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FLAC2D 9.0 NEW FEATURES

	Slope Stability Analysis: FLAC2D's distinct features: ability to model complex geological structures, simulate nonlinear soil and rock behavior, and consider groundwater flow and pore pressure effects.
	Foundation Design and Soil-Structure Interaction: FLAC2D's distinct features: ability to model complex geological structures, simulate nonlinear soil and rock behavior, and consider groundwater flow and pore pressure effects.
	Retaining Walls and Excavation Support: FLAC2D's distinct features: Ability to model complex geometry and reinforcement arrangements, simulate soil-structure interaction, analyze staged construction processes, and assess stability and deformation characteristics.
	Tunnels and Underground Structures: FLAC2D's distinct features: Capability to model complex tunnel geometries, simulate the excavation process, evaluate support systems, consider groundwater flow, and analyze the influence of rock mass behavior.
	Seismic Design and Analysis: FLAC2D's distinct features: Ability to simulate seismic ground motion, model dynamic soil behavior, evaluate liquefaction potential, assess the stability of slopes and foundations under seismic loads, and analyze soil-structure interaction during earthquakes.
	Ground Improvement Techniques: FLAC2D's distinct features: Capability to model various ground improvement methods such as soil reinforcement, grouting, and soil nailing, simulate their installation and behavior, assess their effectiveness in improving soil properties, and optimize design parameters.
	Geotechnical Hazards Assessment: FLAC2D's distinct features: Ability to model complex geological conditions, simulate landslides and rockfalls, evaluate the stability of slopes and rock masses, analyze the impact of groundwater, and design mitigation measures.
	Geotechnical Design Optimization: FLAC2D's distinct features: Capability to analyze multiple design alternatives, assess stability, deformation, and safety factors, optimize parameters, and evaluate the cost effectiveness of geotechnical designs.
	Groundwater Flow and Seepage Analysis: The unique features of FLAC2D that make it possible to solve these applications include its ability to model complex geometries and geological structures, simulate nonlinear soil and rock behavior, consider soil-structure interaction effects, analyze staged construction processes, simulate groundwater flow, and pore pressure, and evaluate stability, deformation, and dynamic response. These features make FLAC2D a powerful tool for geotechnical analysis and enable engineers to tackle a wide range of civil engineering challenges.

 

 

 

 

 Why Choose FLAC2D?

EASE-OF-USE

• Interactively create models from CAD files (DXF, STL), geometry sketching, or images
• Automatic structured and unstructured mesh generation
• Skinning to automatically identify model boundaries to set boundary conditions
• Interactively assign groups, constitutive models, and properties/distributions
• Built-in database to save/import/export material properties
• Automatic stress initialization
• Intuitive commands are easy to learn
• Most UI interactions are automatically translated into commands, which can be saved to a datafile and re-used
• Built-in help / command auto-complete
• Advanced built-in text editor makes creating and running models simple
• With Version 9’s common UI, seamlessly move between programs or easily couple to other licensed (or demo) Itasca software

FASTER

• Multi-threaded to utilize the full power of your computer for faster solutions
• Multi-threaded FISH Lists and Operators to query or modify the model incredibly quickly, even while cycling
• New Maxwell damping for 10-200x faster performance for dynamic models
• FLAC2D plane-strain or axisymmetric models run up to 2-5x faster than equivalent FLAC3D models
• New, faster implicit solvers for fluid flow and thermal calculations

POWERFUL

• Large-strain simulations to capture the full extent of model deformation
• Mixed and Nodal Mixed Discretization (NMD) for accurate plasticity calculations
• Includes over 20 built-in constitutive models for soil, rock, and concrete
• Built-in liquefaction models P2P-Sand and NorSand with PM4Sand, PM4Silt, and UBCSAND liquefaction models coming
• Advanced plotting tools to understand model results and for working with hundreds of plots on real projects
• FISH, Itasca’s scripting language, provides you with unparalleled control over, and customization of, the model
• Built-in Python 3.10 scripting includes SciPy for plotting, NumPy for computing, and Pyside for UI customization
• Statistical generation tools for Discrete Fracture Networks (DFNs)

FLEXIBLE

• Highly customizable UI and modeling
• All licenses permit two instances of FLAC2D to be run on the same computer
• Store custom model data via “Extra” variables, for nearly all model elements, that can be read, written to, and plotted
• Import and export any ASCII data format
• Optional user-defined constitutive models (UDM) can be written in C++ using Visual Studio template

