基坑开挖引起邻侧盾构隧道开裂特性研究*

为探究基坑开挖导致邻侧既有盾构隧道出现开裂破损而带来的不利影响，采用地层-结构法与荷载-结构法相结合的计算方法，同时考虑内置钢筋对混凝土的加强作用，精细化地模拟基坑开挖影响下，非连续盾构管片结构接头处裂缝的扩展过程，揭示其开裂机制。研究结果表明:基坑开挖过程中，管片衬砌“横鸭蛋”变形模式决定了其开裂范围，即左、右拱腰附近为主开裂区；管片的裂损特征为纵向裂缝，初始裂缝由左、右拱腰外弧面逐渐向两侧接头处延展，右拱腰接头处裂缝扩展连接为沿厚度方向的环状裂缝。

Study on cracking characteristics of adjacent shield tunnel caused by foundation pit excavation

In order to explore the adverse effect of the cracking and damage of existing shield tunnel on the adjacent side due to the excavation of foundation pit,a calculation method combining the stratum-structure method and the load-structure method was adopted,and considering the reinforcement effect of the built-in steel bars on the concrete,the propagation process of the cracks at the joints of discontinuous shield segment structure under the influence of foundation pit excavation was finely simulated,and the cracking mechanism was revealed.The results showed that during the process of foundation pit excavation,the cracking range of the segment lining was determined by the ‘transverse duck egg’ deformation mode,i.e.the primary cracking area was near the left and right haunch.The cracks of segment were characterized by the longitudinal cracks,and the initial cracks gradually extended from the outer arc surface of the left and right haunch to the joints on both sides,while the cracks at the right haunch joint extended and connected into a circular crack along the thickness direction.