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16 SAMC
o
T • Annual report 2012
Fig. 4a: The beam test ready to be performed.
Fig. 4b: Thin section showing the vertical ice texture in the beam.
a)
b)
conditions and an improved scheme for classification
of these tests has been suggested to the ice engineer
ing community. SAMCoT has also suggested that ice
strength depends on ice confinement and indentation
velocity, as well as ice temperature. Beam tests of level
saline and fresh water ice were conducted and numeri
cal simulations were initiated to examine the effect of
deformations on surrounding level ice and of varying ice
properties vertically through level ice.
How strong is an ice ridge?
SAMCoT researchers aim to develop physically based
numerical models of ice ridge action on structures
by quantifying micro-macro coupling of ice rubble
behaviour.
An ice ridge consists of a sail and a keel. The sail is above
the water line, has minimal volume and is often relatively
weak. Therefore, it has limited effect on the action of the
ice ridge.
In a first-year ridge, the keel consists of an upper refro
zen or consolidated layer, which is similar to level ice, but
often less than four metres thick. A large ridge can be
more than 30 metres thick. The larger part of the keel
volume in large ridges is unconsolidated, i.e., rubble.
The rubble consists of broken ice pieces partly refro
zen to each other through freeze-bonds and pockets of
water/slush. Although the rubble is significantly weaker
than the consolidated layer, it may account for more
than 90% of the keel volume and contribute significantly
to the total ice ridge action on a structure. When rubble
deforms, the freeze-bonds may break and the resulting
blocks can rotate and break apart or crush other rubble.
It behaves like a granular material, not unlike some
soils, but the rubble particles are much weaker than is
typical for soils.
The model development strategy is to combine in-situ
investigations, laboratory experiments and numerical
simulations with finite elements, discrete elements and
numerical simulations of the heat and mass transfer.