The Settlement Of Tunnel And Ground Surface Caused By Shield Construction Under Grouting Condition And Controlling Method

Since the 21st century,more and more urban tunnels have been constructed by shield tunneling method in China.Shield tunneling technology has become the main construction project of urban metro tunnels by virtue of its advantages of small disturbance to surrounding strata,high quality of tunnel formation,fast tunneling speed,non-interruption of ground traffic,safety and environmental protection,and its engineering cost does not change substantially with the depth of the tunnel.Flow construction method.However,in the process of excavation,it will still cause the deformation and movement of surrounding strata.On the one hand,strata movement will cause surface subsidence,on the other hand,it will cause the displacement of adjacent structures.With the increasing attention of the government and the masses to the degree of environmental friendliness and safety in the construction of urban tunnels,higher and stricter requirements have been put forward for the construction of urban buildings,traffic and municipal tunnels.Deformation and movement of surrounding strata during shield tunneling are complex phenomena interwoven by many factors,such as soil quality,hydrological conditions,tunnel section,burial depth,construction scheme and technology,etc.But for closed-chest shield tunneling machine,the movement of strata and ground settlement are mainly affected by the effect of synchronous grouting during shield tunneling,which directly affects shield tunneling.The stability of road stratum,the rhythm of construction and the safety of surface environment.Based on the engineering practice of Zhengzhou Metro Line 3,four aspects are studied in this paper.In view of the research direction of this paper,the research status at home and abroad is summarized:the development history of shield construction,the working principle of shield machine,and the mechanism of the influence of shield construction on stratum deformation and surface subsidence.The influence scope,factors and rules of shield tunneling on ground deformation,surface subsidence,adjacent pipeline lines and adjacent structures are analyzed.Taking the shield tunneling section of Erqi Square Station to Shunchengjie Station of Zhengzhou Metro Line 3 as the actual engineering background,the engineering geology and hydrology situation,construction technology and monitoring scheme are analyzed in detail.Through real-time monitoring of the ground surface,the main areas that shield tunneling affects the surrounding environment are inferred.Several influencing factors of grouting are simulated and analyzed by FLAC3D.Shield construction as the main track construction has a positive significance.A three-dimensional model for simulating the shield construction of double-track Metro is established by using FLAC3D software.By simulating different supporting conditions,the properties of grout,the grouting pressure and the calculation results of grouting volume,the most suitable grouting parameters for practical projects are obtained.In the simulation of double-line shield tunnel,it is found that the maximum settlement of single-line and double-line tunnels lies in different control ranges.Controlling the change of grouting pressure,grouting volume and elastic modulus of grouting can effectively control the formation deformation and surface settlement.According to the recommended grouting parameters simulated by the foundation model,the simulation prediction is made against the background of the actual project crossing the 27 towers.By comparing the measured data with the results of the simulation prediction,the effective measures to control the formation deformation and surface subsidence during the shield construction are put forward,and the influencing factors of the surface subsidence curve in the actual project are analyzed.Optimizing the concrete construction scheme to control the ground settlement value within the allowable value of the code and to minimize it has important reference and guiding significance for similar construction projects of Zhengzhou metro.