Porous Grain-Based Modeling of Coral Reef Limestone: Revealing Heterogeneity and Strain Rate Effects

Deep coral reef limestone (CRL) exhibits strong heterogeneity due to complex pore and crystal morphology, which significantly affect its strength and damage mechanisms. The scarcity of deep CRL samples limits a comprehensive understanding of its pore characteristics. The computed tomography scan and pore analysis for 112 samples and 3 m drilling cores of deep CRL indicate that the Pearson correlation coefficient of pore principal axes a and b reaches 0.928. The distribution of pore parameters was analyzed by kernel density estimation, and new pores consistent with the characteristics of deep CRL pores were generated by resampling the inverse cumulative distribution function. Subsequently, a porous grain-based modeling strategy was proposed, and the novel finite-discrete element method was adopted to study the effects of pore structure, crystal morphology, and strain rate on the mechanical parameters and macro-micro damage mechanisms of the CRL. The results indicate that the crack propagation under quasi-static and intermediate strain rates is affected by crystal arrangement and pore weak zones, while it is not affected under high strain rates. Strength increases with increasing crystal sphericity, and large-sized pores increase the tendency of sample volume dilatancy. Additionally, the pore size effect was revealed to ensure the mechanical test reliability of deep CRL. This study realized the refined modeling for deep CRL and solved the sample-dependent issue of reflecting CRL pore characteristics in numerical models.