ANALYSES

• Plane-strain
• Axisymmetric
• Static stability
• Dynamic (option) stability
• Automatic factor of safety analysis (shear strength reduction method)
• Back-analyze failure and calibrate forward-prediction
• Service limit state (SLS) and ultimate limit states (ULS) based on displacements
• Zone relaxation simulates gradual excavation for construction sequencing, , including out-of-plane excavation
• Simulate material damage, and failure
• Effective stress using conventional or complex pore pressure distributions
• Fluid flow (single-phase)
• Seepage and consolidation
• Model ground support correctly with coupled ground-structure interaction (beams, cables, piles/rockbolts, and liners are available)
• Simulate discontinuities (faults, joints, bedding planes, and construction boundaries) using interfaces; capture yielding or failure, shear displacements, opening, and closure along them
• Static liquefaction
• Dynamic (option) liquefaction

 FLAC2D Features

USER INTERFACE

FLAC2D features the improved user interface (UI) of Itasca's Version 9 software. The UI consists of the Main Menu; the Project pane to view associated files and plots; the Command Console to input or view model commands and see model output or program messages (information/warnings/errors); the Content Workspace for creating new, and editing existing data files, plots, sketch sets, and the Model pane; the Contextual Tools/Help panel which changes depending on what has focus; the Layout Toggles to hide and show the the Project pane, Workspace, or Command Console; and the Status bar.

Use the Content Selector (the drop-down menu above the Content Workspace) to create plots, data files, sketch sets, or the work in the Model Pane. Then use the split icon (rectangle with a vertical line) to create new content to the left or right, or above or below the existing tile. This can be repeated for several levels of splitting. You may also double-click on certain file types listed in the Project Panel to bring them into the current tile. Each tile has it's own contextual tool bar. Easily manage your data files, sketch sets, saved model states, and hundreds of plots for working on real projects. Tiles can be closed by using X icon. This layout is saved with the Project.

Model execution (green arrow icon) and stop (red stop sign icon) now resides within the Text Editor and each data file making up the model.

 

SKETCH Workspace

The Sketch workspace provides interactive tools for drawing and meshing 2D models. A sketch is a 2D geometric design of a model that can be created interactively. For FLAC2D, zones are directly created from a sketched design (termed a set). Each “sketch” is created within a separate sketch set; a modeling project may contain multiple sets.

Both (a) structured and (b) unstructured meshes may be automatically generated in the Sketch workspace. Any closed (watertight) polygon can be meshed. Structured mesh can be used only for simply-connected 3- or 4-sided polygons, while unstructured mesh can be applied to any closed polygon.

Operations in the Sketch workspace are automatically translated into commands that are sent to the Console pane. You can save or copy the record of these operations to help learn the actual commands, to reproduce the sketch set exactly, or to use as a starting point for parameterizing the sketch.

MODEL PANE

The Model pane is an interactive user interface for displaying the current model. It has tools for selecting, showing, hiding, and grouping objects. As you manipulate your model, most of your actions will be automatically translated into commands that are sent to the Console pane. There are a few tools specific to certain data sets (zones, beam, pile, cable, and zone faces/edges) via the drop-down menu:

 

ZONES

• Assigning a Group Name to a Selection
• Assigning a Constitutive Model
• Set Model Properties
• Access the Materials Database
• Densify Selected Zones
• Set Color Labels

ZONE FACES/EDGES

Automatically "skin" the model to generate face/edge groups. “Skinning” refers to automatic face group generation, which occurs as follows: the program looks for contiguous faces on the boundaries of zone blocks and puts them into automatically named groups within the slot named Skin. Two faces are not considered contiguous if: the angle between two faces exceeds the break-angle, or if the two faces belong to different groups. Unless internal is specified, the operation of the command is restricted to external faces. This is very useful for defining the model boundaries and easily assigning boundary conditions.

TEXT EDITOR

The built-in Text Editor provides the ability to edit text-based project resources (data files, FISH files, etc.). It is limited to the display of text and may be used with any text file, including Python scripts (providing these are saved as *.py files). The main tools for text editing appear on the the toolbar, most of which also appear on the pane’s right-click menu. Users may customize preferences and settings.

The Text Editor provides features specifically designed to work with Itasca software data files, including: automatic syntax highlighting; collapsible FISH blocks, commenting/uncommenting lines, line numbering, and command-authoring assistance tools. Perhaps most importantly, command processing of a data file’s contents is available from within the pane via the “Execute/Stop” button ( run ) on the toolbar. One or more lines of code may be executed using “Run Selection” button on the toolbar (or via the CTRL-SHIFT-E keyboard shortcut).

CONSTITUTIVE MODELS

• FLAC2D includes 23 built-in constitutive models:
  • Null
  • Elastic
  • Anisotropic Elastic
  • Druker-Prager
  • Mohr-Coulumb
  • Ubiquitous-Joint
  • Ubiquitous-Anisotropic
  • Strain-Softening/Hardening
  • Double-Yield
  • Modified Cam-Clay
  • Swell
  • Bilinear Strain-Softening/Hardening Ubiquitous-Joint
  • Hoek-Brown
  • Hoek-Brown-PAC
  • CYSoil
  • CHSoil
  • Plastic-Hardening
  • Soft-Soil
  • Finn
  • NorSand
  • P2PSand
  • Von-Mises
  • Concrete

 

  

What's Different between FLAC and FLAC2D?

