Deformation control strategies for shield tunnel underpassing viaduct of high-speed railway: A case study

Abstract

The impact of shield tunneling in close proximity to existing underground structures is a matter of great concern, especially in the construction of shield tunneling underpassing viaduct of high-speed railway. Improper handling of such situations can lead to a significant risk to the safety of these structures, thereby rendering construction activities particularly challenging. To effectively reduce these effects in the shield tunnel proximity construction, a comprehensive deformation control strategy of implementing isolation pile and steel lateral bracing after sleeve valve pipe grouting is proposed. The internal force and deformation characteristics of existing pile foundation groups are studied and compared with conventional reinforcement measures. The results show that grouting reinforcement and isolation pile reinforcement have limited effect, while the reinforcement efficiency of the comprehensive deformation control strategy exceeds 200%, which is more effective in controlling pile displacement and internal forces. Compared to no reinforcement, the maximum axial force and bending moment of existing pile foundations are reduced by 77% and 60%, respectively, while the maximum horizontal displacement and vertical settlement are reduced by 76% and 19%, respectively. The settlement of the cushion cap is 1.37 mm, which is verified through on-site construction, meeting the requirements for safe construction.