Research On Construction Disturbance And Mechanical Properties Of Parallel Rectangular Pipe Jacking

With the rapid development of tunnel and underground engineering technology,in order to adapt to the efficient use of underground space and optimize the buried underground pipeline,rectangular pipe jacking construction technology has been widely used.In recent years,due to the special construction environment and engineering construction needs,it is inevitable to adopt parallel rectangular pipe jacking engineering scheme.Due to the mutual influence of parallel rectangular pipe jacking construction and the complexity of stratum disturbance,this paper analyzes and discusses the stratum disturbance law and mechanical characteristics of parallel rectangular pipe jacking construction through model test and numerical simulation.The main work and research results are as follows :(1)The factors of stratum deformation caused by rectangular pipe jacking construction are analyzed,and the main influencing factors are classified as back soil effect,stratum loss and pipe-soil friction.The influencing factors of stratum loss are discussed,and some suggestions are given.The calculation method of surface subsidence is summarized,and the application and research of Peck formula,stochastic medium theory and finite element analysis method in engineering are discussed.(2)The scheme of model test was designed : model design,test soil preparation,monitoring scheme design and test process.The model test box was completed by splicing the model steel plates.According to the test requirements,the test soil was prepared,and the relevant parameters were obtained by the geotechnical test.The monitoring equipment was arranged.In the process of model test,the monitoring of surface settlement,formation soil pressure and longitudinal strain of pipe joints was completed.(3)Based on the model test monitoring data,the disturbance law and mechanical characteristics of stratum deformation in parallel rectangular pipe jacking construction are analyzed.The vertical deformation of the ground surface presents the change rule of uplift first and then settlement with the jacking of the pipe.The vertical earth pressure above the pipe axis increases first and then decreases to a stable trend with the jacking of the pipe.The pipe joint strain increases first and then decreases.The jacking of the backward pipe will reduce the maximum ground settlement above the axis of the leading pipe.(4)Midas GTS software is used to establish a three-dimensional finite element numerical analysis model to simulate the whole process of parallel rectangular pipe jacking dynamic construction,and the results are compared with the model test results.The disturbance deformation and mechanical characteristics of parallel rectangular pipe jacking construction are further discussed from the surface settlement,soil pressure,pipe joint strain and other aspects.(5)Numerical simulation analysis shows that the two surface settlement troughs are not completely symmetrical under different pipe jacking sizes.When the large pipe is constructed first,the corresponding surface settlement value is relatively largest,and the final influence range of the surface is also largest.When the distance between parallel rectangular pipe jacking is reduced to 0.5B ～ 0.1B(B is the width of large rectangular pipe jacking),the surface settlement trough is reduced from two to one.The larger the overall size of parallel rectangular pipe jacking,the more obvious the trend is.When the spacing increases to 2B ～ 3B,the interaction between pipe jacking is weak and tends to be independent.