Permafrost

The Thermal Conductivity of Segregated Ground Ice
Rev I. Gavriliev
(Melnikov Permafrost Institute, Siberian Branch, Russian Academy of Sciences, Merzlontaya St. 36, Yakutsk,
Russia, 677010, E-mail: gubanova@mpi.ysn.ru)
Abstract: In order to estimate the thermal conductivity of segregated ground ice, the model of
porous ice with closed bubbles of spherical shape can be used, taking into account additional
convective heat transfer by vapour diffusion in bubbles. Calculations can be made on the basis
of the Maxwell-Rayleigh theory using Schwerdtfeger’s equation. It is shown that the measured
values of the thermal conductivity for segregated ice in Grechishchev et al. (2002, 2003) are
obviously underestimated because of the incorrect application of the temperature wave method
to layered bodies.
Laboratory and Numerical Modeling of Rock and Concrete Fracture
Due to Thermally-Induced Water Migration
Rorik A Peterson 1 , Julian B Murton 2
(1.Mechanical Engineering, University of Alaska, Fairbanks, Fairbanks AK, USA 99775-5905.
2.Department of Geography, University of Sussex, Brighton, United Kingdom BN1 9QJ)
Abstract: Thermally-induced water migration in porous media is a common phenomenon in
arctic and subarctic regions where water saturation levels are high, time periods of
freeze/thaw are long, and thermal gradients are strong. Ice accumulation at the freezing front
leads to ice lensing and frost heave in soils, and can cause fracture in rigid, elastic materials
such as bedrock and concrete foundations. The damage to roadways, pipelines, buildings and
other infrastructure is costly and often difficult to repair. However, mitigation techniques such
as thermosiphon installation or gravel backfilling are also expensive and should be instituted
judiciously. We are studying the thermodynamic and mechanical processes involved through
both physical and numerical modeling to improve engineering techniques and reduce costs in
arctic regions.
The fundamental water migration process occurs due to a gradient in thermomolecular
pressure, also known as a 'disjoining' pressure, caused by thin liquid water films at subfreezing
temperatures. We have utilized previous theoretical models of soil frost heave in a
thermo-mechanical model that describes temperature, pressure, water saturation, and
mechanical stress in elastic materials. When tiny cracks/flaws exist in freezing rock or
concrete, ice can collect and eventually cause fracture. Our numerical model describes this
process in material containing an initial distribution of very small microcracks. The pattern of
macroscopic fracture that develops depends on the thermal regime. For boundary conditions
of cyclic freeze/thaw on top and thermally insulated, unfrozen on bottom, maximum fracturing
occurs just slightly below the top surface. However, when the bottom boundary is constrained
to remain frozen (simulating permafrost), maximum fracturing occurs just slightly below the
depth of maximum thaw. The degree of saturation strongly influences the tendency to fracture
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