Strain-rate effects and energy dissipation of frozen rocks under dynamic impact loading

Abstract

To investigate the dynamic impact response of frozen rocks, this study performed dynamic compression tests on yellow sandstone, white sandstone, and granite under various low temperatures and impact intensities using a modified split Hopkinson pressure bar (SHPB) system, and analyzed the strength, deformation, and energy dissipation characteristics of the three rock types. The results show that low temperature significantly enhances the dynamic compressive strength of the two sandstones, with yellow sandstone being the most strongly affected by temperature. The strength of the specimens exhibits a strain rate effect. The peak stress of yellow sandstone shows a linear relationship with impact pressure and is most significantly affected by temperature, while that of white sandstone follows a quadratic growth pattern, and that of granite also shows a linear relationship. Under impact loading, the three rocks exhibit differences in energy distribution. For yellow sandstone, the proportion of reflected energy is the highest, whereas that of transmitted is energy the lowest, and the dissipated energy increases with decreasing temperature. For white sandstone, both the proportions of transmitted and dissipated energies increase as temperature decreases, and both reflected and transmitted energies show low-temperature sensitivity. For granite, the proportion of reflected energy is the lowest, energy is mainly transmitted through the specimen, and the influence of temperature is weak. The three rocks have different water absorption capacities. The water-ice phase change caused by low temperature alters the rock structure and increases the wave impedance, leading to different temperature sensitivities in energy distribution under impact loading. The low-temperature strengthening mechanism originates from the filling of pores by ice, intergranular cementation, and microcrack closure caused by differential thermal contraction of minerals. The research findings can provide a theoretical basis and experimental reference for the stability evaluation and protective engineering design of rock masses of different lithologies subjected to dynamic loads in cold regions.