Study On Construction Technology Of Large Diameter Shield Tunnel Crossing The Yangtze River

With the rapid development of our country’s economy, more and more tunnels have been built across the river. Shield tunnel construction has the following advantages: less impact on the surrounding environment, the good adaptability of geological conditions, rapid safe construction, etc,so it has become the preferred method of underwater tunnel construction, while slurry shield method has a priority of river tunnel construction. During the process of slurry shield tunneling,the control of pressure of the slurry is the most important part. If the slurry pressure is too large, the surface will uplift, and if the slurry pressure is too small, the surface will be settlement. At the same time, tunnels across the river are under high pressure environment, so that the problem is more complicated.This paper took Nanjing Subway Line slurry shield cross the Yangtze notching as engineering background, with FLAC-3D software, doing the numerical simulation of a slurry shield face stability, which by applying active earth pressure, static earth pressure and passive earth pressure to the excavation face be the cut-off point to analyze the change rule of longitudinal displacement of the varies slurry and the excavation of the settlement parties before excavation face which because of a series of slurry pressure, so as to provide foundation to ensure slurry pressure reasonably. While analyses were made with and without the influence of fluid solid coupling on the stability of tunnel surrounding rock..Firstly it analyzed the change rule of the seepage field caused by tunnel excavation and variation of pore water pressure, and then compared and analyzed the stability and structural forces of the surrounding rock without consideration of fluid-structure coupling and with consideration of fluid-structure coupling. Analyzing stress and displacement of surrounding rock, and stress distribution of segment and the distribution of tunnel surrounding rock splastic zone and making a comment of safety of shield tunnel.Through analyzing the monitoring datas of construction process,it got variation of sheet steel stress tunnel, tube sheet around the earth pressure, pore water pressure and tube sheet’s deformation with time. Finally, it introduced the control measures of slurry shield across the Yangtze notching segment. It done a detailed description of risk for pulp, ground settlement, floating tube sheet, shield tail plasma leakage and other hazards. And introducing its usual control measures to provide technical reference for similar projects.