Basic HTML Version
15
SAMC
o
T • Annual report 2012
How strong is ice?
Ice properties are required for simple engineering
formulas, numerical simulations and when performing
scale-mode experiments. In each estimate of how ice
will interact with a structure, one needs a quantifica
tion of the mechanical behaviour of the ice: in short, its
strength.
The mechanical behaviour of sea ice depends strongly
on its temperature and its brine and gas fraction. The
temperature and the brine and gas fraction change
substantially throughout the seasons, so it is impor
tant to carry out in-situ experiments under different
conditions to capture the variations in ice mechanical
properties.
The research team carried out in-situ tests of both first-
year sea ice (at Spitsbergen and the Barents Sea) and
old ice (in the Fram Strait). Our researchers performed
cantilever beam tests, small-scale uniaxial compres
sion tests, small-scale indentation tests (borehole jack
tests) and dynamic tests of elastic properties.
The 2012 SAMCoT specialized research team consisted
of Professor Aleksey Marchenko, Aleksey Shestov, David
Wrangborg and Joar Aspenes Justad. UNIS students
from the AT-211:
IceMechanics, LoadsonStructuresand Instrumentation,
and AT-332: Physical Environmental Loads on Arctic
Coastal and Offshore Structures, courses also partici
pated in the field work. In addition, international
researchers Evgeni Karulin and Marina Karulina from
Krylov Shipbuilding Research Institute in St. Petersburg,
Russia, contributed to the work as guest researchers.
The beam tests represent the failures in bending when
ice collides with a sloping structure. This failure is
typical of ice interaction with ships and with moored or
fixed structures with sloping water lines. The uniaxial
compression tests and the indentation tests are more
representative for cases when ice hits a vertical faced
structure.
The bending strength cantilever beam tests can easily
be accomplished in both full and small scales. Crushing
strength measures are often difficult to compare, as
uniaxial compression tests are difficult to perform on
scale-model ice.
In basin tests, the crushing strength is often determined
by indentation measures, but few comparable full-scale
indentation experiments are available. SAMCoT devel
oped a rig for in-situ indentation tests so that a reliable
full-scale comparison with scale-model ice properties
can be completed (see Fig. 2). The rig was tested in dry
conditions in 2012 and is scheduled for field testing in
2013.
Several series of small-scale indentation experi
ments (borehole jack) were carried out in different ice
Fig. 3: Students in AT-332 perform an in-situ beam test in
Svalbard.
Fig. 2: The new indentation rig for in-situ ice testing.