Particle breakage evolution of coral sand using triaxial compression tests

Particle breakage continuously changes the grading of granular materials and has a significant effect on their mechanical behaviors. Revealing the evolution pattern of particle breakage is valuable for development and validation of constitutive models for crushable materials. A series of parallel triaxial compression tests along the same loading paths but stopped at different axial strains were conducted on two coral sands with different particle sizes under drained and undrained conditions. The tested specimens were carefully sieved to investigate the intermediate accumulation of particle breakage during the loading process. The test results showed that under both drained and undrained conditions, particle breakage increases continuously with increasing axial strain but exhibits different accumulating patterns, and higher confining pressures lead to greater particle breakage. Based on the test results, the correlations between particle breakage and the stress state as well as the input energy were examined. The results demonstrated that either the stress state or input energy alone is inadequate for describing the intermediate process of particle breakage evolution. Then, based on experimental observation, a path-dependent model was proposed for particle breakage evolution, which was formulated in an incremental form and reasonably considers the effects of the past breakage history and current stress state on the breakage rate. The path-dependent model successfully reproduced the development of particle breakage during undrained triaxial compression using the parameters calibrated from the drained tests, preliminarily demonstrating its effectiveness for different stress paths.