Experimental Studies of Wave Induced Scour Involving Pressures and Forces on Buried and Unburied Pipeline

摘要

Submarine pipelines have been used extensively to transport crude oil from offshore production units to onshore locations and refined petroleum from onshore to ships moored in deep water. A thorough knowledge of wave induced scour under pressure and of forces on the submarine pipeline is essential in the design of oil and natural gas pipelines buried in the marine environment. Experimental investigations of scour due to waves under the submarine pipeline resting on the clay soil bed for different consistency indices of soil were carried out. Experiments were conducted in a 2 m wide, 30 m long and 1.7 m deep wave flume. Based on the scour measurements for a few hours of wave action, the ultimate scour depth is estimated using a hyperbolic model. The equilibrium scour depth below the pipeline is estimated as 45% of the pipe diameter for a consistency index of 0.17 and is 35% of the pipe diameter for a consistency index of 0.23. Investigations on wave pressures around and uplift force on the submarine pipeline (exposed, half buried and fully buried) are also carried out. It is found that the pressure is reduced by about 40% if the pipeline is just buried in clay soil. It is also found that the consistency index of the soil significantly affects the wave-induced pressure and uplift force on a submarine pipeline.