Analyzing the dynamic failure process of coral reef limestone through digital core-based numerical trials

Coral reef limestone (CRL) is a type of highly porous marine carbonate rock, where the pore structure significantly affects its dynamic mechanical properties and the cumulative damage-progressive fracture process. To investigate the dynamic failure mechanisms of CRL, a numerical model considering pore structure was reconstructed based on CT scan experiments. The mechanical parameters of the rock matrix were obtained based on the mineral composition and homogenization theory. The simulation of the Split Hopkinson Pressure Bar (SHPB) test was conducted combining the Riedel-Hiermaier-Thoma (RHT) model, and the effectiveness of the numerical model and RHT model was verified through experiments. The results show that: (1) The numerical model, established using nearest-neighbor interpolation resampling techniques and voxel-to-mesh element mapping methods, can well preserve the complex pore structure characteristics of CRL with an optimal scaling factor f = 0.25; (2) The damage and fracture evolution of porous CRL under impact loads exhibit distinct stage characteristics, and the crack propagation rate follows a log-normal distribution; (3) Pores play a dual role in the dynamic damage and fracture evolution of CRL. The stress concentration and release caused by pores are the main drivers for crack initiation and propagation, yet pores also hinder crack extension and affect the local degree of damage.