Force Performance Analysis Of Buried Oil Pipeline Under Freeze-thaw Cycle

With the rapid improvement of China's comprehensive national strength,the urbanization construction has gradually accelerated.However,oil and gas resources are the important basic guarantee for urban operation and economic development.Because buried pipeline transportation is widely used in oil transportation,which is the main mode of long-distance oil and gas transportation,in recent years,the laying scope of buried oil pipeline is expanding rapidly.When the pipeline is laid in the northwest and northeast of China,it will inevitably cross the frozen soil area.In the frozen soil area,due to the influence of the soil temperature field and the thickness of the frozen soil layer and other factors,especially the phenomenon of freeze-thaw cycle at the turn of seasons,the pipeline is prone to frost heave and thaw settlement.The main research content of this project is to study the mechanical properties of the pipeline under the action of freeze-thaw cycle,study the mechanical characteristics of the pipeline under the action of freeze-thaw cycle,and find the influence of the upper and lower limits of the freeze-thaw temperature,the freeze-thaw cycle,the buried depth of the pipeline,the pipe diameter,the wall thickness of the pipeline and other factors on the mechanical characteristics of the pipeline under the action of freeze-thaw cycle.In this paper,the design test method and software simulation method are used to study and analyze the buried pipeline.There are mainly two aspects as follows:1.Content of finite element simulation: using COMSOL multiphysics multi physical field simulation software to simulate the freeze-thaw cycle environment of the pipeline,and carry out the full coupling of the three fields of water and heat in three-dimensional space.The physical field of soil includes: water separation field,mechanical field,heat transfer field of porous media,considering the unsaturated seepage of water,phase change of ice and water,frost heave of soil,etc.;considering the thermal fluid solid coupling of oil pipeline,the oil temperature in the pipeline changes periodically with time and location.2.Test analysis content: make the experimental model according to the proportion of 1:10 ? 1:20,set different control groups according to the possible influencing factors,use the freeze-thaw box to realize the repeated freeze-thaw cycle process in the laboratory,monitor the change of the internal force of the pipeline under the freeze-thaw cycle in real time,and record it.Finally,through the experimental study,the general law of the stress characteristics of the buried pipeline under the freeze-thaw cycle in the cold area is obtained through the comparative analysis,which provides the basis for the engineering design,reduces the economic loss caused by the freeze-thaw damage of the local pipeline,fills the vacancy of the dynamic analysis process of the freeze-thaw cycle of the pipeline in China,and combines the freeze-thaw cycle process of the soil with the freeze-thaw damage of the pipeline.