Itasca International, Inc

- Version 5.2 - Three-Dimensional Numerical Geotechnical Software



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.

3DEC has been developed primarily for geotechnical engineering applications in the fields of civil, mining, and energy generation. 3DEC is also a valuable tool used for research in rock mechanics, stability of masonry structures, and the behavior of granular systems. Although, through scripting and custom constitutive models, the possibilities are virtually limitless.

Options in 3DEC are sold separately from the general license, allowing users to extend the program’s capabilities as meets their own analysis needs.

  • Dynamic Analysis: 3DEC simulates the nonlinear response of a system (soil, rock, and structures) to excitation from an external (e.g., seismic) source or internal (e.g. vibration or blasting) sources.
  • Thermal Analysis: The thermal option in 3DEC allows the simulation of transient heat conduction.
  • Finite Element Structural Liners: Modeling cables and beams is part of the standard functionality of 3DEC. This option adds the ability to model tunnel liners and external structures (such as dams, bridges, walls, buildings, etc.).
  • User-Defined Constitutive Models: User-defined constitutive models can be written in C++ for both zoned block materials and joint materials calculate new stresses, given strain increments, for a modified or unique material behavior.

3DEC is ideally suited to analyze potential modes of failure directly related to the presence of discontinuous features. Work with either discrete blocks, zoned continuum, or both.

3DEC provides 13 built-in zone material models, three built-in joint models, groundwater flow (solid matrix and joints), coupled mechanical-flow calculation, ground support structural elements, and a built-in scripting language (FISH) that can customize or automate virtually all aspects of program operation, including user-defined properties and other variables.

The software can be extended with four options (dynamic, thermal, Finite Element (FE) liners and blocks, and C++ User-Defined Constitutive Models) that are offered separately from the base program (see Options for more information).

3DEC offers a fully integrated development environment that includes: project management facilities, built-in text editor, automatic movie-frame generation, extensive plotting capabilities, and results monitoring.


  • Analysis of jointed rock and blocky structures based on the Distinct Element Method (DEM)
  • Built-in project management tools, text editor, automatic movie-frame generation, and extensive plotting capabilities,
  • Ideal for modeling large movements and deformations
  • Accurate simulation of fast rotating rigid blocks
  • Blocks may be rigid or automatically zoned (tetrahedral and/or hexahedral) to make deformable blocks
  • Optimized to solve problems requiring non-linear multi-physics
  • 64-bit, double-precision calculations
  • Multi-threaded algorithms with no CPU locks or additional CPU fees
  • Includes groundwater joint fluid-flow
  • Includes groundwater matrix (i.e., permeable solids) fluid-flow between fractures NEW
  • Fluid flow may be either uncoupled or fully coupled hydromechanical
  • Built-in scripting language, FISH, provides powerful user-control to parameterize, analyze, review, and modify nearly every aspect of the simulation, even during cycling
  • Track histories of model properties and results throughout the model to allow for comparison to actual monitoring and instrumentation data

Materials and Constitutive Models

  • Includes 13 built-in constitutive material models:
    • Null
    • Elastic, isotropic
    • Elastic, transversely isotropic
    • Elastic, orthotropic
    • Drucker-Prager
    • Mohr-Coulomb
    • Ubiquitous-joint (UBJ)
    • Strain hardening/softening
    • Bilinear strain hardening/softening UBJ
    • Double yield
    • Modified Cam-clay
    • Hoek-Brown
    • Modified Hoek-Brown
  • Includes 8 built-in creep material models:
    • Classical (viscoelastic)
    • Burgers substance (viscoelastic)
    • Two-component power law
    • Reference creep formulation (WIPP model) for nuclear-waste isolation studies
    • Burgers-creep (viscoplastic; combination of Burgers and Mohr-Coulomb models)
    • Power-law (viscoplastic; combination of the two-component power law and the Mohr-Coulomb model)
    • WIPP-creep (viscoplastic model combining the WIPP model and the Drucker-Prager model)
    • Crushed-salt
  • Includes three built-in joint material models:
    • Elastic
    • Mohr-Coulomb
    • Continuously Yielding
  • Specify statistical distributions for material properties
  • Groundwater fluid flow analysis is included
    • Effective stress (water table)
    • Steady-state
    • Transient
  • Proppant simulation in fluid-filled joints NEW
  • Includes eight creep material models to simulate time-dependent material behavior:
    • a classical viscoelastic (Maxwell) model
    • Burgers substance viscoelastic model
    • a two-component power law
    • a reference creep formulation (the WIPP model) for nuclear-waste isolation studies
    • a Burgers-creep viscoplastic model combining the Burgers model and the Mohr-Coulomb model
    • a power-law viscoplastic model combining the two-component power law and the Mohr-Coulomb model
    • a WIPP-creep viscoplastic model combining the WIPP model and the Drucker-Prager model
    • a crushed-salt constitutive model
  • Create, load, and run customized (user-defined models) zone and joint models via C++ (Option)

