flac 3d 1

INTRODUCTION 1 - 1

1 INTRODUCTION

1.1 Overview

FLAC3D is a three-dimensional explicit finite-difference program for engineering mechanics com-putation. The basis for this program is the well-established numerical formulation used by ourtwo-dimensional program, FLAC.* FLAC3D extends the analysis capability of FLAC into threedimensions, simulating the behavior of three-dimensional structures built of soil, rock or othermaterials that undergo plastic flow when their yield limits are reached. Materials are representedby polyhedral elements within a three-dimensional grid that is adjusted by the user to fit the shapeof the object to be modeled. Each element behaves according to a prescribed linear or nonlinearstress/strain law in response to applied forces or boundary restraints. The material can yield andflow, and the grid can deform (in large-strain mode) and move with the material that is represented.The explicit, Lagrangian, calculation scheme and the mixed-discretization zoning technique usedin FLAC3D ensure that plastic collapse and flow are modeled very accurately. Because no matricesare formed, large three-dimensional calculations can be made without excessive memory require-ments. The drawbacks of the explicit formulation (i.e., small timestep limitation and the question ofrequired damping) are overcome by automatic inertia scaling and automatic damping that does notinfluence the mode of failure. FLAC3D offers an ideal analysis tool for solution of three-dimensionalproblems in geotechnical engineering.

FLAC3D is designed specifically to operate on IBM-compatible microcomputers running Windows98 and later operating systems. Calculations on realistically sized three-dimensional models ingeo-engineering can be made in a reasonable time period. For example, models containing up toapproximately 140,000 elements can be generated within 128 MB RAM. The runtime to perform5000 calculation steps for a 10,000 element model of Mohr-Coulomb material is roughly 18 minuteson a 2.4 GHz Pentium IV microcomputer.† The number of calculational steps required to reach asolution state with the explicit-calculation scheme can vary, but a solution typically can be reachedwithin 3000 to 5000 steps for models containing up to 10,000 elements, regardless of material type.(The explicit-solution scheme is explained in Section 1 in Theory and Background.) With theadvancements in floating-point operation speed, and the ability to install additional RAM at lowcost, it should be possible to solve increasingly larger three-dimensional problems with FLAC3D.

FLAC3D can be operated from either a command-driven mode or graphics menu-driven mode. Thedefault command-driven mode is very similar to that used by other Itasca software products. Youwill find that most of the commands are the same as, or three-dimensional extensions of, those inFLAC. A menu-driven, graphical user interface is also available in FLAC3D for performing plotting,printing and file access.

* Itasca Consulting Group, Inc. FLAC (Fast Lagrangian Analysis of Continua.), Version 5.0, 2005.

† See Section 5 for a comparison of FLAC3D runtimes on various computer systems.

FLAC3D Version 3.0

1 - 2 User’s Guide

With the graphics facilities* built into FLAC3D, high-resolution, color-rendered plots are generatedquite rapidly. We have developed a graphics screen-plotting facility that allows you to instantlyview the model during creation from either command-mode or graphics menu-mode. The modelcan be translated, rotated and magnified on the screen for better viewing. Color-rendered plotsof surfaces showing vectors or contours can be made in 3D, and a two-dimensional plane can belocated at any orientation and location in the model for the purpose of viewing vector or contouroutput on the plane. All output can be directed to a black-and-white or color hardcopy device, tothe Windows clipboard, or to a file.

You will find that FLAC3D offers a facility for problem solving similar to that in FLAC. A comparisonof FLAC3D to other numerical methods, a description of general features and updates in FLAC3D

Version 3.0, and a discussion of fields of application are provided in the following sections. Ifyou wish to try FLAC3D right away, the program installation instructions and a simple tutorial areprovided in Section 2.

* The graphics facilities in FLAC3D utilize the Windows GDI.

FLAC3D Version 3.0

INTRODUCTION 1 - 3

1.2 Comparison with Other Methods

How does FLAC3D compare to the more common method of finite elements for numerical modeling?Both methods translate a set of differential equations into matrix equations for each element, relatingforces at nodes to displacements at nodes. Although FLAC3D’s equations are derived by the finitedifference method, the resulting element matrices, for an elastic material, are identical to those ofthe finite element method (for constant-strain tetrahedra). However, FLAC3D differs in the followingrespects.

