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

Seasonal evolution of strength and thickness of consolidated layer
in hummocks and stamukhas of the Arctic offshore
Alexander T. Bekker1, Egor E. Pomnikov1, Roman B. Guzenko2, Sergey M. Kovalev2,Konstantin A. Kornishin3, Yaroslav O. Efimov3, Petr A. Tarasov3, Teymur E. Mamedov3
1Engineering School, Far Eastern State University, Vladivostok, Russia
2Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia
3Department of Marine Operations, Arctic Research Centre, Moscow, Russia

ABSTRACTINTRODUCTION

The article discusses seasonal variability of the strength properties ofice formations typical for the Arctic offshore. Thermal states ofstamukhas and ice ridges were experimentally studied in the Khatanga
Bay of the Laptev Sea in 2019-2020. Maps of temperature distribution
in the consolidated layer of hummocks/stamukhas were built based ondata from 12 thermistor chains installed on ice formations; ice freezing
rate at the contact of the freezing front with various phases located in
the unconsolidated part of the keel was also measured. Ratios of thethermal conductivity for the sail and the keel of the hummock werecalculated based on the readings from the thermistor chains; it is shownthat the sail provides thermal insulation of the keel zones located underit. The local strength of deformed ice composing a consolidated layer
was determined as a function of the ice temperature. Maps of thestrength distribution of the consolidated layer were constructed for theentire life cycle of the ice formation; these maps were constructed basedon the thermal history of the hummock and obtained dependence of thelocal strength on the ice temperature. The thermal state of the hummockis fundamentally important for assessing its mechanical properties. A
weakened (warm) zone under the hummock sail, as well as the unevengrowth of the consolidated layer, significantly affect the distribution ofinternal stresses in the hummock during its further evolution anddestruction, as well as in the case of interaction with an offshore
structure. The article also discusses strength properties of stamukhas in
the spring-summer period, when they can drift in the sea and interact
with infrastructure facilities. The results presented in the article can beused for modeling of ice loads on offshore structures in the Arctic zone;
they also allow to determine the properties of ice formations in different
seasons.

Loads from ice formations of deformed ice (hummocks and stamukhas)
on offshore structures significantly depend on the size and strength
properties of these formations. At the same time, geometricaldimensions of hummocks and stamukhas remain constant from themoment of their formation, but the internal structure and properties ofcomposing ice change significantly during the formation life cycle. For
valid modelling of formations of deformed ice, it is necessary to
determine their properties at different periods of time. The solution tothis problem requires a large amount of experimental studies of the ice
regime in order to determine the most probable range of functionalparameters that determine mechanics and magnitude of the loads during
the entire ice period, as well as the peculiarities of the ice-structure
system in a specific geographical area. Also, the assessment of thehummocks and stamukhas evolution and their properties is an
important independent scientific problem, the results of which can beapplied in practice, such as Arctic shipping. To study the seasonalvariations of loads from ice formations, the following main directionsof research are be proposed:•
experimental study of the strength properties changes inhummocks and stamukhas located in harsh climatic conditions;•comparison of physical and mechanical properties ofdeformed ice forming a hummock with similar properties of flat ice inthe same area;•determination of the least favorable (worst) conditions for
operation of offshore structures in terms of interaction with hummock
formations.
A complex of field and laboratory tests of the physical and mechanicalproperties of ice formations and sea ice was carried out during 20192020 season at the temporary field base “Khastyr” in the Khatanga Bayof the Laptev Sea.

KEY WORDS: ice strength; consolidated layer; hummocks;
stamukhas; Arctic.

Based on the field and laboratory data, a seasonal variation of thefollowing parameters of the flat and deformed ice was obtained forevery 2 decades:•snow height, ice thickness and draft;

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