Investigation of the Pore Structure Features of Coral Reef Limestone by Combining Polarizing Microscopy and Computed Tomography Scanning Techniques

ABSTRACT An understanding of the pore structure features of coral reef limestone is crucial for studying its distinctive macroscopic qualities, because the pore structure greatly influences its mechanical properties and seepage characteristics. In this study, a comprehensive characterization analysis of the pore structures of two types of coral reef limestone samples from the South China Sea was conducted using a combination of polarizing microscopy and computed tomography scanning technology. A watershed segmentation algorithm, based on extended-minima transformation markers, was used to segment the pore structure of coral reef limestone, and quantitative analysis of the characteristic pore parameters was performed. In addition, the relationship between the pore orientation and coral growth structure was investigated. The results indicate that the watershed segmentation algorithm using extended-minima transformation markers can effectively reduce oversegmentation and accurately segment the pore structure of coral reef limestone. Both types of coral reef limestone samples exhibited high porosity and complex pore shapes with significant differences in pore size. The pore equivalent radius follows a normal distribution, and the fractal dimension ranges from 1.58 to 1.75, indicating high fractal and self-similar characteristics. The pore structures of both types of coral reef limestone showed a clear directionality with a regular pattern in pore arrangement, primarily influenced by growth lines. This study has implications for revealing the pore structure characteristics of coral reef limestone and establishing correlations between the macroscopic and microscopic properties.