The Influence of External Boundary Conditions on Ice Loads in Ice-Structure Interactions

Abstract

Design ice loads are generally derived from field measurements or laboratory experiments. The latter commonly neglect the circumstance that most ice-structure interactions occur underwater, despite the fact that studies report higher ice loads if water is present. Other than a few studies on ice extrusion processes, most investigations on ice loads also do not specifically consider the presence of snow or granular ice at the ice-structure interface. To elucidate the influence of water, snow and crushed ice, as external boundary conditions, on ice load magnitude, 71 small-scale laboratory tests were carried out. Testing involved a hydraulic material testing system (MTS machine) located in a cold room at −7°C. Ice specimens were conical shaped with 25 cm in diameter and with 20° and 30° cone angles. Those were impacted with a flat indentation plate at 1 mm/s, 10mm/s and 100 mm/s indentation rates. Time-penetration and time-force histories from the MTS machine, as well as qualitative contact area and local pressure measurements from tactile pressure sensors were collected. Tests were also recorded with a high speed camera and monitored with still photos. The effect of submergence was most evident at high indentation rate, yielding high ice loads. Snow and granular ice caused comparably high ice loads at the high indentation rate. Moreover, the snow and granular ice conditions also significantly increased loads at the low indentation rate. In all cases, higher ice loads were associated with increased effective contact areas.