Low stress interface shear box testing for assessing axial pipe-soil resistance

Details

Supervisors

Rattez, Hadrien ; Vanden Berghe, Jean-François

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil des constructions, à finalité spécialisée

Abstract

Accurate and reliable assessment of the axial pipe-soil interaction forces is a key factor for the design of on-bottom submarine pipelines, especially for deep water pipelines as they are operated under high pressure and high temperature and are susceptible to large end expansion, axial walking and lateral buckling. A key input to assess the axial pipe-soil resistance is the interface strength between the seabed soil and the pipeline coating. This can be measured in the laboratory but standard direct shear testing apparatus needs to be modified to accurately measure the shear strength at the very low stress level existing between the pipeline and the seabed (i.e. typically in the range 5 to 15 kPa). The modification of the direct shear testing apparatus implies the ability to run interface-soil tests and limitation of the residual stress caused by the friction of the apparatus. The testing procedure then needs to be adapted to realise loop tests with the soil sample. The purpose of the study is to modify a direct shear test apparatus to perform interface-soil tests in the laboratory to investigate the effect of the pipeline coating roughness, shearing velocity, normal stresses, etc., with the view to compare it with already existing datasets, populate a database of results and develop correlations with soil index parameters. Some conclusions can then be drawn from this study, such as the usefulness of these tests compared with theoretical values, the usefulness of carrying out low-stress tests and the accuracy of the modified device.