Theoretical, numerical and field studies of offshore pipeline sleeper crossings

Westgate, Z.J., Randolph, M.F., White, D.J. and Brunning, P. (2010) Theoretical, numerical and field studies of offshore pipeline sleeper crossings. Gourvenec, Susan and White, David (eds.) In Frontiers in Offshore Geotechnics II - Proceedings of the 2nd International Symposium on Frontiers in Offshore Geotechnics. CRC Press. pp. 845-850 .

Abstract

Offshore pipelines experience axial stresses due to internal pressure and thermal cycles during start-up and shut-down, leading to the formation of lateral buckles. Pipeline lay routes often include strategicallyspaced transverse sleepers, creating a vertical imperfection from which a controlled lateral buckle can be initiated. The as-laid pipeline embedment affects the pipe-soil interaction forces and therefore the buckle initiation response. The potential for increased embedment in the touchdown zones to either side of the sleeper exists, which can cause higher than expected lateral breakout forces. The magnitude of this embedment is difficult to quantify due to dynamic lay effects and changes in catenary forces as the pipe is laid over the sleeper. Theoretical solutions for the touchdown force at a sleeper crossing are presented for the case of an elastic seabed, and are compared to as-laid survey data in soft clay. Static and dynamic numerical analyses are also presented to illustrate the changes in pipe-soil contact force as a pipe is laid across a sleeper. This provides a rationale for asymmetry observed in as-laid embedment profiles and its influence from dynamic lay effects. General guidance is provided for pipeline designers to assist the assessment of pipe-soil interaction forces in the vicinity of sleepers.

This record has no associated files available for download.

Contributors

Author: D.J. White

Download statistics