Subscour Displacement in Clays From Physical Model Tests

Abstract

A subscour soil displacement model is a key component to determine the safe burial depth of offshore pipelines in ice scoured environments. In order to calibrate numerical models and physical tests carried out in geotechnical centrifuges, 3D ice scour tests were carried out in a dredging flume at a scale approaching that of observed scour depths in the Caspian sea. Two soil failure mechanisms were observed. For steep keels, the soil is mainly pushed up into a mound in front of the keel. For shallow angle keels most of the scoured soil is forced under the keel and to the side of the indentor. Each mechanism results in a different subscour displacement pattern. Subscour displacement equations that include the effect of soil properties and keel angle are presented. While these equations are considered an improvement on existing sub-scour models, there remain limitations to their application in 3D sub-scour until further information relating scour depth and width to soil strength becomes available.