"The geotechnical behaviour of buried offshore pipelines in clay soils"
By: Dr. T.A.
Newson
Geotechnical Research Centre, Department of Civil & Environmental Engineering,
The University of Western Ontario, London, Ontario. (t.newson@eng.uwo.ca)
Abstract
There is extensive use of buried pipelines within the offshore oil and gas industries to transport commodities from their point of recovery to the shore. Since pipelines are laid in remote and potentially hostile environments the cost of laying the pipe can be extremely high. Trenching and burial is typically achieved by specialised water jetting or ploughing equipment. To achieve high flow rates in pipelines, the gas or oil must be kept at high temperature and pressure. Once commissioned, the pipeline can experience significant axial strain, which is resisted by seabed friction so that compressive forces increase in the pipe. The compressive forces are occasionally large enough to induce vertical buckling of trenched lines, with the pipe emerging from the soil or becoming significantly distorted, so that its ability to withstand further loading is compromised. The soil above the pipeline and the buoyant weight must provide resistance to this uplift force and the embedment depth must be sufficient to prevent vertical pipe movement from occurring. Despite considerable research being reported in the literature on upheaval buckling, there is still much confusion as to the appropriate design parameters and failure mechanisms involved. This presentation will concentrate on the issues related to design of offshore buried pipelines in clayey soils and will cover laboratory, centrifuge and field testing, numerical modelling and design approaches. The additional design criterion of thermal conductivity of the soil and pipe system will also be discussed.
Bio
Dr. Tim Newson has recently moved to the Geotechnical Research Centre from Scotland, where he was an Assistant Professor of Geotechnical Engineering for seven years at the University of Dundee. In Scotland, he managed the Geotechnical Laboratory Facilities and was the Director of the Dundee Geotechnical Centrifuge Centre. Before joining the University of Dundee, he spent four years in Perth as a post-doctoral fellow at the University of Western Australia, working with the gold mining industry on tailings disposal and decommissioning. Prior to this, he worked for Sir William Halcrow and Partners in the UK as a geotechnical engineer on a variety of projects in South Wales and Hong Kong. His research interests and consulting activities include in situ testing, constitutive modelling of clays, disposal of mine wastes, centrifuge and laboratory testing techniques, dynamic soil-structure interaction, contaminant transport through porous media, offshore engineering, fracture behaviour in clayey soils and the biomechanics of the eye.