Monitoring-based analysis of the responses of upper structure and tunnel lining during shield tunneling with pile cutting

Direct cutting of piles using a shield machine has become more common and inevitably causes additional deformation of the existing structures. To ensure the safety of pile cutting, a real-time field monitoring system was established to monitor the responses of upper structure and tunnel lining, and guide the adjustment of tunneling parameters. The underpass settlement and the mechanical behavior of the tunnel lining were analyzed based on the monitoring data. The underpass settlement presented a four-stage development pattern, closely related to the tunneling process. Results of correlation analysis suggest that earth pressure, rotational speed and grouting pressure have more significant influences on the underpass settlement. By adjusting these three parameters and advance rate, the underpass settlement in each stage was controlled within the acceptable range. For the shield tunnel, due to the difference in constraining effect of jack thrust, the rapid uplift of segmental rings mainly occurred in the working phase. As a result, the overall development of tunnel uplift during shield tunneling was characterized by a stepwise pattern. During the tunnel uplift, the circumferential stress sharply fluctuated and tended to recover with the stabilization of tunnel uplift, and the transverse deformation of the tunnel lining behaved as "horizontal ellipse" and "vertical ellipse". The comparison results indicate that the residual pile and the reinforced soil have significant constraining effects on the tunnel uplift, while the residual pile increased the vertical convergence of the tunnel lining. In addition, the dislocation between segmental rings showed a rapid trend with the development of tunnel uplift. The monitored anomalous circumferential stress and observed defects in the tunnel lining were attributed to larger dislocation exceeding 8.0 mm.