soft spot 71

8
Soft Spot Soft Spot Itasca’s Software Newsletter VOLUME 7 number 1 February 1999 In the Spotlight 3DEC was developed in 1988 as the three-dimensional extension of Peter Cundall’s distinct element method. Initially, the program was used as a research tool to sim- ulate the progressive, large-scale movements of blocky rock systems. The first applications were in stability analyses of rock slopes and underground excavations. Over the past ten years, the applica- tion of 3DEC has expanded to several other engineering fields, such as stability assessment of arch dams on rock foundations, design of underground power houses, evaluation of the ulti- mate capacity of masonry struc- tures, and seismic studies of historical columns and arches. 3DEC is now an accepted analy- sis tool for applications involv- ing jointed or blocky materials. This issue of SoftSpot focuses on the recent advancements and applications of 3DEC. The adjacent article describes what is new with the December 1998 release of 3DEC Version 2.0. We have asked some of our 3DEC users to provide examples of recent studies they have performed. These are presented on page 2; a list of recent 3DEC-related publications is provided on page 7. I think you will find that 3DEC offers unique capabilities in modeling large, complex discontinuous systems. —Roger Hart Director, Software Services 3DEC Version 2.0 Released ............... 1 Modeling Hints .............................. 4 In the Spotlight ..................... 1 Linking Itasca Codes: Interactive 3DEC Applications ................... 2 Analyses of Coupled 3D Problems ............. 5 Seismic Response of Stone Masonry Arches Recent 3DEC-Related Publications .............. 7 State-of-Stress Determination SoftNotes................................... 8 3DEC Arch Dam - Safety Analysis of Rock Foundation Training Corner ............................. 8 Soft Spot 3DEC Version 2.0 Released tasca is pleased to announce the release of 3DEC Version 2.0. The new version of the code is specifically designed for static, mechanical analyses in rock mechanics—and is available at a price nearly half that of previous versions. 3DEC was created to model the quasi-static or dynamic response to loading of rock media that contain multiple, intersecting joint structures. 3DEC simulates large displacements, allows multi- ple contact modes between blocks, offers an explicit solution scheme, provides multiple material models, and can simulate excavation or backfilling through the use of “null blocks.” Tools available in the code include a preprocessor that reads AutoCAD files, interac- tive manipulation of screen images, mesh-generation tools, a tunnel generator, and a statistically based joint-set generator. Features new to 3DEC with the release of Version 2.0 include the following items. Built-in Programming Language FISH —The Itasca programming language, FISH, enables users to define new variables and functions to customize a numerical model to suit their particular needs. FISH can vary block and joint properties within the block structure, define variables for plotting, implement joint generation schemes, apply a servo-control of a numerical test, specify different boundary conditions and automate parameter studies. (Continued on page 6) 3DEC model of an arch dam on a jointed rock foundation

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Page 1: Soft Spot 71

Soft SpotSoft SpotItasca’s Software Newsletter

VOLUME 7 number 1

February 1999

In the Spotlight

3DEC was developed in 1988 as the three-dimensional

extension of Peter Cundall’s distinct element method.

Initially, the program was used as a research tool to sim-

ulate the progressive, large-scale movements of blocky

rock systems. The first applications were in stability

analyses of rock slopes and

underground excavations. Over

the past ten years, the applica-

tion of 3DEC has expanded to

several other engineering fields,

such as stability assessment of

arch dams on rock foundations,

design of underground power

houses, evaluation of the ulti-

mate capacity of masonry struc-

tures, and seismic studies of

historical columns and arches.

3DEC is now an accepted analy-

sis tool for applications involv-

ing jointed or blocky materials.

This issue of SoftSpot focuses on the recent

advancements and applications of 3DEC. The adjacent

article describes what is new with the December 1998

release of 3DEC Version 2.0. We have asked some of

our 3DEC users to provide examples of recent studies

they have performed. These are presented on page 2; a

list of recent 3DEC-related publications is provided on

page 7. I think you will find that 3DEC offers unique

capabilities in modeling large, complex discontinuous

systems.

