Dilatancy behaviors and equation of calcareous sand considering stress path and particle breakage

The stress path and particle breakage have an impact on the dilatancy of calcareous sand. A series of drained triaxial compression tests with different stress paths and confining pressures are carried out to investigate the dilatancy of calcareous sand. The results show that the stress path and particle breakage have important effects on the dilatancy of calcareous sand. The relationship between the dilatancy ratio and the stress ratio of calcareous sand under different stress paths is significantly different. Under the same stress ratio, the dilatancy ratio in the constant confining pressure tests is the maximum, and that in the constant axial stress tests is the minimum. The dilatancy ratio in the constant average principal stress tests is between above two tests. The dilatancy ratio corresponding to the peak stress ratio decreases with an increase of the peak stress ratio, which follows a linear relationship, and increases with an increase of the relative breakage index, which is approximated by a power function. These relationships are not affected by the stress paths. The relation between the dilatancy ratio and the parameters related to stress ratio is linear under the condition of ignoring strain softening stage, and its slope is related to the stress path and the consolidation pressure. Based on the test results, a dilatancy equation related to the stress path and particle breakage is proposed and verified. It is shown that the dilatancy equation has better adaptability to different types of granular soils.