Hii
?I was going to ask you about the difference between solve and elastic solve calculations. When I solve the analysis with Elastic solve, it gives more realistic results??

Hi,

The Solve Elastic option means that, regardless of the constitutive model specified for the soil or rock, the program assumes a purely elastic response and does not consider any plasticity. This option is useful for initializing the model without inducing plasticity or excessive deformation.

Once the model is initialized, you can switch to the regular Solve option, which applies the constitutive models specified by the user.

?Roozbeh

I am comparing Plaxis 2D and ADONIS software. First, I solved Tutorial 06 in Plaxis, and the values came out more than 30% higher. Then, I analyzed the transcript in Plaxis. The shear force in Plaxis was 50 kN, while in ADONIS it was considerably higher, almost twice as much. A similar situation occurred with the moment values; the absolute magnitude of the deformation matched, but the deformation direction was not consistent. When I performed an elastic analysis, the values became somewhat closer. For my thesis, I aim to identify the reason behind this discrepancy and conduct a probabilistic analysis to present the percentage difference in results. I initially thought the issue was mesh-related, so I refined the mesh and pushed the program to its limits, but it did not yield the desired outcome. In Plaxis, I start the analysis with gravity loading

"If you?d like, I can present and discuss all 10 of my case studies live with you, sharing them in real time via Zoom or Skype."

rect("startPoint",0,0,"endPoint",30,-30)
 line("startPoint",0,-8,"endPoint",30,-8)
 line("startPoint",0,-10,"endPoint",30,-10)
 line("startPoint",0,-14,"endPoint",30,-14)
 line("startPoint",0,-20,"endPoint",10,-20)
 crack("startPoint",10,0,"endPoint",10,-20)
 line("startPoint",0,-5,"endPoint",10,-5)
 line("startPoint",9,-5,"endPoint",9,-21)     
 line("startPoint",9,-21,"endPoint",11,-21)
 line("startPoint",11,0,"endPoint",11,-21)
 discretize("maxedge",0.25)
 gmsh("maxedge",0.25,"elemtype","Q4")
 material("create","Mohr-Coulomb","matid",1,"matname","Kil-1","density",1936,"shear",2.28571e+06,"bulk",1.06667e+07,"coh",3.5,"fric",25)
 material("create","Mohr-Coulomb","matid",2,"matname","Kil-2","density",1936,"shear",4.71429e+06,"bulk",2.2e+07,"coh",5,"fric",25)
 material("create","Mohr-Coulomb","matid",3,"matname","Kil-3","density",1936,"shear",1.15714e+07,"bulk",5.4e+07,"coh",13.5,"fric",26)
 material("create","Mohr-Coulomb","matid",4,"matname","Kil-4","density",1936,"shear",1.71429e+07,"bulk",8e+07,"coh",20,"fric",26)
 material("assign","matid",1,"region",13.9244,-3.14956)
 material("assign","matid",1,"region",10.7522,-6.10143)
 material("assign","matid",1,"region",9.30148,-6.74144)
 material("assign","matid",1,"region",6.82677,-6.5281)
 material("assign","matid",1,"region",7.04011,-3.92539)
 material("assign","matid",2,"region",21.3286,-9.22765)
 material("assign","matid",2,"region",10.7196,-8.89612)
 material("assign","matid",2,"region",9.44868,-9.22765)
 material("assign","matid",2,"region",5.96759,-9.22765)
 material("assign","matid",3,"region",22.931,-11.8799)
 material("assign","matid",3,"region",5.63605,-11.7141)
 material("assign","matid",3,"region",9.33817,-12.2667)
 material("assign","matid",3,"region",10.4985,-12.322)
 material("assign","matid",4,"region",20.0025,-20.6103)
 material("assign","matid",4,"region",5.5808,-17.2397)
 material("assign","matid",4,"region",9.1724,-19.3394)
 material("assign","matid",4,"region",10.4985,-20.1682)
 applybc("xyfix","xlim",-0.830,30.659,"ylim",-30.659,-29.884)
 applybc("xfix","xlim",-0.719,0.443,"ylim",-30.271,0.332)
 applybc("xfix","xlim",29.386,30.659,"ylim",-30.659,0.443)
 excavate("region",7.50945,-3.45605,"reset","off")
 excavate("region",7.12544,-6.01609,"reset","off")
 excavate("region",9.25881,-6.2721,"reset","off")
 excavate("region",9.21614,-9.08814,"reset","off")
 excavate("region",7.12544,-9.17347,"reset","off")
 excavate("region",6.95477,-12.0749,"reset","off")
 excavate("region",9.30148,-11.7762,"reset","off")
 excavate("region",9.25881,-16.4696,"reset","off")
 excavate("region",6.48543,-16.5123,"reset","off")
 structure("drawliner","beamid",1,"iftype","bothSides","ifid1",1,"ifid2",2,"isconnect","off","xlim",9.9,10.1,"ylim",-20.1,0.1)
 imaterial("edit","ifid",1,"jkn",1e+08,"jks",1e+07,"friction",20)
 imaterial("edit","ifid",2,"jkn",1e+08,"jks",1e+07,"friction",20)
structure("material","beamid",1,"area",0.7854,"I",0.04909,"spacing",1.5,"ymod",3e+10,"dens",2446)
 backfill("region",5.01861,-18.7564)
 backfill("region",9.32752,-17.7933)
 backfill("region",9.27683,-13.1802)
 backfill("region",6.64079,-12.9774)
 backfill("region",9.17544,-8.7699)
 backfill("region",7.19841,-8.82059)
 backfill("region",9.53029,-7.35049)
 backfill("region",6.69148,-7.09703)
 backfill("region",9.02336,-3.85267)
 initial("syy",0,"yvar",18992,"xlim",0,30,"ylim",-30,0)
 initial("sxx",0,"yvar",10974,"xlim",0,30,"ylim",-30,0)
 initial("szz",0,"yvar",10974,"xlim",0,30,"ylim",-30,0)
 applybc("syy",-10,"xlim",15,25,"ylim",-0.1,0.1)
set("gravity",0,9.81)
watertable("add","dens",1000,"elev",-5.5)
solve()
excavate("region",6.46488,-1.4919)
initial("xydisp",0.0)
solve()

