Mechanical responses of underground carriageway structures due to construction of metro tunnels beneath the existing structure: A case study

• Published in: Deep underground science and engineering (Online) Vol. 3; no. 2; pp. 231 - 246
• Main Authors: Han, Xin, Ye, Fei, Han, Xingbo, Ren, Chao, Song, Jing, Zhao, Ruliang
• Format: Journal Article
• Language: English
• Published: Wiley 01.06.2024
• Subjects: metro tunnel; numerical simulation; structural deformation; surface subsidence; underground carriageway structure
• ISSN: 2097-0668; 2770-1328
• DOI: 10.1002/dug2.12057

To understand the mechanical response pattern of the existing structure and ground due to the construction of metro tunnels underneath, the finite difference method is adopted to study the torsional deformation and stress variation of the existing structure and the effect of underground carriageway structures on the surface subsidence. The curves of the maximum differential subsidence, torsion angle, and distortion of the cross‐section of the existing structure show two peaks in succession during traversing of two metro tunnels beneath it. The torsion angle of the existing structure changes when the two tunnels traverse beneath it in opposite directions. The first traversing of the shield tunnel mainly induces the magnitude variation in torsional deformation of the existing structure, but the second traversing of the subsurface tunnel may cause a dynamic change in the magnitude and form of torsional deformation in the existing structure. The shielding effect can reduce the surface subsidence caused by metro tunnel excavation to a certain extent, and the development trend of subsidence becomes slower as the excavation continues. Focusing on the influence of the underground carriageway structures on surface subsidence, some interesting results were obtained: (1) The curves of the maximum differential subsidence, the torsion angle, and the distortion of the cross‐section of the existing structure show two peaks in succession during the traversing of two metro tunnels beneath it. (2) The carriageway structure exerts the “shield effect” on the subsidence of soil mass under the influence of tunnel excavation. The shielding effect can reduce the surface subsidence caused by metro tunnel excavation. Highlights A simulation of the construction process of a shield tunnel and a shallow tunnel traversing beneath an existing underground carriageway is carried out. The torsional deformation features of the existing structure are studied. The mechanism and influence pattern of the “shield effect” of the existing structure on stratum subsidence are examined.