Model Construction

  • Block generation using primitives (face, tetrahedral (NEW), brick, drum, and prism)
  • Bonded block models can be generated based on mesh zones NEW
  • Automatic tunnel region generator using tunnel profile
  • Automatic mesh generation in fully deformable blocks using tetrahedral and hexahedral zones (including mixed-discretization)
  • Easily separate objects into separate geometric regions using geometric surfaces, volumes, or geometry offsets
  • Geometry creation using polygons
  • Results visualization (property/results painting) on DXF or STL geometry
  • Create regions using cubic blocks cut by user-defined outlines (replaces PGEN)
  • Wall-type blocks speed up model runs as motion and wall-to-wall contacts are skipped in solution cycles
  • Built-in block zone densification for hexahedral and tetrahedral (NEW) mesh refinement, including automatic octree generation from surfaces and volumes
  • Built-in ability to assign groups based on counting projection intersections for defining complex groups and ranges for blocks, zones, gridpoints, contacts, and subcontacts:
    • to refine a 3DEC model before identifying a group of blocks as weak material (e.g., faults, damage around an excavation)
    • to assign properties to zones that are inside of some geometric surface that defines a geological unit
    • to define excavation sequences using DXF files representing periodic excavation surfaces
    • to assign different groups to blocks that will be excavated
    • to carve groups out of an existing 3DEC model along multiple surfaces

Joint Sets and Discrete Fracture Networks

  • Joint structures can be built into the model directly from geologic mapping
  • Specify continuous and discontinuous joint sets by orientation, number or spacing, origin, and persistence
  • Random seed values and statistical deviations can be utilized to create multiple realizations (examine sensitivities and risk)
  • Blocks can be hidden (and subsequently restored, similar to a layer) to limit joint cutting or joining
  • Easily define non-persistent joints (e.g., circular) and their properties
  • Blocks can be cut using Discrete Fracture Network (DFN) geometry
  • Incorporate Discrete Fracture Networks (DFNs) by specifying density (e.g., number of fractures per unit distance/area/volume) and orientation-, size-, and position-distributions for circular disks or polygons
  • Import/export both Itasca circular disk or Fracman polygon DFN data formats

Boundaries and Initial Conditions

  • Discontinuities (interfaces, joints, joint sets, and DFNs) are regarded as distinct boundary interactions between blocks; joint behavior is prescribed for these interactions
  • Stress boundary
  • Applied force (load) boundary
  • Velocity boundaries along Cartesian axes and along a normal direction
  • Structural elements for ground support include: beams, cables, and (optionally) liners
  • Add external infrastructure (such as dams, bridges, walls, buildings, etc.) using finite element structures (optional)
  • Time-varying boundary conditions
  • Couple a detailed inner model to a larger far-field model for increased solution efficiency
  • Define in-situ stresses and stress gradients
  • Includes tools to easily transfer field stresses to model stresses
  • Automatically assign in-situ stresses based on model surface topology, depth, material density, and stress-ratio values NEW
  • Quiet (i.e., non-reflecting) and free-field boundaries (with dynamic option)

FISH Scripting

  • Provides powerful functionality to parameterize, analyze, review, and modify nearly every aspect of the simulation, even during model cycling
  • Built-in text editor provides command syntax error checking and context sensitive help for simpler, faster model generation
  • Intrinsic variables and functions (e.g., cos, round, inverse(matrix), clock, max, sqrt, urand, parse, cross, dot, pi, and more)
  • Control statements (e.g., loop, loop-while, command, if/else-if, case, pause/continue, and more)
  • Intrinsic email functions to automate model notifications and result delivery (e.g., attached plots, history CSV data, and parameter values)
  • Input statements to pass data to and from FISH functions
  • Inline FISH (embed FISH calculations within a command)
  • Extra variables for blocks, zones, gridpoints, contacts, and subcontacts permit user-defined parameters to be applied, computed, or measured for each of these data structures
  • Blocks, zones, gridpoints, contacts, and subcontacts and be filtered by groups. Each data structure may be associated with multiple groups using group slots (similar to layers)
  • Error handling functions
  • Full FISH access to geometric data
  • Model data can be exported as a binary or ASCII file for use in, or exchange with, third-party software
  • Call functions at any stage of a calculation cycle (e.g., start of cycle, when contact created/detected, when sub-contact created/detected, and velocity input) using FISHCALL functions
  • Learn more about FISH

