INTRODUCTION TO NUMERICAL MODELING IN GEOTECHNICAL ENGINEERING WITH EMPHASIS ON FLAC MODELING wwwzamirannet By Siavash Zamiran PhD PE Geotechnical Engineer Marino Engineering Associates Inc ID: 773329
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INTRODUCTION TO NUMERICAL MODELING IN GEOTECHNICAL ENGINEERING WITH EMPHASIS ON FLAC MODELING www.zamiran.net By Siavash Zamiran, Ph.D., P.E. Geotechnical Engineer, Marino Engineering Associates, Inc. Adjunct Faculty, St. Louis University Los Angeles, CA January 2019
Outline 2 Introduction to the short course Introduction to computational geotechnics Commercial geotechnical programs Theoretical considerationsNumerical modeling in FLAC and FLAC3DPractical application: Shallow foundationsPractical application: Retaining wall systemsPractical application: Tunnel modelingEarthquake modeling using fully dynamic analysis
FLAC3D Window3
4 FLAC3D
Geometry Modeling 5
Geometry Modeling 6
Geometry Modeling 7
Geometry Modeling 8
Geometry Modeling 9
Geometry Modeling 10
Tunnel Modeling Example 11 new gen zone radcyl group ub & p0 0 0 0 p8 .08 0 0 p1 .4 0 0 p6 .4 .4 0 p3 0 .4 0 p9 0 .08 0 & p2 0 0 -1.2 p10 .08 0 -1.2 p4 .4 0 -1.2 p7 .4 .4 -1.2 p5 0 .4 -1.2 p11 0 .08 -1.2 & size 3 40 18 18 fill group ubhole ratio 1 1 1 1.15
Tunnel Modeling Example 12 gen zone reflect dd 0 dip 90 origin 0 0 0 ;check origin 0 -0.5 0 gen zone reflect dd 90 dip 90dip: angle with xy plane dd : angle with xz plan origin x0,y0,z0
In-situ Analysis 13 model mech mohr prop bulk 5e9 shear 1e9 coh 4e4 fric 30 ini dens 2000 fix y range y -.1 .1 fix y range y 7.4 7.5 fix x range x -.1 .1 fix x range x 12.9 13.1 fix z range z -10.1 -9.9 set grav 0,0,-10 hist add unbal hist add gp xdisp 0,0,11 save tunnel.sav
Create the Support 14 ; Create the support ( linerSELs ). sel liner range cyl end1 (0 0 0) end2 (0 2 0) rad 2 sel liner prop iso=(@ E_s _, @ nu_s _) thick=@thick_ sel liner prop cs_nk @ lk _ cs_sk @ lk _ cs_scoh @ coh _
Liner Properties 15
Outline 16 Introduction to the short course Introduction to computational geotechnics Commercial geotechnical programs Theoretical considerationsNumerical modeling in FLAC and FLAC3DPractical application: Shallow foundationsPractical application: Retaining wall systemsPractical application: Tunnel modelingEarthquake modeling using fully dynamic analysis
Outline 17 Earthquake modeling using fully dynamic analysis Seismic considerations Practical example: Seismic analysis of the cantilever retaining wall
Outline 18 Earthquake modeling using fully dynamic analysis Seismic considerations Practical example: Seismic analysis of the cantilever retaining wall
Pseudo-Static vs. Dynamic Analysis19 Seismic coefficients for pseudostatic slope analysis, Cristiano Melo and Sunil Sharma
Pseudo-Static Analysis20
Dynamic Analysis21
Dynamic Analysis, Important points22 Loading Boundary condition Damping
Boundary Conditions and Loading 23
Boundary Conditions24
Boundary Conditions25
Rigid Base VS Compliant Base 26
Normal and Shear Stress 27
Baseline Correction 28
Damping 29
Local Damping 30 set dyn damp local 0.1571 ; = pi * 0.05
Rayleigh Damping 31 set dy_damp rayl z min f min stiffness mass
Hysteretic Damping 32
Hardin/Drnevich Hysteretic Damping 33 Hardin/ Drnevich model – hardin initial damp hyst hardin .005
Outline 34 Earthquake modeling using fully dynamic analysis Seismic considerations Practical example: Seismic analysis of the cantilever retaining wall
Codes for Dynamic Analysis35 config dyn ;---static analysis set dyn off;---dynamic analysis set dyn on ini xdisp 0 ydisp 0 xvel 0 yvel 0 ;---history monitoring hist reset his sxx i 71 j 35 his xdisp i 72 j 34 his xvel i 72 j 34 his xacc i 43 j 2 his dytime ;---damping set dy_damp rayl .002 3.0 stiffness initial damp hyst hardin .005 ;set dyn damp local 0.1571 ; = pi * 0.05 ;----dynamic analysis setting set corr_ffrot on ;base rotation prevention app ff set dytime 0.0 set large set multi on set step 900000000
Codes for Dynamic Analysis36 ;----earthquake loading FISH program def eqset_1 eq_time =39.88 pgmulti =1.0 c_s1=( shear_a / dens_a )^0.5 multi_sxy1=-0.01*( dens_a )*(c_s1)* pgmulti end eqset_1 ;---compliant base hist 1000 read M7_Loma_Prieta.his hist write 1000 table 100 apply sxy multi_sxy1 hist table 100 from 1,1 to 30,1 apply xquiet yquiet from 1,1 to 30,1 ;---solving solve dytime = eq_time ;---history reading ;set hisfile test1.his ;his write 105 vs 108 skip 100