Analysis Of Force Strength And Stability Of Large Diameter Buried Heating Pipeline

With the rapid improvement of China's economic strength and the continuous improvement of people's living standards,the area of heating in China is increasing year by year.Central heating is more energy efficient and environmentally friendly than traditional regional boiler heating.China's heating industry is developing in the direction of green heat source,centralized heat supply and safe operation.Some domestic thermal pipe network supervisors have reached or exceeded DN1400;the pipe network working pressure has reached 2.5MPa.At present,the main reference for thermal piping design and stress calculation in China is "Technical Regulations for Direct Buried Heating Pipeline Engineering in Urban Areas"(CJJ/T 81-98,CJJ/T 81-2013).The earlier version clearly stipulates that it only applies to direct-buried heating pipes with a pipe diameter less than or equal to DN500.Although the size of the heat pipe is increased after the updated version,and the relevant technical parameters of the large-diameter pipe are supplemented,the pipe network The stress analysis of the pipe fittings in key parts is not comprehensive.The lack of more systematic large-diameter thermal pipe stress analysis can not provide designers with a more comprehensive and reasonable thermal pipe design method.The main research results obtained in this paper are as follows:(1)Using the Fourier series method and the elastic center method,the theoretical solution of the stress analysis of the heating pipeline is considered comprehensively considering the external earth pressure,the uniform pressure of the inner wall,the self-weight of the pipeline,and the water gravity inside the pipeline..(2)Applying the elastoplastic analysis method combined with the Lame coefficient solution to establish the theoretical model of stress distribution of the heat pipe steel pipe,insulation layer and outer casing under the working condition of the multi-layer heat pipe in the water-rich soil layer.(3)According to the thin shell theory and the stability analysis method,the energy analysis method is used to establish the stability analysis model of the heating pipeline steel tube under axial compression,external pressure,axial and radial bidirectional compression,and the calculated loss of the steel tube is obtained.Steady critical force.(4)Combining the actual engineering,survey report and indoor soil mechanics test,the basic soil mechanics parameters of the surrounding soil of the heat pipe are obtained,and the thermo-mechanical coupled finite element model of the multi-layer heat pipe is established,and the heat pipe is analyzed along with the pipe diameter.When the buried depth,internal pressure,operating temperature,etc.change,the stress distribution law of the thermal pipe.(5)Based on the characteristics of non-uniformity,discontinuity and anisotropy of gravel stratum,the photoelastic test is designed,and the digital-graphic processing technology is used to analyze the tube-soil interaction relationship of the heating pipeline in the gravel stratum.The concept of "force chain"was introduced into the analysis of the force law of the heat pipe in the gravel stratum.For special geological conditions,the force analysis of heating pipeline provides a new research method.