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FORCES IN MOVING ICE FIELDS

One of the biggest problems confronting the designer of structures in ice infested waters is the proper design against forces exerted by moving ice fields. Little, if any, experimental data have been available until recently, only a few model tests have been conducted. The situation is even more complicated if one considers that ice formations attacking structures, especially in oceans, hardly satisfy the theoretical requirements of a well defined geometry. For example, pressure ridges, especially old, healed pressure ridges in the Arctic pack ice can exert tremendous forces, ice pileup on structures can modify their response to moving ice fields. Some insight can be gained from systematic observations made from ships negotiating various ice formations since the applied thrust can be calculated. The geometry of the ship bow, however, can be vastly different from the geometry of various structures and harbor installations. The paper presents a systematic discussion starting from the simplest cases up to more complex situations confronted by the designer. The calculation of relevant properties of ice sheets depending upon temperature and salinity is briefly outlined and it is shown how to extrapolate information obtained from one set of conditions to harsher conditions in other locations. The effect of the geometry of structures upon ice forces is shown starting from vertical and sloping cylinders, piles and walls. It appears that the mode of failure, such as buckling, crushing, bending and splitting is governed by the relationship of structure geometry to ice thickness. The relative efficiency of conical structures to combat ice forces is severely impaired by the possibility of ice-up which is discussed in detail and compared with field observations on causeways and similar structures. A possible way to calculate critical ice forces in the presence of this rather chaotic situation is outlined including overturning and possibly torsional moments. This requires a statistical approach. It is shown how to relate such forces to the forces originating between moving ice fields which eventually lead to pressure ridges. Ship observations give rather reliable indication about the relative forces to be expected from various ice formations observed in nature. Available information is summarized and various approaches are discussed.

  • Supplemental Notes:
    • Abstract of paper delivered at the First International Conference on "Port and Ocean Engineering under Arctic Conditions" held at Trondheim, Norway, August 23-30, 1971
  • Corporate Authors:

    POAC Conference

    ,    
  • Authors:
    • Assur, A
  • Publication Date: 1971

Subject/Index Terms

Filing Info

  • Accession Number: 00025700
  • Record Type: Publication
  • Source Agency: Arctic Institute of North America
  • Files: TRIS
  • Created Date: Mar 28 1972 12:00AM