Study on reinforcement of segment lining structure for large-scale underwater shield tunnel

With a large-scale underwater shield tunnel as the background, the mechanical distribution characteristics of the segment lining structure in the stage of operation is analyzed by establishing a 3D shell-spring model, and the rules are verified primarily by an analogy model test, and so the reinforcement optimization measures of major steel are proposed. Then, the stress distribution in the segment structure under the jack thrust action during construction is analyzed by the 3D segment combination model, and the laws are testified by statistics of the segment cracks counted on the construction site, and so partial reinforcement measures for segment lining is derived. The study shows as follows: The maximum bending moments on the edge of the segment width are bigger than those in the middle of the segment width, so we suggest that the reinforcement ratio of major steel changes gradually in ladder-like distribution along the direction of the segment width; the stress concentration of the segment during construction mainly occurs on the edge of the segment, and we propose that the whole steel skeleton with large stiffness be added here; under the jack thrust action, the average stress concentration of the segment is like slope-shaped, but the shearing stress concentration is like shear-shaped, so we advise that partial reinforcement bars will be determined by the stress direction. The paper can provide valuable preference to reinforcement design of the segment structure and security appraisal of segment lining for the shield tunnel.