Author(s): Paul Spencer; Anne Barker; Garry Timco
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Keywords: No Keywords
Abstract: In a previous paper (Spencer et al., 2007), it was shown that under some circumstances, mainly a gravity based structure (GBS) on weak cohesive soils, the cost of the GBS is a strong function of the design ice load. It was also shown that a set of submerged ice barriers around a GBS could reduce the overall system cost. In the current paper, we quantify the ice loads on a submerged ice barrier and the reduction in design ice load on the GBS as a function of the dimensions and location of the barrier, its depth below mean sea-level and the waterline dimension of the GBS. The ice loads for a barrier and a GBS are calculated for the important situation of kinetic energylimited interactions between the barrier and/or the GBS during open water impacts with multiyear ice floes. A Monte-Carlo approach has been used to estimate the 100-year return period ice loads and the statistical description of the multi-year ice floe parameters used is representative of locations in the near-shore Beaufort Sea. Site specific data should be used for a particular location. The details of the calculations are provided along with some parametric trend analysis. Important conclusions from the study are that for a 50% reduction in the design ice load on a GBS due to the installation of the submerged ice barriers, the top of the submerged ice barrier should be located between 3 and 4 m below sea-level for barrier lengths comparable with the waterline width of the GBS. For barriers much less than the GBS width, the ice barrier could reach the water surface. In addition, there are significant cost savings for employing the shorter barriers.
Year: 2010