Super-large-diameter shield tunnel undercrossing an intercity railway with oblique angle: Centrifuge test and numerical analysis

With the development of urban infrastructure, it is inevitable that shield tunnels will undercross intercity railways. However, the safe operation of intercity railways requires strict subgrade deformation. On the basis of the engineering background of the Lianghu Tunnel in Wuhan, the three-dimensional centrifuge test and numerical back analysis were used to study the development of subgrade surface settlement during shield tunneling. A three-dimensional numerical model with the same size as the prototype was subsequently established to further study the settlement development and torsion behavior of the subgrade during tunnel excavation. The results show that the maximum settlement point of the transverse settlement trough gradually moves to the tunnel axis during tunnel excavation and that the entire subgrade experiences torsional deformation. Moreover, the effect of the intersection angle between the axes of the tunnel and the subgrade on the surface settlement of the subgrade was further studied. The results show that the intersection angle has no effect on the maximum settlement, but the width of the settlement trough increases gradually with increasing angle. Finally, on the basis of the soil arching effect caused by tunnel excavation, the subgrade settlement during tunnel excavation is reduced by reinforcing the soil in different zones of soil arching. The results show that the settlement of the subgrade caused by the shield tunnel can be effectively controlled by adding reinforcement directly to the top of the tunnel, and the maximum settlement of the subgrade surface is reduced from 24.41 mm to 9.47 mm, a reduction of approximately 61.2%.