Basic HTML Version
44
SAMC
o
T
• ANNUAL REPORT 2013
geometries and microstructure. This work is based on
fieldwork performed during the UNIS RV Lance expedi-
tion cruise in the Barents Sea and around Svalbard
in April 2013. Polojärvi participated on this cruise
with Professor Jukka Tuhkuri from Aalto University.
In addition to cruise, Polojärvi and Tuhkuri spent a
week in Longyearbyen working in the UNIS cold room
and analysing the samples collected from the field.
Currently, they are preparing a paper on this study
with Tuhkuri and will send it to the IAHR Symposium on
Ice. In spring 2013, Polojärvi participated in organizing
POAC’13, The International Conferences on Port and
Ocean Engineering under Arctic Conditions, in which he
worked as a technical chair in the conference. He also
presented a paper in POAC’13 amongst numerous other
papers by researchers in SAMCoT. In addition to having
a presentation in POAC’13, Polojärvi had two conference
papers written together with Professor Jukka Tuhkuri
in DEM6 conference in Colorado, USA in July 2013. This
conference concentrates on discrete element method
modelling and modelling of granular materials.
PhD candidate Sergey Kulyakhtin has been studying the
ice rubble data that could be used for obtaining material
properties for ice rubble constitutive model. Usage of
available full-scale tests for this purpose, mainly punch
test are complicated by poor control of boundary condi-
tions in those tests and that is why data from laboratory
testing were investigated.
Among laboratory tests, the data from biaxial compres-
sion tests (Cornett and Timco, 1996) seem to be more
relevant in terms of uniformity of stresses inside the
sample and samples preparation. A new way of inter-
preting these data was proposed based on Modified
Calm Clay dissipation potential (Burland, 1965) which
allows deriving a parameter (M) characterizing shearing
resistance of ice rubble which is independent of bound-
ary conditions in contrast to mobilized friction angle
which depends on applied strain ratio Figure 32.
The understanding of physical mechanisms control-
ling the mechanical behaviour of ice rubble is essen-
tial for laboratory tests to ensure that these processes
resemble the in situ conditions as closely as possible.
For granular materials, shape and size distributions of
composing particles are important for shearing resist-
ance of the material. Measurements of ice block sizes
in ice ridges investigated in the Barents Sea over a five-
year period were analysed in order to obtain gradations
of block maximum dimensions normalized by average
thickness (Figure 33). Those gradations will be used as
a reference in future laboratory tests that should help to
improve their representation of real phenomena.
In July, Anna Pustogvar, PhD candidate performed
shear box tests in the cold laboratory of NTNU in order
to estimate effect of the specimen scale on the resulting
mechanical properties of rubble ice. She participated
Figure 32. Comparison of measured mobilized friction angles in biaxial compression (Cornett and Timco, 1996) and the
analytical solution.