Mechanical properties and strength evolution model of sandstone considering the coupling impact of freeze and thaw weathering process and confining pressure

Abstract Freeze and thaw (F&T) weathering cycles induced by day-night and seasonal temperature changes cause a large number of rock mass engineering disasters in cold areas. Investigating the impact of F&T weathering process on strength and deformation characteristics of frozen-thawed rocks is therefore of critical scientific importance for evaluating the stability and optimizing the design of rock mass engineering in these areas. In this research, the evolution characteristics of F&T damage were analysed based on T2 spectrum distribution curves of sandstone specimens before and after F&T weathering cycles. The coupling impact of the quantity of F&T weathering cycles and confining pressure on pre-peak and post-peak deformation behaviours of sandstone specimens were analysed in detail. By introducing the confining pressure increase factor (CPIF), the impact of confining pressure on triaxial compressive strength (TCS) of sandstone specimens after undergoing different quantities of F&T weathering cycles was further investigated. A novel strength evolution model was proposed that could effectively describe the coupling impact of the quantity of F&T weathering cycles and confining pressure on TCS of rocks after undergoing F&T weathering process. The proposed strength evolution model was cross-verified with experimental data from the published literature, and all correlation coefficients are above 0.95, which proves that the strength evolution model proposed in this paper is reasonable; in addition, this model has strong applicability.