Particle Shape Effect on Creep and Fluidity of Granular Packing

The mechanical behavior of granular packing is closely related to the particle shape. This study investigated the macroscopic behavior of mixture specimens with different contents of glass beads and Fujian sand (FS) through macroscale cyclic triaxial creeping tests. At the microscale, the particle shape was quantitatively characterized using shape parameters such as the aspect ratio, sphericity, convexity, and overall regularity (OR). The effects of particle shape on system fluidity were evaluated through the shear strain evolution, state parameter, initial viscosity, characteristic strain, and critical velocity. A unified state evolution model was introduced to interpret and analyze the creep and fluidity behaviors of the granular packing. The results demonstrated that the fluidity of mixture containing FS and spherical glass beads is superior to that of mixture made with FS and crushed glass beads at low-stress level. As the particle shape approached sphericity, the particle surface became smoother, and the OR of the system increased. This transition resulted in an increase in the initial state parameter and a decrease in the initial viscosity of the packing. Moreover, a quantitative relationship between characteristic strain and the particle shape parameter was established. The critical velocity, which serves as an indicator of system stability, demonstrates a positive correlation with OR but a negative correlation with confining pressure. These findings facilitate a comprehensive evaluation of the effects of particle shape on the damage threshold in granular packing systems.