Structural health monitoring and analysis of an underwater TBM tunnel

The safety control of important tunnels is based on the measurement of some important quantities that characterize their behavior. Since Sep 2013, a real-time automatic monitoring system was installed in an underwater TBM tunnel to evaluate its performance under normal operation conditions. The tunnel behavior induced by water level variations, seasonal environmental temperature changes, and time effects was analyzed by a multiple linear regression (MLR) model. The regression results show that temperature is the most important factor that influences the segment strain during normal operation, and the yearly irreversible deformation of segment joints is as remarkable as that caused by water level variations and temperature changes. A finite element method (FEM) analysis was conducted to evaluate the effects of water level and temperature on tunnel segment strain. The influencing factors obtained from the FEM results are consistent with those obtained from the MLR model. This proves that the MLR model has sound physical meanings. Finally, a prewarning method is proposed based on the developed MLR model and regression coefficients. In the prediction of tunel performance, the regression coefficients are periodically updated to incorporate the time-related effects. A comparison of predicted and monitoring results from Sep 2016 to Jun 2017 verifies the applicability of prewarning method.