Abstract:

A design model that can reflect the structural characteristics of largediameter shield tunnels in soft ground and ensure the safety of lining structures is a necessary. Hence, a calculation model for design of lining structure of largediameter metro shield tunnel used in soft ground of South Extension Line on Guangzhou Rail Transit Line No. 4 is established by software ANSYS. And then the sensitivity of the factors affecting the lining structures of largediameter shield tunnels, i.e. horizontal lateral pressure coefficient, foundation spring stiffness, segment thickness, segment joint position and segment partitioning number, is analyzed based on back analysisobtained design model. The results show that: (1) A calculation model that can reflect actual mechanical behaviors of lining structure and ensure the structural safety can be obtained by adopting soil spring to simulate the bottom reaction force and adjusting the range of the spring in the design model. (2) The structural performance of the lining is sensitive to the lateral pressure coefficient and the thickness of the segment, but not to the stiffness of the foundation stiffness. (3) The segment joint position and segment partitioning number mainly affect the mechanical performance of the segments within the range of foundation springs.

Key words: soft soil foundation, largediameter metro shield tunnel, lining structure, foundation spring, design model, numerical analysis