Experimental study on crack propagation process of rock-concrete interface in hot-dry curing environment at different temperatures

The effect of hot-dry environment in the high-temperature geothermal tunnel increases the initial defects on the bonding surface of the shotcrete and surrounding rock, which intensifies the generation and development of interface cracks. In this context, a wedge splitting test is used to study the fracture performance of the rock-concrete interface in the hot-dry environment at different temperatures. Based on the digital image correlation test, the development law of interface cracks is observed, the determination method of interface crack size is introduced, and the evolution process of interfacial fracture process zone is analyzed. The results show that the peak loads and the interface fracture energies of the specimens under the hot-dry environment are significantly smaller than the standard curing environment, and decrease with the increase of temperature. In the standard curing environment, the cracks rapidly spread to the edge of the specimen near the peak load, while the cracks expand more slowly in the hot-dry environment. The opening displacement of interface crack is linearly distributed along the height of specimen, and its value is much larger than the sliding displacement. The maximum interface fracture process zone length in hot-dry environment is greater than that in standard curing environment.