软土地基大直径地铁盾构隧道衬砌结构受力特性数值分析研究

Numerical Analysis of Mechanical Behaviors of Lining of Large-diameter Metro Shield Tunnel in Soft Ground

为得到能真实反应软土地基大直径盾构隧道结构受力特点又能保证衬砌结构安全的设计模型,结合广州轨道交通4号线南延段大直径地铁盾构隧道结构现场实测结果,采用ANSYS软件研究适用于软土地基大直径盾构隧道衬砌结构设计的计算模型。基于反分析得到的设计模型,对水平侧压力系数、地基弹簧刚度、管片厚度、管片接头位置、管片分块数量等影响大直径盾构隧道衬砌结构受力特性的因素进行敏感性分析。结果表明:1)采用地基弹簧模拟底部反力并通过调整弹簧的范围可得到既能真实反映衬砌结构受力特性又能保证结构安全性的计算模型; 2)衬砌结构受力对侧压力系数和管片厚度敏感,对地基刚度不敏感; 3)接头位置变化和管片分块数量主要影响布置地基弹簧范围内的管片受力。

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.