Microscopic study of the impact of particle morphology on the compressibility of calcareous sands

As a kind of unique marine sediment, Calcareous sand exhibits high compressibility because its irregular particle morphology leads to the formation of large interparticle voids. In this study, using calcareous sand samples from the South China Sea, we employed X-ray CT scanning technology to reveal the microstructural evolution of calcareous sand during compression. This allowed us to establish correlations between particle morphology, relative density, vertical stress, and microstructural parameters. The research findings are as follows: (1) Samples with a higher proportion of cube shape particles have larger initial void ratios, and experience a more significant decrease in void ratio under stress. Dense samples exhibit greater deformation resistance and lower particle breakage rates, resulting in a slower reduction in void ratio under stress. (2) The number of pores in the samples follows a V-shaped trend with an increase in the proportion of cube shape particles, reaching its minimum when the proportions of cube shape and platy shape particles are balanced. The number of pores increases with an increase in vertical stress and relative density. (3) The equivalent pore diameter and pore volume of the samples exhibit an inverted V-shaped trend with an increase in cube shape particle content, reaching their maximum when the proportions of cube shape and platy shape particles are balanced. (4) The more cube shape particles in the sample, the more irregular the pore shapes become. Under vertical stress, the influence of particle morphology on pore shape gradually diminishes until it disappears. (5) The particle coordination number in the samples predominantly falls within the range of 3.79-5.68. The coordination number increases with increasing relative density and vertical stress, with vertical stress exerting a significantly greater influence on the coordination number than relative density. Under vertical stress, samples with more cube shape particles exhibit smaller coordination numbers and higher particle breakage rates.

Automated summary

In this study, the microstructural evolution of calcareous sand during compression was revealed using X-ray CT scanning technology. The findings indicate that particle morphology, relative density, and vertical stress have significant influences on the pore characteristics and deformation behavior of calcareous sand.