SAMCoT - Annual Report 2015

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14 SAMC oT • ANNUAL REPORT 2015
Arctic drift ice was performed to the north of Spitsbergen.
During the experiment RV BjorkHoug penetrated through
MIZ for 2 nm. Wave measurements were performed on
several stations by two sensors (SBE 30plus) mounted on
the same rope fixed on the ship board. In the same place ice
trackers equipped with thermistor strings were deployed
on the drift ice ridge with 8 m draft.
Other field activities performed by WP1 researhcers aimed
to the collection of data and further studies were performed
during a field campaign in 2015 on the level, land-fast ice in
Van Mijen Fjord, Spitsbergen.
Sveabukta Bay in Van Mijen Fjord is a natural field polygon
for research and educational studies of sea ice at UNIS. An
extensive knowledge of ice mechanics has been developed
over the last 20 years at the Arctic Technology Department.
Several small- and large-scale in situ experiments on ice
mechanics are conducted yearly. The aim of the present
work was intended to complement existing knowledge on
the physical properties of sea ice through the season, to give
a better understanding for the planning and preparation of
further field experiments. This work is valuable even as a
standalone study. Starting on February 12th and continuing
until April 29th the site was visited several times. During
this period, several cores were taken to perform studies
on the microstructure and the physical and mechanical
properties of ice. In addition, temperature profiles through
the ice and conductivity below the ice were logged over
time. All results were presented in the paper `Hydrology
of Braganzavågen under ice-covered conditions` in the
Proceedings of the 23rd International Conference on Port
and Ocean Engineering under Arctic Conditions.
As a key result of the work done in monitoring sea ice and
iceberg drift, WP1 researchers were able to formulate
a model of the passive turn of a vessel with an internal
turret in conditions of close drift ice using the method of
limit stress analysis in plasticity and the theory of granu-
lar materials. Model equations consist of the kinematic and
dynamic equations describing the movements of the vessel
and the ice loads on the vessel hull when solid ice drifts
against the vessel. It is shown that movements of the vessel
before it takes final position parallel to the ice drift, consist
of translational displacements, rotation without axial
displacement and rotation with axial displacement. On the
last stage of the turn the vessel rotates as a whole, together
with the effective mooring line, around the elasticity center
of the mooring system. Tension of the mooring line reaches
maximum at this stage.
Sea Ice Actions in the Coastal Zone
Laboratory works included a set of original experiments
on the investigation of thermo-elastic waves in saline ice.
Cylindrical ice samples were insulated by foamplastic from
their lateral sides and from the bottom. Their surface was
under periodical cooling with a 12 minute period produced
by a cooling system at the cold laboratory of UNIS. During
the 12 minute period the room temperature was varied
with an amplitude of about 1˚C. Fibre Bragg Grating (FBG)
strain sensors registered vertical displacements of the ice
surface within the same period and an amplitude of about
1 m. The dependence of the amplitude on ice salinity and
temperature was investigated during the experiments.
An elaborated theory, based on modified Darcy’s law,
describing liquid brine migration through the ice is used
to explain the dependence of the amplitude of the thermo-
elastic waves on the ice temperature and salinity.
Figure WP1_5. Installation of synthetic net on the surface
of cantilever beam (a). Flexural strength test with frozen
synthetic net (b).
Figure WP1_4. In-situ test for tensile strength of floating ice
a) b)