Study On Ground Settlement Mechanism And Prediction Analysis Caused By Double-Line Tunnel In Taiyuan Clay Silty Soil And Sand Layer

The surface settlement caused by double-line tunnel construction is not only related to the safety and reliability of the tunnel itself,but also has a great impact on the underground pipelines around the subway tunnel and the structures around the tunnel.The law of lateral settlement along the lateral direction is an important manifestation of the disturbance effect of tunnel construction,and it is the basis for mastering the stability of the tunnel and the degree of influence on the surrounding.Based on the geological conditions in Taiyuan area,this paper studies the lateral variation law of ground subsidence caused by shield tunnel construction of subway tunnel,and explores the prediction method of ground surface settlement during shield tunnel construction of double-line tunnels,which is the spatial position,prediction method and stability of double-line tunnel.The control measures and other reasonable determinations provide the basis.Taking Zhongxinxijie Station-Nanzhonghuan Station as research background and considering the influence of the tunnel section,the net burial depth is defined as the closest distance from the outer contour of the tunnel tothe surface,and the net spacing is defined as the closest distance between the outer contours of the two tunnels.Through engineering geological survey,numerical calculation,theoretical analysis,grey correlation analysis and measured data analysis,the hydrogeological conditions,groundwater,tunnel section and clear spacing of the double-line shield tunnel in Taiyuan River are studied.The degree of correlation between various factors and surface subsidence was determined,and the primary and secondary relationships of influencing factors were obtained.Based on the measured data,the key parameters of surface subsidence prediction by the Peck method in this area are studied.From the technical and economic point of view,the measures and methods for controlling the surface settlement of the double-line tunnel are further proposed.the main research contents and conclusions are as follows:(1)The Zhongxinxijie Station-Nanzhonghuan Station of Taiyuan are studied.The research shows that there were different thicknesses of silty silt and sand layer in the subway construction section,and the variation of groundwater level Larger,more permeable,liquefied layer and other poor soil conditions,it is easy to cause instability of the excavation surface,large surface settlement,and accidents such as pipe flow.(2)Through the collection and consolidation of the existing achievements of China and foreign countries,the lateral surface settlement of the double-line tunnel is studied from the aspects of mechanism,process,changing law,influencing factors and prediction methods,and the law of lateralsurface settlement of some subway shield construction is obtained.(3)Based on the engineering geological conditions of the silty silt and sand layer of Taiyuan,numerical simulation and grey correlation analysis method are used to study the characteristic mechanism of the change of surface settlement curve caused by double-line shield tunnel under the conditions of different clay soil and sand ratio,different groundwater level,different tunnel excavation diameters,different net depths and net spacing.The influence of different environmental factors and design factors on the surface settlement disturbance,curve shape and settlement maximum of double-line tunnels are studied.The correlation between related parameters and surface settlement is obtained.Some ground settlement laws of double-line tunnel can be guided.(4)According to the above research,based on the empirical formula of Peck,through the analysis of measured data,the key parameters of the Peck empirical formula of the Taiyuan are obtained,and the prediction formula under different disturbance intervals of the double-line tunnel is obtained.so as to be quick and convenient for similar subway.From the perspective of design,environmental and construction factors,the measures and methods for controlling the surface settlement of the double-line tunnel are proposed.