Dynamic splitting mechanical properties and strength prediction model of freeze–thawed water-saturated sandstone

To evaluate the effects of freeze–thaw (F–T) cycling on the tensile performance and energy evolution of water-saturated sandstone, this study utilized slope rock specimens collected from a high-altitude open-pit mine in western China. Dynamic Brazilian disc tests were conducted using a split Hopkinson pressure bar (SHPB) system under four distinct strain rate conditions. The specimens were pretreated with varying numbers of F–T cycles before testing. Experimental analysis revealed that under constant F–T conditions, both the tensile strength and energy dissipation ability under impact loading increased with increasing strain rate. In contrast, when the strain rate remained steady, a greater number of F–T cycles led to decreases in the splitting strength and energy dissipation capacity. Moreover, the dynamic increase factor (DIF) increased progressively with increasing strain rate and F–T cycle number. The deterioration in dynamic performance is attributed to internal degradation mechanisms, including the dissolution of cementing materials and the development of microcracks and pores, which reduce the overall integrity of the rock and promote more fragmented macroscopic failure modes. F–T-induced damage is identified as the primary factor responsible for the decrease in impact resistance and increase in the fragmentation of the specimens. Moreover, a scaling law model grounded in weakest-link theory was established to estimate the tensile capacity of F–T-degraded water-saturated sandstone.