复杂条件下盾构隧道用复合管环结构的力学机理研究

The composite segment has been used in the deep, long large, and multi-cross-section shield tunnels of the subway, underground road, underground pedestrian passage and underground reservoir, etc. However, the mechanical behavior of the composite segment is not clarified, because the structural type is complicated. Meanwhile, the selected structure model and parameters are not reasonable. Therefore, the designed composite segment linning of a shield tunnel has the disadvantages of safety and economy.Firstly, the combined method of 3D FEM and discontinuous boundary element is proposed based on the cohesive zone theory for considering interface slip, local buckling and damage. The stiffness reduction method using the discrete layers of segment height and the slices of segment width for considering confined effect is adopted in order to avoid the computations convergence, and has high degree of precision and clear physical meaning. Secondly, the research will study the following issues based on the experimental tests of main members and segment ring, theoretical analysis, and numerical simulation. Studies are on the differences of the mechanical behavior and failure mode between the segment and the segment ring, the effects of the dimension and material of joint, the type of segment assembly and the position of Key Segment on the stiffness and deformation, and the mechanical behavior of the the segment ring under the omplicated conditions. As a result, the proposed methods can be used to solve the coupling of multi-material and composite segment ring under multi-material and multi-scale for the composite segment ring, and are suitable for a rational design of the composite segment,and the managements of safaty and durability for shield tunnel.

复合管片已用在深长大、断面多样化的地铁、地下公路、地下人行通道和地下蓄水池等盾构隧道，但因结构形式复杂，力学机理不明确，设计模型及关键参数的选取不确定，导致其存在安全性和经济性缺陷。项目拟综合考虑复合管片界面滑移、局部失稳和损伤，首先建立一种基于内聚力理论的三维有限元和非协调边界元组合法，引入考虑约束条件的复合管片厚度分层、幅宽条分的刚度折减法，避免计算不收敛，具有较高精度和明确物理意义。其次，通过局部结构实体试验和管环结构相似模型试验，综合上述提出的力学模型和数值模拟方法，揭示单体复合管片和复合管环结构的力学和破坏特征差异；阐明接头尺寸和材质，管片拼装形式及封顶块位置对复合管环结构刚度和变形的影响规律；探究复杂条件下复合管环结构的力学机理。研究成果为复合管环结构多材质、多尺度耦合问题求解提供了一种新的思路，同时为复杂条件下复合管片结构科学设计、盾构隧道的安全性和耐久性等研究工作奠定基础。

本项目主要研究包括：.针对局部结构实体的受力变形特性分析，设置了不同的钢板厚度、主桁梁厚度、接头板厚度以及剪力键布置形式，进行了16组试验盾构隧道钢混复合管片的力学性能试验分析上述因素的敏感度；基于钢板和填充混凝土界面应变间的差值预测管片的界面滑移量，得出管片上下界面的滑移应变公式，提出了在不同荷载下的挠度修正公式。.针对复合管环结构的受力变形特性分析，建立复合管片螺栓接头模型，得出环向抗弯刚度计算公式；建立盾构隧道壳—弹簧模型，得出环间接头承载力和损伤高度的理论公式；采用混凝土塑性损伤本构模型，得出了管环结构破坏过程中接头的破坏特点；建立多材料、多尺度耦合数值模型和复杂地层条件下复合管环模型，得出了在盾构隧道复合管环结构在不同条件下的受力特性和变形规律。.针对特殊荷载下的复合管环结构的受力变形特性分析，分析总结千斤顶偏心荷载和盾尾刷反力作用下管环损伤及纵向接缝张开量的特点；建立了拼装式衬砌复合管片模型，研制了多功能管片加载模拟试验系统，得出了内水压对于接缝张开量和管环错台量的影响规律。.通过理论分析、数值模拟和试验等多方面研究，建立了能反映复合管片实际性能的多种数值模型，推导并验证了盾构隧道复合管片界面滑移应变公式、挠度修正公式和抗弯刚度公式，分析了复合管环结构在复杂条件下的力学特性。通过数值模型分析与模型试验验证表明，上述成果可以为盾构隧道复合管片的研究做理论指导，完善了盾构隧道复合管片的设计理论体系和试验方法。