Abstract:In order to explore the reasonable cross-section form and optimization ideas of open-cut super-span stacked tunnels, relying on the project of Wanghai Road, with the help of numerical simulation methods, the structural stress characteristics of super-large-span double-layer tunnels were analyzed. The selection of cross-section form, span optimization and the influence of overburden for super-span stacked tunnels are also studied. The results show that the bending moment of the roof and floor of the super-span stacked tunnel is too large, and the middle plate is eccentrically pulled. The tension of the middle plate is attributed to the excessive span and insufficient restraint of the lateral soil to the structure. In terms of mechanical performance, the micro-arch section of the open-cut tunnel frame structure is better than the straight wall folded plate section, and the straight wall folded plate section is better than the straight wall flat top section. Considering the mechanical performance of the structure, the section utilization rate and the economy, it is recommended to use the straight wall folded plate section for the open-cut long-span laminated tunnel. Reducing the structural span can significantly improve the stress of the super-span double-layer tunnel, especially the axial force and bending moment of the middle plate can be greatly reduced. Section 1 has the greatest comprehensive advantages in terms of mechanical performance and engineering consumption.Under the condition of shallow burial, it is recommended to replace the overlying soil with foamed concrete to reduce the bulk density of the overlying soil. It can reduce the internal force of the roof section of the tunnel structure and improve the stress conditions of the roof plate.
