为研究紧旁侧深基坑开挖对已运营盾构隧道精细结构产生的不利影响，依托杭州某紧邻地铁盾构隧道的深基坑项目，通过接头受力-位移方程与结构间相互作用关系构建盾构隧道结构模型，采用地层-盾构隧道整体有限元三维精细化的数值模拟方法，研究旁侧卸荷作用下已有盾构隧道的管片、接头等精细结构的受力变形规律，通过现场监测数据的对比验证该方法的有效性。研究结果表明： 1)盾构隧道的变形可分为收敛变形区和环间错台区2部分； 2）盾构隧道产生7.5 mm的竖向沉降和8.5 mm的朝向坑内的水平位移，同时位移沿纵向的分布均因环间接头错台而出现阶梯状变化； 3)收敛变形区内管环出现椭圆化收敛变形，拱顶和拱腰处纵缝分别朝内和朝外张开，环内最大压应力的最高值达7.66
MPa，导致纵缝在拱顶处的渗水和拱腰处的压缩裂缝； 4）环间错台区内管环间受剪切作用导致错台变形，诱发环缝渗水； 5)基坑降水是造成隧道位移的重要影响因素，对隧道沉降量和水平位移量的贡献分别为82％和46％。
To clarify the adverse
effects induced by lateral unloading of an adjacent foundation pit excavation,
a shield tunnel structure model is established based on the joint force-displacement equation and the interaction relationship between a
metro shield tunnel and a foundation pit in Hangzhou, China. Then, an elaborate
stratum-shield tunnel finite numerical simulation
method is used to explore the force and deformation mechanisms of the segments
and joints of the existing shield tunnel caused by lateral unloading. The
effectiveness of the proposed method is validated by comparison with field
monitoring data. The results reveal the following: (1) The deformation of the
shield tunnel can be divided into a convergence deformation zone and a ring
dislocation zone. (2) A 7.5 mm vertical settlement and an 8.5 mm horizontal
displacement towards inner foundation pit are induced, and the displacement
along longitudinal direction shows a stepped shape due to dislocation between
segmental rings. (3) The segmental ring exhibits an elliptical convergence
deformation, and the longitudinal joints at the tunnel crown and the arch waist
open towards inside and outside of the tunnel, respectively. The maximum in-ring compression stress reaches 7.66 MPa, leading to leakage of the
longitudinal joints at the tunnel crown and compression crack at the arch
waist. (4) Dislocations between adjacent rings occur at circumferential joints,
leading to leakage. (5) Foundation pit dewatering is a primary factor affecting
tunnel displacement, which contributes 82% of settlement and 46% of horizontal
displacement, respectively.
