Research on the Effect of Pore Characteristics on the Compressive Properties of Sandstone after Freezing and Thawing

Freeze-thaw (FT) cycles in cold regions have a huge effect on the stability of surrounding rock. Sandstone in the Tongchuan area of northwestern China was used as the research object to study the changes in physical and mechanical properties of rocks after FT cycles. After analyzing the force of the internal pore boundary of the rock, it is found that the internal large pores are more likely to make the rock unstable after being stressed. A FT damage model considering the weight of different pore sizes is established. Through static and dynamic tests, the mechanical properties of FT sandstone are studied. The study found that the static and dynamic peak stresses of sandstone decrease with the increase of FT times, and the dynamic increase factors (DIF) shows an increasing trend with the increase of FT times and impact speed. The mechanical test further proves that the compressive strength of sandstone decreases with the decrease of damage factor. The static and dynamic compressive strength showed a good exponential relationship with the damage factor. The relationship between dynamic compressive strength and initial static compressive strength considering the damage factor and impact speed is established.