Study On The Influence Of Underground Tunnel Jacking Construction On Subway Tunnel

With the rapid development of China's economy and the acceleration of the urbanization process,the development and utilization of urban underground space complexes,the impact of new tunnels such as underground connecting passage and pipe gallery close to the existing subway tunnel gradually highlights.In actual engineering,many connecting passages or pipe corridors adopt box culvert jacking construction technology,but the research in this filed is not perfect.Therefore,it is an important problem to be solved urgently to study the influence law of box culvert jacking construction on existing tunnels.The completion of this paper provides an effective reference for similar projects.This subject relies on the underground connecting passage project of an underground transportation hub in Zhengzhou.The underground connecting passage adopts the construction process of box culvert jacking,and at the same time the underground connecting passage crosses the Zhengzhou Metro Line 1.The finite element method was used to establish a three-dimensional numerical analysis model that simulates the construction process of box culvert jacking through an existing subway tunnel,and analyzes the deformation law of the existing tunnel during box jacking.At the same time,a comprehensive analysis of the main factors that affect the deformation of the existing tunnel during the jacking construction of the box culvert.Finally,combining with the engineering case,the paper analyzes the case of existing tunnel reinforcement.The main contents and conclusions of the study are as follows:(1)Based on the engineering background,the overall structure of the underground connecting channel,the overall construction plan in the jacking construction of the box culvert,and the technological process of the jacking construction of the box culvert structure are systematically introduced.(2)The numerical analysis model of box culvert jacking horizontally and vertically crossing the existing subway tunnel is established by finite element method.The vertical displacement,horizontal displacement law and soil displacement law of the subway tunnel during jacking of the box culvert are simulated and analyzed.It is found that the impact of the jacking construction of the box culvert on the existing tunnel underneath is three-dimensional,including the vertical and horizontal effects.With the increasing of vertical and horizontal displacement values of the existing tunnel during the jacking construction.After the jacking is completed,the tunnel ascends and moves forward in the direction of jacking of the box culvert.The closer the tunnel is to the box culvert,the larger the deformation value of the tunnel is,and the deformation rate of the tunnel is the largest when the box culvert passes through the existing tunnel.With the increase of the jacking distance of the box culvert,the vertical displacement value and the influence range of the soil gradually increase and spread spatially.(3)The deformation laws of the existing tunnel caused by the jacking of the box culvert under different soil quality,different distances between the box culvert and the tunnel,different positions of the box culvert and the tunnel,and different sizes of the box culvert are studied.The research shows that the deformation of the existing tunnel will increase when the geological conditions of the existing tunnel are more complex or the soil is softer;the displacement value of the existing tunnel gradually decreases with the increase of the vertical distance between the box culvert and the tunnel;The deformation law of the tunnel changes when the spatial position of the tunnel is different.Symmetric jacking can effectively reduce the impact on the existing tunnel;as the width of the box culvert increases,the displacement value of the existing tunnel increases gradually,and the vertical displacement growth rate increases but the horizontal displacement growth rate fluctuates.(4)Based on the engineering case,the numerical simulation analysis of the tunnel deformation control effect is carried out for the two reinforcement measures: soil grouting reinforcement and uplift pile pipe screen reinforcement.The research shows that the grouting reinforcement of the soil within the jacking range of the box culvert can reduce the vertical displacement value of the tunnel,but the horizontal displacement value of the tunnel does not decrease significantly;the vertical displacement and horizontal displacement of the existing tunnel can be effectively reduced by the anti pulling pile and the pipe curtain door reinforcement,and the tunnel deformation is greatly reduced,especially the horizontal deformation.