Influence of spatial distribution of fine sand layers on the mechanical behavior of coral reef sand

Fine coral sand commonly distributes in coral sand artificial foundation due to the effect of gravity sorting during hydraulic process and the particle breakage of coarse particle. Considering that the significant impact of the distribution form of fine sand on the strength and deformation properties of coral sand foundation, the effect of spatial distribution of fine sand layers on the mechanical behavior of coral sand was studied. The mechanical behavior of coral sand in the consolidated undrained (CU) shear tests were simulated by discrete element models (DEM) analysis method, and the impact mechanism of fine sand interlayers on mechanical strength was analyzed. The effect of thickness and number of fine sand interlayer on the mechanical behavior and shear deformation of coral sand specimens were analyzed based on the proposed uniformity degree, a parameter that quantify the spatial distribution of fine particle interlayers. The results show that the mechanical behavior of coral sand was simulated well by DEM based on particle scanning results. Under the condition of constant fine particle content, the average coordination number of particles increased and the minimum contact force between particles decreased when fine particles were distributed in the form of interlayer. It indicates that the fine particle interlayer has a diffusion effect on stress transfer, which revealed the mechanism of the macro increasing strength of 10%-20% under the same confining pressure. A linear relationship was found between the proposed parameter uniformity and the peak deviator stress of specimens, and the impact of uniformity on the strength was particularly significant under high confining pressures.