Research On The Mechanical Response Of Shield Tunnel Segment During The Construction Of Cross Passage

With the rapid development of China’s railway network,large-diameter shield tunnels have been increasingly applied to underground projects that penetrate urban structures and core areas.The construction of a cross passage between the large-diameter single-line and double-hole shield tunnels has put forward higher requirements for the stability and safety of the main tunnel.During the construction process of cross passage,the stress and deformation of the large-diameter shield segments at the opening of the main tunnel is a problem worth studying.Based on the Wangjing tunnel project of Beijing-Shenyang Passenger Line,this paper uses theoretical analysis,numerical simulation,field test and other methods to clarify the force deformation law of the large-diameter railway shield segment in the construction of the cross passage,and points out that the edge of shield segment which close to the segment firstly removed is the weak part of the tunnel structure.The main works are as follows:(1)The existing cross passage construction methods and application engineering examples are investigated,and the construction methods of the cross passage are summarized and compared.The construction method of the Wangjing tunnel cross passage is introduced in detail.(2)A three-dimensional numerical model for the simulation of the cross passage excavation process is established.The variation of the displacement,stress,and bolt internal force during the construction of the cross passage is analyzed for different assembly methods,tunnel depths,construction methods and soil parameters.The result shows that the force of the staggered-jointed segment is less than that of the continuous-jointed segment.The shield segment which close to the segment firstly removed is under an unfavorable stress-strain condition,and this adverse effect increases as the depth of the burial increases and the parameters of the soil layer decrease.(3)An on-site monitoring program is formulated,and the field test method for the force of large-diameter segments is developed.For some representative monitoring sections,the vibrating wire sensor is used to monitor the internal force of the lining reinforcement and the bolts,the earth pressure behind the lining,and the strain of the concrete.Through the analysis of the monitoring data,it is found that the construction of the cross passage will cause a significant change in the stress mode of the segment,the local tensile stress will occur in the segment reinforcement,and the tension of the circumferential bolt will increase.(4)The on-site monitoring data and the three-dimensional numerical simulation results are compared and analyzed,the reliability of the calculation results is verified.The calculation results provide reference for the design and construction of similar projects.