1. The “mixed discretization” scheme (Marti and Cundall, 1982) is used foraccurate modeling of plastic collapse loads and plastic flow. This schemeis believed to be physically more justifiable than the “reduced integration”scheme commonly used with finite elements.

2. The full dynamic equations of motion are used, even when modeling sys-tems are essentially static. This enables FLAC3D to follow physically unstableprocesses without numerical distress. The approach to provide a time-staticsolution is discussed in the definition for “Static Solution” given in Section 2.3.

3. An “explicit” solution scheme is used (in contrast to the more usual implicitmethods). Explicit schemes can follow arbitrary nonlinearity in stress/strainlaws in almost the same computer time as linear laws, whereas implicit solu-tions can take significantly longer to solve nonlinear problems. Furthermore,it is not necessary to store any matrices, which means: (a) a large numberof elements may be modeled with a modest memory requirement; and (b) alarge-strain simulation is hardly more time-consuming than a small-strain run,because there is no stiffness matrix to be updated.

4. FLAC3D is robust in the sense that it can handle any constitutive model with noadjustment to the solution algorithm; many finite element codes need differentsolution techniques for different constitutive models.

These differences are mainly in FLAC3D’s favor, but there are two disadvantages.

1. Linear simulations run slower with FLAC3D than with equivalent finite elementprograms. FLAC3D is most effective when applied to nonlinear or large-strainproblems, or to situations in which physical instability may occur.

2. The solution time with FLAC3D is determined by the ratio of the longest naturalperiod to the shortest natural period in the system being modeled. This pointis discussed in more detail in Section 1 in Theory and Background, butcertain problems are very inefficient to model (e.g., beams, represented bysolid elements rather than structural elements, or problems that contain largedisparities in elastic moduli or element sizes).

FLAC3D Version 3.0


1.3 General Features

1.3.1 Basic Features

FLAC3D offers a wide range of capabilities to solve complex problems in mechanics, and espe-cially in geomechanics. Like FLAC, FLAC3D embodies special numerical representations for themechanical response of geologic materials. The program has twelve basic built-in material models:the “null” model; three elasticity models (isotropic, transversely isotropic and orthotropic elas-ticity); and eight plasticity models (Drucker-Prager, Mohr-Coulomb, strain-hardening/softening,ubiquitous-joint, bilinear strain-hardening/softening ubiquitous-joint, double-yield, modified Cam-clay and Hoek-Brown). These models are described in detail in Section 2 in Theory and Back-ground. Each zone in a FLAC3D grid may have a different material model or property, and acontinuous gradient or statistical distribution of any property may be specified.

Additionally, an interface, or slip-plane, model is available to represent distinct interfaces betweentwo or more portions of the grid. The interfaces are planes upon which slip and/or separation areallowed, thereby simulating the presence of faults, joints or frictional boundaries. The interfacemodel is described in Section 3 in Theory and Background.

FLAC3D contains an automatic 3D grid generator in which grids are created by manipulating andconnecting pre-defined shapes.* The generator permits the creation of intersecting internal regions(e.g., intersecting tunnels). The 3D grid is defined by a global x,y,z-coordinate system (rather thanin a row-and-column fashion as in FLAC). This provides more flexibility in model creation anddefinition of parameters in a three-dimensional space. Grid generation procedures are described inSection 1 in the Command Referenceunder the GENERATE command.

Boundary conditions and initial conditions are specified in much the same way as in FLAC. Eithervelocity (and displacement) boundary conditions, or stress (and force) boundary conditions, maybe specified at any boundary orientation. Initial stress conditions, including gravitational loading,may also be given, and a water table may be defined for effective stress calculations. All conditionsmay be specified with gradients. Boundary conditions are primarily assigned via the APPLY com-mand, and initial conditions via the INITIAL command, as described in Section 1 in the CommandReference.

FLAC3D incorporates the facility to model groundwater flow and pore-pressure dissipation, and thefull coupling between a deformable porous solid and a viscous fluid flowing within the pore space.(The coupled interaction is described further in Section 1.3.3.) The fluid is assumed to obey eitherthe isotropic or anisotropic form of Darcy’s law. Both the fluid and the grains within the porous solidare deformable. Non-steady flow is modeled, with steady flow treated as an asymptotic case. Fixedpore pressure and constant-flow boundary conditions may be used, and sources and sinks (wells)may be modeled. The flow model can also be run independently from the mechanical calculation,and both confined and unconfined flow can be simulated, with automatic calculation of the phreaticsurface. The fluid-flow model is described in Section 1 in Fluid-Mechanical Interaction .

