Typical rock berms used to protect submarine pipelines may be damaged under shear by a first year grounded ice rubble keel. Physical model tests in a centrifuge have indicated that such damage occurs under loads less than those typical of actual design conditions. These novel tests have reproduced both failures of the rock berm and identified failure criteria for the ice rubble. The tests are of a preliminary nature given the discrete, rather than continuum, nature of the interaction event. The model freshwater ice rubble behaved as a frictional granular material under the shear test conditions with a peak friction angle of 38 degrees. Measured ice rubble shear strengths exceeded 65 kPa.
First year freshwater ice rubble large scale tests were conducted as part of the Pipeline Ice Risk Assessment and Mitigation (PIRAM) and Development of Ice Ridge Keel Strength (DIRKS) Joint Industry Projects. New finite element analyses of the PIRAM test set up indicate the boundary constraints on the test results. The measured PIRAM ice rubble shear strengths exceeded 35 kPa.
The first two test series indicate that ice rubble shear strength may exceed currently accepted design limits.