—Roger Hart

Director, Software Services

3DEC Version 2.0 Released . . . . . . . . . . . . . . . 1 Modeling Hints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

In the Spotlight . . . . . . . . . . . . . . . . . . . . . 1 Linking Itasca Codes: Interactive

3DEC Applications . . . . . . . . . . . . . . . . . . . 2 Analyses of Coupled 3D Problems . . . . . . . . . . . . . 5

Seismic Response of Stone Masonry Arches Recent 3DEC-Related Publications . . . . . . . . . . . . . . 7

State-of-Stress Determination SoftNotes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3DEC Arch Dam - Safety Analysis of Rock Foundation Training Corner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Soft Spot

3DEC Version 2.0 Released

tasca is pleased to announce the release of 3DEC Version

2.0. The new version of the code is specifically designed

for static, mechanical analyses in rock mechanics—and is

available at a price nearly half that of previous versions.

3DEC was created to model the quasi-static or dynamic

response to loading of rock media

that contain multiple, intersecting

joint structures. 3DEC simulates

large displacements, allows multi-

ple contact modes between blocks,

offers an explicit solution scheme,

provides multiple material models,

and can simulate excavation or

backfilling through the use of

“null blocks.” Tools available in

the code include a preprocessor

that reads AutoCAD files, interac-

tive manipulation of screen

images, mesh-generation tools, a

tunnel generator, and a statistically

based joint-set generator.

Features new to 3DEC with the release of Version 2.0

include the following items.

Built-in Programming Language FISH —The Itasca

programming language, FISH, enables users to define new

variables and functions to customize a numerical model to

suit their particular needs. FISH can vary block and joint

properties within the block structure, define variables for

plotting, implement joint generation schemes, apply a

servo-control of a numerical test, specify different boundary

conditions and automate parameter studies.

(Continued on page 6)

3DEC model of an arch damon a jointed rock foundation

Page 2: Soft Spot 71

2

3DEC Applications

Seismic Response of Stone MasonryArches

DEC is well suited to perform both static and dynamic

analyses of masonry structures. In this application, 3DEC

is applied to evaluate the seismic behavior of stone masonry

arches. The code performs a detailed simulation of the

architectural components of stone masonry arches under

earthquake loading. Free-standing arches are often found in

partially ruined structures, and their safety is always a cause

for concern. 3DEC models have been created for several

types of arches. A pointed arch model with a T-shape section

is illustrated in Figure 1.

The arch is first subjected to self-weight, and then

dynamic loading is applied in the form of a prescribed

motion at the support blocks. Pointed arches are shown to

withstand a higher loading than circular arches.

Out-of-plane collapse is a predominant failure mode, as

shown in Figure 2. Lemos (1997) provides further informa-

tion on this analysis, including evaluation of other arch

shapes.

The article mentioned above appears in the list of recent

3DEC-related publications that appears on page 7.

1.0 m

0.55 m

7.5 m

5.3 m

Figure 1 Pointed arch model

Figure 2 Failure mode for pointed arch model

State-of-Stress Determination

nowledge of the virgin stress field is obtained from

3DEC analyses in the design for a nuclear-waste reposi-

tory site in Switzerland. The 3DEC model simulates the

topography, complicated geology and applied tectonic forces

at the site. The model is calibrated using hydrofrac stress

measurements, borehole breakout data and geological

indicators.

Figure 3 illustrates the 3DEC model for the repository site.

The different colored blocks in the model correspond to the

various geologic materials at the site. The blocky model con-

sists of approximately 365,000 cubic blocks and is considered

sufficient to evaluate the regional stress state. Figure 4 shows

the inner region of the model in the vicinity of the repository

horizon. The virgin stress field is indicated in Figure 5 by

the plot of principal stress tensors and contours of maximum

principal stress through the repository horizon. Compari-

sons to stress measurements are made at the locations shown

on the figure.

Drs. Heinz Konietzky and Lothar te Kamp of Itasca’s

office in Germany provided this contribution.

3DEC Arch Dam - Safety Analysis ofRock Foundation

he Santa Maria arch dam is located in the eastern Swiss

Alps. It is 117 m high and has a crest length of 650 m.

