In this paper, unlike most previous investigations have been limited to the purely wave conditions or combined wave and current condition, a numerical model for random wave-induced seabed response around a pipeline in a trenched layer is established. Based on Longuet-Higgins random wave theory and finite volume method. The seabed is treated as a poro-elastic medium and characterized by Biots consolidation equations (QS model). The B-M spectrum is considered in the new model for the simulation of random waves. Numerical examples demonstrate the significant influence of irregularity of random waves on the wave-induced pore-water pressures and the resultant seabed liquefaction around the trenched pipeline, which is different from the cases under the regular waves or waves plus ocean current loading.
Trenching pipelines are an effective solution for the transportation of offshore fossil energy resources, i.e., oil and natural gas in either shallow or deep water. As the seabed level changing during the event of a storm, the liquefaction of the seafloor around pipelines subjected to the combined action of non-linear ocean state becomes increasingly important (Palmer and King, 2008; Fredsøe, 2016). For all these, the numerical analysis of trenching pipelines can highlight how the stability of its nearby seabed affected by nonlinear sea loads, and improve its hydrodynamic load prediction.
For this purpose, there are numerous studies related to the seabed response caused by waves around partially buried pipelines in trench layers available in the literature. Among these, most previous studies considered the momentary soil response near the pipeline is subjected to (1) regular wave loadings (Lin et al., 2016; Wang et al., 2019), or (2) combined wave and current loadings (Duan et al., 2017; Liang et al., 2020). Some recent investigations considered the case of the residual soil mechanism (Zhao and Jeng, 2016; Chen et al., 2019). Apart from numerical works, limited experimental studies on the stability of trenching pipelines under regular wave loads (Zhai et al., 2018; Sun et al., 2019) are available in the literature. However, these aforementioned studies have been limited to the safety assessment of trenched pipelines under purely wave conditions or combined wave and current condition, whereas waves in nature are seldom purely regular.
