A new method was proposed to protect submarine pipelines. Flexible spoilers were installed under the submarine pipeline to change the flow field and pressure distribution, and reduce the pressure gradient between both sides of the pipeline, so that to decrease or prevent submarine pipeline being washed out. Pressure on the surface of the pipe, pressure gradient between both sides of the pipeline and scour under the pipelines with flexible spoilers, rigid spoilers and without spoilers were compared under unidirectional current and reversing current. Experiment results indicated that rigid spoilers increase the pressure gradient between both sides of the pipeline, increase the scour depth and range, and make the pipe suffer a down pressure, and therefore make pipelines self burying under the sandy seabed. However, they are not fit for the rocky seabed because rocky span shoulders support parts of the pipeline and prevent it sinking, fatigue failure is easy to happen due to part of the pipeline impending. leading to the seabed erosion and environmental damage. Flexible spoilers decrease the pressure gradient and the scour depth and increase the lift force so that to keep the pipe stable under unidirectional current. And the protective effects of bidirectional flexible spoilers are better. When the flexible spoilers reach a certain length, the pressure gradient is close to zero and the bottom scour almost disappears. So the effective protection for submarine pipeline can be obtained.