Due to the wide span, the dam is subjected to large displace-

ments in the center part of the dam foot. The dam survives

these displacements without cracking because several large

joints in the ground open and allow movement. The arrange-

ment of those joints led to the investigation of the safety of

the foundation of the dam. All the major joints down to a

spacing of 15 m were modeled. It can be shown that the

foundation can withstand an increase of the load from full

reservoir by at least a factor of 2. This is much greater than

can be expected due to an earthquake or an overtopping of

the water. Figures 6 and 7 show the components of the arch

dam represented by the 3DEC model.

We thank Mr. Christian Moor of Nordostschweizerische

Kraftwerke (NOK), Baden, Switzerland, for providing this

3DEC application.

For other studies on modeling arch dams with 3DEC, see

Lemos (1996) in the bibliography of recent 3DEC-related

publications that appears on page 7.

Page 3: Soft Spot 71

3

Figure 3 3DEC model of nuclear-waste repository site

Figure 4 Inner region of model inthe vicinity of the repository S B 1

S B 2

S B 3

S B 4

7 200 0 72 50 0 7 300 0 73 50 0 7 400 0 74 50 0 7 500 0

X (m od el coo r d in a t e )

91 50 0

92 00 0

92 50 0

93 00 0

93 50 0

94 00 0

94 50 0

95 00 0

Z(m

od

el

co

or

din

ate

)

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

Figure 5 Plan view of repository region showing principal stresstensors and contours of maximum principal stress (in MPa)

250m

540m

1300 m

1000m

1700 m ü.M.

1400 m ü.M.

AnzahlBlöcke

Volumen[m3]

642'000369

114

178

736

487'000

Total

75

20.5 Mio

715 Mio

737 Mio

Modell-teil

X

Y

Z

model

compo-

nent

number

of

blocks

Volume

[m3]

106

106

106

above sea level

above sea level

Figure 6 3DEC model of Santa Maria arch dam

Figure 7 Arch dam model with addition of major faultsin dam foundation (6700 blocks total)

Page 4: Soft Spot 71

4

Modeling Hints

Changing the Water Level

Settlement or heave resulting from the lowering or raising

of the groundwater table is a common situation in soil engi-

neering. The analysis of this condition can be conducted

with FLAC for various types of problem settings. When a

fully coupled calculation is performed, the displacement

changes arise automatically as the phreatic surface changes.

However in many cases—for example, in the dewatering of

an excavation—it may often be assumed that the water level

is instantaneously changed; thus, a steady-state flow state is

obtained without performing a fluid-flow calculation. The

pore pressure is then changed to correspond to the change in

the water level.

This simplified analysis may be run either outside the

groundwater configuration or within the groundwater con-

figuration—but with flow turned off. For both approaches,

there is an imposed change in the pore pressures: outside of

CONFIG gw, this can be done with either the WATER table

or INI pp command; within CONFIG gw, it can be done

with the INI pp and INI sat commands.

In addition, for both approaches, there must also be an

adjustment made to the total stresses in zones in which pore

pressures are changed. The total stresses must be corrected

because an imposed instantaneous change in pore pressure in

a material does not affect inter-granular forces; hence, the

effective stress is unchanged in the short term.

The adjustment to total stress can be done conveniently by

subtracting the pore-pressure change from the total stresses

in the affected zones, using the INI sxx add -Dp, INI syy

add -Dp and INI szz add -Dp commands, where Dp is the

change in the pore pressure in the zone affected by the

change in the water level (Dp = p(new) - p(old)).

A simple demonstration of the effect of changing water

level is given by the accompanying data file. A box filled with

soil is initially dry. The soil is instantaneously saturated, and

the soil heaves as indicated in the plot.

Note that gravity is not acting in this example. Saturated

and unsaturated densities must also be adjusted if gravity is

acting and the water level is changed. In CONFIG gw

mode, this is performed automatically for zones in which the

pore pressure is changed; only the unsaturated density needs

to be specified. Outside of the CONFIG gw mode, the

unsaturated density must be assigned by the user to all zones

above the water table and the saturated density to all zones

below, when the water level is changed.

For further discussion and examples on changing the water

level, see Section 6.11.9 of the Theory and Background vol-

ume of the FLAC Manual.