Factor of Safety Analysis

  • Automatic, fast solutions using the shear strength reduction (SSR) method and a converging bracket approach
  • May include strength properties for certain zoned material models and the Mohr-Coulomb joint model
  • Applicable for Mohr-Coulomb, Ubiquitous-Joints, Hoek-Brown, and Modified Hoek-Brown constitutive models
  • Color blocks by excess shear stress or factor of safety for a given hypothetical set of joints NEW

User Interface

  • Similar interface to Itasca's FLAC3D and PFC software
  • Project file and project management tools simplify organizing data files, save files, plots, etc.
  • Associated files in a project can be bundled together into a single file to easily share and archive work
  • Multiple layout configurations and customization are possible
  • Advanced ranging and filtering of model regions
  • Built-in, advanced text editor with command and FISH context coloring
  • Command-level UNDO: a record of all commands used to create a model is recorded in the SAV file, permitting the model to be rebuilt to the previous state
  • Advanced methods of filtering objects (connected to interfaces, on model surface, and by object extent)

Post Processing

  • Extensive visual plotting capabilities, including contouring on blocks, zones, and joint-surfaces; scalar, tensor, and vector plots, 3D isosurface contouring of gridpoint and zone data;
  • Cut-planes, clip-boxes, and transparency settings to assist with engineering analysis and high-quality results plotting
  • Equal area and equal angle stereonet plotting of DFN joint orientations
  • Equal angle stereonet plotting of joint normal orientations and orientations of major, minor, and intermediate principal stresses
  • Export plots as PNG, DXF, VRML, SVG, or PostScript formats
  • Easily export history results to spreadsheet-compatible CSV files
  • Import and export tables, histories, and model variable data to ASCII files
  • Automatically export a series of PNG images at regular cycle intervals to create a video-ready image set (third party software required for video assembly)
  • Ability to export plot views as data files permits favorite views (orientation, plot-items, property settings, etc.) to be saved and restored in the same, or another, model
  • Track and plot fragments (i.e., disconnected groups of blocks) NEW

Responsive Help

  • In addition to an extensive, ten-volume set of physical and PDF manuals, interactive HTML manuals are embedded in 3DEC
  • Contextual help is available. The relevant HTML help section can be accessed for any command or FISH function simply by pressing the F1-key

Dynamic Analysis

3DEC simulates the nonlinear response of a system (soil, rock, and structures) to excitation from an external (e.g., seismic) source or internal (e.g. vibration or blasting) sources. It can reproduce the evolution of permanent movements due to yield. This option models the full dynamic response of a system in the time domain. Capabilities include specification of velocity or stress-wave input, quiet (i.e., viscous) boundaries, free-field conditions (ideal for earthquake simulation), and damping.

Two types of damping are available in 3DEC: mass-proportional and stiffness-proportional. Mass-proportional damping applies a force which is proportional to absolute velocity and mass, but in the direction opposite to the velocity. Stiffness proportional damping applies a force, which is proportional to the incremental stiffness matrix multiplied by relative velocities or strain rates, to contacts or stresses in zones. Either form of damping may be used separately or in combination (i.e., Rayleigh damping).

In 3DEC, the dynamic input can be applied as either a prescribed velocity history or as a stress history. An acceleration history needs to be integrated numerically first to produce a velocity history for 3DEC.

Thermal Analysis
The thermal option in 3DEC allows the simulation of transient heat conduction. There are two separate formulations of the thermal logic. The first is a numerical formulation using the explicit or implicit finite difference method. This method is more accurate for short times, and includes thermal-mechanical fluid coupling. The second is an analytical formulation that uses superposition of point heat sources* in an infinite medium. This method is suitable for long thermal times, and is very fast.

Comparison of features available with numerical vs analytical formulations.

*Point heat sources may be placed individually, in lines, or in grids, to represent point, line, or plane sources of heating. This formulation yields rapid calculations, correct application of mechanical boundary conditions, incorporation of the infinite thermal boundary,and the ability to use inhomogeneous and anisotropic mechanical properties.

Finite Element Structural Liners

Modeling cables and beams is part of the standard functionality of 3DEC. This option adds the ability to model tunnel liners and external structures (such as dams, bridges, walls, buildings, etc.). The tunnel liner logic automatically places equally spaced triangular-shaped plates on the inside surface of an excavation or tunnel. External structures can be modeled using finite elements that are attached to the 3DEC model.

User-Defined Constitutive Models

User-defined constitutive models can be written in C++ for both zoned block materials and joint materials. These are compiled as DLL files that can be loaded whenever needed with this option. Microsoft Visual Studio 2010 is used to compile the DLL files. The main function of the constitutive model is to return new stresses, given strain increments. However, the model must also provide other information (such as name of the model and material property names) and describe certain details about how the model interacts with the code. Itasca maintains an online library of UDM C++ models where users can submit and download novel and useful constitutive models.

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