A bending-shear-torsion resistant beam foundation model for segmental tunnels in longitudinal direction

• Published in: Tunnelling and underground space technology 2023-10, Vol.140, p.105296, Article 105296
• Main Authors: Liu, Yingbin, Liao, Shaoming, Liu, Mengbo, Chen, Lisheng
• Format: Article
• Language: English
• Subjects: Bending-shearing-torsion mode; Longitudinal torsional stiffness; Segmental lining structures; Soil-tunnel interaction; Torsional deformation
• ISSN: 0886-7798
• DOI: 10.1016/j.tust.2023.105296

•A bending-shear-torsion resistant beam foundation model is proposed;•The torsional behaviors induced by asymmetric loading are investigated;•The effect of design parameters on longitudinal torsional performance is studied; Segmental tunnels constructed by Shields / TBMs are easily subjected to uneven longitudinal cross-sectional torsion because of asymmetric external loads or deformations along the tunnel. However, the conventional models for soil-tunnel interaction in the longitudinal direction generally regard the tunnel as a one-dimensional beam on elastic springs, ignoring its cross-sectional torsion. To mitigate this gap, the paper proposed a bending-shear-torsion-resistant beam foundation model to explore the effects of cross-sectional torsion on tunnel performance. Firstly, an analytical solution for the longitudinal bending-shearing-torsion stiffness of a segmental tunnel was derived, then a soil-tunnel interaction model based on torsional Timoshenko beam on Winkler foundation was proposed with three-dimensional soil reactions incorporated. The present model is verified by comparing it with the Finite Element program and other published methods based on two case studies. The new contributions and findings are as follows: (1) The longitudinal torsional stiffness is proposed, and it is found that it is greatly affected by the number of bolts and segment size. (2) The governing differential equations and the closed-form solution for the soil-tunnel interaction model under bending-shear-torsion mode are derived, regarding arbitrary loading and two typical boundary conditions. (3) By considering the sectional torsion and three-dimensional soil reactions, the proposed method is proved to be actually more reasonable than the existing analytical methods. (4) A parametric analysis for the proposed solution was conducted to investigate the influence of key parameters on the torsional performance of segmental tunnels, which revealed the effect of torsional stiffness, soil resistance and elastic boundary conditions. The proposed solution and results could promote tunnel engineers better understand the anti-torque behaviors of segmental tunnels and improve the tunnel design in case of complicated circumstances.