Sammendrag
Laboratory and field experiments together with analytical and numerical simulations were
performed to study the scaling of the ice ridge consolidation. Such experiments and
corresponding thermodynamic models are an important method for describing and predicting
morphological, physical, and mechanical properties of the consolidated layer, corresponding
atmospheric heat fluxes, and structural loads.
The laboratory-scale experiments covered ice ridges, grown from freshwater, seawater, and
water-ethanol solution with different types of morphology including with parallel blocks. Such
morphology was used to decrease effects from the ridge inhomogeneity, and to increase the
measurement accuracy of the ridge macroporosity and the ice thickness. This allowed for
separate investigations of the effects from the other ridge parameters including block thickness,
ice initial temperature, and the ridge sail height. The effect of the faster growth rate of the
consolidated layer over the level ice for small-scale ridges observed experimentally was found
to be related to the difference in convective-conductive coupling for the two types of ice, which
can be increased by the extended ridge sail surfaces. The experiments with water-ethanol ice
showed no significant difference in consolidation rates with the freshwater ice ridges.
The full-scale experiments covered saline ice ridges artificially made from the surrounding level
ice. This method allowed us to increase the accuracy of the macroporosity and initial ice
temperature values. The results of the field measurements confirmed the thickness
overestimation based on the measured temperature profile in the ridge blocks in comparison to
the ridge voids. This thickness overestimation was also observed in small-scale experiments.
The effect of slower consolidation rates for the full-scale ridges during the initial phase
observed experimentally was found to be related to the significant deviation of those ridges
from the homogeneous approach.
Simulations of the ridge consolidation were performed using a two-dimensional finite element
method with the moving boundary and the discrete rubble blocks. It was validated by the
performed laboratory and field experiments for different scales and different types of ice. It
allowed deeper investigations of the effects from the ridge sail, rubble block initial temperature
and thickness, ridge keel, and the thickness estimation methods for the consolidated layer. It
has also been able to describe the scale-effects in the previous ridge experiments. The
simulations helped to provide insight into the analysis of the ice ridge thermal investigations,
the estimation algorithms for the consolidated layer thickness, and on the distribution of the
heat transfer through the different ridge parts. The difference between fresh and saline ice
growth was equally important for level ice and ice ridges, but its values were becoming
significant during the initial and warming phases.
The analytical model of ridge consolidation was also formulated and validated using numerical
simulations, field, and laboratory experiments. This model also allows to consider sail height,
block thickness, initial ice temperature, ice salinity, and snow thickness, but cannot consider
the thermal inertia. This analytical ridge model could be used for the prediction of the
consolidated layer thickness in the probabilistic analysis of ice actions on structures.
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