Investigations on mechanical behaviors and failure mechanisms of rock-concrete composite specimens with different interface inclinations subjected to freeze-thaw cycles and uniaxial compression

Abstract

The purpose of this study is to investigate how long-term freeze–thaw (F-T) cycles affect the failure mechanisms of rock-lining structures in tunnels of chilly areas. F-T cycling and uniaxial compressive strength (UCS) tests are conducted on rock-concrete composite specimens with varying interface angles (0°, 30°, 45°, 60°, and 90°) under 0, 4, 8, and 16F-T cycling. The classification and evolution of cracks during the uniaxial failure process of the composite specimens are explored using PFC2D, which is the novelty of this study. The experiment results are as follows: The F-T cycles will primarily generate tensile-type frost heave cracks, and the sensitivity to crack initiation increases with the cycles. The failure mechanism of the specimens is influenced by both the interface inclination angles and the F-T cycling. For the same interface angle, the crack initiation stress of specimens steadily decreases as the number of F-T cycles increases, while the percentage of shear cracks among all cracks gradually increases. Within the same F-T stage, the crack initiation stress decreases with increasing interface angles ranging from 0° to 60°, and the percentage of shear cracks relative to all cracks gradually rises. However, a sudden increase in crack initiation stress occurs at an angle of 90°.