Study on Deformation Characteristics of the Segment in the Underwater Shield Tunnel with Varying Earth Pressure

The segment in an underwater shield tunnel is influenced by the change of earth pressure and water pressure. Therefore, the law of segment deformation should be mastered for the safe operation of the tunnel. To obtain the law of segment deformation under varying earth pressure, loading conditions of constant water pressure and without water pressure were considered. In this study, the numerical simulation and scale model experiment were carried to analyze the strain, curvature, and displacement of the segment. The results show that the strain amplitude of segments is reduced by the water pressure under a range of earth pressure. When the earth pressure ranges from 0 MPa to 2.4 MPa and the water pressure 0.33 MPa, the displacement of the vault and arch waist exhibit a decreased rate of 7.916 mm/MPa and an increased rate of 5.416 mm/MPa, respectively. Under the combined effects of constant water pressure and varying earth pressure, the curvature of the segment tends to stabilize after a rapid change with a maximum of 0.004 m−1.