FLAC, Fast Lagrangian Analysis of Continua, is numerical modeling software for advanced geotechnical analysis of soil, rock, groundwater, and ground support in two dimensions. FLAC is used for analysis, testing, and design by geotechnical, civil, and mining engineers. It is designed to accommodate any kind of geotechnical engineering project that requires continuum analysis. FLAC utilizes an explicit finite difference formulation that can model complex behaviors, such as problems that consist of several stages, large displacements and strains, non-linear material behavior, or unstable systems (even cases of yield/failure over large areas, or total collapse).
FLAC has been developed primarily for geotechnical engineering applications in the fields of civil, mining, oil and gas, and power generation. FLAC is also a valuable tool used for research in rock- and soil-mechanics, particularly of localization and evolution of shear bands in frictional materials. FLAC has also been used in the manufacturing field where the analysis of highly deformable materials is needed.
The explicit, time-marching solution of the full equations of motion (including inertial terms) permits the analysis of progressive failure and collapse, which are particularly important phenomena for mine design and geotechnical construction.
Options in FLAC are sold separately from the code license, allowing users to extend the program’s capabilities as meets their own analysis needs.
Dynamic Analysis: Can be performed with FLAC using the optional dynamic calculation module. User-specified acceleration, velocity, or stress waves can be input directly to the model either as an exterior boundary condition or an interior excitation to the model.
Creep Analysis: This option can be used to simulate the behavior of materials that exhibit time-dependent material behavior.
Two-phase Flow: The two-phase flow option in FLAC allows numerical modeling of both fluid-flow and fully coupled simulations (with optional capillary pressure) of two immiscible fluids through porous media.
Thermal Analysis: The thermal analysis option in FLAC permits both conduction and advection to be incorporated into models.
FLAC offers large strain simulation of continua using interfaces that simulate faults, joints, or boundaries. It utilizes an explicit solution scheme that can model unstable physical processes.
The program provides 19 built-in material models, groundwater flow, coupled mechanical-flow calculation, inclusion of structural elements, plotting statistical distribution of any property, optional automatic remeshing during solution, 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 program can be extended with options that are offered separately from the base program (see for more information).
FLAC offers a fully integrated development environment that includes: project management facilities, built-in libraries of materials, pre-defined meshes, movies, extensive plotting capabilities, and run-time monitoring of results.
GENERAL
MATERIALS and CONSTITUTIVE MODELS
FACTOR OF SAFETY ANALYSIS
POST PROCESSING
GRIDS and GEOMETRY
BOUNDARIES and CONDITIONS
SOLUTIONS
FISH SCRIPTING
Options in FLAC are sold separately from the code license, allowing users to extend the program’s capabilities as meets their own analysis needs. Modules available as options for FLAC include: Dynamic, Creep, Two-Phase Flow, Thermal, and User-Defined C++ Constitutive Models.
Dynamic Option
Dynamic analysis can be performed with FLAC using the optional dynamic calculation module. User-specified acceleration, velocity, or stress waves can be input directly to the model either as an exterior boundary condition or an interior excitation to the model. FLAC contains absorbing and free-field boundary conditions to simulate the effect of an infinite elastic medium surrounding the model. The dynamic calculation can be coupled to the structural element model (soil-structure interaction), to the standard groundwater flow model (liquefaction), and to the optional thermal model.
This option can be used to simulate the behavior of materials that exhibit creep (i.e., time-dependent material behavior).
There are nine available optional material models that simulate viscoelastic and viscoplastic (creep) behavior: the classical viscoelastic (Maxwell) model; a two-component power law; a reference creep formulation (the WIPP model) implemented for nuclear waste isolation studies; a Burger's creep viscoplastic model; a WIPP-creep viscoplastic model; a ubiquitous viscoplastic creep model; a crushed-salt constitutive model; a power-law viscoplastic creep with ubiquitous joints, and a NEW soft-soil creep model.
All nine models are available with the creep option. A FLAC grid can be configured for both a creep calculation and a dynamic calculation. However, both modes cannot be active simultaneously because of the widely different timesteps.
The two-phase flow option in FLAC allows numerical modeling of both fluid-flow and fully coupled simulations (with optional capillary pressure) of two immiscible fluids through porous media. The formulation applies to problems in which a fluid displaces another, and simultaneous flow of the two fluids takes place in the porous medium with no mass transfer between them. This optional feature extends the facility of the standard groundwater flow model.
The thermal analysis option in FLAC incorporates both the conduction and advection models (conduction: transient heat conduction and the development of thermally induced displacements and stresses; advection: transport of heat by convection — it can simulate temperature-dependent fluid density and thermal advection in the fluid). A thermal model can be run independently or coupled to the mechanical stress calculation or pore pressure calculation, either in static or dynamic mode.
New constitutive models can be added to FLAC as DLLs that are written and compiled in C++. The DLLs can be loaded in FLAC whenever needed, via the MODEL load command, or automatically if they are placed in the “exe64\plugins\models” folder.
By implementing this optional feature, users can access new constitutive models from Itasca’s online . An advantage of these models is that they run at nearly the same speed as built-in models, and noticeably faster than FISH constitutive models.
This option is required to both load and run UDM models.
Geared toward new users, FLAC Basics is an introduction to the application of Itasca's FLAC software in geotechnical engineering. FLAC 8 Basics is based on the original FLAC Basics text first written in 1993 and extends the documentation to demonstrate the power and ease-of-use of FLAC's graphical user interface and new features in FLAC version 8.0 to facilitate the solution of complex geotechnical problems.