Damage Characteristics of Limestone under Freeze-Thaw Cycle for Tunnels in Seasonal Frozen Areas

Frost heave failure often occurs after the completion of tunnels in seasonal frozen areas. The safe operation of tunnels is impacted by freeze-thaw-damaged surrounding rocks. Therefore, the deterioration mechanism of surrounding rocks during a freeze-thaw cycle in a seasonally frozen area is of great significance for tunnel stability analysis. This study investigates the physical and mechanical characteristics of Houwai tunnel limestone samples after freeze-thaw cycles. Testing was conducted using freeze-thaw cycle tests, which yielded variations in the mass, longitudinal wave velocity, and uniaxial compressive strength of rock samples subjected to freeze-thaw cycles. A rock damage model of the Houwai tunnel was established based on the existing rock damage model combined with the parameters before and after freezing and thawing of the Houwai tunnel limestone after seasonal freeze in the Jilin Province. The relationship between the total damage variable and the strain of limestone was obtained under the freeze-thaw cycle, and the damage deterioration mechanism of the limestone was examined after the freeze-thaw cycle. The mechanical characterization of the deterioration damage of the surrounding rock predicted using the deterioration damage model is of great significance for the determination of freeze-thaw damage and prevention and control of freezing damage in tunnel engineering in seasonally frozen areas. The study on the damage characteristics of limestone in the study area can lay a foundation for the freeze-thaw failure mechanism of tunnels in seasonal frozen area.