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FLAC3D is the best solution to solve complex geotechnical problems for three-dimensional analyses of soil, rock, concrete, structural ground support, and groundwater flow. Options can be added to expand analyses (dynamic, creep, thermal, and IMASS) and to create user-defined constitutive models (UDMs). FLAC3D 9 has an improved user interface (UI) and new interactive tools to construct and interpret models easily. FLAC3D provides an incredibly accurate simulation of real-world geotechnical conditions for engineering applications, such as slope stability, underground excavation behavior, and earthquake simulations. Flexible commands and scripting allow for model parameterization, flexibility, customization, and automation.

 

 

Seriously Faster

 

SOLVE FASTER

FLAC3D 7 saw some impressive solution performance improvements over previous versions, but with FLAC3D 9 we've pushed this even further by optimizing the zone stiffness stability calculations, so that static and dynamic models run pproximately 2-3 times faster for zones using the SOLVE command.

 

SHAKE FASTER

Maxwell Damping, an improved form of damping, is now available for zones, structures, and deformable links. With Maxwell damping, FLAC3D is a dynamics dynamo - making the analyses of large 3D site response and soil-structure interaction practical, while maintaining the high accuracy FLAC3D is known for.

 

FLOW & HEAT FASTER

Implicit solvers for saturated-fluid flow and thermal calculations have been implemented for much faster analyses. For example, the new solvers provided the same response for a nuclear waste repository thermal model run over 10,000 years of simulated time, but required less than 30 minutes to run in FLAC3D 9. The same model requires 43 hours of modeling time using FLAC3D 7. Fast analytical temperature calculation for specified sources has also been implemented.

 

FISH FASTER

For math calculations, assigning stresses, and accessing properties FLAC3D 9 has a modest 10% boost in performance compared to Version 7. However, if you are still running Version 6 or older, update to Version 9 and see performance improvements of between 2 and 100 times using FISH splitting (more efficient than looping) and FISH operators (multithreaded FISH functions). Actual performance gains will depend on the FLAC3D version and your computer hardware.

 

WORK FASTER

Zone plotting is now multi-threaded for 10x faster plot generation. And the saving/restoring algorithm is faster, especially for models with many groups and slots.

 

 

Highspeed Dynamics

 

MAXWELL DAMPING

Systems undergoing dynamic loading, such as an earthquake or explosive blast, naturally dissipate vibrational energy over time. For a dynamic numerical analysis, some form of artificial damping needs to applied so that the model should reproduces such energy losses.

FLAC3D 9 introduces Maxwell dynamic damping for time-domain seismic deformation analyses. FLAC3D models using Maxwell damping can be 10-200 times faster, and as accurate, than those models using Rayleigh damping. With Maxwell damping, large, 3D site response and soil-structure interaction are now practical to analyze.

 

SOIL STRUCTURE INTERACTION

For example, the FLAC3D 9 model shown below simulates a caisson foundation, using shell elements, which is much stiffer than the surrounding soils. This model consists of nearly 100,000 zones and over 15,000 structural shell elements.

An analysis of a 30-second earthquake input time history for this model, using a typical computer, requires approximately 10 hours using Maxwell damping, whereas it would require more than 50 days when Rayleigh damping was used. In other words, using Maxwell damping, the calculation is 120 times faster for this model. This is a substantial benefit for similar practical projects.

RAMBERG-OSGOOD HYSTERETIC DAMPING

The Ramberg-Osgood model has also been added as one of several hysteretic damping calculations for dynamic modeling. The Ramberg-Osgood hysteretic model overcomes the shortcoming of overly large damping at large shear strains by other available hysteretic damping models in FLAC3D. Hysteretic damping may be preferred where: (1) designers and licensing authorities do not accept fully nonlinear simulations and (2) faster model run times are desired, as additional damping (e.g., Rayleigh) may not be necessary.

 

 

Zone Joints

 

Similar to 3DEC and PFC joints, Zone Joints are an alternative to Interfaces and better represent multiple intersecting joints, faults or discontinuities in small-strain FLAC3D models. The advantage of Zone Joints is that they are two-sided, so the order in which they are created does not affect the results, and forces/displacements at the intersections are more accurate. Contacts are created between separate Zone Joints, defining a two-sided, internal surface that forces can be transmitted across. Mohr-Coulomb is the default joint behavior, but all built-in contact models can be used.

