NUMERICAL SIMULATION OF SUBSEA SHIELD TUNNELING PROCESS

To accurately simulate the construction mechanical effects of the subsea shield tunneling process, this study develops a three-dimensional numerical model of shield machine-grouting body-surrounding rock-seawater interaction based on the subsea shield section of Xiamen Metro Line 2. By validating the analysis results with measured data of the project, the effects of four main factors(excavation face support pressure, formation loss rate, grouting pressure, and jacking force) are further investigated. The results show that the water and soil pressure of the segment is strongly disturbed by the construction at the initial stage, and then decreases sharply and rapidly at a decrease of about 100kPa, and then decreases slowly at a decrease of about 20kPa, and finally tends to be stable. It is most reasonable to set the support pressure of the excavation face at about 320kPa. The increase of the support pressure only affects the soil deformation within a certain range in front of the excavation. Due to the large buried depth, the vertical displacement of the surface is basically not affected. The ground layer loss rate has a great influence on ground settlement, segment buoyancy, and segment internal force. As the stratum loss rate increases by 1%, the surface subsidence increases by 241.3%, the segment buoyancy decreases by 38.2% and the bending moment decreases by 23.9%. The grouting pressure has a great influence on segment buoyancy and internal force. The grouting pressure increases by 10%, segment buoyancy increases by 32.1%, and bending moment increases by 24.3%. The study also demonstrates that the jacking force has a certain influence on the axial force of the segment along the tunnel axis but has little influence on the segment floating and bending moment. This research provides a reliable analysis of the construction mechanical effects of the subsea shield tunneling process, which has an in-depth influence on the segment structure design and subsea shield construction parameter control.