Pit excavation will cause deformation of the shield tube sheet, but there are fewer studies related to the refinement model of shield tunnel under the consideration of peripheral pressure. Based on the formula for calculating the additional peripheral pressure of tunnel lining, the article establishes a refined model of a three-ring shield tubular sheet in combination with practical cases, carries out structural calculation and analysis, and compares the calculated values of tunnel deformation with the measured values to verify the reliability of the model in this paper. Ellipticity and standard deformation control values are used as indicators to assess the tunnel’s safety condition. The influence law of pit excavation and unloading on the tunnel is studied. The results show that: In the process of foundation pit excavation, tunnel segments gradually change from soil unloading control under the tunnel to unloading control caused by foundation pit excavation, and the horizontal displacement gradually increases. Under the same excavation schedule, the vertical displacement at the top of the tunnel changes more than that at the bottom; the stress at the joints between the tube pieces is larger, the maximum stress of concrete occurs in the connection place of the standard block, and the maximum stress of bolts occurs in the connection place of the bolts between the rings; the clear distance of the tunnel from the bottom of the foundation pit is larger than that between the tunnel pieces. The larger the clear distance of the tunnel from the bottom of the pit, the smaller the displacement at the top of the tunnel and the larger the displacement at the bottom, and the horizontal displacement gradually increases; the deformation and ellipticity of the tunnel are strictly controlled in the process of excavation of the pit, and the deformation and ellipticity of the tunnel will gradually exceed the control value if the excavation is continued after the pit is finished.

Theoretical research is conducted on the soil deformation caused by the construction of overlapping tunnels under composite geological conditions. Based on the theoretical method of combining analogous considering the shielding effect of the stochastic medium theory and the three-dimensional unified solution, a computational model was established considering the shielding effect of the underground tunnel on the deformation of the upper tunnel is taken into account. The calculation formula for soil deformation was derived. The theoretical method in this article was applied to multiple sets of measured cases for verification. Research indicates that: The calculation results have a good degree of fit, proving the feasibility of this method. Through single factor analysis, it is found that the soil conditions near the upper tunnel in overlapping tunnels have a significant impact on the deformation of surface soil. Compared to single line construction, the soil deformation caused by the upper tunnel in the overlapping tunnel from bottom to top is shallower and narrower due to the influence of the lower line shielding effect. The shielding effect coefficient proposed in this article can better reflect the influence of the lower line tunnel on the soil deformation of the upper tunnel. The magnitude of the shielding effect coefficient is inversely proportional to the distance between the tunnel axes, and the smaller the tunnel spacing, the greater the shielding effect coefficient.