particularly metal mining fields. In order to further promote their application in rock tunneling engineering, this paper conducted a series of I-model fracture tests on hard rock (granite) to explore the impact of liquid nitrogen, microwave, and liquid nitrogen and microwave pretreatment on the fracture characteristics of hard rock. The results showed that compared with the control group, all pretreatment groups had varying degrees of reduction in wave speed and fracture toughness, especially the microwave and liquid nitrogen group.