Thermo-mechanical loads of sea ice on structures

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• Aleksey Marchenko (University Centre in Svalbard (UNIS))
• Monday 06 November 2017, 16:00-17:00
• Seminar Room 1, Newton Institute.

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SIPW03 - Ice-structure interaction

Thermally induced loads of ice on structures and shorelines occur due to thermal deformations of confined ice. Thermally induced stresses in the ice follow the temperature changes, depend on the coefficient of thermal expansion of ice and are reduced due to the relaxation. Temperature changes in sea ice occur due to conductive heat transfer characterized by specific heat capacity and thermal conductivity of ice and due to the advection of liquid brine depending on sea ice permeability. Coefficient of sea ice thermal expansion depends on the amount of liquid brine trapped in closed packets inside the ice. Proportion between the amounts of liquid brines trapped in closed packets and existing in permeable channels depends on the ice temperature and salinity. Relaxation and creep rheology of sea ice also depends on the temperature and ice structure.

Thermo-mechanical model of saline ice taking into account above described properties was recently formulated by Marchenko and Lishman (2017). The dependence of the coefficient of thermal expansion of saline ice from the temperature was reconstructed from the laboratory experiments. In the present work the model equations are used to estimate and compare the heat fluxes and thermal deformation of sea ice caused by the heat conduction and brine advection. Further the model is used for numerical simulations of ice loads on the cofferdam of coal quay in Kapp Amsterdam, Spitsbergen.

Field observations and records of the loads from sea ice confined inside the cofferdam were performed since 2013 (Marchenko et al, 2013; Wrangborg et al, 2015). Sea ice temperature was measured synchronously with the loads over entire ice thickness using thermistor string frozen into the ice. It was discovered that sea water brine migrates through the confined ice with thickness of 2-3 m under the influence of the water overpressure below the ice caused by semidiurnal tide. Horizontal ice loads on the cofferdam walls are also changed according to the semidiurnal cycle. Thermo-mechanical model of saline ice is used in numerical simulations of the observed phenomena by finite element method realized in Comsol Multiphysics software.

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