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Continuum Modeling for Geomechanics in 3D

Choose FLAC3D for advanced geotechnical problem solving. Ideal for 3D soil, rock, concrete analysis, structural ground support, and groundwater flow. Optimize solutions now and check out the latest version, FLAC3D 9.1!


What Kinds Of Problems Can FLAC3D Solve?

Magnified horizontal soil displacement, showing the pile pinning effect, of a pile-supported wharf subjected to liquefaction-induced lateral spreading.

Modeling of an underground station construction in Paris. Contour of soil displacements at the end of the excavation phase. Courtesy of VINCI Construction.

Exaggerated deformations within a drift in a nuclear waste repository due to thermal effects.

FLAC3D model of the mechanical response of dual-purpose spent nuclear fuel canisters to internal pressurization.

FLAC3D model of shaft and surrounding excavations for an underground facility showing calculated major principal stress. Courtesy of ITASCA Sweden.

Displacement field around two salt caverns visualized with contours, isosurfaces, and user-customized streamlines.

Displacement vectors and magnitude contours in the concrete and intermediate principal stresses in the cavern.

Petroleum reservoir highlighting the complex fault geology.

Displacements of ground near a hydroelectricity generating arch dam.

Model to estimate the loads applied to the buried penstock of a pumped storage hydroelectricity project.

Vertical displacements in the foundation of a wind turbine.

Block cave geometry.

Block cave strength-stress ratio contours.

Displacement isocontours 4x3.

Open pit mine with many major faults showing factor of safety contours.

Pit stresses.

Pit faces.

Mining trim.


Underground cable and shell.

Underground mine support.


Blast movement simulation of the dynamic rock movement and muck pile formation informed by FLAC3D models to predict burden velocity and time-dependent gas pressure.

A cylindrical sample composed of aggregates and asphalt binder mastic to simulate the laboratory dynamic modulus test.

Coupled simulation showing a FLAC3D metallic platen being pressed into a material represented by PFC3D bonded particles.

Virtual UCS lab test using a strain-softening model. One half of the model is plotted showing contours of maximum shear strain rate and the other zones that have yielded.


Why Choose FLAC3D?

Explore FLAC3D's comprehensive features and user-friendly interface. Unlock powerful computing capabilities, including the ability to run two instances simultaneously. Discover why FLAC3D is the ideal choice:
  • Small-strain mechanics (gridpoints remain fixed)

  • Large-strain mechanics (gridpoints move with displacement)

  • Effective stress (pore pressure)

  • Automatic factor of safety

  • Back-analyze failure and calibrate forward-prediction

  • Multiple, simultaneous failure mechanisms

  • Zone relaxation for gradual excavation and construction sequencing

  • Groundwater flow

  • Service limit state (SLS) and ultimate limit states (ULS) based on displacements

  • Liquefaction

  • Settlement and consolidation

  • Surface subsidence

  • Recovery and dilution

  • Coupled ground-structure interaction (beams, cables, piles, shells, geotextiles, liners)

  • Options available: Dynamics (Earthquakes, Blasting, Vibration), Thermal, Creep, User-Defined Constitutive Models (UDM), IMASS Damage Model

  • FLAC3D models use a combination of interactive tools and commands. FLAC3D simplifies modeling with interactive features such as CAD file compatibility, built-in mesh generation, intuitive boundary skinning, and automatic stress initialization.


    For advanced meshing, use Griddle and Rhino 3D CAD to build and precisely mesh complex models as a FLAC3D grid. Easily define groups in the model pane and assign constitutive models and material properties using the built-in database.

  • FLAC3D utilizes multi-threading and optimized solutions for fast, responsive, and accurate simulations. Maxwell damping for dynamic simulations and enhanced solvers for fluid flow and thermal simulations enable efficient solution times.


    Multi-threaded FISH and Python libraries provide extremely efficient model scripting when user customization is chosen. Users may also run two instances of FLAC3D on the same computer simultaneously, cutting down on overall time to solution for multiple models.

  • FLAC3D offers robust simulation capabilities, including large-strain simulation to visualize the full extent of model deformation, 26 built-in constitutive models for different ground behaviors, dynamics analysis to simulate earthquakes and liquefaction, and nonlinear deformable structures to design ground support.


