| Résumé | To test the Blade Runners concept for reducing ice induced vibration and loads on structures a simple configuration consisting of a single stationary blade on a rigid flat metal crushing plate was chosen for ice crushing tests in NRC-OCRE’s Large Cold Room facility. Five wedge-shaped columnar-grained freshwater ice samples were crushed against a thick plate with a low-profile blade on it and the results were compared with those from another five crushing experiments using a plate without a blade. The two crushing plates were made of aluminum and had identical characteristics other than that one of them had a blade on it. The blade had an isosceles right triangular section profile with a height of 1 mm and base of 2 mm. The blade spanned the length of the plate and was centered relative to the wedge-shaped ice samples and parallel with their long axes. Tests were conducted at -10oC and the nominal crushing plate displacement rate was 10 mm/s. High-speed imaging was used to observe the ice contact zone, by viewing through the ice samples, as it evolved and moved around somewhat during the tests. Load records from the tests using the bladeless crushing plate exhibited a high-amplitude sawtooth load pattern, resulting from fairly regular ice spalling events, that is typical of ice crushing in the brittle regime. This type of spalling behaviour, and associated sawtooth load pattern, is responsible for ice induced vibration of structures when ice sheets encroach on them. The average loads were roughly the same during either set of tests. However, for those tests where the plate with the blade on it was used it was observed that when the blade was in the hard zone region of the ice contact area the load pattern was dramatically affected. In those cases the blade effectively smoothed the sawtooth loading pattern by greatly increasing the spalling rate and reducing the spall size. Consequently the amplitudes of the load sawteeth were significantly reduced. |
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