* An optional meshing preprocessor is also available, see Section 1.3.2.

FLAC3D Version 3.0

INTRODUCTION 1 - 5

Structures, such as tunnel liners, piles, sheet piles, cables, rock bolts or geotextiles, that interactwith the surrounding rock or soil, may be modeled with the structural element logic in FLAC3D. It ispossible to either examine the stabilizing effects of supported excavations, or to study the effects ofsoil or rock instability on surface structures. The different types of structural elements are describedin Section 1 in Structural Elements.

A factor of safety can be calculated automatically for any FLAC3D model composed of Mohr-Coulomb material. The calculation is based on a “strength reduction technique” that performs aseries of simulations while changing the strength properties to determine the condition at which anunstable state exists. A factor of safety which corresponds to the point of instability is found, andthe critical failure surface is located in the model. The factor-of-safety algorithm is described inSection 3.8.

FLAC3D also contains a powerful built-in programming language, FISH, that enables the user todefine new variables and functions. FISH offers a unique capability to users who wish to tailoranalyses to suit their specific needs. For example, FISH permits:

• user-prescribed property variations in the grid (e.g., nonlinear increase in modulus withdepth);

• plotting and printing of user-defined variables (i.e., custom-designed plots);

• implementation of special grid generators;

• servo-control of numerical tests;

• specification of unusual boundary conditions; variations in time and space; and

• automation of parameter studies.

An introduction to FISH is given in Section 4. See Section 2 in the FISH volume for a detailedreference to the FISH language.

FLAC3D contains extensive graphics facilities for generating plots of virtually any problem variable.Three-dimensional graphics rendering is provided in high-resolution video modes. Plotting featuresinclude hidden surface plots, surface contour plots and vector plots. Plotted variables can be viewedin front of, behind, or on an arbitrary cross-section plane through, the model. This version of FLAC3D

has been compiled as a native Windows executable using the WIN32 API to support execution underWindows 98 and later operating systems. The program has the look and feel of a typical Windowsprogram; however, most modeling operations are performed in the command-driven mode, whilethe graphical user interface supports file-handling, model and response visualization (plotting),and printing (using standard Windows file-handling and printing facilities). Plotting operations aredescribed in Section 1 in the Command Referenceunder the PLOT command.

FLAC3D Version 3.0


1.3.2 Optional Features

Four optional features (for dynamic analysis, thermal analysis, modeling creep-material behavior,and writing user-defined constitutive models) are available as separate modules that can be includedin FLAC3D at an additional cost per module. Also, a fifth optional feature, a hexahedral-meshingpreprocessor (3DShop), is available as a separate program.*

Dynamic analysis can be performed with FLAC3D, using the optional dynamic-calculation module.User-specified acceleration, velocity or stress waves can be input directly to the model either asan exterior boundary condition or an interior excitation to the model. FLAC3D contains absorbingand free-field boundary conditions to simulate the effect of an infinite elastic medium surroundingthe model. The dynamic calculation can be coupled to the groundwater flow model; the level ofcoupling, including dynamic pore-pressure generation (liquefaction), is discussed in Section 1.3.3.The dynamic analysis capability is described in Section 3 in Optional Features.

There is a thermal analysis option available as a special module in FLAC3D. This model simulatesthe transient flux of heat in materials and the subsequent development of thermally induced stresses.The thermal model can be run independently, or coupled to the mechanical-stress calculation orpore-pressure calculation, either static or dynamic. (The coupling interactions are described inSection 1.3.3.) The thermal analysis capability is described in Section 1 in Optional Features.

There are eight optional material models available that simulate time-dependent (creep) materialbehavior (All creep models are described in Section 2 in Optional Features.):

(1) the classical viscoelastic (Maxwell) model;

(2) a Burger’s substance viscoelastic model;

(3) a two-component power law;

(4) a reference creep formulation (the WIPP model) implemented for nuclear waste isolationstudies;

(5) a Burger-creep viscoplastic model combining the Burger’s model with the Mohr-Coulombmodel;

(6) a power-law viscoplastic model combining the two-component power law and the Mohr-Coulomb model;

(7) a WIPP-creep viscoplastic model combining the reference creep formulation with theDrucker-Prager plasticity model; and

(8) a “crushed-salt” model that simulates both volumetric and deviatoric creep compaction.

