Abstract: A series of dynamic uniaxial compression, dynamic triaxial compression and dynamic tensile tests with different strain rates are conducted on homogeneous sandstone samples by using the RMT－150C testing machine and the multifunction split Hopkinson pressure bar (SHPB) device. The results show that, when the confining pressure remains constant, the compressive strength of sandstone increases with the magnitude of strain rate when the strain rate is less than 102 s-1, the increment trend of the compressive strength is proportional to 1/3 power of the strain rate when the strain rate is larger than 102 s-1. The similar rule above also applies to the tensile strength. Currently, no rock dynamic strength criterion is available for the strain rate in the range of 101- 102 s-1. Based on the analysis of data from dynamic uniaxial tests, dynamic triaxial tests and dynamic tensile tests under low-high strain rates and the principle of Mohr-Coulomb criterion, Hoek-Brown criterion and Griffith criterion, the dynamic Mohr-Coulomb criterion and the dynamic Hoek-Brown criterion under different strain rate ranges are formulated. The experimental results show that the dynamic Mohr-Coulomb criterion and the dynamic Hoek-Brown criterion can be applied to estimate the dynamic strength in the low strain rate range. In the high strain rate range, the dynamic strength can be estimated by using the dynamic Mohr-Coulomb criterion; but the dynamic Hoek-Brown criterion is not applicable. The Griffith criterion can be used to estimate the dynamic uniaxial compressive strength and dynamic tensile strength in high strain rate range only.

Key words: strain rate, rock, dynamic strength criterion, dynamic triaxial compression test, split Hopkinson pressure bar