; add water to a box of soil and produce heave

config gw

grid 4 8

m elas

prop dens 1500 sh 1e8 bu 2e8

water dens 1000 bulk 0

set flow off

fix x i 1

fix x i 5

fix x y j 1

ini sxx -1e4

ini szz -1e4

solve ; Initial equilibrium

;

ini pp 1e4 ; Add water

ini sxx add -1e4 ; Adjust total stresses

ini syy add -1e4 ; to account for pore-pressure

ini szz add -1e4 ; change

;

his ydisp i 1 j 9

solve

plot hold bo disp str

FLAC (Ver s io n 3.40)

LEGEND

7-Jan-99 15:01

step 614

-3.333E+00 <x< 7.333E+00

-1.333E+00 <y< 9.333E+00

Boundary plot

0 2E 0

Displacement vectors

Max Vector = 2.390E-04

0 5E -4

Principal stresses

Max. Value = 1.603E+04

0 5E 4

0.000

2.000

4.000

6.000

8.000

-2.000 0.000 2.000 4.000 6.000

JOB TITLE :

Itasca Consulting Group, Inc.

Minneapolis, Minnesota USA

Heave resulting from adding water to a box of soil

End Bearing Piles

Pile elements in FLAC are specifically designed to simulate

the effect of a soil squeezing around a single foundation pile.

The pile element transfers loads to the soil via the coupling

springs connected between the pile nodes and the grid. Pile

elements are thus intended to represent the behavior of fric-

tion piles.

It is possible to also model end-bearing loading with

FLAC’s pile elements. This can be accomplished by neglect-

ing the shear friction along the bottom segment of the pile,

adjusting instead the properties of the corresponding cou-

pling shear spring to account for the pile bearing capacity.

The end-bearing spring can be assigned a limit load evaluated

using an engineering bearing capacity formula. An example

application of this approach is provided in Section 5.4.4.1 in

the Theory and Background volume of the FLAC Manual.

Page 5: Soft Spot 71

5

Linking Itasca Codes: InteractiveAnalyses of Coupled 3D Problems

s publicized in the last SoftSpot, transfer of information

between Itasca codes is now possible by using FISH.

Recently, this feature was used to couple FLAC3D and PFC3D

to investigate the effects of a coupled mechanical and fluid

flow response. FLAC3D was used to model the fluid flow,

while PFC3D was used to model the porous solid response.

Exchange of necessary information between the two codes

was accomplished by binary file exchange through respective

FISH functions, using a simple DOS batch-file to manage the

sequential execution of the two codes.

The physical scenario is that of fluid flow through a weak

porous medium as a result of a relatively sudden pressure

drop in a local region. The fluid passing through the pore

space imposes drag forces on the solid material that tend to

“push” the material in the direction of flow. Deformation

and break-up of the porous solid occurs as a result of the drag

forces, and affects its local permeability.

Asgian et al. (1995) derived an expression for the drag

force when an assembly of bonded particles represents the

solid material. The pore pressure gradient is part of this

expression and can be obtained from the FLAC3D fluid flow

model. This gradient is output and subsequently used in the

PFC3D model to determine the individual drag force (i.e.,

body force) on each particle.

The permeability associated with any volume in the PFC3D

solid model can be estimated from porosity using the

Kozeny-Carman equation, for example. Updated

permeabilities resulting from deformations of the porous

solid are passed to the FLAC3D model to determine a new

fluid flow state.

Depending on the selected time increment, discrete calcu-

lations of fluid flow and mechanical states can be used in this

manner to simulate a 3D transient dynamic coupled fluid

flow/mechanical response. Figure 1 outlines the approach.

The approach requires a division of the PFC3D model into

a virtual 3D cell space equivalent to that of the FLAC3D

model grid. Information is exchanged between the virtual

cell space in PFC3D and the cell space of the equivalent

FLAC3D grid. Note that,

while the FLAC3D flow

model must encompass the

entire geometric domain of

the PFC3D solid model, the

opposite is not necessary.

Figure 2 shows an example

of volumes occupied by the

two models. As seen in

Figure 2, only the blue vol-

ume in the FLAC3D model

is represented by the

PFC3D model. Figure 2 also

shows a cut through the

models, illustrating the vir-

tual cell space in PFC3D

and the equivalent cell

space in FLAC3D. The

boundary location of low

pressure is also indicated.

