Vertical upheaval buckling of submarine buried heated pipelines with initial imperfection

Abstract

In this paper, a theoretical solution of vertical buckling is proposed with regard to the typical initial imperfection cases of submarine pipelines. Analytical tools are applied to predicting the occurrence and consequence of inservice buckling of a buried heated pipeline in Bohai Gulf. An evaluation is performed to ensure the pipeline structural integrity during operation under loading conditions. Different protection measures are proposed and their validities are analyzed. Analyses show that for the same magnitude of initial imperfection, the upheaval buckling of pipeline with isolated prop model is the most likely to occur. The empathetic model represents a special sub-case of continuous prop model, and the calculated buckle temperature is between the first stage and the second stage of post-upheaval buckling of continuous prop model. And the larger the initial imperfection, the less the axial force required for the upheaval buckling. Meanwhile, it can be seen that a peak point appears on the curves of temperature difference against buckling amplitude for small initial imperfection. Besides, trenching-burial is one kind of protection measures preventing the pipeline from thermal upheaval. The covered depth-to-diameter ratio depends on the design conditions and subsoil properties. For the given pipeline in this paper, the covered depth-to-diameter ratio is recommended to be 5.

Keywords

submarine buried pipeline / thermal stress / initial imperfection / upheaval buckling / protection measure

References

[1] Hobbs R. E. In-service buckling of heated pipelines[J]. ASCE, Journal of Transportation Engineering, 1984, 110(2): 175-189.

[2] Taylor N., Tran V. Experimental and theoretical studies in subsea pipeline buckling[J]. Marine Structures, 1996, 9(2): 211-257.

[3] Maltby T. C., Calladine C. R. An investigation into upheaval buckling of buried pipelines-II. Theory and analysis of experimental observations [J]. International Journal of Mechanical Sciences, 1995, 37(9): 965-983.

[4] Liu R., Yan S., Sun Guomin. Improvement of the method for marine pipeline upheaval analysis under ther mal stress[J]. Journal of Tianjin University, 2005, 38(2): 124-128.

[5] Taylor N., Aik B. G. Submarine pipeline buckling imperfection studies[J]. Thin-Walled Structures, 1986, 4(4): 295-323.

[6] Pedersen P. T., Jensen J. J. Upheaval creep of buried heated pipelines with initial imperfections[J]. Marine Structures, 1988, 1(1): 11-22.

[7] Taylor N., Tran V. Prop-imperfection subsea pipeline buckling[J]. Marine Structures, 1993, 6(4): 325-358.

[8] Croll J. G. A. A simplified model of upheaval thermal buckling of subsea pipelines[J]. Thin-Walled Structures, 1997, 29(1–4): 59-78.

[9] Hunt G. W., Blackmore A. Homoclinic and heteroclinic solutions of upheaval buckling[J]. Philosophical Transactions of the Royal Society of London, 1997, 355(6): 2185-2195.

[10] Villarraga J. A., Rodríguez J. F., Martínez C. Buried pipe modeling with initial imperfections[J]. Journal of Pressure Vessel Technology, 2004, 126(2): 250-257.

[11] Mohammed Raoof, Emil Maschner. Thermal buckling of subsea pipelines[C]. In: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering-OMAE. Glasgow, 1993. 21–29.

[12] Yun H. Model for beam-mode buckling of buried pipelines[J]. Journal of Engineering Mechanics, 1985, 111(2): 235-253.

[13] Bransby M. F., Newson T. A., Brunning P. The upheaval capacity of pipelines in jetted clay backfill[J]. International Journal of Offshore and Polar Engineering, 2002, 12(4): 280-287.

[14] Hobbs R. E. Pipeline buckling caused by axial loads[J]. Journal of Constructional Steel Research, 1981, 1(2): 2-10.