摘要
随着大跨度盾构隧道工程数量的不断增加和运营时间的延长，其独特的内部构件问题日益突出，表现出独特的特点。为揭示中隔墙顶部混凝土开裂机理，以南京地铁某大跨度盾构隧道段为背景，采用现场调查和扩展有限元分析相结合的方法，研究了隧道结构内部混凝土的开裂模式、分布特征及开裂过程。结果表明：（1）中隔墙顶部混凝土裂缝96处。根据裂纹的扩展路径、数量和形状，可分为Ⅰ型、Ⅱ型、Ⅲ型、Y型和Z型，其中Y型和Z型为Ⅰ型。（2）裂纹开始于烟道板水平差位移的对面。ⅰ型和ⅱ型裂纹长度和端宽的发展曲线表现出明显的三阶段特征。裂纹端宽与长度呈非线性关系，随着i型和ii型裂纹端宽的快速增长，临界裂纹长度分别为250 mm和225mm。(3)在ⅱ型裂纹中,在相同工况下,两个裂纹的扩展曲线基本一致,板缝间距对曲线各阶段的长度和斜率影响很大。Ⅲ型裂纹的第一裂纹扩展过程与Ⅰ型和Ⅱ型裂纹基本一致，另外两种裂纹的扩展具有明显的脆性特征。
Abstract
With the ever-increasing number of large-span shield tunneling projects and the extended operational time, their distinctive internal component issues are becoming more pronounced and exhibiting unique characteristics. In order to reveal the cracking mechanism of concrete on the top of the middle partition wall, based on a large-span shield tunnel section of Nanjing Metro, the crack mode, distribution characteristics, and cracking process of concrete inside tunnel structure were studied by combined field investigation and extended finite element analysis. The results showed that: (1) there were 96 cracks of concrete on the top of the middle partition wall in the interval. Based on the propagation path, number, and shape of cracks, they could be divided into type I, II, III, Y, and Z, with type-Y and type-Z being subtypes of type-I. (2) The crack started at the opposite side of horizontal differential displacement of the flue plate. The development curves of the length and end width of type-I and type-II cracks showed the significant characteristics of three stages. The relationship between crack end width and length was nonlinear, showing that 250 and 225 mm, respectively, were the critical crack lengths growing with the rapid growth of the end width of type-I and type-II cracks. (3) In type-II cracks, the propagation curves of two cracks under the same working condition were consistent, and the spacing of plate joints greatly influenced the length and slope of each stage of the curve. For type-III cracks, the first crack propagation process was basically consistent with type-I and type-II cracks, and the propagation of the other two cracks had obvious brittle characteristics.
NETL
NSTL
Wiley