Effect of Subsequent Tunnel Driving on Preceding Tunnel of Parallel Shield Tunnels with Small Clear Distance in Soft Soil
Focusing on the effect of subsequent tunnel driving on preceding tunnel of the parallel shield tunnels with small clear distance in soft soil,a three-dimensional numerical analysis model was established based on the soft soil in Ningbo city.The rationality of the parameters,boundary conditions and tunneling process of the model was verified by the measured data.The displacement and segment internal force of the preceding tunnel during the subsequent tunnel driving stage were calculated under different clear distance.The results show that when the two lines are parallel,the driving of the subsequent tunnel mainly leads to the rigid displacement of the preceding tunnel,and causes a large increase in the internal force of the preceding tunnel segments.To quantify the impact of the driving of the subsequent tunnel on the internal force of the preceding tunnel segments,the clear distance influence coefficient of the maximum bending moment and the maximum axial force are introduced.The driving of subsequent tunnel will have an influence on the preceding tunnel within the range of 2～3 times the tunnel diameter in front of the preceding tunnel and 2 times the tunnel diameter in the rear of the preceding tunnel.The results were validated by the design and selection of small clear distance segment from Wangchunqiao Station to Tianyi Jiayuan West Station of Ningbo Urban Rail Transit Line 6.The results can provide guidance for similar engineering design and construction.
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