Study on the Correlation between Convergence and Structural Damage Characteristics and Performance of Shield Tunnels

The study is based on the long-term monitoring convergence data and the detection results of the structural state of Nanjing Metro Line 3 JiuLonghu~ChengXin Avenue tunnels. The study conclusions are obtained statistically and analytically for convergence forms, data, and structural diseases and performance indicators. The convergence form of an elliptic tunnel segment is a horizontal expansion type, and its long axis direction and horizontal deflection angle are between ±1°~±30°, respectively. The tunnel convergence is correlated with the number of cracks and leakage area. However, it has no obvious correlation between the structural strength, the amount of stagger, and the holes behind the lining. When the tunnel convergence value in soft soil layer is greater than 60mm, the longitudinal through cracks increases significantly, and the maximum width reaches or exceeds 0.2mm. It is suggested to use steel ring reinforcement for the shield tunnel when convergence reaches 60mm in the soft soil layer. Joint leakage is mostly caused by segment converging deformation, which is further confirmed by the fact that segment leakage usually occurs in the range of ±30° along the horizontal tunnel line. This range is comparable with the maximum deformation δ_max along the long axis of the converging ellipse of the "outward-expanding type."