Dynamic activity and crushed ice behavior in medium-scale ice-structure interactions

Kennedy, Kurt Patrick (1990) Dynamic activity and crushed ice behavior in medium-scale ice-structure interactions. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (17MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Experimental procedures and results from ice indentation programs conducted by Mobil Oil Canada at Pond Inlet (1984) and by Memorial University of Newfoundland on Hobson's Choice Ice Island (1989) are detailed. Both field programs utilized a hydraulically powered servo-controlled indentation system with a series of spherical and flat indenters. Nominal contact areas in the experiments ranged from 0.02 m² to 3.0 m². The most significant observation in the testing programs was the development of a dynamic load-time trace, i.e., ice-induced vibrations, with frequencies in the area of 30 Hz. Alternate pulverization of ice and clearing (extrusion) of crushed ice products from the impact zone is suggested as the primary mechanism for the observed dynamics, consistent with previous research. -- The Pond Inlet and Ice Island data sets are examined with emphasis on the behavior of crushed ice during the extrusion cycle and its importance to the overall dynamic process, including crushed ice layer thickness, impact area reduction by spalling, and dynamic response spectra. Crushed ice layer thickness is observed to vary across the impact zone and, together with highly variant local pressures, suggests that crushing and extrusion takes place in localized areas. These high pressure zones, or "hot spots", vary both spatially and temporally and make it difficult to infer a pressure distribution across the entire impact zone. Rather, the impact area may be thought of as a collection of small hot-spots (high pressure zones) linked by a matrix of highly damaged or pulverized ice under low pressure. -- Loads and pressures observed in the experiments are simulated by treating crushed ice as an incompressible linear viscous fluid during the extrusion cycle. Simulation of load and central pressure for a spherical patch loading case is discussed in greatest detail and a body of data is developed for an indentation test which exhibited dynamic behavior in both load and central pressure. Examples of a two-dimensional incremental analysis for irregular crushed ice layer thickness profiles and extrusion over a three-dimensional elliptical contact zone are also presented.

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