Research On Frost Heave Characteristics And Optimization Design Of Pipelines In Gas Pressure Regulating Stations In Beijing Area

With the increase of natural gas transmission volume,the pressure of pipeline has been rising continuously,and the problem of frost heaving of gas transmission pipeli ne has attracted wide attention.After the gas transmission pipeline is throttle through t he pressure regulating station,the underground buried pipeline often runs below 0 cent igrade.This low temperature causes the freezing of soil moisture around the pipeline,so that the volume of soil expands,that is,frost heave appears.Under the influence o f frost heaving,the deformation of gas pipeline station will cause deformation failure.It will easily endanger the safety of pipeline operation and cause significant economic losses.In the stage of engineering design,the effect of frost heave and frost heave o n pipeline should be analyzed by reasonable method according to the specific engineer ing properties,so as to facilitate the practical construction process and appropriate fros t heave prevention measures to minimize the risk of pipeline operation.In view of thi s,this paper systematically combs the existing theory of frost heave in pipe and soil structure by means of theoretical analysis and numerical simulation.Combined with ac tual engineering and climate data,the frost heaving law of soil and frost heave charac teristics of the frost heave are deeply analyzed.In addition,considering the limit cond itions of the outer surface temperature of the pipe,the frost heave treatment scheme f or the low temperature gas buried pipeline is given,which provides some theoretical g uidance for the prevention and control of frost heave.The main research contents and results are as follows:(1)Based on the theoretical study of the gas adiabatic throttling process,the theor etical calculation method is adopted to predict the outlet temperature and adiabatic thr ottling coefficient of the natural gas after adiabatic throttling,and the natural air temp erature drop and the regular flow law under different pressure regulating pressure are analyzed in combination with the range of the pressure regulating range of the urban pressure regulating station in Beijing.(2)Based on the two development technology of the ABAQUS finite element soft ware,a user subroutine for the frost heave deformation of the pipe soil structure is co mpiled,and the prediction model of the thermal coupling frost heave of the pipe soil structure is proposed.(3)Taking into account the properties of frozen soil temperature,moisture and me chanical parameters,a coupled mathematical model of water and thermal mechanical a nalysis for frost heaving of pipe structure is built.The calculation of frost heave defor mation of pipe soil structure is realized based on ABAQUS simulation platform,whic h lays a theoretical foundation for the calculation and characteristic analysis of the fro st heave deformation of the pipe and soil structure.(4)In order to consider the external surface temperature limit conditions for the p revention and control of frost heave,the frost heave treatment scheme of the low tem perature gas buried pipeline is given,and the effect of the treatment is analyzed by n umerical simulation,which provides the technical basis for the optimization design of the low temperature gas buried pipeline.