Mechanical Behavior of Urban Rail Transit Station Structure Based on Existing Shield Tunnel Interval Underground Excavation Construction

Abstract

Objective Cancer Hospital Station on Shenzhen Rail Transit Line 14 adopts a scheme of large-diameter (8.5 m) shield tunnel expansion featuring tunnel-first and station-later. During the connection of the main station structure and auxiliary entrances in underground excavation, the construction of large local openings in tunnel lining is required. To ensure the structural safety during tunnel opening construction, it is necessary to study the mechanical behavior of urban rail transit station structure based on existing shield tunnel interval underground excavation. Method To simulate the station underground excavation process under various working conditions, a multi-ring shell-rigid beam-contact lining calculation model considering the effects of lining structure circumferential and longitudinal joints is adopted. The scenarios include full-opening lining ring control condition (opening condition) and half-opening lining ring control condition (support removal condition). Key design parameters, such as the position of capping block, the forms of internal support, and the dimension of tunnel longitudinal opening, are analyzed for their impact on station structure. Result & Conclusion Based on the stress characteristics of ring beams, it is recommended to use steel or embedded steel components for the upper and lower ring beams in the design. It is recommended that the arrangement of through-joint assembled segments in the opening area should be adopted according to segment stress characteristics, and the capping block of tunnel opening section through-joint assembled segments be designed at the tunnel top for Cancer Hospital Station. The bending moment distribution of opening lining ring segments throughout construction process is closely related to the effective constraint points of internal supports, and the premise of internal supports forming effective constraint is a complete axial force transmission path. The integrity of opening lining ring structure is contingent upon the lateral constraints of circumferential joints during the local tunnel opening construction.

Keywords

• urban rail transit
• station structure
• mechanical behavior
• existing shield tunnel interval
• underground excavation construction