Study Of Vertical Pressure On The Roof Of Buried Pipe Caused By Vehicle Load

With the continuous construction of cities and the continuous development of social economy,buried pipelines play an increasingly important role.Correct calculation of pipe top pressure is the basis of pipe structure design.Based on the research background of buried pipeline roof pressure caused by vehicle dynamic load,through the study of existing calculation methods and load models,using theoretical analysis,program calculation and numerical simulation research,this paper makes a thorough study on the variation law and influence factors of buried pipeline roof pressure caused by vehicle dynamic load.The research contents are as follows:(1)This paper summarizes the current calculation methods of earth pressure on pipe roof,vehicle load,current mainstream pipeline design methods and simplified analysis model of vehicle load,which lays a foundation for future calculation and analysis.(2)The software program was designed,and the influence of different parameters on the top pressure was compared and analyzed.When calculating the earth pressure on pipe top,the influence of pipe diameter,burial depth,internal friction angle of backfill soil and backfill soil weight on the earth pressure on pipe top is analyzed under different calculation methods;when calculating vehicle load,the influence of wheel load,pipe top burial depth and load distance on the additional pressure on pipe top is analyzed;and the methods used in current mainstream national pipeline design are compared.The results show that the vertical pressure on the top of the pipe increases with the increase of the buried depth of the pipe,and Zeng Guoxi's algorithm is generally smaller than Marston's calculation value;the internal friction angle of backfill soil has little effect on the vertical earth pressure on the top of the pipe;the vertical stress on the top of the pipe increases linearly with the increase of the volume weight of backfill soil;and the vertical stress on the top of the pipe increases linearly with the increase of vehicle wheel load.The Boussinseq solution is generally larger than the distribution angle method solution,and the additional load on the top of the pipe decreases rapidly with the increase of the distance between the vehicle load and the pipeline axis.(3)A three-dimensional numerical model was established by using FLAC3 D to further analyze the influence of different traffic load parameters on the pipe top pressure.The uniform load model is used to analyze the static and wave load models respectively.Static analysis compares the influence of different pipeline buried depth on the top pressure,the change of the additional pressure on the top,and the influence of load distance on the additional pressure on the top.At the same time,the calculation results of Boussinesq method and distribution angle method are compared.In the dynamic analysis,the influence of different load amplitudes on the vertical stress on the top of the pipe,the change of the additional stress on the top of the pipe with the loading time,the distribution of the additional stress on the top of the pipe and the influence of vehicle speed on the vertical stress are analyzed.The results show that there is a minimum total pressure on the top of the pipe,and the corresponding buried depth is the optimal buried depth of the pipe according to the minimum vertical total stress on the top of the pipe;the maximum vertical stress on the top of the pipe is approximately linear with the load amplitude;with the extension of loading time,the variation of vertical stress on the top of the pipe increases rapidly at first,then tends to be stable,and then decreases gradually.