FIRST YEAR RIDGE ACTING ON A VERTICAL SIDED STRUCTURE PLACED IN SHALLOW WATER

摘要

First year ridges or hummock fields will give a design global ice load acting on offshore structures placed in sub-arctic region like the Sea of Okhotsk. The global loads are calculated by the sum of forces from consolidated and unconsolidated layers. Although the force from unconsolidated layer is thought to be much smaller than one from consolidated layer, there exist unknown factors in terms of effects of grounding, velocity dependence and interaction with consolidated layer etc. The Authors performed extensive model tests in ice tank using 1/100 scale model to clarify interference between unconsolidated and consolidated layers. From the series of tests, the authors showed that both loads due to consolidated and unconsolidated layers would increase by grounding of rubbles, and proposed the multiplier factors for load calculations separately with and without grounding. Furthermore we evaluated the load due to hummock ice in full scale when water depth is shallow on the basis of the test results.