Study on the influence of different discrete forms of DDA block on mechanical properties of coarse granular material

Abstract

In the triaxial compression test of soil engineering, particle breakage may occur under the double action of axial and lateral loads. So, for the DDA simulation, the internal discretization of DDA block should be carried out at first. However, different discretization may affect the final simulation results. To solve this problem, the DDA numerical models based on triangular discretization, Voronoi discretization and no discretization are established to carry out the triaxial test simulation of coarse granular material, and the influence of different discretization of DDA block on mechanical properties of coarse granular materials was compared. An improved DDA was used to simulate the triaxial tests under different confining pressures, The numerical results show that the deviatoric stress-strain curves of the three discrete forms become steeper and the peak strength also increases with the increase of confining pressure. Under the same confining pressure, the deviatoric stress-strain curve with no discretization is the steepest and the peak strength is also the largest. Although deviatoric stress-strain curve of the triangular discretization is gentler, its peak strength is closer to that with no discretization compared with the Voronoi discretization. The triangular discretization model gradually changes from contraction to dilation in the loading process, and the higher the confining pressure is, the more obvious the contraction is. At the same time, the direction of contact force gradually changes from the initial minor principal stress direction to the major principal stress direction, forming an obvious force chain, and the final particle breakage mostly occurs in an ‘X’ shaped region. The developed DDA method can accurately reflect the evolution of mechanical properties of coarse granular materials under various working conditions, and the research results can provide reference for the discrete form of blocks in similar simulation.