Analysis of construction response for mechanized construction of metro connecting passages

To investigate the influence of mechanized pipe jacking construction for connecting passages in weathered granite strata on the settlement and deformation of left and right shield sections of metro tunnels and ground surface, this paper takes the pipe jacking project of No.1 connecting passage in a typical weathered granite stratum as the research background. Numerical analysis software was used to model and analyze the whole construction process of the connecting passage using the mechanized pipe jacking method. The accuracy of the numerical model was verified by comparison with field monitoring data. On this basis, the influence laws of stratum cohesion, internal friction angle, clear distance between main tunnels, and burial depth on the deformation of the main tunnels and ground surface were systematically analyzed. The results show that: 1) The tunnel at the launching end experienced two sudden deformations during the portal breaking stage, with the bending moment increasing sharply first and then decreasing slowly; the deformation at the receiving end increased linearly with the pipe jacking advance, and reached the peak synchronously with the bending moment at the moment of portal breaking. 2) A centrally symmetrical settlement trough was formed on the ground surface, with a maximum settlement value of 2.3 mm; the maximum vertical and horizontal deformations of the main tunnel were 1.7 mm and 1.4 mm, respectively. 3) The improvement of stratum strength can reduce ground surface settlement but increase the horizontal deformation of the tunnel; the increase of the clear distance between main tunnels leads to the expansion of the settlement trough width; the increase of burial depth reduces ground surface settlement while increases the horizontal deformation of the tunnel.