Microstructure evolution of coral sand during impact liquefaction process

Coral sand is a special calcium carbonate-rich sediment used in island reef engineering, and the microstructural changes in coral sand liquefaction under impact loading have been less studied. A three-dimensional X-ray microscope CT (μCT) was used to reconstruct the coral sand in three dimensions. Based on three-dimensional image reconstruction, numerical simulation methods were used to perform a finite element analysis of the impact liquefaction of saturated coral sand in an undrained state. The changes in the coordination number of coral sand particles, interparticle force chain, and overall void ratio before and after the impact were investigated, revealing the liquefaction evolution of the coral sand liquefaction process. In the indoor one-dimensional impact test, the changes in the coordination number of coral sand were positively correlated with the supervoid ratio pressure ratio, and the uniformity of the pore diameter was reduced by the impact. During impact loading, coral sand was subjected to high-intensity extrusion, and the void ratio decreased simultaneously. The coral sand, which originally had larger particles, broke into multiple smaller particles, resulting in a decrease in the coordination number. The change in the coordination number of coral sand was positively correlated with the burial depth (pre-pressure), and the coordination number of coral sand decreased after liquefaction, whereas the overall void ratio of the coral particles decreased. This study provides a deeper understanding of the microevolution of coral sand liquefaction.