Evolution of Particle Breakage for Calcareous Sands during Ring Shear Tests

Ring shear tests were performed in this work to investigate the characteristics of shear band formation and particle breakage for calcareous sands sampled from the South China Sea. The tests focused on the formation of shear band and the evolution of particle breakage under various levels of loading stress, together with sensitivity analyses of the initial sample grading and shear rate. The breakage of particles has a significant influence on the stress-strain relationship, volumetric deformation, and final grading of calcareous sands. In particular, the calcareous sand specimen tends to remain at a constant volume and a stable grading at shear strains larger than 2,000%. The change of the microstructure of calcareous sands during shearing has been illustrated by scanning electron microscopy (SEM) images, showing clear evolution of particle breakage and surface smoothness within the shear band. A considerable amount of fine particles (<0.074 mm) was produced during the tests, and the final complete particle-size distribution was obtained with a laser diffraction particle-size analyzer. The findings of this study improve the understanding of calcareous sands by showing that they can be crushed readily under normal loading stress levels as long as the shear strain continues.