Research On Prediction,Monitoring And Early Warning Of Non-uniform Settlement Stress Of Offshore Natural Gas Pipeline

Pipeline transportation is widely used in natural gas transportation.A large number of different natural gas pipelines have been laid in various offshore areas of the world.my country's land natural gas resources are not abundant,and it is an inevitable trend to import and obtain natural gas from the sea.The geological conditions in relatively low-lying areas such as seashores,beach seas,and river coasts are mostly soft soil foundations with low strength and high compressibility.Due to their rheology and unevenness,uneven settlement is likely to occur,which affects the safe operation of pipelines.Natural gas is flammable and explosive,so it is very easy to cause fire and explosion accidents after the natural gas pipeline is damaged.In order to ensure the safe operation of natural gas pipelines,the stress analysis of the natural gas pipeline under the uneven settlement of the beach sea,the stress prediction model and the risk Management and control research is of profound significance.(1)On-site stress testing of offshore natural gas pipelines.According to the research object's on-site environmental conditions,through the resistance strain gage test,the stress monitoring results are analyzed.Among the four measuring points,the maximum axial additional stress is 95.07 MPa and the maximum circumferential additional stress is 95.43 MPa.Calculate the allowable stress of the pipeline to be 360 MPa,check the monitoring data for the pipeline stress,the pipeline stress is less than the allowable stress,the pipeline is in a safe operation state,monitor the technology,and analyze the external factors that lead to the error of the measurement result.(2)Construct a prediction model for the uneven settlement of off-shore natural gas pipelines.Analyze the load and stress on the pipeline during operation,divide the calculation formula for the uneven settlement stress of the beach natural gas pipeline into three parts,collect and process related data of influencing factors,and choose to build a pipeline uneven settlement stress prediction model based on multiple linear regression after comparison.Optimize the prediction model according to the actual engineering application results and get the best use range of the model: the monthly average rainfall is 500?650mm and the tide level is at 2.0?2.5m.(3)Natural gas pipeline stress finite element analysis and prediction model verification.Based on the material constitutive relationship,pipe-soil interaction and contact analysis theory,using Ansys Workbench software to perform finite element simulation analysis on the pre-built three-dimensional model,and calculate the maximum Von-Mises stress value of the pipeline under normal working conditions to be 228.76 MPa.The model studies the influence of pipeline parameters and soil parameters on pipeline stress,and verifies the pipeline stress prediction model proposed in Chapter 3.(4)Research on monitoring and early warning of pipeline non-uniform settlement stress.Based on the Kent scoring method and analytic hierarchy process,the pipeline risk factors are analyzed,the natural gas pipeline stress monitoring criteria and the pipeline non-uniform settlement stress warning system are proposed,and the monitoring data are organically combined to complete the development and design of the pipeline stress monitoring and warning platform based on C++ language.The overall situation,operation interface,operation mode and functional modules of the platform,and put the risk warning platform into actual engineering applications,put forward natural gas pipeline safety measures for the pipeline construction and operation process to ensure the safe operation of the pipeline.