Deformation Control Method of"S"Type Tunnel Passing Through Existing Shield Tunnel at Short Distance
Relying on the Hohhot new"S"type underground connecting passage passing through the existing Metro Line 2 project in a short distance,this paper uses the method of finite element numerical simulation and field moni-toring to compare and analyze the sand bag weight range,the sand bag weight height and the removal method of the middle wall,and obtains the optimal scheme for the deformation control of the existing shield tunnel.The research shows that:① The maximum deformation position of the existing shield tunnel in each stage changes dynamically with the excavation of the new tunnel,and the maximum deformation occurs at the far end of the existing shield tunnel after the construction is completed,because when the new tunnel is excavated directly above the shield,the position is the key area of deformation control,which is the most affected by the construction disturbance;② The deformation control effect of using sandbag weight on existing shield tunnels is relatively obvious,and the deformation control effect is basically between 25％and 30％,but increasing the weighting range and height has little effect on reducing the uplift deformation amplitude,which is basically between 4％and 6％.Considering the construction economy,the sand bag weighting measure scheme with a weighting range of 49～87 pieces and a weighting height of 2.0 m is selected;③ The different demolition methods of the middle diaphragm wall have a great impact on the tunnel uplift deformation.In order to form a stable stress system in time,the demolition method of"one partition and two demoli-tion"is selected.The uplift deformation of the existing shield tunnel was effectively controlled in the upper crossing construction by taking reasonable sand bag weighting measures and the removal of the middle wall.After the con-struction,the deformation of the existing shield tunnel track bed was 2.68 mm,which was close to the measured data of the track bed of 2.51 mm,meeting the specification requirements(4.00 mm),which can provide relevant reference experience for similar projects.
"S"tunnelup-crossingshield tunnelsand bag weightremoval method of center diaphragms
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