## 6 Conclusions  
Taking the Wushan open-pit mine slope in cold regions as a case study, this research systematically investigates the mechanical degradation mechanism of infilled fractured rock masses and the corresponding slope stability response under freeze-thaw (F-T) cycles. By analyzing in situ temperature data to determine the F-T influence range, conducting shear tests on infilled structural planes, and implementing fracture network modeling and numerical simulations, a degradation model that accounts for the infill effect was developed. A revised _GSI_ calculation method and an extended form of the Hoek-Brown criterion were proposed, achieving spatial parameter field construction and dynamic  
Figure 13: Contribution of intact rock and infilling material to the degradation of rock mass properties under different freeze–thaw cycles as a function of burial depth: (**a**) internal friction angle; (**b**) cohesion. stability evaluation under the coupled effects of freeze-thaw, burial depth, and structural degradation. The findings provide theoretical support and parameter guidance for slope design and operational management in cold-region open-pit mines. The main conclusions are as follows:  
1. The slope rock temperature field in the Wushan open-pit mine shows significant variation with depth. Shallow rock masses are strongly influenced by atmospheric temperature, exhibiting frequent and large fluctuations, while deep rock masses show milder temperature changes. Based on the relationship between temperature extremes and depth, the maximum freezing depth was determined to be approximately 7.5 m. This indicates that the primary freeze-thaw affected zone is concentrated in the shallow layer, which should be considered a key zone for slope protection and instability control. 2. The shear strength of infilled structural planes decreases significantly during F-T cycles, with infill thickness playing a decisive role in degradation severity. Direct shear tests indicate that a 10 mm thick infill layer can result in a nearly 30% reduction in cohesion after 20 F-T cycles. This confirms that infill materials are the dominant factor in early-stage strength degradation, and mechanical parameters should be adjusted using correction coefficients accordingly. 3. Both the internal friction angle and cohesion exhibit exponential degradation trends under the combined influence of F-T cycles and burial depth. A dual-exponential fitting model was established to describe the evolution of shear strength, with fitting coefficients of determination (R\({}^{2}\)) of 0.67 and 0.75, respectively. These results reveal that shallow-buried rock masses are more susceptible to strength degradation due to temperature gradients and structural weakening, providing theoretical support for parameter field construction and predictive analysis. 4. Numerical modeling based on the fracture network indicates that a 9 \(\times\) 9 m domain can be considered a representative elementary volume (REV), exhibiting stable mechanical responses and representative plastic strain distribution. Based on this REV, slope strength spatial assignment and stability calculations were conducted. Results show that the slope safety factor decreases exponentially with increasing F-T cycles, dropping from an initial value of 2.25 to 1.53 after 20 cycles. Regression model prediction suggests that once F-T cycles exceed 42, the safety factor drops below 1.0, entering a critical instability state. This highlights the cumulative effect of freeze-thaw as a key factor in controlling the service life of cold-region slopes. Conceptualization, P.Z. and Q.Y. ; Methodology, J.H. and P.Z. ; Software, J.H. and Q.Y. ; Validation, J.H. and W.Y. ; Formal analysis, J.H., W.Y. and Q.Y. ; Investigation, J.H., N.G. and W.Y. ; Resources, P.Z. ; Data curation, J.H., N.G. and W.Y. ; Writing--original draft, N.G. ; Writing--review & editing, P.Z. and N.G. ; Supervision, P.Z. and Q.Y. All authors have read and agreed to the published version of the manuscript.