Influence of Shield Launching and Receiving on Working Shaft Retaining Structure

Abstract

[Objective] Generally, shield machines are launched or received after completing the construction of shield working shaft main structure. However, due to various constraints, considering SLR (shield launching and receiving) beforehand is often necessary. Therefore, it is important to study the impact of SLR on shield working shaft retaining structure. [Method] Taking a standard three-storey island-type underground station of Chengdu Metro as example, the force and deformation of shield shaft retaining structure during SLR are studied when the main lining structure is not yet constructed. The impact of SLR on retaining structure stability is also analyzed. [Result & Conclusion] The research results indicate that: during SLR in an unlined working shaft, the maximum horizontal displacement and maximum bending moment of the retaining structure piles both occur at the fourth steel support of the shield working shaft end wall. The maximum shear force of the retaining structure occurs at the bottom plate of shaft end wall midspan. When main lining structure is not constructed for the shaft, the deformation and force of the retaining structure piles increase, but the displacement and mechanical indicators still meet the requirements of the specifications. The retaining structure can withstand the load and strength requirements under the action of shear force and bending moment. Therefore, SLR in an unlined shaft can improve construction efficiency, effectively saving construction time and reducing engineering costs.

Keywords

• metro
• shield launching and receiving
• working shaft retaining structure