 

FLAC2D is different from FLAC in several important ways:

1. The most apparent difference is the new user interface (UI). All Itasca Version 9 programs use the our updated common framework and UI. This permits users to seamlessly move between Itasca programs and, for FLAC2D, to easily couple to PFC2D 9.0 (now available as an Alpha demonstration version). Also, as new features and capabilities are created in one program, they can become available in all the other common-framework programs.
2. FLAC2D does not use i, j space — making it easier to build, and work with, models. Grids may be structured or unstructured, but in either, case zones and gridpoints are identified by IDs, spatial location (i.e., x,y-coordinates), or group names — rather than by regular i, j indexes.
3. FLAC2D commands and FISH syntax have been updated and match closely those in the current version of FLAC3D and, in many cases, they are exactly the same, absent the z-coordinate. While there will be a learning curve for FLAC users (that users in 3DEC, FLAC3D, PFC, and UDEC have already undergone), this change provides a major performance improvements (e.g., multi-threaded FISH), improved functionality, more built-in functions, and new capabilities (e.g., inline FISH). See Mapping in the Help in Transitioning section below.
4. Built-in and integrated Python scripting to control and modify models. Python includes NumPy, SciPy, and PySide for powerful computing, advanced scientific graphics, and creating custom UI tiles (respectively).
5. There is no Project Tree. Commands and FISH functions are stored in data files that are listed in the Project tile on the left – similar to the Project Tree in FLAC. The difference is that the data files may be called in any order. Commands generated though UI interactions (sketch sets, model pane, plotting, etc.) are still found in the Record. To save these commands as data files, view the Record tab at the bottom, right click and select “Save as Data File”. You may also copy text from the Record tab. To save these commands as data files, view the Record tab at the bottom, right click and select “Save as Data File”. You may also copy text from the Record tab and paste into a data file.
6. Although FLAC has a built-in text editor, the FLAC2D built-in text editor is far more powerful and easier to work with for all your FISH scripting needs. Data files may also contain Python code; just save the data file as a *.py file to run it using Python. Python has its own space, as a Console tab, to issue code and review output.

Stress Initialization and Boundary Conditions

It is important to appreciate that, like FLAC3D, FLAC2D initializes stress from the model origin (0, 0), whereas FLAC initializes stress from the starting position of the specified range. Also, stress gradations should be specified in terms of change in stress per unit length, whereas FLAC bases the stress variations on the total length of the boundary.

For example, for a 60 m deep model domain with rock density of 2700 kg/m³ and a k_o ratio of 0.5, model stresses can be initialized using the commands:

FLAC

set gravity 9.81

initial syy -1589220 var 0.0, 1589220 ;(2700. * 9.81 * 60)

initial sxx -794610 var 0.0, 794610 ;(2700. * 9.81 * 60 * 0.5)

initial szz -794610 var 0.0, 794610 ;(2700. * 9.81 * 60 * 0.5)

 

FLAC2D

model gravity 0 -9.81

zone initialize stress-yy 0.0 gradient 0, [2700.*9.81]

zone initialize stress-xx 0.0 gradient 0, [2700.*9.81*0.5]

zone initialize stress-zz 0.0 gradient 0, [2700.*9.81*0.5]

The square brackets above indicate an inline FISH function, which is useful for embedding calculations or FISH variables into commands.

Where stress initialization is based simply on gravitational loading, in FLAC2D the previous three commands can simply be replaced with the the following command, which will automatically accounts for any material density variation over the model domain. They keyword ratio refers to the k_o ratio of horizontal to vertical stress.

zone ini-stress ratio 0.5

Ranges

In FLAC, zones and gridpoints are identified by their i,j coordinates. For example, to fix the gridpoints on the left side of a model, you may give a command like fix x i=1. In FLAC2D, you must use the keyword range when identifying things. Since there is no i,j, things are commonly identified with coordinates or group names. A possible equivalent to the previous command in FLAC2D would be zone gridpoint fix velocity-x range position-x 0.

How are FLAC and FLAC2D alike?

