Study of shear induced stress redistribution in gap-graded soils by discrete element method

Combined effects of shear stress ratio, density, and fines content on stress redistribution during shearing and their implications for internal instability were investigated in this study using the discrete element method. The widely used stress reduction factor was modified in this study by introducing the Voronoi cell to account for the volume change during shearing. The response of stress in finer fraction and its relative contribution to the overall stress of the specimen as evaluated by the established stress reduction factor showed inconsistent trends. The relationship between the mean stress in finer fraction and the shear stress ratio of the entire specimen was found to be dependent on FC and density during pre-peak stress condition. At post-peak, the relationship was only governed by the soil load-bearing skeleton. The stress redistribution of dense transitional soils exhibited the most pronounced changes. The mean stress in finer fraction reached the peak and steady values quicker than the shear stress ratio. This could be attributed to the decrease in critical hydraulic gradient under a high shear stress ratio, as evidenced from previous experimental works. These nonsynchronous performances could be explained by the shift of contact force and volume change.