Triaxial Compression Test with Hoek-Brown Model
Note
To view this project in FLAC3D, use the menu command . Choose “ConstitutiveModels/TriaxialCompressionHoekBrown” and select “TriaxialCompressionHoekBrown.f3dprj” to load. The project’s main data file is shown at the end of this example.
The triaxial compression tests performed using the Hoek-Brown-PAC model are repeated for the Hoek-Brown model, with the same material properties:
\(m_b\) | 5 |
\(s\) | 0.5 |
\(\sigma_{ci}\) | 1.0 MPa |
\(\sigma^{cv}_3\) | 1.5 MPa |
\(E\) | 100 MPa |
\(\nu\) | 0.35 |
Two compression loading tests are performed:
at zero confining stress, \(\sigma_{3}/\sigma_{ci}\) = 0, and
at high confining stress, \(\sigma_{3}/\sigma_{ci}\) = 1.
For the zero confining stress case, we specify an associated flow rule; this is done with the command:
zone property flag-dilation = -1
For the higher confining stress case, we need to specify a dilation angle that is consistent with the limiting constant-volume stress, \(\sigma^{cv}_3\) = 1.5, chosen for the triaxial compression test for the Hoek-Brow-PAC model. We linearly interpolate a value for dilation corresponding to the current confining stress level of \(\sigma_{3}\) = 1, relative to a nonassociated zero dilation at \(\sigma^{cv}_3\) = 1.5. The current dilation, \(\psi_c\), is then taken to be a fraction of the current friction angle, \(\phi_c\), using the linear interpolation:
The following commands are used to apply the modified Hoek-Brown model for this case:
zone property flag-dilation = 0.333
The FLAC3D results for the zero confining stress case are compared to the analytical solution (see Triaxial Compression Test with Hoek-Brown-PAC Model) in Figure 1 and Figure 2, and the results for the high confining stress case are compared in Figure 3 and Figure 4.
Data File
; Triaxial tests on a Modified Hoek-Brown material,
model new
model largestrain off
fish automatic-create off
model title "Triaxial Test on a Hoek-Brown material"
call 'input_record'
@input
zone create brick size 1 1 1
zone cmodel assign hoek-brown
zone property density = 1.0 shear=@shear bulk=@bulk
zone property constant-sci=@sig_ci constant-mb=@mb constant-s=@s constant-a=@a
@locptrs
zone face apply velocity-y @y_vel range position-y 1.0
zone face apply velocity-y [-y_vel] range position-y 0.0
fish history @record_variables
history interval 1000
fish history @eps_xx
fish history @eps_yy
fish history @eps_yy
fish history @sig_xx
fish history @sig_yy
fish history @sig_zz
model save 'ini'
; unconfined
zone property flag-dilation = -1
fish set @sig_conf = 0.0
zone face apply stress-xx = @sig_conf
zone face apply stress-zz = @sig_conf
zone initialize stress xx = @sig_conf yy = @sig_conf zz = @sig_conf
model step @cyc
model save 'conf0'
; confined
model restore 'ini'
zone property flag-dilation = 0.333
fish set @sig_conf = -1.0 ; negative is compression
zone face apply stress-xx = @sig_conf
zone face apply stress-zz = @sig_conf
zone initialize stress xx = @sig_conf yy = @sig_conf zz = @sig_conf
model step @cyc
model save 'conf1'
⇐ Isotropic Consolidation Test with Modified Cam-Clay Model | Triaxial Compression Test with Hoek-Brown-PAC Model ⇒
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