• FLAC2D provides Sketch sets and the Model Pane, which are similar to the Geometry Builder and Virtual Grid editors in FLAC. Sketch sets allow you to import DXFs or background images, draw lines and shapes, assign groups, and specify zoning densities.
• There is a Record which tracks anything that modifies the model state, including most UI interactions. Parts of the Record may be reviewed to aid in learning commands and copied into a data file to reproduce some functionality in the future.
• Model groups, properties, and constitutive models can be assigned interactively using the Model Pane.
• You can add, import, and export material properties using a built-in materials database. The database includes an example set of soil properties.
• The common-framework uses Projects to manage any data files, plots, saved states, and the model record.
• Like FLAC, FLAC2D has a Console where any commands issued and program output (warning/error messages or data) are displayed. There are also two tabs associated with the Console to display any information lists and the model state Record.
• Generating plots in FLAC2D is similar to FLAC. You need to create a new plot and then add specific plot items to it (e.g., zones, vectors, structural elements). One difference is that there is not a long list of possible plot items to choose from. Instead, you just choose what needs to be plotted (zones, for example) and then specify a label (e.g., groups) or a contour (e.g., displacements).

  FLAC2D Options

 

Options in FLAC2D are sold separately from the base license, allowing users to extend the program’s capabilities as meets their own analysis needs while minimizing costs for features that aren't needed. Modules available as options for FLAC2D include: Dynamic, Creep, Thermal, and C++ Plug-ins for creating and running custom user-defined constitutive models (UDMs) and functions.

 

Dynamic Option

• The dynamic analysis option permits two-dimensional, fully dynamic analysis with FLAC2D. 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. FLAC2D contains absorbing and free-field boundary conditions to simulate the effect of an infinite elastic medium surrounding the model.
• This option can be coupled to the structural element model, thus permitting analysis of soil-structure interaction brought about by ground shaking. The dynamic feature can also be coupled to the groundwater flow model. This allows, for example, analyses involving time-dependent pore pressure change associated with liquefaction. The dynamic model can likewise be coupled to the optional thermal model in order to calculate the combined effect of thermal and dynamic loading. The dynamic option extends FLAC2D's analysis capability to a wide range of dynamic problems in disciplines such as earthquake engineering, seismology, and mine rockbursts.

 

Thermal Option

The thermal option of FLAC2D incorporates both conduction and advection models. The conduction models allow simulation of transient heat conduction in materials, and the development of thermally induced displacements and stresses. The advection model takes the transport of heat by convection into account; it can simulate temperature-dependent fluid density and thermal advection in the fluid. This thermal option has several specific features:

1. Four thermal material models are available: isotropic conduction, anisotropic conduction, isotropic conduction/advection, and the null thermal model.
2. As in the standard version of FLAC2D, different zones may have different models and properties.
3. Any of the mechanical models may be used with the thermal model.
4. Temperature, flux, convective and adiabatic boundary conditions may be prescribed.
5. Heat sources may be inserted into the material as either point sources or volume sources. These sources may decay exponentially with time
6. Both explicit- and implicit-solution algorithms are available.
7. The thermal option provides for one-way coupling to the mechanical stress and pore-pressure calculations through the thermal expansion coefficients.
8. Temperatures can be accessed via FISH for users to define temperature-dependent properties.

 

Creep Option

This option can be used to simulate the behavior of materials that exhibit creep (i.e., time-dependent material behavior).

There are ten available material models in FLAC2D that simulate viscoelastic and viscoplastic (creep) behavior:

1. Maxwell model — A classical viscoelastic model known as the Maxwell substance.
2. Burgers model — A classical viscoelastic model known as the Burgers substance, composed of a Kelvin model and a Maxwell model.
3. Power model — A two-component power law model used for mining applications (e.g., salt or potash mining).
4. WIPP model — A reference creep model commonly used in thermomechanical analyses associated with studies for the underground isolation of nuclear waste in salt.
5. Burgers-Mohr model — A viscoplastic model combining the Burgers model and the Mohr-Coulomb model.
6. Power-Mohr model — A viscoplastic model combining the two-component power model and the Mohr-Coulomb model.
7. Power-Ubiquitous model — A viscoplastic model combining the two-component power model and the ubiquitous-joint model.
8. WIPP-Drucker model — A viscoplastic model combining the WIPP model and the Drucker-Prager model.
9. Soft-Soil-Creep model — A soft soil model considering the time-dependent secondary compression.
10. WIPP-Salt model — A viscoplastic model modified from the WIPP model; includes volumetric and deviatoric compaction behavior for salt-like materials.

All ten models are available with the creep option. A FLAC2D grid can be configured for both a creep calculation and a dynamic (option) calculation. However, both models are generally not used simultaneously because of the widely different timesteps. In addition, it is also possible for users to write their own creep constitutive models using the C++ UDM option.

C++ User Defined Constitutive Models Option

• With this option, you may create your own user-defined constitutive model (UDM) for use in FLAC2D.
• The main function of the constitutive model is to return new stresses, given strain increments. However, the constitutive 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 FLAC2D. This option is required to both load and run UDM models.
• This option is required in order to run user constitutive models from Itasca’s online UDM Library.