Study on Deformation Effect of Double-Line Shield Tunneling Under the Existing Tunnel Construction
In order to explore the influence of underpass construction of new double-line tunnel on the existing tunnel structure,based on the Kunming Metro shield underpass tunnel construction project,the crossing angle,clear distance and formation loss rate are taken as influencing factors,and the deformation rule of the existing tunnel caused by double-line excavation is studied.The relationship between surface settlement,clear distance and formation loss rate is analyzed by model test and verified by numerical simulation.The results show that:(1)when the crossing angle and the formation loss rate are constant,the clear distance is negatively correlated with the surface settlement and positively correlated with the vertical maximum displacement.(2)With the increase of the net distance,the surface settlement trough curve gradually transitions from'W'to'U' shape,and the maximum surface settlement moves to the central axis of the double-line tunnel,and the maximum settlement value is 13.96 mm;however,with the increase of formation loss rate,the surface settlement trough transitions into a'W'shape,and the maximum settlement appears on the central axis of the left and right lines of the tunnel,with the maximum value of 21.94 mm.(3)The results of model test and numerical simulation analysis are mutually verified,which can provide early warning information for the maximum settlement value exceeding the control value.
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