* The hexahedral-meshing preprocessor, 3DShop, enables the creation of complex meshes forFLAC3D. 3DShop can substantially reduce model creation time. See Section 1 in the Hexahedral-Meshing Preprocessor —3DShop volume for more information and a tutorial on 3DShop.

FLAC3D Version 3.0

INTRODUCTION 1 - 7

User-defined constitutive models can be written in C++ and compiled as DLL (dynamic link library)files that can be loaded whenever needed with this optional feature. A Visual C++ Version 7.1compiler is used to compile the DLL files. The procedure to write new constitutive models andcreate DLLs is described in Section 4 in Optional Features.

1.3.3 Modeling Physical Processes and Interactions

The default calculation mode in FLAC3D is for static mechanical analysis. Alternatively, a ground-water flow analysis or a heat-transfer analysis can be performed, independent of the mechanicalcalculation. Both the groundwater flow and thermal models may be coupled to the mechanical stressmodel and to each other. Because the full equations of motion are used in FLAC3D, the couplingmechanisms operate in dynamic analyses as well as static analyses.

The coupling mechanisms are divided into three types of interaction: mechanical and groundwaterflow; mechanical and thermal; and thermal and groundwater flow. The level of interaction modeledin FLAC3D for each type is described below.

Mechanical-Groundwater Flow Coupling — Several types of fluid/solid interaction can be spec-ified in FLAC3D. One type of interaction is consolidation, in which the slow dissipation of porepressure causes displacements to occur in the solid (e.g., soil). Two mechanical effects are at workin this case: (1) the fluid in a zone reacts to mechanical volume changes by a change in the porepressure; and (2) the pore-pressure change causes changes in the effective stress that affect the re-sponse of the solid (e.g., a reduction in effective stress may induce plastic yield). Coupling betweenfluid and solid due to deformable grains can also be specified.

FLAC3D can calculate pore-pressure effects, with or without pore-pressure dissipation, simply bysetting the flow calculation on or off. Also, dynamic pore-pressure generation (e.g., related toliquefaction) can be modeled by accounting for irreversible volume strain in the constitutive model.This is done with two different built-in constitutive models: the “Finn” model, and the “Byrne”model. Both models are provided with the dynamic option.

By default, porosity and permeability are assumed constant. However, these properties can bemade a function of volumetric strain via a FISH function. As a consequence, two-way coupling ofmechanical stress and groundwater flow can be modeled with FLAC3D.

Other types of interaction, such as capillary, electrical or chemical forces between particles of apartially saturated material are not modeled directly by FLAC3D, but some of the effects may beincluded by providing suitable FISH functions. Similarly, a FISH function may be used to vary thelocal fluid modulus as a function of other quantities such as pressure or time.

Thermal-Mechanical Coupling — The thermal-mechanical coupling in FLAC3D is one-way: tem-perature change may induce a mechanical stress change as a function of the thermal-expansioncoefficient. Mechanical changes in the body, however, do not result in temperature change orchanges to thermal properties. Additionally, mechanical properties can be made a function oftemperature change, since FISH permits access to both temperatures and properties.

FLAC3D Version 3.0


Thermal-Groundwater Flow Coupling — The thermal calculation may be coupled to the ground-water flow calculation by making pore pressures a function of temperature change. Volumetricstrain can arise from thermal expansion of both the fluid and the grains within a saturated matrix.Pore pressure change results from this volumetric strain, as well as from mechanical volumet-ric strain. Groundwater flow can also influence heat transfer; an advection model that takes thetransport of heat by convection into account is provided. The advection model can also simulatetemperature-dependent fluid density and thermal advection in the fluid.

As with mechanical properties, groundwater properties can be made a function of temperaturechange by accessing temperature and property values via FISH.

FLAC3D Version 3.0

INTRODUCTION 1 - 9

1.4 Summary of Updates from Version 2.1

FLAC3D 3.0 contains several improvements; the new features are summarized in the followingsections. Existing data files created for Version 2.1 should still operate as before. You should beaware, however, that FLAC3D 3.0 will not be able to restore files saved by versions earlier thanFLAC3D 2.10.

