Authors

1 College of Engineering, University of Tehran

2 University of Tehran

3 Department of Civil Engineering, Science and Research Branch, Islamic Azad University

Abstract

Offshore pipelines used for oil and gas transportation are often buried to avoid damage from fishing activities and to provide thermal insulation. Thermal expansion and contraction of the pipeline during operation can lead to lateral or upheaval buckling. A safe buried pipeline design must take into account a reliable evaluation of soil uplift resistance and pipe embedment depth. While the cost of burying a pipeline for tens or hundreds of kilometer is significant, it is important to optimize the required soil cover depth. In this paper a parametric study of pipeline upheaval buckling in clayey backfill has been conducted using finite element analysis. Three different embedment depths are considered. Uplift resistance is calculated and failure mechanism is obtained. To simulate the large penetration of the pipe into clayey backfill a novel Arbitrary Lagrangian Eulerian (ALE) finite element technique was employed in this paper. The results reveal that as embedment depth increases, uplift resistance increases and also uplift mechanism changes. However, uplift resistance differ less than 5% for deep embedment case. In addition, the amount of pore pressure is investigated beneath the pipe for deep embedment cases and it reveals that negative excess pore pressure occurs under the pipeline.

Keywords

Bransby, M.; Newson,T.; Brunning, P., (2002). Centrifuge modelling of the upheaval capacity of pipelines in liquefied clay. Isope 2002.
Bransby, M.F.; N. T. A. B. P., (2002). Physical modelling of the upheaval resistance of buried offshore pipelines. International conference on physical modelling in geotechnics. Kitakyushu, japan.
Cheuk, C.; Take, W.; bolton, M.; Oliveira  J., (2007). Soil restraint on buckling oil and gas pipelines buried in lumpy clay fill. Engineering structures,
29, 973-982.
Cheuk, C.; White, D.; Bolton, M., (2008a). Uplift mechanisms of pipes buried in sand. Journal of geotechnical and geoenvironmental engineering, 134, 154-163.
Cheuk, C.; White, D.; Bolton, M. D., ( 2008b). Uplift mechanisms of pipes buried in sand. Journal of geotechnical and geoenvironmental engineering, 134, 154-163.
Dickin, E. A., (1994). Uplift resistance of buried pipelines in sand. Soils and foundations, 34, 41-48.
Dnv (2007). Dnv-rp-f110,global bucklingOf submarine pipelines det norske veritas.
Finch, M., (1999). “upheaval buckling and floatation of rigid pipelines”: the influence of recent geotechnical research on the current state of the art. Offshore technology conference. Houston, texas: offshore technology conference.
Maltby,T. C.; Calladine, C. R., (1995). An investigation into upheaval buckling of buried pipelinesii. Theory and analysis of experimental observations. International journal of mechanical sciences, 37, 965-983.
Merifield, R.; White, D.; Randolph,M., (2008). The effect of pipe-soil interface conditions on undrained breakout resistance of partially-embedded pipelines.  Proceedings of the 12th international conference of international association for computer methods and advances in geomechanics, goa, india, 1-6.
Moradi, M.; Craig, W., (1998). Observation of upheaval buckling of buried pipelines. Proc. Of inter. Corf. Centrifuge, 98, 693-698.
Newson, T. A.; Deljoui, p., (2005). Finite element modelling of upheaval buckling of buried offshore pipelines in clayey soils. Soil and rock behavior and modeling.
Randolph, M. F.; Houlsby, G. T. (1984). Limiting pressure on a circular pile loaded laterally in cohesive soil. Geotechnique, 34,  613-623.
Sheng, D.; Nazem, M.; Carter, j. P., (2009). Some computational aspects for solving deep penetration problems in geomechanics. Computational mechanics, 44, 549-561.
Tho, K.;, Leung, C.; Chow, Y.; Swaddiwudhipong, S., (2012). Eulerian finite-element technique for analysis of jack-up spudcan penetration. International journal of geomechanics, 12, 64-73.
Thusyanthan, N.; Ganesan, S. A.; Bolton, M. D.; Peter A., (2008). Upheaval buckling resistance of pipelines buried in clayey backfill.  Proceeding of isope 2008, the eighteenth  international offshore and polar engineering conference, 6-11.