    Advanced plotting tools, FISH scripting, and Python integration provide unparalleled model control and customization, while statistical tools and data import options expand modeling possibilities.

  • Enjoy flexibility in modeling and your workspace with FLAC3D’s highly adaptable tiled user interface that allows users to layout the program as preferred, work with hundreds of plots efficiently, as well as build, construct, and modify the modeling workflow as needed.


    Use FISH and/or Python scripting for model parameterization, custom visualizations, adding new physics, and/or model run control. Use one of the 26 built-in constitutive models for material behavior or develop a custom user-defined constitutive model (UDM). FLAC3D licenses allow for two instances to run on the same computer simultaneously.

  • In conjunction with interactive tools, FLAC3D uses commands to provide a compact representation of the model (as a data file) for repeatability, to ensure path dependency (excavation sequence and any other sequence of events, such as boundary conditions or material properties), and for flexibility.


    Intuitively structured commands, built-in contextual help, and command auto-completion help users learn and work with commands. Most user interface interactions are automatically translated into commands so you can see how they are composed and reuse them. The built-in text editor adds efficiency to creating and running models with commands.

  • Improved Fluid Flow and Thermal Analyses

    The mechanical-fluid and mechanical-thermal commands and workflow have been significantly simplified, improving the usability and learnability of fluid flow analyses.


  • Improved Multi-Process Modeling

    Multi-process models contain two or more coupled or decoupled solutions (mechanical/static, fluid, dynamic, thermal, and creep). Significant improvements have been made to simplify multi-process models, making analyses easier to use and understand.


  • Updated Null Logic

    Zones may be nulled to represent removal of material that you may want to backfill later or cycle through glaciation periods (ice/no ice). When a zone is nulled, the model behaves as if the zone has been deleted, but the zone position and shape continue to be tracked for easy reuse later.


  • Better Scripting

    • Python can now access the built-in geometry logic (user-defined nodes, edges, faces, volumes, etc.).
    • The contourpy Python library (for calculating contours of 2D quadrilateral grids) is now built-in.

  • And More!
    • Grouping operations are now faster.
    • New Hoek-Brown curve fitting and plotting tool – then add these value as PROPERTY commands right into your model.
    • QT 6 user interface libraries have been updated:
    – User interface appearance is improved on high-resolution monitors.
    – No need to specify OpenGL Mode.
    • By place an * at the start of a command, all related warning messages will be suppressed.


See What Users Have To Say

"[FLAC3D] excels in modeling intricate geomechanical behaviors in three dimensions, offering an invaluable tool for our team. Its user-friendly interface was easy to navigate, enabling us to swiftly model scenarios we once found challenging to conceptualize.”
Sofiane Djezzar, EERC/UND
"FLAC2D and FLAC3D have proven to be essential tools in the fields of geomechanics and geotechnical engineering. These two codes represent an absolute benchmark for performing slope stability analyses and for solving soil-structure interaction problems with particular reference to bridges and viaducts."
Walter Salvatore, Consorzio Fabre
"The recent changes and enhancements made to [ITASCA's] FLAC2D & 3D codes cover very well our increasing professional demands in advanced Civil Engineering Applications – well done."
Fulvio Besseghini, Lombardi Engineering Ltd.
“[ITASCA] software [including] FLAC3D, UDEC, and 3DEC are quite powerful and user-friendly.”
Jung Wang, PhD Candidate
“In addition to its technical prowess, the support provided by the creators of FLAC3D [ITASCA] deserves commendation. Their commitment to user assistance through well-documented resources, tutorial videos, and responsive support channels greatly facilitates the learning curve for newcomers, ensuring a smooth and productive experience.”
Zarina Mukhamedyarova, PhD Candidate
“Integrating FLAC3D has unquestionably transformed our approach to geotechnical challenges. The unparalleled confidence and accuracy it provides make it an indispensable asset.”
Sofiane Djezzar, EERC/UND
“The software [is] very stable and the software manual is very well-organized and clear. [Also], the software integration between PFC3D and FLAC3D makes it easier to create coupled finite difference and discrete element models than [ever] before.”
Chong Wei, PhD
“I’ve been using [ITASCA] software, mainly FLAC2D and FLAC3D and UDEC, for the past 20+ years. It helped solved complex problems and allow me to customize the solution through coding. [ITASCA] software is my ultimate go-to for difficult geotechnical problems.”
Farzaan Abbasy, PhD
“The numerical modelling for mitigating the liquefaction risk is a challenging [task] which would be otherwise impossible without a finite difference code like FLAC3D.”
Gianluca Fasano, PhD
"The precision that FLAC3D offered, especially in visualizing potential subsurface movements and stresses, empowered us to make more insightful decisions throughout the project. The end result was both safer and more efficient."
Sofiane Djezzar, EERC/UND
"The implementation of finite difference method ensures high-quality results, and the new versions of the codes have been significantly improved with a new user interface while the technical support from ITASCA is absolutely outstanding."
Walter Salvatore, Consorzio Fabre
“I used FLAC3D for a slope stability project and I was really impressed with its simplicity and, of course, the FISH [scripting] language.”
Wenbo Zheng, PhD
“This software has proven to be an exceptional tool, offering an array of features that greatly facilitate various aspects of research work. FLAC3D's user-friendly interface, coupled with its comprehensive documentation and extensive video materials, makes it accessible and approachable for users of all skill levels.”
Zarina Mukhamedyarova, PhD Candidate
"The GUI, FISH language, constitutive models, & formulation make FLAC my go-to analysis tool for project & research work."
Richard Armstrong, Geoanalysis Support/ CSU, Sacramento

