Analysis Of The Influence Of Shield Tunnel Construction On The Settlement Of Existing Tunnel

With the rapid development of urbanization in China,urban rail transit has increasingly become an important form of transportation in large and medium-sized cities.In the process of urban subway line construction from single line to network,it is inevitable that multiple lines will cross up and down.Therefore,it is of great significance to study how to ensure the structure of the existing tunnel and the safety of subway operation in the process of shield tunnel construction.In this paper,based on the engineering background of Hangzhou Metro Line 7 section a shield passing through the existing line 1 Section B,theoretical calculation,engineering measurement and numerical simulation methods are used to study the vertical displacement variation of the existing tunnel structure during the shield passing through construction,summarize the variation law,and analyze the influence of different construction parameters on the vertical displacement of the existing tunnel structure,The specific research contents and conclusions are as follows:(1)The influence of shield tunneling on the vertical displacement of existing tunnels is lagging behind.After the right line crossing,the vertical displacement deformation of the existing tunnel is similar to the normal distribution of single peak.The wave peak appears at the intersection of two tunnels.After the second crossing of the left line,the curve state changes from the approximate single peak normal distribution to the "M" double wave peak type,and the wave peak will generate a 3m offset,the position of wave peak will not change with the change of shield construction stage.(2)The deformation of the existing tunnel vertical displacement mainly occurs in the shield crossing stage,shield tail separation stage and subsequent settlement stage,accounting for more than 70% of the total vertical displacement change.At the same time,the deformation of the first vertical displacement caused by the new station before the shield starts can not be ignored,which accounts for about 18% of the total cumulative change.(3)The influence area of the construction on the right line of the new shield tunnel on the vertical displacement of the existing tunnel is 2.5D on both sides of the axis of the new shield tunnel,and the more significant influence area is 2.5D-5D.The obvious influence area of the left line crossing construction on the vertical displacement of the existing tunnel will increase,but the area of the more significant influence area will remain unchanged.(4)Combining with the actual engineering case,FLAC3 D model is established,the simulation results are consistent with the actual data.The maximum vertical displacement and the trend of change are consistent.The rationality of the model is verified.,the simulation results can guide the construction in the field to a certain extent(5)The influence of the earth silo pressure,synchronous grouting pressure and the clearance distance on the existing tunnel are analyzed by FLAC3 D simulation.The pressure of the soil silo,the synchronous grouting pressure and the clearance between the two tunnels are controlled at 0.2MPa、 0.2MPa and 4m respectively.The vertical displacement of the existing tunnel is well controlled,and the economic benefits are maintained.