Structural Force Monitoring and Calculation of the Metro Shield Tunnel in Subsea Weathered Slot

Objective In order to explore the load distribution characteristics of shield tunnel structures in subsea weathered slot, a study on the internal force response law of the segment structures is carried out. Method Relying on a cross-sea metro shield tunnel project, systematic monitoring of water-soil loads and structural internal forces of the segments is carried out for the subsea weathered slot section. Through data analysis, the distribution characteristics of the tunnel structural loads and internal forces in this area are revealed. The fatigue characteristics of the segments under tidal load are further verified. Result & Conclusion ① The monitoring results show that the soil and water pressures and the internal forces of the reinforcement tend to stabilize after significant fluctuations in the initial stage. In the stable stage, water-soil pressure is maintained within the range of 0.1~0.4 MPa, the stress range of the inside reinforcement is -2.19~-38.60 MPa, and that of the outside reinforcement is -6.95~-34.59 MPa. The ratio between the calculated and measured values of the reinforcement stress is 0.6~1.8, which shows a good consistency. ② The water-soil loads on the segments show corresponding fluctuations with the periodic changes of the tidal water level (period of 12 h). The maximum main stress level at the segment joint is -2.45~-2.60 MPa, the stress amplitude is between 0.31~0.34 MPa, and the stress ratio is between 0.87~0.96. ③ Under different tidal load amplitude conditions, the segment stress level remains relatively stable, while the stress amplitude increases linearly with the increase of tidal load amplitude, and the stress ratio shows a linear downward trend. When the tidal load amplitude reaches 5 times of the actual measured value, the main stress amplitude of the segment increases to 1.70 MPa, and the stress ratio decreases to 0.84, at this time the maximum value of the concrete main stress ranges from -1.6 to -3.6 MPa.