 

Zone joints also use an incremental formulation for normal stress thereby resolving some Interface related penetration issues. Although FLAC3D does not support any joint cutting functionality, Griddle generated FLAC3D grids include external/interval face groups representing discontinuities. 3DEC generated model zones, joints, and groups can also be easily converted to FLAC3D grids using the new block to-flac3d command.

 

OPEN PIT EXAMPLE

Below you can see a series of plots for a 500-meter deep open pit with several large faults. The model mesh was generated using Griddle. The site geology includes several rock lithologies and there is a nearby waste dump. One critical fault has a lower friction angle than the others. This example demonstrates the main considerations for modeling faults in FLAC3D and will be available shortly in the FLAC3D 9 documentation.

 

 

Non-Linear Structural Elements

 

FLAC3D 9 introduces new non-linear structural elements for ground support for beams and piles/rockbolts and for shells, geogrids, and liners. Simple plastic hinges have been supplemented with a numerical integration scheme.

 

BEAM-TYPE STRUCTURES

• The beam-type plastic constitutive models update the internal element forces by integrating the internal stress over the beam volume using a numerical integration scheme.
• The plasticity is induced by axial and bending deformations; twisting deformation induces an elastic response.
• The beam may have either a rectangular or circular cross section.
• Integration points are distributed throughout the volume of the beam elements.
• There are three beam plastic constitutive models, each of which is a one-dimensional version of the corresponding 3D model used by the zones:
  • von Mises (steel beams)
  • Mohr Coulomb (concrete beams)
  • Strain Softening/Hardening Mohr Coulomb (concrete beams)

The following commands are for an rectangular cross-section aluminum ally beam:

struct beam cmodel assign von-mises struct beam cmodel plastic-integration rectangular cross-section rectangular layout 3 5 3 struct beam property direction-y (0,1,0) young 68e9 poisson 0.33 strength-yield 270e6 modulus-plastic 0.0; 6061-T6 Al alloy

 

SHELL-TYPE STRUCTURES

• The plastic constitutive models update the internal element forces by integrating the internal stress over the shell volume using a numerical integration scheme.
• There are a group of integration points distributed throughout the volume of each shell element.
• There are three shell plastic constitutive models, each of which is a plane-stress version of the corresponding 3D model used by the zones:
  • von Mises (steel shells)
  • Mohr Coulomb (concrete shells)
  • Strain Softening/Hardening Mohr Coulomb (concrete shells)
• Plasticity is provided by the DKT, CST and DKT-CST finite elements.

 

 

Concrete, Rock, Metal

 

With the addition of three new constitutive models, FLAC3D now includes 27 built-in constitutive models, not including any options.

 

CONCRETE CONSTITUTIVE MODEL

This Concrete model is a plastic-damage model where damage is based on fracture-energy and modulus degradation. Damage may be both extension and compression. It is compatible to Mohr-Coulomb yielding criteria.

 

COLUMNAR-BASALT CONSTITUTIVE MODEL (COMBA)

The Columnar-Basalt (COMBA) model accounts for the presence of up to four arbitrary orientations of weakness (ubiquitous joint) in a non-isotropic elastic matrix. The model can be applied to model quadrangular (hexagonal) columnar basalt with cross-joints by specifying that two (three) of the ubiquitous joints are oriented along the column axis, and another along the cross-joints.

The model's elastic behavior accounts for the compliance of the column matrix and that of the joints. The criterion for failure on the planes consists of a strain hardening/softening Coulomb envelope with tension cutoff; the strain hardening/softening behavior can be specified (using a table) for joint cohesion, friction, dilation, and tension. In addition, an amplification factor can be applied to joint dilation that depends on the angle between a set direction (i.e. the column mean axis) and the direction of slip on the joint.

Creep on weak planes is available with the Creep Option.

 

VON-MISES CONSTITUTIVE MODEL

The Von-Mises model has a yield envelope based on a von-Mises criterion. The position of a stress point on this envelope is controlled by an associated flow rule for shear failure. This model is suitable for metal-like materials and includes optional kinematic hardening. This model may be applied to both for solid zones or ground support structural elements.

 

IMPROVED PLASTC-HARDENING (PH) MODEL

The Plastic-Hardening (PH) model is a shear and volumetric hardening constitutive model for the simulation of soil behavior. FLAC3D 9 uses a new implementation based on the new Brick algorithm which considers the unloading-reloading strain-dependent stiffness modulus. This overcomes shortcomings in the previous algorithm which demonstrated poor performance for nested hysteretic loops (e.g., overshooting problem), making the PH model a more practical dynamic model.

