Effect of different span heights on the pipeline impact forces induced by deep-sea landslides

With the development of marine energy in full swing, an increasing number of pipelines are being installed in deep-sea areas, which inevitably pass through extremely complex topographic conditions, to form natural sections of suspension over submarine canyons. The seabed is easily eroded and shaped by active deep-sea bottom currents and watercourses, resulting in different span heights for pipelines originally laid on the seabed. In particularly, deep-sea geological hazards frequently occur, and submarine landslides seriously threaten the safe operation of the pipelines. To address these problems, an improved numerical analysis method combined with low-temperature rheological models of landslides and the optimization design method of the geometric model, is developed to simulate the landslides' impacts on pipelines. Based on these, the effect of the span heights on the pipelines' impact forces induced by deep-sea landslides is systematically investigated, and three modes of the forces on pipelines under the impact of landslides and related mechanism are proposed. Further, the span height ratio is put forward, and four formulas for evaluating the forces on pipeline are established. Through the analysis of calculation results, the lift force coefficient even increases nearly 20 times considering different span heights. This research provides a theoretical basis for the design and protection of deep-sea pipelines.