1.4.1 Hysteretic Damping

A new damping facility for dynamic calculations, hysteretic damping, is now available in FLAC3D

Version 3.0. This form of damping allows strain-dependent modulus and damping functions to beincorporated directly into the FLAC3D simulation. This makes it possible for direct comparisonsbetween calculations with the equivalent-linear method and a fully nonlinear model, without anycompromises in the choice of constitutive model.

In addition, the need to introduce additional damping, such as Rayleigh damping, is greatly reducedand, consequently, the solution time is substantially reduced, by using hysteretic damping. The newdynamics-analysis chapter provides a detailed description of hysteretic damping, in Section 3.6.5.1in Optional Features, and a comparison of a FLAC3D model with hysteretic damping to that usingSHAKE91, in Section 3.6.2 in Optional Features.

1.4.2 Hoek-Brown Constitutive Model

The Hoek-Brown failure criterion is implemented as a built-in constitutive model in FLAC3D 3.0.The failure surface is nonlinear and is based on the relation between the major and minor principalstresses. The model incorporates a plasticity flow rule that varies as a function of the confiningstress level. The new constitutive models chapter contains further information and examples usingthe Hoek-Brown model — see Section 2.5.8 in Theory and Background. A verification problemfor the case of a cylindrical hole in a Hoek-Brown medium is given in Section 2 in Theory andBackground.

1.4.3 Thermal Advection Logic

The mechanisms of convective heat transfer (forced convection and free convection) in porousmedia are now provided with the thermal-analysis option in FLAC3D Version 3.0. Forced convectioncan be implemented with or without the fluid-flow configuration; in the latter case, fluid-specificdischarge is assigned as a property. Free convection is activated in FLAC3D zones containing thenew isotropic advection/conduction model (MODEL th ac). See Section 1.3.2 in Optional Featuresfor a description of the thermal advection logic, and Section 1.7 in Optional Featuresfor severalverification problems.

FLAC3D Version 3.0


1.4.4 Hydration Models

Hydration is defined as the chemical absorption of water into a substance, a process by which heatis generated — the so-called hydration heat. The setting of concrete, which can be considered as atransition from liquid to solid phase, is the most relevant example for the hydration process in theengineering world.

FLAC3D now includes two different thermal hydration models: one for concrete and one moregeneral hydration model. In these models, the thermal capacity, thermal conductivity and theactivation energy are dependent on the hydration grade.

During the hydration process, the mechanical properties of the material change permanently as afunction of the hydration grade. To support this, FLAC3D incorporates a modified version of theDrucker-Prager constitutive law, in which elastic and strength properties depend on the hydrationgrade.

The hydration models can only be applied with the thermal option. These models are not fullytested and should be used with caution. Documentation on the models is available at the ItascaConstitutive Models web site at www.itasca-udm.com.

1.4.5 Computation Enhancements

FLAC3D Version 3.0 runs approximately 10-20% faster than Version 2.1, as a result of modificationsto optimize the calculation cycle and use of an updated optimizing compiler.

All calculations and data in FLAC3D have been converted to double precision floating-point numbers.

1.4.6 Movie Feature

FLAC3D can generate movie files in two industry standard formats: AVI and DCX. The “movie” isa set of AVI or DCX images that are strung together and can then be repeated rapidly as a movie.The MOVIE and SET movie commands are used to invoke the movie feature.

1.4.7 Network Key Facility

A network-key version of FLAC3D 3.0 is available. This version allows a single hardware key tobe installed on a central (server) computer for a network. Individual users can then run FLAC3D

from any computer(s) on the network. (The number of instances in which FLAC3D can be run islimited by the network key.) Network keys require a special licensing arrangement and installation.Contact Itasca for details.

FLAC3D Version 3.0

INTRODUCTION 1 - 11

1.4.8 3DShop Compatibility

FLAC3D Version 3.0 has the ability to import grids generated by 3DShop. 3DShop is a powerfulsolid modeler and all-hexahedral grid generator that is available through Itasca. 3DShop will greatlysimplify the creation of grids for complex geometries. A description of 3DShop and a tutorial areprovided in Section 1 in the Hexahedral-Meshing Preprocessor —3DShop volume.

1.4.9 Fluid-Flow Particle Tracking

Particles can now be released into a flow field and their paths can be recorded and plotted. See theTRACK command.

