Physical and mechanical properties of brash ice in Luleå Harbour

Brash ice forms when vessels navigate in level ice breaking it, and subsequently along the same track breaking the partly or fully consolidated broken ice field. The formation and growth of brash ice can be rapid and present a hazard for shipping operations, often requiring icebreaker assistance. Compared to other deformed ice structures such as pressure ridges, the physical and mechanical properties of the brash ice formed in heavily navigated harbours or ship channels have not been studied much. In the current study, individual brash ice pieces were sampled from two different harbours in Luleå, Sweden, in March 2020 and March 2021. The brash ice piece size distribution, the compressive strength of individual ice pieces, density, microporosity, and microstructure were measured. The brash ice piece size followed a three-parameter log-normal distribution. The brash ice samples collected in the first year (2020) hada microstructure similar to level ice while the ice pieces collected in the second year (2021) had a mixed microstructure (columnar and granular) similar to deformed ice. For an increase in strain rates from 10-5 s-1 to 10-3 s-1, the maximum strength increased when the brash ice samples were exposed to cyclic loading. The maximum strength was not significantly different between the different locations. Funder: TotalEnergies; Kolarctic ICEOP