SAMCoT - Annual Report 2015

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22 SAMC oT • ANNUAL REPORT 2015
Frozen soil
SAMCoT PhD Candidate Yared Bekele has been working in
the development and completion of a fully coupled thermo-
hydro-mechanical (THM) finite element model for frozen
soil is completed. The numerical tool developed has the
following important features:
• Isogeometric analysis with B-splines used as a numeri-
cal solution method leading to a local mass and energy
conserving simulation, unlike the standard finite
element method
• Full nonlinear implementation using Newton-Raphson
iterations with implicit time stepping
• Volume expansion and contraction incorporated into
the governing equations
The developed numerical tool is used to simulate frost
heave where a field-scale experimental data set is
Figure WP2_1 Initial and final configurations of a heave displacement observed at the centerline of the pipe.
available; see Smith and Patterson (1989). The experiment
was performed on a pipeline buried in silt with an initial
temperature of +4ºC and transporting chilled gas at -5ºC.
The external environment also has a subzero temperature
of -0.75ºC. Freezing is thus initiated from two fronts. The
frost heave simulation using the developed THM numeri-
cal tool resulted in heave displacements that are in good
agreement with the experimental data. A heave displace-
ment of about 20 cm is observed at the centerline of the
pipe. See the initial and final configurations shown below
(Figure WP2_1).
Bekele`s research within WP2 is continued within WP6,
Post-Doc Seyed Ali Amiri will use Bekele’s THM numerical
Framework and implement his own material model.