Stability deterioration and failure analysis of dangerous rock masses in cold regions under the influence of freeze-thaw cycles

Dangerous rock masses in cold regions subjected to repeated freeze–thaw cycles can cause progressive deterioration in structural planes and rock mechanical properties, which significantly reduces the overall stability and often triggers collapses or landslides. Existing studies focus mostly on single-scale or single-factor analyses but cannot fully capture the coupled mechanisms driving instability under freeze-thaw conditions. This study aimed to establish a theoretical framework to quantitatively characterize the evolution of rock mass stability, thereby providing a sound basis for hazard prediction and prevention. By integrating limit equilibrium theory with rock frost heave and circular hole expansion theory, mechanical models for sliding- and toppling-type dangerous rock masses were established. Three key factors were incorporated: frost heave forces acting on throughgoing structural planes, rock property deterioration in nonpenetrative sections, and progressive freezing depth development. A theoretical relationship between the stability coefficient and the number of freeze-thaw cycles was derived. By considering the Zimei Peaks rock masses in Gansu Province as the case study and conducting parametric analyses, the results revealed that the stability coefficient rapidly decreases during the initial cycles, followed by a slower decrease and eventual stabilization. The coefficient decreased 4.5 times more during the first 15 cycles than during the subsequent 15 cycles. Moreover, stability degradation was strongly influenced by the freezing temperature, initial porosity, and rock debris loss ratio, with critical thresholds determined at a 3.8% porosity and a 0.83 debris loss ratio. The findings indicated that stability deterioration is governed by the coupled effects of frost heave loading, microstructural damage accumulation, and freezing depth development, with clear stage-dependent and threshold-driven patterns. This work provides not only a quantitative explanation of instability mechanisms in cold-region rock masses but also practical guidance for engineering stability assessment and disaster mitigation.