Variation of local pressures during ice-structure interaction

Johnston, Michelle (1994) Variation of local pressures during ice-structure interaction. Masters thesis, Memorial University of Newfoundland.

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Abstract

Ice-structure interaction is characterized by a nonuniform distribution of pressure across the impact zone. The interface between the structure and the parent ice consists of a matrix of crushed and sintered ice, throughout which regions of intense pressure are randomly dispersed. -- The variation of localized pressures generated during ice-structure interaction was examined for several sets of data. Ice indentation tests conducted at Hobson's Choice Ice Island (1989), ship ramming trials of the Louis S. St. Laurent and the CanMar Kigoriak, and one ice event which involved the offshore drilling structure 'Molikpaq' each exhibited rapid fluctuations of pressure in space and in time. -- Small regions of intense pressure are termed critical zones and are identified as important elements in the crushing process. Fundamental properties of the high pressure zones such as the average size, force and spatial density are quantified. Critical zones are of the order of 0.10m² and may experience forces ranging from 0.1-4MN. The analyzed data exhibited a reduction in the average pressure of a critical zone with increasing area of instrumentation. A decrease in the spatial density of the critical zones (from 0.80 to 0.62 zones/m²) is proposed as a possible explanation for the noted scale effects. -- Due to the random nature of the critical zones, a design methodology which combines the statistical distributions for the zonal force, size, and number is proposed. Design pressures over small areas may be obtained from a preliminary design curve which is fitted to data from ice interactions with ships and stationary structures.

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