is a highly non-linear system due to non-linearity within blocks and between blocks, Chang et al. implemented a material non-linearity model to DDA using strain hardening curves. Ma developed a non-linear contact model for analysis of slope progressive failure including strain softening using the stress and strain curve. Recent progress in DDA algorithm is reported by Kim et al. and Jing et al. which considers coupling of fluid flow in fractures. The hydro-mechanical coupling across rock fracture surfaces is also taken into account. The program computes water pressure and seepage throughout the rock mass of interest. In its original formulation, a rock bolt was modeled as a line spring connecting two adjacent blocks. Later, Te-Chin Ke suggested an improved bolt model, followed by the rudimentary formulation of lateral constraint of rock bolting. References Additional references Shi GH. Block system modeling by discontinuous deformation analysis. Computational Mechanics Publications; 1993. Shi GH. Discontinuous deformation analysis technical note. First international forum on discontinuous deformation analysis, June 12–14. Berkeley, California; 1996. Computational physics Deformation (mechanics)