Stress Monitoring And Analysis Of Station Pipeline Based On Ground Frost Heave

Oil and gas pipeline is the safest and effective way of energy transmission in China.Urban gas gate station is one of the important links.The high-pressure natural gas from the upstream is transported to the downstream after pressure reduction.When the air consumption increases in winter,the station pressure regulation will cause the temperature of natural gas to drop suddenly,which will cause the soil around the buried pipeline to freeze and lift the pipeline of the station,namely,the pipeline frost heaving.The local stress is too large under the action of frost heaving,which threatens the safe operation of the pipeline.Therefore,it is very important to evaluate the stress safety of the pipeline.In the past,the stress analysis of the pipeline in the station often relies on the finite element simulation and empirical formula,and does not grasp the real deformation of the pipeline,and lacks rationality.This paper applies the stress monitoring system to the pipeline of the station.Combined with the monitoring data and the finite element simulation results,the stress safety state of the pipeline under the frost heaving action is analyzed.The specific research content and results are as follows:(1)Based on the concept of smart pipe network and Internet of things technology,an on-line stress monitoring system for oil and gas pipelines is built,and the working principle of the monitoring system is described.The cantilever beam test is designed to verify the test accuracy,linearity,long-term monitoring stability and the influence of temperature on the measured value of the monitoring system.The test results show that the reliability of the monitoring system meets the actual requirements of the project.(2)By comparing the methods of obtaining station pipeline stress field with and without monitoring system,this paper expounds the necessity and engineering significance of station pipeline installation monitoring system,and formulates the monitoring scheme of station pipeline,that is,the selection of monitoring section and the layout of strain gauge on the section;by analyzing the relationship between axial monitoring data and pipeline axial stress,the model based on axial monitoring data is established According to the stress early warning model.(3)A city gas gate station is selected to monitor a section of frost heaving pipeline for a long time to obtain the deformation and stress during the monitoring period.Based on the monitoring data,the frost heaving mode of the outlet pipeline is identified by finite element simulation,and the real strain field distribution of the outlet pipeline is inversed,and the identification accuracy of the method is further calculated.(4)According to the real situation,the three-dimensional finite element model of the station pipeline is established,and the safety state of the station pipeline during the monitoring period is evaluated by finite element simulation.Taking 50% of the yield stress of the pipeline material as the allowable stress,the displacement warning value of the station pipeline under frost heaving is calculated to be 38 mm,and the influence of pipeline parameters and soil properties on the displacement warning value is further studied.