Study On The Construction Technolgy Of Towing Pipes On The Bottom For Laying Pipeline In The Extreme Shallow Water

With the development of ocean oil engineering, as an important part of oil transportation and storage, pipeline has been used broadly in the ocean oil engineering. The construction technology of pipeline is complicated and has lot of risk in the laying pipeline ,the important part is to transport the pipeline to the certain sea area in the construction process. During the process of transportation, the pipeline is affected by the wind, wave and ocean current, it is very important for the safety of the pipeline and reduction of transportation cost to calculate the environment loads of the pipeline, to analyze the strength and determine reasonable towing methods. The main contents and results are in the following:Some home and oversea pipeline of laying methods are summarized, and suitable condition of different pipeline construction projects are compared and analyzed. The methods, principles and equipments of towing pipeline are introduced detailed. Take the example of double wall pipeline, which the inner pipeφ273×8 , outer pipeφ325×6,the possibility of the pressing pipeline straightly in the seabed is discussed. The soil data are obtained by testing. The pipeline laying on seabed is considered as a beam on an elastic foundation, using the FEA Ansys program, the values of sink of the pipeline are calculated for different press force acted on the pipeline. Considering different phases of towing pipeline progress, the analysis models of different phases of towing pipeline are set up. The loads values, distributing and the stress and defections of the pipeline are calculated particularly in different phase. With the velocities of flow 0.4m/s,0.6 m/s,0.8 m/s,1.0 m/s,1.2 m/s, the angles of flow 30°,45°,60°,90°, the strength of the pipeline is calculated by Ansys softwire for the 3~5 side labels and the 300m long pipeline and 400m long pipeline.The results and analyses show that towing pipeline on seabed is suit for extreme shallow water pipeline laying, the affection of draft and environment on laying pipeline is small. After the pipeline is settled, it is feasible for embedding pipeline to dig a ditch or to press pipeline with injecting water into the soil. On the base of calculation, the technical projects of the construction of towing pipeline on seabed are brought forward, including the pipeline span and the number of label under different velocities and angles of flow.