Pore pressure contours in

the FLAC3D model and the

corresponding drag forces

Figure 1 Linkage of FLAC3D and PFC3D

Pressurized Medium

Point

5 m

5 m

2 m

1 m3

Low Pressure

Figure 2 Volumes occupied by FLAC3D (left) and PFC3D (right) models

(Continued on page 8)

Page 6: Soft Spot 71

6

High-Resolution Graphics

—The video card installed in your

computer can be directly accessed

for a high-resolution graphics

screen plot using the SET mode

command in the DOS version of

3DEC 2.0.

Improved Contact Logic

—The contact logic allows large

displacements for deformable as

well as rigid blocks. Every contact

is discretized into sub-contacts,

where interaction forces are

applied. Sub-contacts are updated

to allow a smooth transition of

forces as one block slides over

another block.

New Block Type —A prism-shaped

block is available (command POLY prism).

This type of block can be used, for example, to create blocky

structures such as a masonry wall or arch bridge.

New Block Material Models —Two new material models

are available: an anisotropic elasticity model and a bilinear

plasticity model that incorporates strain-hardening/softening

and ubiquitous jointing for both the matrix and the ubiqui-

tous joints. The anisotropic elasticity model can represent an

orthotropic elastic material and a transversely isotropic elastic

material. Mohr-Coulomb, ubiquitous-joint, and strain hard-

ening/softening behaviors can be obtained as special cases of

the bilinear model.

Pore-Pressure Generation —A pore-pressure gradient can

now be specified for both block zones and joints. This

allows an effective-stress calculation to be performed.

Graphics Enhancements —User-defined graphics can be

added to 3DEC plots via the PLOT label and PLOT overlay

commands. For example, user-defined labels can be added to

the axes of table and history plots. An overlay file contains

(x,y,z) coordinates that define line segments that can be cre-

ated by the user to define an arbitrary shape. The shape can

then be overlaid on the 3DEC plot. The MOVIE facility has

been modified to create much smaller movie files. PCX out-

put of the graphics screen image is available.

Revised User's Manual —The 3DEC Manual has been

revised and expanded to eight volumes. More explanations

are provided for the features in 3DEC, existing examples have

been expanded, and several new examples have been added.

The 3DEC Manual

User's Guide

an introduction to 3DEC and

its capabilities

Command Reference

descriptions of all 3DEC commands

FISH in 3DEC

a complete guide to FISH and FISH functions

Theory and Background

detailed descriptions of the built-in features

Optional Features

detailed descriptions of the optional features

Verification Problems & Example Applications

a collection of verification problems and example

applications

Command and FISH Reference Summary

a quick summary of all 3DEC commands and FISH

statements

Index

a subject index for all volumes of the 3DEC Manual

The entire manual is also provided on CD-ROM. The man-

ual can be viewed with Acrobat Reader, and users can search

for specific topics across all volumes by implementing the

search facility available in Acrobat.

If you are interested in obtaining 3DEC Version 2.0, please

contact your nearest Itasca office or your software agent.

(The information may be obtained from the Itasca web site,

www.itascacg.com.) The bibliography that follows is an

abbreviated version of the full list of 3DEC-related publica-

tions that is also available from the Itasca web site.

3DEC Version 2.0 (Continued from page 1)

Page 7: Soft Spot 71

7

Recent 3DEC-Related Publications

3DEC has been applied in a wide variety of engineering stud-

ies. The references below describe some of the more recent

applications.

Christianson, M., J. Itoh, and S. Nakaya. “Seismic Analysis

of the 25 Stone Buddhas Group at Hakone, Japan,” in Rock

Mechanics (Proceedings of the 35th U.S. Symposium, Univer-

sity of Nevada, Reno, June 1995), pp. 107-112. J.J.K.

Daemen and R.A. Schultz, Eds. Rotterdam: A.A. Balkema.

Dasgupta, B., and L.J. Lorig. “Numerical Modelling of

Underground Power Houses in India,” in Proceedings of the

International Workshop on Observational Method of Con-

struction of Large Underground Caverns n Difficult Ground

Conditions, (8th ISRM International Congress on Rock

Mechanics, Tokyo, September 1995), pp. 65-74. S. Sakurai,

Ed.

