Performance of steel–polymer–steel seafloor pipeline buried in earthquake fault zones

Steel tubular structures are widely used in offshore structures, such as fixed, floating, and seafloor pipelines. The earthquake can cause relatively large pipe displacement, especially in the fault zone. Therefore, single-wall buried pipelines or piles of the offshore fixed platform in these zones could be under buckling and wrinkling which would lead to the severely deteriorated performance of the pipelines or costly failure. The purpose of this research is to prevent these types of failures by developing innovative double-wall steel–polymer–steel (SPS) composite pipes in place of single-wall pipes. In the double-wall pipe, the annulus of the inner and outer pipe was grouted with polymer. Verification exercises for single-wall pipe in air and buried in clay, and double-wall pipes in the air were performed. Thereafter, an analysis of laterally loaded SPS double-wall composite pipes in clay was performed and the pipe responses were examined. A comparison of performance behaviors for single and double-wall pipes was also performed. It was found from this research that double-wall SPS composite pipes demonstrated increased tolerance for higher levels of displacements, strain, stress, and ovality under work environments where pipelines could be subjected to large displacement in the earthquake fault zone. For those composite pipes in which there is no bond between the polymer layer and inner/outer steel pipes, the composite pipes showed wrinkles on the compression side of the pipe even under a small displacement. So, the polymer and steel must be bonded to have a good composite section. The composite pipes with stiffer polymer grout showed a better performance while soft polymer did not contribute to the overall stiffness of the composite pipes. In addition, the effects of weld on the outer steel pipes were also studied and the results were documented.

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Opracowanie rekordu ze środków MEiN, umowa nr SONP/SP/546092/2022 w ramach programu "Społeczna odpowiedzialność nauki" - moduł: Popularyzacja nauki i promocja sportu (2022-2023)