FLAC3D Theory and Background • Constitutive Models

Drained Triaxial Test with CYSoil Model — Dilation Hardening

Note

To view this project in FLAC3D, use the menu command Help ? Examples…. Choose “ConstitutiveModels/ DrainedTriaxialDilationHardeningCYSoil” and select “DrainedTriaxialDilationHardeningCYSoil.f3dprj” to load. The project’s main data file is shown at the end of this example.

The simulations of drained triaxial test with constant dilation are repeated here by with dilation hardening, this time also using a dilation hardening law as described in the dilation hardening section of the CYSoil model. Initial dilation is zero, and the ultimate values of dilation are 10, 5, and 0 degrees for dense, medium, and loose sand, respectively. Test results for all three cases are written to table files.

The simulation results of deviatoric stress and volumetric strain versus axial strain are plotted in Figure 1 and Figure 2, respectively. The non-monotonic volumetric behavior is apparent in the second plot: all soil types do compact initially, and the denser soil is shown to dilate upon further shearing.

Figure 1: \(\mid \sigma_1 - \sigma_3 \mid\) (in kPa) versus axial strain for dense, medium, and loose sand—dilation hardening.

Figure 2: Volumetric strain versus axial strain for dense, medium, and loose sand—dilation hardening.

Data File

; Drained Triaxial Tests - Dilation Hardening
model title "Drained triaxial test - cap-yield-soil"
model largestrain off
;
zone create brick size 1 1 1
zone face skin
zone cmodel assign cap-yield
;
zone initialize stress xx -100. yy -100. zz -100.
zone face apply stress-norm -100. range group 'East' or 'West'
zone face apply stress-norm -100. range group 'North' or 'South'
zone face apply velocity-z     0. range group 'Bottom'
zone face apply velocity-z -1e-6  range group 'Top'
;
zone property density 1000 pressure-reference=100. exponent=1.0 beta=0.35 poisson 0.2
zone property flag-dilation=0 friction-mobilized=0 
zone property shear-reference=@_Gref friction=@_friu cohesion=@_coh dilation=@_dilu 
zone property flag-cap=0 pressure-initial=100. 
;
fish define _cy_q
    local _z = zone.head
    global _cy_q = zone.prop(_z, 'stress-deviatoric')
    global _vsi  = zone.strain.vol.inc(_z)
end
zone history displacement-z position (1,1,1)
fish history @_cy_q
fish history @_vsi
history interval 50
;
model step 50000
;
history export 2 vs 1 reverse table 'deviatoricStress'
history export 3 vs 1 reverse table 'volumetricStrain'
table 'deviatoricStress' export [string.build('deviatoricStress%1', _IChoice)] truncate 
table 'volumetricStrain' export [string.build('volumetricStrain%1', _iChoice)] truncate 
;
return