Physical property evolution and damage characterisation of rocks in cold regions under freeze-thaw cycles

Freeze-thaw damage of rock slopes in open-pit mines in cold regions is a critical factor affecting slope stability. This study presents a novel multi-parameter integration framework for freeze-thaw damage characterisation that addresses fundamental limitations of conventional single-parameter approaches. The core innovations include: (1) a unified damage parameter D constructed through multiplicative coupling of three geophysically measurable parameters (longitudinal wave velocity, shear wave velocity, and resistivity), which captures the synergistic evolution of rock physical properties during freeze-thaw damage—this multiplicative coupling approach has not been previously applied to freeze-thaw damage characterisation; (2) a single-parameter damage model (with only k to calibrate) that balances simplicity with physical meaningfulness, enabling practical engineering application; and (3) the damage rate k as a novel quantitative indicator for lithology sensitivity ranking, providing a practical metric for engineering decision-making. Five typical lithologies from an open-pit coal mine in Zhundong, Xinjiang were systematically tested under different numbers of freeze-thaw cycles (0–30 cycles). The results indicate that both longitudinal wave velocity and shear wave velocity exhibit nonlinear attenuation characteristics, with a faster attenuation rate in the initial stage and gradual stabilisation in the later stage. The resistivity shows a decreasing trend, reflecting the evolution of internal pore structure of rocks. The D value shows good consistency with the reference damage derived from failure confining pressure, validating the effectiveness of the proposed parameter. The lithology-specific k values (coal: 1.074, mudstone: 1.057, siltstone: 0.921, medium-fine sandstone: 0.829, coarse sandstone: 0.780) provide a new quantitative framework for comparing freeze-thaw vulnerability across different rock types—a capability not offered by traditional single-parameter damage models. This research establishes a new paradigm for quantitative evaluation of rock freeze-thaw damage and provides a foundation for non-destructive monitoring of slope freeze-thaw damage using geophysical exploration methods.