Full-scale test on seismic performance of circumferential joint of shield-driven tunnel

A shield-driven tunnel is deformed along the longitudinal direction when subjected to seismic loadings; the circumferential joint is the key position of the shield-driven tunnel when such longitudinal deformation occurs. In this study, the variations of the internal forces (including both axial forces and bending moments) in the longitudinal direction of the tunnel are analyzed through a numerical method based on the longitudinal equivalent continuous model (LECM). The results show that the internal forces of the tunnel are mainly an axial force caused by longitudinal excitation, and a vertical bending moment caused by transverse excitation. Based on the stress distribution of the circumferential joint, a full-scale test is conducted, and the test results are compared with those obtained by a refined numerical model with 16 segmental rings. It is shown that the variation of the opening and bolt strain of the circumferential joint follows that of the internal force. When the tunnel is subjected to longitudinal tensile forces or bending moments, the distribution rules for the bolt stress at the position of the largest opening are essentially the same. Moreover, the distribution characteristics of the concrete strain on the segment surface at the position of the largest opening are essentially the same. The maximum tensile strain appears on the outer surface of the sleeve side segment. However, the maximum compressive strain appears on the inner surface of the hand hole side segment. The maximum principal stress and damaged plasticity of the segment generally appear near the sleeve and hand hole, and have a limited influence on the segment surface. Finally, a failure test shows that the segment becomes damaged before the bolt yield, with more severe damage occurring in the sleeve side segment.