Flac 3D 50教程.docx
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Flac 3D 50教程.docx
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Flac3D50教程
第二章完成第一个简单分析计算样例
bytypingthecommandsfromthekeyboard,pressing
new
genzonebricksize688
(Thiscommandwillcreateaninitialmeshthatissixzonesinthex-direction,eightzonesinthey-directionandeightzonesinthez-direction.Forourmodel,thez-axisisorientedintheverticaldirection.)
Plot
(thePlotBase/0>promptwillappear.Aslongasthispromptappears,anysubsequentcommandswillbeassociatedwiththePLOTcommand.TheplotviewisidentifiedasBase/0,whichisthedefaultview.)
createTrench
addsurfaceyellow
addaxesblack
show
Now,givethezonesamaterialmodelandproperties.Forthisexample,weusetheMohr-Coulombelastic-plasticmodel.GobacktotheFlac3D>promptinthecommandwindowandtypeinthefollowingcommand:
modelmohr
ThiswillspecifytheMohr-Coulombmodel.Everyzoneinthegridcouldconceivablyhaveadifferentmaterialmodelandproperty.However,bynotspecifyingarangeofzonesaftertheMODELcommand,FLAC3DassumesthatallzonesaretobeMohr-Coulombmaterial.
propbulk=1e8shear=0.3e8fric=35
propcoh=1e10tens=1e10
Youseethatveryhighcohesionandtensilestrengthvaluesaregiven.Theseareonlyinitialvaluesthatareusedduringthedevelopmentofgravitationalstresseswithinthebody.Ineffect,weareforcingthebodytobehaveelasticallyduringthedevelopmentoftheinitialinsitustressstate.*Thispreventsanyplasticyieldduringtheinitialloadingphaseoftheanalysis.
Forthisproblem,loadingisduetogravity.Toapplygravity,usethecommands
setgrav0,0,-9.81
inidens=1000
Inordertodevelopagravitationalbodyforce,themassdensitymustalsobeinitialized.TheINIcommandisusedtoinitializethemassdensityto1000kg/m3forallzonesinthemodel.
Next,theboundaryconditionsfortheproblemareset.AttheFlac3D>prompt,type
fixxrangex-0.10.1
fixxrangex5.96.1
fixyrangey-0.10.1
fixyrangey7.98.1
fixzrangez-0.10.1
Withthesecommands,rollerboundariesareplacedonfivesidesofthemodel.Theboundariesare“fixed”onlyinthespecifieddirection(i.e.,nodisplacementorvelocityisallowed).TheFIXcommandsperformthefollowingfunctions.
1.Thegridpointsalongtheboundaryplanesatx=0andx=6arefixedinthex-direction.ThesetwoplanesfallwithinthecoordinaterangesspecifiedbytherangekeywordsforthefirsttwoFIXcommands.
2.Thegridpointsalongtheboundaryplanesaty=0andy=8arefixedinthey-direction.TheseplanesfallwithintherangesspecifiedforthethirdandfourthFIXcommands.
3.Thegridpointsalongthebottomboundary(z=0)arefixedinthez-direction.ThisplanefallswithintherangeforthefifthFIXcommand.
Wewishtomonitorthechangeinthevaluesofselectedvariablesinthemodelduringthecalculationalstepping.AHISTORYcommandcanassistinhelpingusdeterminewhetherastableequilibriumsolutionorunstablecollapseisoccurring.Wetypethefollowingcommands:
histn=5
histunbal
histgpzdisp4,4,8
Wechoosetomonitorthechangeinvariableseveryfivecalculationsteps.Itisalwaysagoodideatomonitorthemaximumunbalancedforceinamodel.Iftheunbalancedforceapproachesaverysmallvalueanddisplacementhistoriesbecomeconstant,thisindicatesthatanequilibriumstateisreached.
Toallowgravitationalstressestodevelopwithinthebody,wetimestepthesimulationtoequilibrium.HeretheSOLVEcommandisusedtodetectequilibriumautomatically.
setmechforce=50
solve
Whentheunbalancedforcefallsbelowthelimitingvalue(alimitingforceof50NisspecifiedwiththeSETcommand),therunwillstop.*Theplotsareupdated,sincetheyarestillvisibleonthescreen.Shuttingdowntheplotswillcausethemodeltocyclefaster.
plot
hist1
hist2
Theunbalancedforcehistoryapproacheszero,andthedisplacementhistorybecomesconstant;bothareindicatorsthatanequilibriumstatehasbeenreached.
Notethateachhistoryisnumberedsequentiallyfrom1asitisenteredviatheHISTcommand.ReturntotheFlac3D>promptandtype
printhist
foralistingofthehistoriesandtheircorrespondingnumbers.
Plot
creattrench
addcontourdisp
addaxesblack
show
clear
addbcontourszz
addaxes
plotcreateGravV
plotsetplanedip=90dd=0origin=3,4,0
plotsetrot15020
plotsetcenter2.54.24.0
plotaddboundbehind
plotaddbcontszzplane
plotaddaxes
plotshow
Thissequencewillcreateaview,whichwehavecalledGravV,andmakeitthecurrentview.Wethensetaplaneforthatvieworientedatadipangleof90◦(fromthexy-plane,assumingthatnegative-zis“down”),adipdirectionof0◦(measuredclockwisefromthepositivey-axisinthexy-plane)andwithonepointontheplaneat(x=3,y=4,z=0).Weaddawire-frameboundaryplottedbehindtheplaneandablockcontourplotoftheverticalstresscomponent,σzz,ontheplane.Finally,themodelaxesareadded.Theblockcontourplot,asopposedtoaninterpolatedcontourplot,displaysthevalueofthestresscalculatedateachzonecentroid.Thecolorofeachzonecorrespondsdirectlytothezone-basedstress.
