Effect of the structure of intra-particle pores on suffusion in coral sand

Abstract

Coral sand, as a primary material for constructing artificial islands and reefs, is known for its high porosity. This porosity arises from the presence of intra-particle pores within individual particles and inter-particle pores between neighboring particles, forming a unique double-porosity structure. The pores within a particle usually exhibit a tubular structure with preferential directions, which may affect the hydraulic behaviors of coral sand at the macroscale. This work aims to investigate the influence of the tubular structure of intra-particle pores on suffusion in coral sand. A numerical approach that couples the discrete element method (DEM) with the dynamic fluid mesh (DFM) is employed to simulate the suffusion process in coral sand with the tubular structure. In particular, the effect of the preferential direction of the tubular structure is examined. The insights gained from this research show that the inter-particle porosity and fluid velocity increase with the erosion of fine particles. However, the intra-particle fluid velocity holds steady due to the unchanged average hydraulic gradient of the sample. Moreover, with diminishing angle between the direction of the intra-particle fluid channel and flow direction, the intra-particle fluid velocity increases, resulting in a slight increase in the eroded mass.