Abstract: Uniaxial impact tests with different strain rates were carried out on -30 ℃ water-saturated sandstone with the help of split Hopkinson pressure bar to investigate the dynamic compression failure mechanism of Cretaceous frozen sandstone.Results reveal that the frozen sandstone experienced four stages of dynamic damage: linear elastic deformation,microcrack evolution,unstable crack propagation,and strain softening.The damage comes from the interactive evolution of initial macro- and micro-defects and new cracks.The change of dynamic growth factor demonstrates significant strain rate strengthening effect of sandstone’s strength and deformation.The initial damage is composed of the accumulation of macro- and micro-defects,and the dynamic total damage is formed by the coupling of damage and defects of different scales.The damage evolution of rock under uniaxial impact compression is orthotropic.The dynamic damage constitutive relationship of sandstone is modified based on the isotropic equation.Critical damage is a comprehensive quantity involving initial damage,dynamic elastic modulus,dynamic compressive strength and peak strain.The theoretical results are in good agreement with the experimental curves,with a decisive coefficients over 0.910.The present constitutive relation well reflects the strength characteristics of frozen sandstone before reaching peak.

Key words: cretaceous frozen sandstone, Hopkinson pressure bar, initial damage, orthotropic, constitutive model