Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Strength properties of deformed ice in the Kara, Laptev and East Siberian Seas
Yaroslav O. Efimov1, Konstantin A. Kornishin1, Petr A. Tarasov1, Alexander T. Bekker2, Evgeniy E. Pomnikov2,Pavel V. Anokhin2, Roman B. Guzenko3, Sergey M. Kovalev3
1Department of Marine Operations, Arctic Research Centre, Moscow, Russia
2Engineering School, Far Eastern State University, Vladivostok, Russia
3Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia

ABSTRACTINTRODUCTION

The article describes correlations between the strength and physical(salinity, temperature) properties of deformed sea ice, determined
during ice research in 2013-2017 in the Kara, Laptev and East Siberian
Seas. It also provides results of special polygon studies of the ice
hummock strength conducted in 2019-2020 in the Khatanga Bay of theLaptev Sea. It is shown that there is no significant difference between
level ice and deformed ice (consolidated layer of ice hummocks) interms of the strength/temperature dependence. Furthermore one-yearlevel ice and two-year level ice, as well as one-year ice hummocks
formed on drifting sea ice, can be combined into one group in terms ofstrength properties (in dependence on the ice temperature). Near
mouths of large rivers fast ice and ice hummocks formed on it arecharacterized by lower salinity and have another characteristic.
Correlations between temperature/salinity and the following strengthcharacteristics of level and deformed ice are proposed and refined: localstrength, uniaxial compression strength, central bending strength. The
coefficients of variation of ice strength have been specified for researchsites of 50x50 meters on ice of various types. Regardless of the ice type,these coefficients take typical values in the range of 5-15%. Ratio of
local strength to uniaxial compressive strength for the entire set ofstudied ice has been also determined. A new method is proposed for
calculating the level ice strength averaged on its thickness and for
calculating the strength of consolidated layer in ice hummocks. The ice
strength is defined as a function of the ice temperature in upper horizon(45 cm from the ice surface). The biggest one-year ice hummock of theEast Siberian Sea was comprehensively studied: the strength of its
consolidated layer (330 cm) was measured with a bore hole-indenterand its cross-section was reconstructed. The obtained data can be used
to assess the typical and extreme strength properties of ice hummocks
and for calculation of the ice loads on offshore structures in the Arctic.

Information about the strength properties of deformed sea ice thatcomposes hummocks is essential for assessing ice loads on hulls of
icebreaking vessels and infrastructure facilities in the Arctic region.
Assessment of extreme values of ice strength (1 in 100 years) is
important for determining ice loads on offshore facilities. Navigationin sea ice also requires information on operational conditions aroundthe vessel, especially the current strength of the ice. In order to solve
both of these problems, it is necessary to obtain and justify reliablecorrelations between the strength and physical (temperature, salinity)
properties of ice, that is impossible without a series of experimental
studies of ice properties. Sea ice can be studied either during large-scale
expeditions across the seas from research vessels or at a special ice
research sites. Each of these methods has advantages anddisadvantages. Expeditionary surveys accumulate significant statistics
on ice properties, but are limited to 1-2 months. At research site it ispossible to study ice for 7-8 months, but in one geographical location.
For a substantiated numerical assessment of the strength properties ofdeformed ice under various environmental conditions, a combinationof the above methods is required; at the same time, an important issue
is "linking" the results of the expeditionary and field results. For a highquality numerical assessment of deformed ice strength properties undervarious environmental conditions, a combination of both these methods
is required. At the same time, there is an important scientific problem –to achieve a trustful correlation between expeditionary results obtainedwith icebreaker and site results. In 2013-2015 and 2017 authors carriedout expeditionary ice studies in the Kara, Laptev and East Siberian seas.
During 2019-2020 ice hummocks were studied at the research site
“Khastyr” located in the Khatanga Bay of the Laptev sea. An important
issue is correspondence between the correlations for level anddeformed ice. For each of the strength characteristics of ice (localstrength, uniaxial compressive strength, central bending), it isnecessary to obtain correlations of ice temperature/salinity, and thenmake a reasonable comparison. Data amount in the samples should be
sufficient for regression analysis. This article discusses deformed sea
ice strength properties and is a logical continuation of (Kornishin et al.,2021), in which the strength properties of level ice were considered.
Information on geometric parameters of hummocks and the propertiesof ice fields studied in 2013-2017 can be also found in the following

KEY WORDS: ice strength; hummocks; local strength; central
bending strength; modelling.

1206