Static and dynamic mechanical tests and numerical simulation on the Holmquist-Johnson-Cook constitutive model for red sandstone

Rock materials are extensively employed in protective engineering and various civil-works structures such as tunnels; investigating their dynamic mechanical behaviour is therefore of great significance. Red sandstone from a stone quarry in Jinan, was selected as the test material. A triaxial testing machine and a split Hopkinson pressure bar (SHPB) apparatus were used to study the mechanical properties of the sandstone under different confining pressures and strain rates, respectively. On the basis of the static and dynamic test data, the parameters of the Holmquist-Johnson-Cook (HJC) constitutive model for red sandstone were calibrated. Using these calibrated parameters, a finite-element model of the dynamic compression test on a large-diameter SHPB was established; verification was performed by comparing the numerical results with the experimental results in terms of both the failure pattern of the red sandstone and the corresponding stress-strain curves. The results show that: (1) under confining pressure, the propagation direction and extent of internal cracks are constrained, preventing rapid crack penetration, so that the peak stress increases with increasing hydrostatic pressure; (2) under different loading air pressures, red sandstone exhibits a pronounced strain-rate effect, with both dynamic compressive and splitting tensile strengths positively correlated with the average strain rate; (3) analysis of the dynamic increase factors for compressive strength (DIFc) and tensile strength (DIFl) indicates that the strain-rate effect on the dynamic tensile peak stress is more pronounced. The calibrated HJC constitutive parameters accurately reproduce the damage and fracture process of red sandstone under dynamic impact in LS-DYNA; prior to the maximum peak stress, the stress-strain curves obtained numerically are essentially consistent with the experimental curves. The calibrated parameters for this dense, high-strength red sandstone can serve as a reference for future studies on the dynamic mechanical properties of red sandstone and for its engineering applications.