Analysis on mechanical characteristics of suspended oil pipeline under sand dune geology

Key words:  sand dune flow  suspended pipeline  thermal-fluid-solid coupling  safety assessment

Abstract:

Sand dune flow can cause buried oil pipelines to become suspended, and oil pipelines in a long distance suspended state may experience failure forms such as fracture and deformation. In order to explore the mechanical characteristics of oil pipelines under different suspended states, a finite element model of pipeline sand soil using the software ANSYS Workbench was established. Based on the comprehensive consideration of the physical characteristics of sand and the nonlinear contact between the pipeline and the sand, the stress and deformation characteristics of suspended oil pipelines under multiple loads under different working conditions were analyzed using the method of thermal-fluid-solid unidirectional coupling. Based on the above results, the safety assessment of the limit state of suspended oil pipelines was conducted. The results indicate that the influence of thermal stress on the mechanical properties of suspended oil pipelines cannot be ignored. As the length of the suspension increases, the location where the maximum Mises equivalent stress occurs changes from the center of the suspension to the boundary between the suspended section and the buried section. On the basis of considering thermal stress, the maximum Mises equivalent stress shows a trend of firstly increasing, then decreasing, and then increasing with the increase of the suspension length. Under the comprehensive influence, the ultimate length of the suspended oil pipeline in the calculation example is 77.41 m.