Estimation of Pipeline Embedment in Soft Submarine Soils by Different Methods

Year 2020, Volume: 12 Issue: 1, 300 - 306, 31.01.2020

Zeynep Huri Özkul Birgören

https://doi.org/10.29137/umagd.626609

Abstract

The embedment of subsea pipelines in soft submarine clay is a key parameter in pipe-soil interaction studies of offshore deep water oil and gas field developments. A number of calculation methodologies exist, some of which are based on empirical evidence.  Pipeline embedment depends on the active undrained shear strength and unit weight of the soil and the properties of the pipeline (i.e. weight and dimensions).  The embedment is also influenced by stress concentrations occurıng due to the geometry of the pipe catenary and by the cyclic motion of the catenary at the touchdown point. In this study, the methods typically used in the industry, such as those proposed by Terzaghi (1967), Dunlap et al. (1990) and Verley & Lund (1995) are compared with the methods recommended in DNVGL-RP-F114 (2017).  The calculated embedment from each method are compared for typical pipe properties and soil strength and discussed in view of field observations reported in the literature. The older methods were found to typically underestimate embedment for low shear strength profiles.

Keywords

pipeline embedment, bearing capacity, marine clays, pipe-soil interaction

References

• Allen, D.W., Lammert, W.F. and Hale, J.R. (1989). Submarine Pipeline On-Bottom Stability: Recent AGA Research. Proc. 21. Offshore Tech. Conf. OTC 6055.
• Bruton, D. A. S., White, D. J., Langford, T. and Hill, A. J. (2009). Techniques for assessment of pipe/soil interaction forces for future deepwater developments. Proc. Offshore Tech. Conf. OTC 20096.
• DNVGL-RP-F114. 2017. (2017). Pipe-soil Interaction for Submarine Pipelines. DNVGL-RP-F114, Det Norske Veritas.
• Dunlap, W.A., Bhojanala, R.P. and Morris, D.V. (1990). Burial of Vertically Loaded Offshore Pipelines in Weak Sediments. Proc. 22. Offshore Tech. Conf., May 7-10, Houston, Texas, OTC 6375, 263-270.
• Hale, J.R., Lammert, W.F. and Jacobsen, V. (1989). Improved Basis for Static Stability Analysis and Design of Marine Pipelines. Proc. 21. Offshore Tech. Conf. OTC 6059.
• Martin, CM., White, D.J. (2012). Limit analysis of the undrained bearing capacity of offshore pipelines. Geotechnique, Vol. 62, No. 9, 847-863.
• Murff, J.D., Wagner, D.A., and Randolph, M.F. (1989). Pipe Penetration in Cohesive Soil. Geotechnique 39(2), 213-229.
• Randolph, M. F. and White, D. J. (2008). Pipeline Embedment in Deep Water: Processes and Quantitative Assessment. In Proc. of the Offshore Tech. Conf., 5-8 May, Houston, Texas, OTC 19128.
• Terzaghi, K. (1943). Theoretical Soil Mechanics, John Wiley & Sons, Inc.
• Verley, R. and Lund, K.M. (1995). A Soil Resistance Model for Pipelines Placed on Clay Soils. ASME J. Offshore Mechanics and Arctic Engineering, Vol. V, pp. 225-232.
• Wagner, D.A., Murff, J.D., Brennodden, H. and Sveggen, O. (1987). Pipe-Soil Interaction Model. Proc. 19. Offshore Tech. Conf., OTC 5504.
• Westgate, Z.J., White, D.J., Randolph, M. F. and Brunning, P. (2010). Pipeline Laying and Embedment in Soft Fine-Grained Soils: Field Observations and Numerical Simulations. In Proc. Offshore Tech. Conf., Houston, Texas, OTC 20407.
• White, D. J., Westgate, Z. J., Ballard, J-C., de Brier, C. and Bransby, M. F. (2015). Best Practice Geotechnical Characterization and Pipe-Soil Interaction Analysis for HPHT Pipeline Design. In Proc. Offshore Tech. Conf., 4-7 May, Houston, Texas. OTC-26026-MS.
• White, D. J., Clukey, E. C., Boylan, N. P, Bransby, M. F., Zakeri, A., Hill, A. J. and Jaeck, C. (2017). The State of Knowledge of Pipe-Soil Interaction for On-Bottom Pipeline Design. In Proc. Offshore Tech. Conf., 1-4 May, Houston, Texas. OTC-27623-MS.
• Wolfram, W.R., Getz, J.R. and Verley, R.L.P. (1987). PIPESTAB Project: Improved Design Basis for Submarine Pipeline Stability. Proc. 19. Offshore Tech. Conf. OTC 5501.
• Zhao, B., Gao, F., Liu, J. and Wu, Y. (2009). Vertical Bearing Capacity of a Partially-Embedded Pipeline on Tresca Soils. In Proc. International Offshore and Polar Engineering Conf., June 21-26, Osaka, Japan, pp.469-473.