| With the continuous development of urban underground rail transit and municipal construction,tunnels cross each other and bring complex mechanical properties and engineering risks,the construction process of pipe jacking will inevitably cause disturbance to the surrounding soil,and the disturbance of the soil layer will often cause a series of displacement and deformation of the tunnel,affecting the normal operation of the subway train.Based on the background of the case of a new jacking pipe passing through the existing shield tunnel in the coastal area,this paper uses finite element software to establish numerical models,and combines the on-site measured data to systematically analyze the impact of pipe jacking construction on existing shield tunnels under different working conditions.The research results can provide a theoretical basis and experience reference for the future pipe jacking through the existing tunnel project.The main research contents are as follows:(1)The mechanism of soil deformation caused by pipe jacking construction was analyzed,and the causes of disturbance caused by pipe jacking construction were explored.It is found that the position relationship between the pipe jacking and the existing shield tunnel,the distance and the diameter of the pipe jacking will affect the existing tunnel.(2)Relying on the pipe jacking through the existing shield tunnel project,Sorting out and analyzing the vertical displacement of the existing subway shield tunnel vault and arch bottom during the construction process of pipe jacking,it is found that the maximum vertical displacement of the vault and the arch bottom appears directly below the axis of the pipe jacking,and the farther away from the pipe jacking axis,the smaller the deformation of the segment.The MIDAS GTS finite element software was used to simulate the jacking pipe through the existing shield tunnel,the simulation results are analyzed and it is found that the existing tunnel has the highest proportion of uplift during the pipe jacking crossing stage,and the existing shield tunnel moves upward as a whole.During the construction of the pipe jacking,its influence area on the existing shield tunnel is roughly located between 20 m in front of the excavation and 30 m behind the excavation surface,and has a great influence on the vertical displacement of the surface within 10 m in front of excavation and 20 m behind the excavation surface.The measured values are compared with the simulation results to verify the reliability of the model.(3)Change diameter,crossing angle and distance from right line tunnel of the pipe jacking,establishing models of pipe jacking through existing shield tunnels under different working conditions,and the simulation results were analyzed to obtain the influence of factors such as pipe jacking crossing angle,pipe jacking diameter,distance on the crosssectional deformation and internal force of existing shield tunnels.The analysis results show that the crossing angle of the pipe jacking is different,the cross-sectional deformation shape and internal force change position of existing shield tunnels are also different,when the distance between the pipe jacking and the right line tunnel decreases,the change of axial force and bending moment of the right tunnel increases,with the increase of the diameter of pipe jacking,the change of axial force and bending moment of the right line tunnel gradually increases.(4)The analysis of the horizontal displacement of the right waist of the right line tunnel during the construction process with different diameters and different distances of the jacking pipe shows that the main disturbance range of the right line tunnel during the construction of the pipe jacking is 20 m before and after excavation.The grey correlation method was used to explore the sensitivity of distance and jacking pipe diameter on the maximum deformation value of existing subway shield tunnels,and the results showed that the sensitivity of pipe jacking diameter was greater than that of distance. |
PDF Full Text Request