Ice loads on the caisson structures in the Canadian Beaufort Sea

Abstract

This paper presents a comprehensive overview of the characteristics, instrumentation and measured ice loads on the caisson structures that were used for exploratory drilling in the Canadian Beaufort Sea in the 1970s and 1980s. Details are presented on the Tarsiut Caisson, the Single-Steel Drilling Caisson (SSDC), the Caisson-Retained Island (CRI), and the Mobile Arctic Caisson (MAC) Molikpaq. The global loads on the structures are presented as a Line Load (Global Load per unit width of the structure) and the Global Pressure (Line Load per unit ice thickness). Over 170 loading events are documented. There is excellent agreement amongst the measured loads on all of the structures if factors such as ice rubble and ice thickness are considered. Global loads are shown to be a function of the ice macrostructure (level first-year sea ice, multi-year ice, first-year ridges, hummock fields, isolated floes) and failure mode of the ice (bending, creep, mixed mode, crushing). The analysis shows that there is a general increase in the Line Load with increasing ice thickness. Empirical equations are presented to predict the global load in terms of the ice thickness and structure width for different ice failure modes. The most significant result of the analysis shows that the maximum Global Pressure measured for all types of ice loading events never exceeded 2 MN/m 2, with the vast majority less than 1.5 MN/m 2.