We present a generalized contact computation model for arbitrarily shaped polyhedra to simplify the contact analysis in discontinuous deformation analysis. A list of generalized contact constraints can be established for contacting polyhedra during contact detection. Each contact constraint contains information for 2 contact points, unique contact plane, and related contact modes (open, locked, or sliding). Computational aspects of the generalized contact model include identification of contact positions and contact modes, uniform penalty formulation of generalized contact constraint, and uniform updating of contact modes and contact planes in the open-close iteration. Compared with previous strategies, the generalized contact computation model has a simpler data structure and fewer memory requirements. Meanwhile, it simplifies the penalty formulation and facilitates the open-close iteration check while producing enough accuracy. Illustrative examples show the ability of the method to handle the full range of polyhedral shapes. KEYWORDS contact formulation, contact identification, generalized contact model, open-close iteration, threedimensional discontinuous deformation analysis 1 | INTRODUCTIONCorrectly modeling contact interaction of discrete bodies is the key issue in discontinuous computation methods. 1-5 Focusing on polyhedral bodies, resolving the contact interaction is difficult as the non-smooth change of polyhedron face normal. In DEM and FDEM modeling, the common plane model, 2 the energy-conserving contact interaction model, 6 the triangulated rounded bodies model, 7 the polygon-based description, 8 the potential particle model, 9,10 dilated polyhedra 11,12 and the potential function model 13,14 have been applied to treat contact of polyhedra. These contact models are mostly for granular materials such as ballast and soils, and the contact interaction law is based on the overlap of 2 contact bodies. However, for the 3-dimensional (3-D) discontinuous deformation analysis (DDA) method, 3,4 a strict "no penetration" requirement leads to very small overlap during contact interaction. The resolution algorithms for both convex and concave polyhedral blocks are mostly depending on the classification of the contact types. [15][16][17] The final contact constraint information can be obtained according to the first entrance rule or shortest exist rule. 5 A 4-type identification phase 15-17 and the separate treating of the vertex-to-face model 18,19 and edge-to-edge models [20][21][22] are used, which may complicate the data structures and contact analysis procedure of the program. A more general contact model for polyhedral blocks that strictly fits the contact constraint requirement and the implicit solution approach