Revealing degradation mechanisms of rock joint under freeze-thaw cycles using a modified joint roughness coefficient-joint wall compressive strength model

In cold-region rock mass engineering, freeze-thaw cycles can substantially deteriorate the mechanical properties of rock joints, consequently jeopardizing the overall stability of the rock mass. To address this issue, this study systematically investigates the shear mechanical behavior of rock joints subjected to freeze-thaw cycles. Furthermore, a modified joint roughness coefficient (JRC)-joint wall compressive strength (JCS) model tailored for freeze-thaw environments is established to elucidate the evolutionary laws and regulating mechanisms of peak shear strength. The results indicate that: (1) Freeze-thaw cycling causes a progressive degradation in the matching degree between the upper and lower blocks of the specimen. Meanwhile, the JRC remains relatively stable with only minor fluctuations within a narrow range, and the basic friction angle ( ) exhibits a steady increasing trend. (2) Freeze-thaw cycling induces progressive degradation of the shear resistance of rock joints, characterized by a sustained reduction in peak shear strength and an expansion of the shear failure zone. (3) An increase in normal stress significantly enhances peak shear strength while enabling a transition in the failure mode from a dispersed pattern to localized continuity. (4) The modified JRC-JCS model demonstrates exceptional agreement with experimental measurements ( R 2 >0.9), thereby verifying its reliability and elucidating JCS as the primary governing factor for the continuous degradation of peak shear strength. This study extends the applicability of the JRC-JCS model to freeze-thaw environments, offering a theoretical foundation for the stability analysis of rock engineering in cold regions.