1.4.10 New Features in FISH

The following new FISH functions have been added to FLAC3D 3.0 (see FISH in FLAC3D formore details):

do update updates all grid-related quantities

gp dynmul returns the dynamic multi-stepping multiplier to the global timestep

z dynmul returns the dynamic multi-stepping multiplier to the global timestep

z facenorm returns area and normal to a zone face

z fri returns the full rate of rotation increment tensor

z frr returns the full rate of rotation tensor

z inimodel initializes all derived model properties for a zone

z pstress returns the principal stress magnitudes and directions

z sonplane returns the normal and shear stress on a user specified plane

1.4.11 New Command and Utilities

The following new commands have been added to FLAC3D Version 3.0 (see the Command Refer-encefor more details):

GENERATE separate

separates a group of zones from the grid by duplicating gridpoints atshared boundaries

FLAC3D Version 3.0


GENERATE zone uwedge

a uniform wedge meshing primitive is now available

GROUP none

unassigns a group name from zones

GROUP remainder

allows assignment of a group name to all zones that belong to the nullgroup

IMPGRID

EXPGRID allows the importing or exporting of 3DShop grid files

INTERFACE wrap

simplifies creation of interfaces on group boundaries

MOVIE allows the creation of AVI or DCX animations

PDELETE allows deletion of particles in a fluid flow simulation

PLOT block state

state colors are now based on the state flags and no longer changewhen the view is changed

PLOT extract

allows extraction of numerical values from the grid into a FISH array

SOLVE fishhalt

allows user to specify termination criteria for solving through a FISHfunction

TRACK allows particle paths to be traced in a fluid flow simulation

1.4.12 New Example Applications

Two new example applications have been added to the Examples volume: Example Application12 — Embankment Loading on a Cam-Clay Foundation (see Section 12 in the Examples volume);and Example Application 13 — Impermeable Concrete Caisson Wall with Pretensioned Tiebacks(see Section 13 in the Examples volume).

FLAC3D Version 3.0

INTRODUCTION 1 - 13

1.5 Fields of Application

FLAC3D was developed primarily for geotechnical engineering applications. Section 6 contains abibliography of publications on the application of FLAC3D to geotechnical problems in the fieldsof mining, underground engineering, rock mechanics and research.

Some possible applications of FLAC3D are noted below. Because FLAC3D now has essentiallythe same capabilities of FLAC, many of the FLAC applications can now be extended into threedimensions with FLAC3D :

• mechanical loading capacity and deformations — in slope stability and foundation design;

• evolution of progressive failure and collapse — in hard rock mine and tunnel design;

• factor-of-safety calculation — in stability analyses for earth structures, embankmentsand slopes;

• evaluation of the influence of fault structures — in mine design;

• restraint provided by cable support on geologic materials — in rock bolting, tiebacks andsoil nailing;

• fully and partially saturated fluid flow and pore-pressure build-up and dissipation forundrained and drained loading — in groundwater flow and consolidation studies of earth-retaining structures;

• time-dependent creep behavior of viscous materials — in salt and potash mine design;

• dynamic loading on slip-prone geologic structures — in earthquake engineering and minerockburst studies;

• dynamic effects of explosive loading and vibrations — in tunnel driving or in miningoperations;

• seismic excitation of structures — in earth dam design;

• deformation and mechanical instability resulting from thermal-induced loads — in per-formance assessment of underground repositories of high-level radioactive waste; and

• analysis of highly deformable materials — in bulk flow of materials in bins and minecaving.

FLAC3D Version 3.0


1.6 Guide to theFLAC3D Manual

The FLAC3D Version 3.0 manual consists of eleven documents. This document, the User’s Guide, isthe main guide to using FLAC3D and contains descriptions of the features and capabilities of the pro-gram, along with recommendations on the best use of FLAC3D for problem solving. The remainingdocuments cover various aspects of FLAC3D, including theoretical background information, veri-fication testing and example applications. The complete manual is available in electronic formaton the FLAC3D CD-ROM (viewed with Acrobat Reader*), as well as in paper format. Specifictopics or keywords can be found across all volumes by implementing the search facility availablein Acrobat.

The organization of the eleven documents, and brief summaries of the contents of each section,follows. Please note that, if you are viewing the manual in the Acrobat Reader, by double-clickingon a section number given below, you will immediately open that section for viewing.

User’s Guide

Section 1 Introduction

This section introduces you to FLAC3D and its capabilities and features. An overviewof the new features in the latest version of FLAC3D is also provided.

