Test Research On Scour Around And Wave Pressures On Submarine Pipeline

Submarine pipeline is one carrier transporting oil or gas from platform to land .It is used extensively in ocean engineering because of its many merits, such as continuous and vast transportation, convenient management. However, the marine environment around submarine pipeline is very execrable generally. The exterior factors, such as seabed soil, tide, storm, wave, vortex, earthquake, floating ice, anchor attacking, all can resulting in lapse of submarine pipeline. The effect of wave or tidal current hydrodynamic force can arose scour around pipeline, accordingly result in span on pipeline partly. The effect of vortex-induced vibration etc may make span into fatigue ruption, even can make pipeline into fracture. It can induce base oil leaking. The problem, hydrodynamic force aroses scour around pipeline and make pipeline into fracture, more and more arouses the attention of ocean energy resources corporations. It is a important content in design, construction and forecasting the stability of pipeline. The study on the interactional local problem of pipeline-seabed is a challenge to academia, and it plays important role in engineering.The mechanism of the scour around and wave pressures on submarine pipeline in the wave field is very complicated, the existing study on it is still not clear, there are many works to do to study the rule under different conditions. The problem on the stability of pipeline on clayey seabed is still not resolved. This paper is on the study and analysis on the scour around and wave pressures on submarine pipeline by experimentation. In The experimentation, the seabed is fabricated by simulating Yellow River delta, beginning from knowing the mechanism of interactional wave-pipeline-seabed, studying the pipeline on the clayey seabed barely and be buried in the seabed. At the same time, the experimentation tests the model about calculate critical erosion depth and wave pressures on pipeline.The experimentation testifies that there is a critical erosion depth when the wave scours around pipeline. When the scour reaches critical erosion depth, the bottom most is below of the pipeline, the scour depth, from the two sides of pipe to farer position, becomes shallower then deeper. The erosion hollow is steeper at upstream side, milder at downstream side. The scour to downstream side of the erosion hollow, when the scour near critical erosion depth, continuative scour can restore primary landform. Accompanied by scouring and hollowing, pipeline wave action transform regularly from positive action to negative force gradually, which can be divided into four developing stages. The initial erosion stage during which pipeline wave function is mainly the positive. Pipeline behaves vibration under positive force; Tunnel development stage: pipeline vibrates up and down under the wave crest lifting force and through downward pulling force; Pipeline suspension stage: pipeline vibrates forward and backward according to the wave crest negative and through positive effort appearing alternately; Eroding equilibrium stage: pipeline vibrates mainly under the negative force. It is unfit to calculate the wave pressure on the pipeline posited on the seabed with Morison equation.