Direct shear interface tests for pipe-soil interaction assessment

© 2015 Taylor & Francis Group, London. Pipe-soil interface friction parameters are a key input for assessing axial pipe-soil interaction behaviour. A series of direct shear interface tests have been performed on reconstituted natural clay from Onsøy, Norway, using polypropylene interface blocks with three different surface roughnesses. The testswere performed at very low effective normal stresses, typical for seabed pipelines (1 to 10 kPa), and at shearing rates of between 0.001 and 0.023 mm/s. Good agreement is observed between the friction coefficients determined from these tests and those from axial model pipe tests performed on the same soil. The results demonstrate the potential of such element tests to define the interface friction parameters for use in effective stress-based axial pipe-soil interaction models. The test results show the strength envelope is a power function of stress level (with no cohesion intercept), with variations due to interface surface roughness and shearing rate.