Mechanical Response Characteristics of Shallow-buried Concealed Rectangular Large-section Tunnel in Soft Soil Stratum

Abstract

Objective The study aims to explore the technical methods for safe and effective construction of shallow-buried concealed rectangular large-section tunnels in urban soft soil stratum, so as to achieve safety control of the construction process. Method Taking a subway section tunnel project as example, the 4-guiding hole excavation and the 6-guiding hole with middle-guiding hole leading excavation two schemes are proposed. A three-dimensional numerical simulation model is established using finite difference software, to simulate the tunnel construction process and analyze the vertical displacement of the stratum and the changes in the initial support internal force during the tunnel construction process in detail. By analyzing and comparing with the on-site monitoring data, the rationality and effectiveness of the proposed scheme are verified. Result & Conclusion During the guiding hole excavation phase, the vertical stratum displacement at the top and bottom of the tunnel is most significant, and the excavation of the adjacent guiding hole has limited influence on the displacement. Using the 6-guiding hole excavation scheme, the maximum displacement value at the bottom is significantly reduced by 21.5% compared with the 4-guiding hole excavation scheme. At the same time, the vertical displacement rate at the bottom is also reduced by 6.1% during the construction process. In particular, during the construction of the middle guiding hole, the change rate of the vertical stratum displacement is about 1.2 times of that of the side guiding hole, indicating that the middle guiding hole has a more significant impact on the stratum. The 6-guiding hole excavation scheme is more effective in controlling stratum deformation and structural stress during construction, especially during the construction stage of the middle guiding hole, thus requiring special attention and strengthened monitoring and support measures.

Keywords

• subway
• tunnel construction
• soft soil stratum
• shallow-buried concealed scheme
• rectangular lager-section