Multi-scale simulation of pore structure and permeability of brittle coral gravel using X-ray computerized tomography and pore network modeling

● X-ray CT combined with computer simulation was used to analyze pore structure evolution of coral gravel during fragmentation. ● A multi-scale method for simulating particle breakage was proposed. ● The pore network models were built to analyze the pore structural parameter characteristics. ● The positive exponential correlation between Through porosity and permeability was established. ● A framework interpreting particle fragmentation considering its dependence on porosity and permeability was presented. As a distinctive geotechnical material commonly found in coastal and island strata, coral gravel (CG) has irregular morphology and high porosity and susceptibility to breakage because of its biological origins and carbonate brittleness. These properties have significant influences on the mechanics and hydraulics of CG, but how its pore structure and permeability characteristics evolve during particle fragmentation is yet to be studied. This study uses X-ray computed tomography (X-CT) in combination with pore network modeling to develop a multi-scale analytical approach for the nondestructive dynamic simulation of particle breakage, investigating the morphological features, pore structure, and permeability of various types of CG. The multiscale analysis validates the classification of CG pores into three categories, i.e., intraparticle pores, blind pores, and through pores, and CG is found to have generally higher intraparticle porosity (about 5% on average) than calcareous sand. Also, the positive correlations between the permeability k and both the through porosity ɸ t and the pore structure parameters (PSPs) of CG are established as k = 8.23 × 10 –12 × ( ɸ t ) 0.57 and k = C ln ( PSP ) + D. A mechanism is proposed for how the pore structure evolves during particle breakage, focusing on changes in porosity and permeability. The X-CT-based multi-scale simulation method provides valuable insights into how microscopic pore structures influence the mechanical properties and fluid permeability of CG during particle fragmentation. These findings offer insights into the properties of CG in order to promote marine engineering construction.