RHT constitutive parameters of sandstone under static and dynamic loading

Sandstone is a typical surrounding rock in deep underground engineering, and its dynamic mechanical response under impact and blasting loads is critical for construction safety and disaster control. The RHT constitutive model performs well in characterizing the dynamic failure behavior of brittle materials like rock, but existing parameter sets for sandstone are mostly calibrated by quasi-static tests only, lacking systematic validation under medium-to-high strain rates, leading to large deviations in high-speed impact simulations. This study determines the constitutive parameters of sandstone via an integrated methodology integrating a series of quasi-static, dynamic experiments and numerical simulations. Via quasi-static uniaxial compression tests and Brazilian splitting tests, the fundamental mechanical properties of the studied sandstone were derived: an elastic modulus of 53.478 GPa, a uniaxial compressive strength of 153.235 MPa, a tensile strength of 16.38 MPa, and a Poisson's ratio of 0.26. To examine the strain rate dependency of the sandstone, impact tests were conducted using a split Hopkinson pressure bar (SHPB) at loading rates of 100 s⁻¹ and 1000 s⁻¹ . Test results reveal that the dynamic compressive strength of the sandstone exhibits increases of 22.69% and 76.08%, respectively, relative to its quasi-static counterpart, confirming a pronounced dynamic strengthening effect. For RHT constitutive model parameters that cannot be theoretically derived, a combined methodology of SHPB experimental data and numerical simulations was employed to calibrate critical parameters, including damage evolution mechanisms and residual strength properties. The calibration results demonstrate excellent agreement between numerical simulations and experimental data of both 100 s⁻¹ and 1000 s⁻¹ strain rate. This work provides a validated dual-strain-rate calibrated parameter for sandstone, which can improve the simulation accuracy of deep sandstone under impact and blasting loading conditions.