Itiswisetosavetheinitialstatesothatyoucanrestoreitatanytimetoperformparameterstudies.
savetrench.sav
WecanchangethecurrentviewfromGravVtoTrenchwiththecommand
plotcurrentTrench
Nowwecanexcavateatrenchinthesoil.First,type
propcoh=1e3tens=1e3
Thiswillsetthecohesionandtensilestrengthforallzonesto1000Pa.Thesevaluesforstrengtharehighenoughtopreventfailureinourinitialstate(i.e.,unexcavated),butyoushouldalwayscheckforpossiblefailureintheinitialstatebyperformingafewcalculationsteps.Toexcavatethetrench,enter
modelnullrangex=2,4y=2,6z=5,10
Withalowcohesionandverticalunsupportedtrenchwalls,collapseshouldoccur.Becausewewanttoexaminethisprocessrealistically,thelarge-strainlogicisspecified.Thisisdonebytyping
setlarge
Forplottingpurposes,wewishtoseeonlythechangeindisplacementsfromthetrenchexcavation,andnotfromthepreviousgravitationalloading,sowezerooutthex-,y-andz-displacementcomponents:
inixdis=0ydis=0zdis=0
Wepurposelysetthecohesionlowenoughtoresultinfailure,sowedonotwanttousetheSOLVEcommandwithalimitforout-of-balanceforce(whichchecksforequilibrium).Oursimulationwillneverconvergetotheequilibriumstate.Instead,wecanstepthroughthesimulationprocessonetimestepatatime,andplotandprinttheresultsofthecollapseasitoccurs.Thisistherealpoweroftheexplicitmethod.Themodelisnotrequiredtoconvergetoequilibriumateachcalculationcyclebecauseweneverhavetosolveasetoflinearalgebraicequationssimultaneously,asisthecaseforimplicitcodes,withwhichmanyengineersarefamiliar.weusetheSTEPcommand:
step2000
第三章FLAC3D基础知识
gridpointzonehorizontalboundarystressstructuralcables(tiebacks)modelboundaryinternalboundaries(excavation)rollerbottomboundary
NamedObjects
MacroObject—Typically,suchanobjectcontainsalong,complexstringthatmaybeusedrepeatedlyinthemodel.Thepre-processorcomparesastringofcommandtokenstothelistofdefinedmacrosandreplacesanymatchingmacroobjectwithitsfullyexpandedcontents.
macroPt0’p0000’
macroPt1’p1add1000’
macroPt2’p2add0100’
macroPt3’p3add0010’
macroModel_Size’size456’
macroBig_Brick’zonebrickPt0Pt1Pt2Pt3Model_Size’
.
genBig_Brick
.
macro’Pt0’’p0151515’
genBig_Brick
Thispre-processinghastwoeffects:
(1)macroobjectsmaybenested(butnotrecursively);and
(2)themacroobjectnameisremovedfromthecommandstring.
ModelObject—Modelobjects,suchasrangesinspace,groupsofzonesinamodel,orplotviews,canbegivenuserdefinednames.Thoseobjectscanthenbereferredtobytheirnames.
genzonebricksize666
groupTunnelrangex15y06z15
modelmohr
.
.
modelnulrangegroupTunnel
.
Thenamedrangeandthenamedgrouparetwoverydifferentmodelobjects.Therangepertainstoaspecifiedvolumeofspace(orrangeofvalues),whereasthegroupidentifiesacollectionoffinitedifferencezonesinthemodel.
SignConventions
DIRECTSTRESS—Positivestressesindicatetension;negativestressesindicatecompression.
第四章初级实体建模技术
GridgenerationisperformedviatheGENERATEcommandandassociatedkeywordsthatbothdefinethenumberofzonesinamodelandshapethegridtofitaspecifiedproblemregion.Thenumberofzonesisspecifiedbythesizekeyword.
Itisbesttostartwithagridthathasfewzones(say,1000to1500)toperformsimpletestrunsandmakerefinementstothegrid.Then,increasethenumberofzonestoimprovetheaccuracy.
Usingactualcoordinates
genzonebricksize6,8,8p0-10,-10,-20&
p110,-10,-20&
p2-10,10,-20&
p3-10,-10,0
plotsurf
Onlyfourcornersarerequiredtodefineaparallelepiped-shapedmesh.Morecornerscanbespecifiedtodefineanirregularsurface.Example2.14showshowtomakeaslopingsurfaceatthetopofthemesh.
genzonebricksize6,8,8p0-10,-10,-20&
p110,-10,-20p2-10,10,-20&
p3-10,-10,0p410,10,-20&
p5-10,10,10p610,-10,0&
p710,10,10
plotsurf
Inthetutorialexample,wenotedthattheboundariesofthemodelwereinfluencingtheresults(seeFigure2.6).Theboundarymustbeplacedfarenoughawayfromtheexcavationtoreducetheseeffects.AgraduallygradedmeshcanbecreatedinFLAC3Dtomovethemodelboundariesfartheroutwithoutsignificantlyincreasingthenumberofzones.Forexample,thecommandGENzoneradbrickcreatesaradiallygradedmesharoundabrick-shapedmesh.ThecommandinExa
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