| In the 21st century,because of the fast growth of population density,building's density and height in China's cities,traffic is getting more and more congested.Therefore,it is imperative to build subways in densely populated cities.With the increased of subway lines and more new tunnels need to pass through existing tunnels,the depth of subway tunnels is deeper and deeper.Which has led to more and more groundwater problems.Such as diving,upper water retention,and confined water that have caused tremendous difficulties in construction.Moreover,because of seasonal changes,rainfall and other reasons,the groundwater level is constantly changing.Which increased more difficults for tunnel construction projects.Therefore,it is necessary to study the impact of water level changing on tunnel excavation.Based on the research of a tunnel under-penetration project.The new tunnel is in a water-rich sand-pebble stratum,and there is confined water at 4m below the tunnel floor.The minimum distance between the newly-built tunnel and the existing shield structure is 2.5m.Analyzing on-site monitoring data and performing numerical calculations,so the main research contents of this article are as follows:?1?FLAC3D5.0 software was used to establish a model,which is based on the actual construction scheme for under-approaching,and select a reasonable stratum parameter by the geological survey report.Through compared the simulated data with the measured data,the model was applicable in this paper.?2?Because diving and confined water both are existing in this project,so control variable method was used to analyze.Firstly changed the level of diving water and maintained the head of initial confined water,to analyze the variation law of the displacement and stress of the existing shield structure and to optimize the reinforcement measures.?3?Secondly,changed the head of confined water and maintained the level of initial diving water,to analyze the change law of the displacement and stress of the new tunnel. |
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