 

IMPROVED UBIQUITOUS-ANISOTROPIC MODEL (CANISO)

The Ubiquitous-Anisotropic Model combines the Anisotropic (Transversely) Elastic Model and the ubiquitous-joint model. In FLAC3D 9, this model has been improved through the addition of a Mohr-Coulomb matrix option. The joint behavior in both cases is based on a Mohr-Coulomb law.

 

 

Improved User Interface

 

NEW LOOK AND FEEL

The most apparent change with FLAC3D Version 9 is the new user interface (UI). It's designed to be flexible, fit the way you work, and have more efficient plotting. Rather than fixed layouts, dynamically add what you want, where you want it, by splitting new windows in the work space. The UI is organized into the following:

1. Main Menu.
2. Project pane to view associated files, sets, and plots.
3. Command Console to input or view model commands and see model output or program messages (information/warnings/errors)
4. Content Workspace for creating new, and editing existing, (a) data files, (b) plots, (c) sketch sets, geometry sets, building block sets, and (d) the Model pane.
5. Contextual Tools/Help panel which changes depending on what has focus.
6. Layout Toggles to hide and show the the Project pane, Workspace, or Command Console.
7. Status bar.

Split the workspace into as few, or as many, windows as you want. View, create, and edit the model pane, data files, plots, and more in any of them.

Use the Select Content drop-down menu to view the model pane; or create a new (or modify an existing) data file, plot, sketch-, geometry-, or building blocks-set. Use the Split drop-down menu to divide the work space into a new window (left, right, above, or below the current window) to view additional data files, plots, sets, or the model pane.

 

EXTRUDER NOW SKETCH

The Extruder is now part of a new Sketch tool. The Sketch tools includes 2D drawing, DXF import, and meshing tools to generate structured and unstructured 2D meshes automatically. Use the extruder tools to extend the model into 3D. Structured meshes may also be further modified using Building Blocks.

 

New Tools:

• Slope wizard for simple, 1-, 2-, and 3-bench, and dam profiles (similar to FLAC/Slope)
• Tunnel wizard for circular, rectangular, arched roof, double arch, 3-arch horseshoe, and 5-arch horseshoe profiles
• Revolve a 2D Sketch along a vertical or horizontal axis
• As well as linear extrusions, now extrude a 2D Sketch along a curved path interactively. For a structured mesh, generate models and modify them in Building Blocks.

{insert image carousel of sketch, wizards, 2-tunnel extrusions, curved tunnel extrusion (with bounds & topo)}

MODEL PANE

The Model Pane includes tools for selecting model objects for:

• Manually or automatically grouping zones and zone face
• Assigning zone constitutive models
• Densifying zones (into more, finer zones)
• Creating 2D structural elements (shells, liners, etc.)

In FLAC3D 9, new tools have been added to the Model Pane:

• Define and interactive specify material properties
• Create, then import/export material properties in a built-in properties database

BETTER PLOTTING

• Added more contour plot control. including user-defined contour ramp.
• Format and precision of the contour legends can be specified.
• Added option to swap axes for table and profile charts.
• Added option to include minor gridlines to charts.
• Added improved chart logarithmic scale.
• Added option to omit “past” states when plotting yield states.
• Added more contour plot-items (e.g., fos, fluid-head, and histories).

 

Powerful Scripting

 

PYTHON

The Python programming language is embedded inside FLAC3D. Python is a general purpose programming language with good support for scientific and numerical programming. Python has been extended to allow models to be manipulated from Python programs. The Python modules NumPy, SciPy, and Pyside are included with FLAC3D for scientific computing, science and engineering tools (optimization interpolation, integration, etc.), and customizing the user interface, respectively.

With FLAC3D 9, Python has been updated to version 3.10.5 to let you work with the latest available modules.

 

FISH

FISH is an embedded programming language that enables the user to interact with and manipulate models, defining new variables and functions as needed. These functions may be used to extend, add to, or control the program.

FLAC3D 9 includes the latest version of FISH and updated documentation for working with multithreaded FISH splitting and operators.

 

MULTITHREADED FISH

If you are modeling using FISH, be sure to use splitting rather than loops and use operators in order to best utilize your multithreaded computer hardware and minimize your modeling time.

