Lateral force on buried pipelines caused by seabed slides using a CFD method with a shear interface weakening model

Abstract

With the extensive laying of subsea pipe networks, interactions between seabeds and pipelines are attracting increasing attention; nevertheless, the study of buried pipelines impacted by sliding seabed sediments with low strength and high sensitivity characteristics has been overlooked. In this paper, a computational fluid dynamics (CFD) model considering the interface shear weakening effect of seabed sediment and a pipeline is proposed to simulate the impact of seabed sediments with shear behavior of non-Newtonian fluids on pipelines buried at different depths in the overlying water. The CFD method is validated using analytical solutions, numerical solutions, and physical model experiments. Various CFD-based cases with different pipeline burial depths and interface contact coefficients are then systematically investigated. The lateral bearing capacity of seabed sediments on pipelines is quantified in the framework of soil mechanics, and the pipeline buried depth and interface contact coefficient significantly affect the lateral bearing capacity. The lateral bearing capacity factor gradually increases and tends to stabilize with increasing pipeline buried depth, reaching a maximum gap of 62%, and the critical buried depth is 2–3 times the pipeline diameter. The lateral bearing capacity factor increases with increasing interface contact coefficient, reaching a maximum gap of 57%. Variations in the velocity, pressure, and shear rate of the seabed sediment are discussed, revealing the physical mechanism leading to changes in bearing capacity factors. Finally, a method to evaluate the lateral bearing capacity factor is established, providing a reference for pipeline design, construction, and safe operation.