Section 2 Getting Started

If you are just beginning to use FLAC3D, or use it occasionally, we recommend thatyou read Section 2. This section provides instructions on installation and operationof the program, as well as recommended procedures for running FLAC3D analyses.

Section 3 Problem Solving

Section 3 is a guide to practical problem solving. Turn to this section once you arefamiliar with the program operation. Each step in a FLAC3D analysis is discussed indetail, and advice is given on the most effective procedures to follow when creating,solving and interpreting a FLAC3D model simulation.

Section 4 FISH Beginner’s Guide

Section 4 provides the new user with an introduction to the FISH programminglanguage in FLAC3D. This includes a tutorial on the use of the FISH language.FISH is described in detail in Section 2 in the FISH volume.

* “Acrobat(R) Reader copyright (C) 1987-1999, Adobe Systems Incorporated. All rights reserved.Adobe and Acrobat are trademarks of Adobe Systems Incorporated.”

FLAC3D Version 3.0

INTRODUCTION 1 - 15

Section 5 Miscellaneous

Various information is contained in this section, including the FLAC3D runtimebenchmark and procedures for reporting errors and requesting technical support.Descriptions of utility files to assist with FLAC3D operation are also given.

Section 6 Bibliography

This section contains a bibliography of published papers describing some uses ofFLAC3D.

Command Reference

Section 1 Command Reference

All the commands that can be entered in the command-driven mode in FLAC3D aredescribed in Section 1 in the Command Reference.

FISH in FLAC3D

Section 1 FISH Beginner’s Guide

Section 1 in the FISH volume provides the new user with an introduction to theFISH programming language in FLAC3D. This includes a tutorial on the use of theFISH language.

Section 2 FISH Reference

Section 2 in the FISH volume contains a detailed reference to the FISH language.All FISH statements, variables and functions are explained and examples given.

Section 3 Library of FISH Functions

A library of common and general purpose FISH functions is given in Section 3 in theFISH volume. These functions can assist with various aspects of FLAC3D modelgeneration and solution.

Theory and Background

Section 1 Theoretical Background

The theoretical formulation for FLAC3D is described in detail in Section 1 in Theoryand Background. This includes both the description of the mathematical modelthat describes the mechanics of a system and the numerical implementation.

FLAC3D Version 3.0


Section 2 Constitutive Models: Theory and Implementation

The theoretical formulation and implementation of the various built-in constitutivemodels are described in Section 2 in Theory and Background.

Section 3 Interfaces

The interface logic is described and example applications are given in Section 3 inTheory and Background. A discussion on interface properties is also provided.

Fluid-Mechanical Interaction

Section 1 Fluid-Mechanical Interaction

The formulation for the fluid-flow model is described, and the various ways to modelfluid flow, both with and without solid interaction, are illustrated in Section 1 inFluid-Mechanical Interaction .

Structural Elements

Section 1 Structural Elements

Section 1 in Structural Elements describes the various structural element modelsavailable in FLAC3D. These include beams, cables, piles, shells, liners and geogrids.

Optional Features

Section 1 Thermal Option

Section 1 in Optional Features describes the thermal model option, and presentsseveral verification problems that illustrate its application both with and withoutinteraction with mechanical stress and pore pressure.

Section 2 Creep Material Models

The different creep material models available as an option in FLAC3D are described,and verification and example problems are provided in Section 2 in Optional Fea-tures.

Section 3 Dynamic Analysis

The dynamic analysis option is described, and considerations for running a dynamicmodel are provided in Section 3 in Optional Features. Several verification examplesare also included in this section.

FLAC3D Version 3.0

INTRODUCTION 1 - 17

Section 4 Writing New Constitutive Models

Users can write their own constitutive models for incorporation into FLAC3D. Themodels are written in C++ and compiled as a DLL file (dynamic link library) that canbe loaded whenever it is needed. The procedure to create new models is describedin Section 4 in Optional Features.

Hexahedral-Meshing Preprocessor —3DShop

Section 1 3DShop

3DShop is a hexahedral-meshing preprocessor that enables the creation of complexmeshes for FLAC3D. 3DShop uncouples the model building from the meshing pro-cess. The model is built via a menu-driven graphical interface, and then meshed usinga fully automatic all-hexahedral mesh generator. See Section 1 in the Hexahedral-Meshing Preprocessor —3DShop volume for details.

