Study on Longitudinal Stiffness Enhancement Measures of Large Diameter Shield Tunnel

In order to study the enhancement effect of different annular joint structures on the longitudinal stiffness of shield tunnel, the influences of section diameter on the longitudinal tension and compression, longitudinal shear and longitudinal bending stiffness of tunnel are calculated by equivalent continuous model. The longitudinal stiffness enhancement measures are related to the annular joint structure of segment. Additionally, the mechanical properties of nine annular joint structures are deeply explored by numerical simulation, and the annular joint structure with the best effect of enhancing the tunnel longitudinal stiffness is obtained by comparison. The results show that the diameter has little effect on the longitudinal tension and compression and longitudinal bending stiffness, but has a great influence on the longitudinal shear stiffness. The stiffness enhancement measures of the circumferential joint can significantly reduce the displacement of the segment and improve the tunnel longitudinal stiffness. The enhancement effect is: oblique bolt > bend bolt, positioning tenon > shear pin > concave tenon; at the same time, both the bolt type and the longitudinal stiffness enhancement measures have a great influence on the maximum shear stress of the bolt. The shear stress of the bolt is significantly influenced by the bolt type at vertical load and is significantly influenced by the longitudinal stiffness enhancement measures at horizontal load. Combining economy and effectiveness, when the joint bolt is a curved bolt, setting the positioning tenon is a relatively better choice.