Dasgupta, B., R. Dham, and L.J. Lorig. “Three-Dimensional

Discontinuum Analyses of the Underground Power House

for Sardar Sarovar Project, India,” in Proceedings of the

Eighth International Congress on Rock Mechanics (Tokyo,

Septber 1995), Vol. II, pp. 551-554. T. Fujii, Ed. Rotterdam:

A.A. Balkema, 1995.

Fairhurst, C. “Three Gorges Dam Reservoir, Yangtze River,

China,” Felsbau, 13(6), 390-394 (1995).

Hammer, H., H.C. Siegfried Niedermeyer, and T.

Niedermeyer. “Untersuchen zu Gebrigsspannungen

und-bewegungen in der Schwabischen Alb,” Felsbau, 13(6),

367-373 (1995).

Hella, P., and P. Saksa. “3D Geological Modelling, Model

Transfer and Validation,” in Proceedings of the SCSC ‘95

Conference (Ottawa, July 1995), pp. 967-971. T.I. Oren and

L.G. Birta, Eds. Place: SCS, 1995.

Hökmark, H. “Acceptance of Emplacement Hole Positions -

Stage 1 Thermomechanical Study,” in Preprints of Contribu-

tions to the Workshop on Computational Methods in Engi-

neering Geology (Lund, Sweden, October 1996), pp. 42-51.

R. Pusch and R. Adey, Eds. Lund: Clay Technology AB,

1996.

Hökmark, H. “Numerical Study of the Performance of

Tunnel Plugs,” in Preprints of Contributions to the Workshop

on Computational Methods in Engineering Geology (Lund,

Sweden, October 1996), pp. 212-221. R. Pusch and R. Adey,

Eds. Lund: Clay Technology AB, 1996.

Johansson, E.J.W. “Treating Sewage Underground,” Tunnels

& Tunneling, 21-23 (July 1995).

Johansson, E.J.W., and H. Kuula. “Three-Dimensional

Back-Analysis Calculations of Viikinmaki Underground

Sewage Treatment Plant in Helsinki,” in Proceedings of the

Eighth International Congress on Rock Mechanics (Tokyo,

September 1995), Vol. II, pp. 597-600. T. Fujii, Ed.

Rotterdam: A.A. Balkema, 1995.

Lemos, J.V. “Discrete Element Modelling of the Seismic

Behaviour of Stone Masonry Arches,” Computer Methods in

Structural Masonry – 4 (Proceedings of the 4th International

Symposium Num. Methods in Structural Masonry -

STRUMAS IV, Florence, September 1997), pp. 220-227.

G.N. Pande, J. Middleton, and B. Kralj, Eds. London:

E&FN Spon, 1997.

Lemos, J.V. “Discrete Element Modelling of Historical

Structures,” in Proc. Int. Conf. New Technologies in Struc-

tural Engineering, Lisbon, Vol. 2, pp. 1099-1106. S.P. Santos

and A.M. Baptista, Eds. Lisbon: LNEC, 1996.

Lemos, J.V. “Modelling of Arch Dams on Jointed Rock

Foundations,” in Prediction and Performance in Rock

Mechanics & Rock Engineering (Proc. of ISRM International

Symposium EUROCK ‘96, Turin, September 1996), Vol. 1,

pp. 519-526. G. Barla, Ed. Rotterdam: A.A. Balkema, 1996.

Lemos, J.V. “Assessment of the Ultimate Load of a Masonry

Arch Using Discrete Elements,” in Proc. Int. Conf. Comp.

Meth. in Struct. Masonry, Lisbon, Portugal, April 1995.

Thorval, A., H. Baroudi, J.P. Piguet, E. Vuillod, G. Abdallah,

A. Hosni, and J. Lin. “Couple Thermo-Hydro-Mechanical

Phenomena in Fractured Rocks: Recent Developments in

Modelling Methods and Validation Tests (in French),” in

Proceedings of the 8th International Congress on Rock

Mechanics (Tokyo, September 1995), Vol. 2, pp. 703-706. T.

Fujii, Ed. Rotterdam: A.A. Balkema, 1995.

Tolppanen, P.J., E.J.W. Johansson, and R. Riekkola. “Com-

parison of Vertical and Horizontal Deposition Hole Concept

for Disposal of spent Fuel Based on the Rock Mechanical In

Situ Stress/Strength Analyses,” in Preprints of Contributions

to the Workshop on Computational Methods in Engineering

Geology (Lund, Sweden, October 1996), pp. 230-237. R.

