Coupling Analytical Investigation on the Response of an Existing Tunnel Subjected to Underpassing Shield Tunneling

ABSTRACT Shield tunneling beneath an existing tunnel can significantly impact the safety and stability of the existing tunnel. A clear understanding of the response of the existing tunnel subjected to underpassing shield tunneling is therefore essential for maintaining its operational safety. In view of this, this study proposes a coupling analytical method to investigate the behavior of an existing tunnel subjected to underpassing shield tunneling. First, the vertical free displacement corresponding to the existing tunnel position is determined using the virtual image method, and the additional vertical displacement of the existing tunnel is derived through tunnel–soil displacement coupling analysis. The corresponding bending moment and shear force in the existing tunnel are subsequently obtained by differentiating its displacement profile. The validity of the proposed method is demonstrated through two engineering case studies, and the results show good agreement not only with field observations but also with numerical simulations and results from other analytical approaches. Results from the parametric analysis reveal that increasing the bending stiffness of the existing tunnel reduces its maximum displacement while simultaneously amplifies the maximum bending moment and shear force. Moreover, the bending moment of the existing tunnel increases linearly with the gap parameter, while increasing both the intersection angle and the vertical clearance between the existing and shield tunnels effectively mitigates its maximum displacement. The proposed analytical method provides a valuable tool for predicting the response of existing tunnel subjected to underpassing shield tunneling.