Volumetric Strains After Undrained Cyclic Shear Governed by Residual Mean Effective Stress: Numerical Studies Based on 3D DEM

A series of numerical tests is performed using the three-dimensional discrete element method to study the volume contraction characteristics of granular material during the reconsolidation process following undrained cyclic shear. Results show that post-liquefaction reconsolidation can be categorized into a liquefied and a solidified portion. The decrease in the void ratio in the liquefied portion is not accompanied by an increase in the mean effective stress, while the opposite is true for the solidified part. The residual mean effective stress affects the volumetric strain significantly during reconsolidation. The decrease in void ratio during the reconsolidation beginning from effective stress reduction ratios of 0.1, 0.5, and 0.9 is 86%, 37%, and 7% of that beginning from the initial liquefaction state, respectively. In addition, the volumetric strain during reconsolidation is associated with the change in pore uniformity.