Unfortunately, I am not familiar with how your Plaxis model was developed; however, to ensure a meaningful comparison, all conditions must be identical between the two models. Otherwise, the comparison may not be valid.

All modeling conditions were kept identical and applied on a one-to-one basis in both software packages. Given this level of consistency, the presence of such a significant discrepancy raises the question of whether the difference originates from the matrix solution strategy used in the numerical analysis. In this context, it is necessary to investigate which matrix solution method is employed by ADONIS in its finite element analysis framework

Based on your statement above, gravity was used to initialize the PLAXIS model; however, this differs from the stress initialization applied in the ADONIS model. Are the stress conditions comparable between the two models prior to excavation?

In addition, double-check the cohesion values, as they appear to be near zero. I assume higher cohesion values were intended, particularly since you mentioned that the results are comparable when elastic behavior is assumed.

You also applied a near-zero surcharge load (i.e., 10). Please ensure that the units are consistent between the two models.

For reference, I recreated your model in FLAC, and the results are very comparable between the two programs. Below is the FISH script used in FLAC, in case you would like to rerun the analysis yourself.


new

grid 91 90
m m
m n i 31

gen 0 -30 0 0 10 0 10 -30 i 1 31 j 1 91
gen 10 -30 10 0 30 0 30 -30 i 32 92 j 1 91

group 'Soil4' j 1 48 notnull
group 'Soil3' j 49 60 notnull
group 'Soil2' j 61 66 notnull
group 'Soil1' j 67 90 notnull


prop dens 1936 shear 2.28571e+06 bulk 1.06667e+07 coh 3.5 fric 25 group 'Soil4'
prop dens 1936 shear 4.71429e+06 bulk 2.2e+07 coh 5 fric 25 group 'Soil3'
prop dens 1936 shear 1.15714e+07 bulk 5.4e+07 coh 13.5 fric 26 group 'Soil2'
prop dens 1936 shear 1.71429e+07 bulk 8e+07 coh 20 fric 26 group 'Soil1'


struct node 1 10 -20
struct node 2 10 0

struct beam begin node 1 end node 2 prop 1001 seg 60
struct prop 1001 dens 2446 e 3e+10 area 0.7854 i 0.04909 spacing 1.5

interface 1 aside from 31 91 31 90 to 31 31 bside from node 1 3 to node 2
interface 2 aside from 32 31 32 32 to 32 91 bside from node 2 61 to node 1

interface 1 unglued kn=1.0E8 ks=1.0E7 cohesion=0.0 dilation=0.0 friction=20.0
interface 2 unglued kn=1.0E8 ks=1.0E7 cohesion=0.0 dilation=0.0 friction=20.0

attach aside from 31 1 to 31 31 bside from 32 1 to 32 31

set grav 9.81
water density=1000.0

ini sxx 0 var 0 10974 j 1 91
ini szz 0 var 0 10974 j 1 91
ini syy 0 var 0 18992 j 1 91

apply syy -10 i 47 77 j 91

table 1 -100 -5.5 100 -5.5
water table 1

fix x i 1
fix x i 92
fix y j 1

solve

ini xdis 0
ini ydis 0

m n i 1 30 j 76 90
solve