Evolution of particle damage of sand during axial compression via arrested tests

Abstract

A series of axial loading and unloading compression tests was conducted on siliceous and calcareous sand, using a modified oedometer apparatus. Samples were prepared using aspect ratios of 6:1 and 1:1 (diameter:height) and loaded at uniform axial strain rates of 0.01 and 10%/s. Compression was arrested at various strains up to 30%, after which the size distribution of the sand particles was determined using a dynamic particle size analyzer capable of identifying particle shapes and sizes in the 10–3000 µm range. Samples responded slightly stiffer and experienced more crushing in the 1:1 aspect ratio tests. For silica sand, significant reduction in grain size was observed beyond 10% strain, with modest rate dependency observed. Faster breakage and greater rate sensitivity were seen in the softer coral sand, where particle breakage was observed to start at 5% strain. Strain-hardening behavior and hysteresis were observed in the stress–strain behavior and correlated with the size reduction observed in the arrested tests. In addition, it was noticed that smaller particles break more than larger particles. Both sands exhibited fractal particle evolution, i.e., when particles fracture, daughter particles preserve a similar sphericity to that of the parent material.