Investigation of the Torsional Behavior of Circumferential Joints in a Large-diameter Curved Tunnel

Unlike a straight tunnel, a curved tunnel is subjected to torque in the out-of-plane direction. However, the effect of torque is seldom considered in the structural design of curved tunnels. This paper investigates the torsional behavior of circumferential joints in a large-diameter curved tunnel by the finite element method (FEM). The parameters used in the three-dimensional model are verified through a prototype test. Graphs of torque vs. twist angle for a typical tapered ring lining model are obtained and the torsion stiffness is calculated and compared with results from a parallel ring lining model under different conditions (angle of bolts, strength grade of bolts, residual longitudinal load). The results indicated that the structural behavior of the tapered ring lining cannot be approximated by a parallel ring lining; the torsional stiffness depends on the working conditions. The results of this research may provide guidance for the design of similar tunnels.