Discontinuous Deformation Analysis with Potential Contact Forces
In conventional discontinuous deformation analysis (DDA), the procedure called open–close iteration is adopted to enforce the contact condition, which needs to repeatedly fix and remove the artificial springs between blocks in contact to determine real contact states. The open–close iteration belongs to the category of trial-and-error methods, in which convergence cannot be always guaranteed. Meanwhile, the contact force is treated as concentrated force, leading to the difficulties in determining the shear strength from cohesion and stresses in the contact area. The so-called potential contact force concept adopted in the combined finite-element method and discrete–element method (FEM-DEM) has been proved efficient and robust. In the FEM-DEM the contact force is treated as a distributed contact force, which is more realistic and was utilized in this study to tackle contacts. A major advantage over the conventional DDA lies in the elimination of the need to handle singular contact types that would incur huge difficulties in three-dimensional simulations. Therefore, a contact potential–based DDA (CPDDA) was developed by introducing potential contact forces. Some typical examples, including those originally designed by the DDA inventor, are reanalyzed, proving the feasibility of CPDDA.