Expand Your Software Capabilities With These Options:

Expand your FLAC3D software capabilities with our range of add-on options, designed to tackle diverse engineering challenges effectively. Explore our selection of options to customize your FLAC3D experience.

  • FLAC3D offers three-dimensional, fully dynamic analysis that extends simulation capabilities to a wide range of dynamic problems in earthquake engineering, soil liquefaction, seismology, blasting, and mine rockbursts.

    You can specify acceleration, velocity, or stress waves as an exterior or interior boundary condition and include wave absorbing and free-field boundary conditions. Dynamics supports soil-structure interaction, can be coupled to thermal analysis, and includes a Dynamics Wizard to pre-process ground motions. Couple Dynamics to groundwater flow for analyses involving time-dependent pore pressure changes associated with liquefaction. FLAC3D includes several dynamic and liquefaction constitutive models and includes Maxwell damping, resulting in fast dynamic model run times.


  • FLAC3D’s thermal analysis combines conduction and advection models to simulate heat transfer and thermal-induced displacements for modeling geothermal and nuclear waste applications. Thermal provides for one-way coupling to the mechanical stress and pore-pressure calculations. It includes four thermal material models and variable boundary conditions. Heat sources may be inserted into the model, which may decay exponentially with time.

    The Hydration-Drucker-Prager constitutive model is also included, which can adjust the mechanical properties of a material corresponding to the hydration grade (or equivalent concrete age). Implicit solvers are now included in FLAC3D, making thermal model run times incredibly fast.


  • FLAC3D’s creep analysis can be used to simulate the behavior of materials that exhibit time-dependent material behavior. FLAC3D provides 11 constitutive models for simulating creep, which cover both viscoelastic and viscoplastic behavior.

    You can also modify these models or create new creep constitutive models using C++ for a user-defined constitutive model (UDM). Applications include oil and gas reservoirs, compressed-air energy storage, mining, frozen-soils, nuclear waste disposal, and deep tunnels.


  • FLAC3D’s user-defined constitutive model (UDM) greatly expands the software’s versatility by permitting users to develop their own constitutive models, using C++ scripting, to describe a material behavior that differs from ITASCA’s built-in library. Templates and instructions are provided. Start by modifying one of the built-in constitutive models or create an entirely new material behavior.

    UDMs can be automatically loaded into your FLAC3D project and may be freely distributed (as a DLL file). ITASCA maintains a UDM Library on our website should you want to share your constitutive model. With the UDM you may also download and run constitutive models from the UDM Library, including PM4 and UBC liquefaction models.


  • FLAC3D’s IMASS is designed to simulate the rock mass response to excavation-induced stress changes. IMASS captures damage progression from intact rock to bulked material considering dilation and bulking effects in plastic deformation. Its unique two-stage softening behavior distinguishes damage from subsequent disturbance, making it a crucial tool for accurate post-peak rock mass representation in mining.



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