ABSTRACT:

A theoretical analysis of interactions between homogeneous masses of broken ice and structures in dynamic formulation is discussed. The problem is solved in the terms of soil mechanics.

INTRODUCTION

A most important task in designing engineering structures intended for offshore hydrocarbon exploration and production in freezing waters is to correctly establish external ice loads acting on these structures under various ice conditions. Numerous analytical and experimental studies have greatly enhanced our knowledge of the forces grouped under the first, the second and the fourth categories. The present level of research on the third group is, however, markedly lower. At the same time for many freezing sea areas, e.g. the Barents Sea, this very type of ice effects plays a decisive role. For other regions it is considered that interactions with ice fields are more characteristic for winter period while in spring/summer the structures are opposed by broken ice (Tunik at al, 1989). Numerous full-scale studies of ice interaction with engineering structures: lighthouses and drilling platforms (Määttanen, 1986) indicate that a moving ice field most often transfers its force upon a face surface not directly, but through ice rubble which forms an "ice cusion" in front of the structure. Similar phenomena can be observed when there is a high compression of ice near flat ship sides, when icebreakers with flat fore or stern-lines move in brash ice or when an ice field or the broken ice interacts with a structure of considerable (compared to the ice thickness) cross-section. Neglect to studies on lcebreaker/brash ice interaction often leads to erroneous conclusions about advantages of this or that innovate shape of the bow. The bows which perform in an excellent way while in an ice field turn out to fail in channels with broken ice blocks or in brash ice.

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