Basic HTML Version
18 SAMC
o
T • Annual report 2012
have on the observed ice rubble failure modes in scale-
model experiments of ice ridge-structure interaction.
Dr. Heinone’s analysis also argues that scale-model
rubble is substantially weaker than full-scale rubble
and that scale-model rubble has a greater tendency to
compact than full-scale rubble. This finding is impor
tant, as it demonstrates how rubble accumulates in
front of a structure and how it flows around and below it.
In addition, two rounds of shear box tests in the NTNU ice
laboratory showed a clear connection between strength
of the individual freeze-bonds between ice blocks and
the mechanical behaviour of the shear box. These
tests were conducted in the spring of 2012 by Master’s
students Oda Skog-Astrup and Henning Helgøy, and by
PhD candidate Anna Pustogvar in the autumn of 2012.
How does sea ice expand?
Fresh water ice expands when it is heated, as do most
other materials. In sea ice, brine volume rises as
temperatures increase.
Because the density of brine is higher than the density of
pure ice, the increasing brine content should decrease
the volume, thereby countering the effect of thermal
expansion of pure ice. However, brine may also drain
from the ice, in turn reducing the effect of higher brine
volume with increasing temperature.
The unpredictable variations of thermal expansion of
sea ice are often more complicated but at the same time
less critical than fresh water ice. However, in situations
where sea ice is physically confined and exposed to
tides and large temperature variations, thermal expan
sion can be critical.
Fig. 6a and b: The deformation of the sheet-pile wall in
the main coal harbour at Spitsbergen (Kapp Amsterdam,
Svea). Above: a) Local deformation. Below: b) Sketch of ice
and water at respectively high and low tides.