Pusch and R. Adey, Eds. Lund: Clay Technology AB, 1996.

Tolppanen, P.J., E.J.W. Johansson, and J.P. Salo. “Rock

Mechanical Analyses of In-Situ Stress/Strength Ratio at the

Posiva Oy Investigation Sites, Kivetty, Olkiluoto and

Romuvaara” in Prediction and Performance in Rock

Mechanics & Rock Engineering (Proc. of ISRM International

Symposium EUROCK ‘96, Turin, September 1996), Vol. 1,

pp. 435-442. G. Barla, Ed. Rotterdam: A.A. Balkema, 1996.

Page 8: Soft Spot 71

8

is Itasca’s software

newsletter. It is published twice annu-

ally for clients and friends.

Soft SpotITASCA

Itasca Consulting Group, Inc.

708 South Third Street, Suite 310

Minneapolis, MN 55415 USA

Phone: 612-371-4711 • Fax: 612-371-4717

Email: [email protected] • Web: www.itascacg.com

FLAC Beginners’Course

28 - 30 April 1999

Itasca Consulting Group, Inc.

Minneapolis, Minnesota USA

An introductory course on practical application of FLAC

in geoengineering will be offered at Itasca’s Minneapolis

office. This training is specifically designed to provide

new users with a recommended approach to apply FLAC

most efficiently for geomechanics analysis and design.

Itasca engineers have used FLAC and other Itasca soft-

ware in a wide variety of geoengineering studies. This

experience will guide the teaching and presentations dur-

ing the 3-day course.

One computer will be provided for every two partici-

pants. Topics will include hands-on exercises throughout

the training program. A training notebook will also be

provided for each participant.

The course is restricted to 12 participants, accepted in the

order of the date of payment of the fee ($815). Please

contact Itasca to register or for further information.

Further information and a schedule of the three-day

course is available from Itasca’s web site,

www.itascacg.com.

TrainingCorner

Soft Notes

Printing on Non-PostScript Printers

With the Windows versions of our codes, FLAC 3.4 and

FLAC3D 2.0, plots can be sent directly to the Windows native

printer drivers, when running under Windows 95/98/NT. In

time, all Itasca software will be offered as Windows applica-

tions. Presently, with our DOS codes, plots can be sent

directly to PostScript printers, and there are utilities available

to print these graphics on non-PostScript printers. We have

recently found a shareware program, RoPS, that enables

users to print PostScript graphics files on any Windows com-

patible printer. We find this program easier to install and use

than Ghostview/Ghostscript and recommend it to users. We

now include RoPS on the Itasca CD-ROM, or you can

obtain a copy by visiting the RoPS web page at

www.giant-technologies.com/rops.

Rainbow Keys

We have been pleased so far with our switch from Unikeys

to Rainbow keys. We are not aware of any hardware failures

of the Rainbow keys. We have had some difficulties with

the installation of the software drivers (in WinNT) that were

due to errors in the install scripts for some of the CD-ROMs

(prior to CD-ROM version ITASCA2E).

for particles on the mid- vertical plane

through the PFC3D model appear in Figure 3.

Contact forces between these particles are

also illustrated, with blue indicating com-

pression and red indicating tension. It is seen

that, after some erosion of the porous solid, a

stable state has been achieved.

Asgian, M.I., P.A. Cundall, and B.H.G.

Brady. (1995) “The Mechanical Stability of

Propped Hydraulic Fractures: A Numerical

Study,” in Proceedings of the SPE 69th

Annual Technical Conference and Exhibition

(New Orleans, September 1994), Vol. 1, pp.

475-489. Richardson, Texas: Society of

Petroleum Engineers, 1994; also J. Pet. Tech.,

203-208 (March 1995).

Linking Itasca Codes (Continued from page 5)

Pore Pressure Contours

Pore Pressure Contours

Particle Drag Forces

Contact Forces - Stable

Figure 3 Pore pressure contours (FLAC3D, left), corresponding drag forces (PFC3D, top right),and contact forces from the final stage (PFC3D, bottom right).