Study On The Calculation Method Of Force And Deformation In The Laying Process Of Marine Flexible Pipe

The development and utilization of offshore oil and gas energy is one of the key issues for China’s rapid and stable development in recent years.The vast ocean contains abundant oil and gas resources.In order to develop marine resources safely,quickly and effectively,it was necessary to continue to promote the research and development of major marine engineering equipment and the construction of high-precision technology.Pipelines were widely used in the exploitation,development,transportation and utilization of offshore oil and gas resources due to the advantages of good transportation sealing,good transportation continuity,small loss,low land occupation rate,and terrain adaptability.Traditional offshore oil and gas pipelines were steel pipelines,but steel pipes have many disadvantages in the marine environment,such as being vulnerable to electrochemical and physical corrosion and perforation,and difficult to repair and maintain.Compared with steel pipes,the emerging flexible pipes have the characteristics of good adaptation to the marine working environment,such as strong corrosion resistance,good aging resistance,good electrical and thermal insulation,low friction coefficient,and high interchangeability.Therefore,flexible pipelines are gradually being used in the development of offshore oil and gas resources.Flexible pipes are composed of multi-layer structures.Although the laying and application research of flexible pipes is difficult,it has developed rapidly in recent years,and the calculation methods of force and deformation in the laying process of flexible pipes have been continuously innovated.In this paper,a set of calculation method of stress and deformation of flexible pipe considering the joint movement of pipeline and pipe laying ship was proposed.The overall and local evaluation form were used to identify the dangerous parts of flexible pipe along the length direction and analyze the stress and deformation between local structures.The work of this paper mainly focused on the following aspects.(1)The development background and research significance of marine flexible pipelines at home and abroad,the forms,advantages and disadvantages of marine pipeline laying,and the main technical bottlenecks in engineering design were investigated.(2)By analyzing the research results of domestic and foreign scholars on the stress and deformation of the flexible pipe,this paper proposed a set of calculation methods for the force and deformation of the flexible pipe considering the joint motion of the pipeline and the pipe-laying vessel.The dangerous parts of the flexible pipe along the length direction and the stress and deformation between the local layers of the structure were analyzed.(3)Taking a glass fiber reinforced flexible pipe as an example,the tensile,bending and torsion tests were carried out to obtain the critical failure stress values under various deformations of the pipe,which provided the basis for the definition of nonlinear material mechanical properties of the numerical model.(4)The global strength calculation of the loaded dangerous section under the influence of the joint motion of the pipeline and the pipe-laying vessel in the marine environment was carried out,the dangerous areas were determined,the tensile,bending and torsional loads of the dangerous part were quantified,and the distribution of local stress and deformation of flexible pipe under combined load was analyzed.(5)In this paper,the influence of marine environmental parameters on the loading characteristics of flexible pipes during the laying process were studied,and the safety assessment of flexible pipes was carried out based on the failure criterion,so as to provide useful suggestions for laying engineering design.