 

For example, taking the FLAC3D Hoek-Brown Slope example in the documentation, rather than using a constant value for the Hoek-Brown constitutive model property constant-sci, let's assign a value to each zone using a pseudo-random uniform distribution within 30 ±10 MPa, to provide a degree of rock strength variability across the model as shown below.

 

A timing test was run five times for each of the FISH functions above by calling the time.clock intrinsic function at the start and end of the function and calculating the difference. The following figure shows the average time required for each approach discussed above (in hundredths of a second) for a model with 228,000 zones. The test was performed on an i9 CPU (3.7 GHz) with 64 GB RAM and 10 cores (20 logical processors).

 

While any of the methods reviewed above are effectively instantaneous, the performance will become more important for very large models with millions or tens of millions of objects (zones, blocks, etc.) and/or if such functions are being called during cycling (i.e., each step). As such, a method (operators) that is over 260,000 times faster than another (loop while) becomes highly desirable.

 

 

FLAC3D Options

 

Options in FLAC3D 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 FLAC3D include: IMASS, Dynamic, Creep, Thermal, and C++ Plug-ins for creating and running custom constitutive models and FISH intrinsic functions.

 

IMASS

The Itasca Constitutive Model for Advanced Strain Softening (IMASS) has been developed to represent the rock mass response to excavation induced stress changes. IMASS represents the damage around an excavation, slope, or caving process by accounting for the progressive failure and disintegration of the rock mass from intact, jointed, and/or veined rock to a disaggregated, bulked material. IMASS is based on empirical relationships and uses strain and zone-size dependent properties that reflect the impacts of dilation and bulking as a rock mass undergoes plastic deformation.

IMASS uniquely contains two softening (or residual) yield envelopes to represent the two-stage softening behavior for a rock mass that distinguishes between damage (caused by fracturing and the associated loss of cohesion and tensile strength) and the subsequent disturbance (due to bulking) in rock mass behavior. This two-stage softening/weakening behavior in IMASS is critical to accurately represent the rock mass post-peak behavior for underground and surface mining applications.

IMASS is available as a built-in, optional constitutive model for FLAC3D (version 7.0 or later) and is sold as a separate, monthly or annual lease, license.

 

DYNAMIC OPTION

The dynamic analysis option permits three-dimensional, fully dynamic analysis with FLAC3D. 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. FLAC3D 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 FLAC3D's analysis capability to a wide range of dynamic problems in disciplines such as earthquake engineering, seismology, and mine rockbursts.

 

CREEP OPTION

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

There are eleven available material models in FLAC3D 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.
11. Columnar-Basalt (COMBA) Model — The Columnar-Basalt (COMBA) model accounts for the presence of up to four arbitrary orientations of weakness (ubiquitous joint) in a non-isotropic elastic matrix. NEW

 

All eleven models are available with the creep option. A FLAC3D grid can be configured for both a creep calculation and a dynamic 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.

 

THERMAL OPTION

The thermal option of FLAC3D 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 FLAC3D, 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.

 

HYDRATION

Hydration is defined as the chemical absorption of water into a substance, a process by which heat is generated (hydration heat). The setting of concrete (which can be considered as a transition from liquid to solid phase) is the most relevant example for the hydration process in the engineering world.

The effects of the hydration process can be separated into different physical parts, where the thermal and mechanical parts are the most relevant. The implementation of hydration models in FLAC3D follows this separation, as the hydration heat generation and heat transfer are dealt with in thermal models, material hardening and strength development are implemented as constitutive models of mechanical behavior. The hydration model is based on a procedure that considers empirical rules, theoretical considerations, and practical experiences (Onken and Rostásy 1995).

A thermal hydration constitutive model is implemented in FLAC3D. For simulating a hydration process, a mechanical constitutive model that can adjust the mechanical properties corresponding to the hydration grade (or equivalent concrete age) is also required. The Hydration-Drucker-Prager model is provided to handle those mechanical aspects.

 

USER-DEFINED CONSTITUTIVE MODELS

You may create your own user-defined constitutive model (UDM) for use in FLAC3D. The model must be written in C++ and compiled as a DLL file, and can be loaded whenever needed or loaded automatically if placed in the “exe64\plugins\models” folder. 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 FLAC3D. A Visual Studio 2010 "Project Template" is provided to start development quickly, or users can create a project from scratch. 

By implementing this optional feature, users can access new constitutive models from Itasca’s online UDM Library. 

This option is required to both load and run UDM models.