Study On Impa CT And Control Technology Of Shenzhen Metro Shield Tunnel Undercrossing The Existing Buildings

Although shield tunnels have many advantages,the construction of shield tunnels will inevitably result to deformation of the surround strata.Relying on the project of the tunnel between Futian Port Station and Fumin Station of Shenzhen Metro Line 10 undercrossing the buildings called Tianzhiyuan and Tianyayuan in Tianze Garden,the construction i MPact and control of shield tunnel undercrossing existing buildings with close distance were studied in this paper.Based on the analysis of the difficulties,focal points and current research status,the key technologies of shield tunneling undercrossing the buildings,such as the selction of the reasonable working chamber pressure of shield tunneling and the pre-reinforcement of the building foundation through the sleeve valve tube grouting,were analyzed by using three-dimensional finite element numerical simulation.The evolutions of mechanical properties of displacement field and stress field under various construction conditions were obtained,and some useful construction control measures of shield tunnels undercrossing buildings with pile foundation were put forward.The main research contents and conclusions are as follows:1.The construction risks,the difficulties and the focal points of shield tunnels unercrossing buildings with the conditions of upper soft and lower hard geological were analyzed;in addition,the safety control standards of shield tunnels undercrossing buildings were clarified.2.By three dimensional numerical calculation,the influence of working chamber pressure on safety control of shield tunnel undercrossing buildings with the conditions of upper soft and lower hard geological was revealed and its reasonable range of values was given: In order to effectively control the building deformation,the working chamber pressure should be set from 1 to 1.2 times the theorectically balanced water and soil pressure of tunnel face,and should not be greater than 1.2 times the theorectically balanced water and soil pressure of tunnel face.3.By three dimensional numerical calculation,the effect of pre-reinforcement of the building foundation through the sleeve valve tube grouting on enhancing the construction safety of shield tunnel undercrossing buildings with the conditions of upper soft and lower hard geological was demonstrated.The results show that the pre-reinforcement of the building foundation through the sleeve valve tube grouting can not only effectively reduce the settlement value of buildings caused by the construction of the shield tunnel,but also make the values of the building settlement and the corresponding building inclination fall into the safe range.Therefore,it is suggested that the pre-reinforcement of the building foundation through the sleeve valve tube grouting should be adopted before the construction of the shield tunnel.4.According to the characteristics,control difficulties and focal points of the present project and the similar projects,special researches of the construction technology were also carried out.Researches show that adopting the pre-reinforcement of the building foundation through the sleeve valve tube grouting strictly,strengthening the construction control of shield tunnel undercrossing buildings,and conducting the on-site monitoring and information feedback timely can effectively ensure the controllability and safety of the construction process.