Verification Problems

This volume contains a collection of FLAC3D verification problems. These are testsin which a FLAC3D solution is compared directly to an analytical (i.e., closed-form)solution. See Table 1 in the Verifications volume for a list of the verificationproblems.

Example Applications

This volume contains example applications of FLAC3D that demonstrate the variousclasses of problems to which FLAC3D may be applied. See Table 1 in the Examplesvolume for a list of the example applications.

Command andFISH Reference Summary

A quick summary of all FLAC3D commands and FISH statements is contained in theCommand andFISH Reference Summary.

FLAC3D Version 3.0


1.7 Itasca Consulting Group, Inc.

Itasca Consulting Group, Inc. is more than a developer and distributor of engineering software.Itasca is a consulting and research firm comprised of a specialized team of civil, geotechnical andmining engineers with an established record in solving problems in the areas of:

Civil Engineering

Mining Engineering and Energy Resource Recovery

Nuclear Waste Isolation and Underground Space

Defense Research

Software Engineering

Groundwater Analysis and Dewatering

Itasca was established in 1981 to provide advanced rock mechanics services to the mining industry.Today, Itasca is a multidisciplinary geotechnical firm with 50 professionals in offices worldwide.The corporate headquarters for Itasca is located in Minneapolis, Minnesota. Worldwide officesof Itasca are operated as subsidiaries of HCItasca, Inc.: Hydrologic Consultants, Inc. (Denver,Colorado); Itasca Geomekanik AB (Stockholm, Sweden); Itasca Consultants S.A. (Ecully, France);Itasca Consultants GmbH (Gelsenkirchen, Germany); Itasca Consultores S.L. (Llanera, Spain);Itasca S.A. (Santiago, Chile); Itasca Africa (Johannesburg, South Africa); Itasca Consultants CanadaInc. (Sudbury, Canada); and Itasca Consulting China, Ltd. (Wuhan, China).

Itasca’s staff members are internationally recognized for their accomplishments in geological, min-ing and civil engineering projects. Itasca staff consists of geological, mining, hydrological andcivil engineers who provide a range of comprehensive services such as (1) computational anal-ysis in support of geo-engineering designs, (2) design and performance of field experiments anddemonstrations, (3) laboratory characterization of rock properties, (4) data acquisition, analysis,and system identification, (5) groundwater modeling, and (6) short courses and instruction in thegeomechanics application of computational methods. If you should need assistance in any of theseareas, we would be glad to offer our services.

Itasca Consulting Group is a subsidiary of HCItasca, Inc. HCItasca was formed in 1999 withthe merger of Hydrologic Consultants, Inc. (HCI) of Denver, Colorado with Itasca ConsultingGroup, Inc. of Minneapolis, Minnesota. HCI adds advanced groundwater modeling and dewateringexpertise to Itasca.

FLAC3D Version 3.0

INTRODUCTION 1 - 19

1.8 User Support

We believe that the support Itasca provides to code users is a major reason for the popularity of oursoftware. We encourage you to contact us when you have a modeling question. We provide a timelyresponse via telephone, electronic mail or fax. General assistance in the installation of FLAC3D

on your computer, plus answers to questions concerning capabilities of the various features of thecode, are provided free of charge. Technical assistance for specific user-defined problems can bepurchased on an as-needed basis.

If you have a question, or desire technical support, please contact us at:

Itasca Consulting Group, Inc.Mill Place111 Third Avenue South, Suite 450Minneapolis, Minnesota 55401 USA

Phone: (+1) 612-371-4711Fax: (+1) 612·371·4717Email: [email protected]: www.itascacg.com

We also have a worldwide network of code agents who provide local technical support. Detailsmay be obtained from Itasca.

FLAC3D Version 3.0


1.9 References

Byrne, P. “A Cyclic Shear-Volume Coupling and Pore-Pressure Model for Sand,” in Proceedings:Second International Conference on Recent Advances in Geotechnical Earthquake Engineeringand Soil Dynamics (St. Louis, Missouri, March, 1991), Paper No. 1.24, 47-55.

Marti, J., and P. A. Cundall. “Mixed Discretization Procedure for Accurate Solution of PlasticityProblems,” Int. J. Num. Methods and Anal. Methods in Geomech., 6, 129-139, 1982.

FLAC3D Version 3.0

flac 3d 1

Documents