Quasi-Rectangular Shield Tunneling Technology in the Ningbo Rail Transit Project: Fid-Bau Portal

Quasi-Rectangular Shield Tunneling Technology in the Ningbo Rail Transit Project

Liu, Xian / Liu, Zhen / Yuan, Yong / Zhu, Yaohong

Abstract The cross-section form of shield tunnels has gone through several phases, from rectangular to circular, and then to non-circular. When a tunnel is constructed in city centers, a suitable cross-section for the tunnel is rather important because of space restriction. The quasi-rectangular shield tunnel is a new alternative for shield driven tunnels in urban railway transportation which combines the advantages of DOT shield tunnel and rectangular shield tunnel. In order to study the key design and construction techniques of this new tunnel structure, the world’s first quasi-rectangular shield tunnel is designed and utilized in one interval of Ningbo Metro Line 3. In this paper, scientific research as well as engineering application during the whole process of this tunnel project are introduced. Scientific research includes shield design, lining design, full-scale ring test, model test for synchronous grouting and ground settlement induced by tunneling, etc. Because the bearing capacity of this new structure is of great importance during its utilization period, as it is related to the safety reserve. So the mechanical behavior of this quasi-rectangular segmental tunnel lining is particularly investigated by conducting a full-scale ring test. In engineering application, great attention is paid to ground deformation, axis deviation and lining floating of the tunnel. By utilizing technical system to solve the problems of space restriction in high-density city area. Reasonable research plans and technical routes are presented through the analysis of some key points of quasi-rectangular shield tunnel, which laid the foundation for the further application and achievements of this new type shield tunnel.