Investigation on the triaxial creep characteristic of coarse granular materials with different initial void ratios

Abstract

The creep deformation of coarse granular materials is closely related to the state of creep stress and the degree of compaction. A serious of triaxial creep tests using the single-line method were carried out to investigate the influence of initial void ratio and triaxial stress state on the creep deformation and creep strain direction of coarse granular materials. The test results primarily indicate that the creep strain increases with an increase in initial void ratio under identical stress conditions, and the volumetric creep strain decreases with an increase in stress ratio under high confining pressure conditions. Furthermore, the variation in the initial void ratio has little influence on the direction of creep strain under the same creep stress state. The effect of generalized stress on the final creep strain and creep dilation ratio were further discussed. It was observed that the final deviatoric creep strain exhibits a stronger correlation with the deviatoric stress q compared to the mean normal stress p. Additionally, the creep dilatancy decreases with an increase in stress magnitude under identical stress ratio conditions. Based on the test results, a computation model for the final deviatoric creep strain with the consideration of initial void ratio and creep stress was proposed by modifying a basic power function with deviatoric stress q as the variable. After that, a modified stress-dilatancy equation for coarse granular materials was used to predict the direction of strain during creep process. Finally, the final volumetric creep strain was indirectly calculated by integrated the computation model for the final deviatoric creep strain and the creep stress-dilatancy equation. The reasonable of the proposed model was verified through a comparison of computation results and test results.