3DEC is a three-dimensional numerical modeling code for advanced geotechnical analysis of soil, rock, ground water, structural support, and masonry. 3DEC simulates the response of discontinuous media (such as jointed rock or masonry bricks) that is subject to either static or dynamic loading. The numerical formulation It is based on the distinct element method (DEM) for discontinuum modeling. UDEC is the two-dimensional version.

The discontinuous material is represented as an assemblage of discrete blocks. The discontinuities are treated as boundary conditions between blocks; large displacements along discontinuities and rotations of blocks are allowed. Individual blocks behave (based on constitutive and joint models) as either rigid or deformable (i.e., meshed into finite difference zones) material. Continuous and discontinuous joint patterns can be generated on a statistical basis. A joint structure can be built into the model directly from the geologic mapping. 3DEC also contains Itasca's powerful built-in scripting language FISH. With FISH, you can write your own scripts for users who wish to add functionality for custom analyses.