Deterioration and strain energy development of sandstones under quasi-static and dynamic loading after freeze-thaw cycles

Abstract

Rocks in cold regions are often exposed to extreme temperature change, and different loading conditions, therefore, will be subjected to deterioration. In this study, the deterioration of sandstone after freeze-thaw (F-T) cycles under quasi-static and dynamic loading conditions is investigated. In doing so, physical and mechanical properties of sandstone samples were studied after 20, 60, 100 and 140 F-T cycles. An increase in porosity and decrease in P wave velocity demonstrated a degradation in physical properties after F-T cycles. In addition, peak strengths of specimens were observed to be higher in the dynamic loading conditions as compared with the quasi-static conditions; while Young's modulus almost remained constant. Furthermore, a decay model was used to predict the deterioration of sandstone under different loading conditions and F-T cycles. Finally, the effects of F-T cycles on a brittleness and strain energy development were investigated. It was observed that rock became more brittle in the pre-peak regime after F-T cycles. It also demonstrated strain energies including the pre-peak, the peak, the post-peak and the total strain energies decrease after F-T cycles while variations of elastic strain energy with F-T cycles doesn't show any conclusive trend. Correlations between porosity and strain energies implied that porosity is a key factor in strain energy development for this kind of sandstone except that of elastic strain energy.