基坑开挖对既有盾构隧道的影响研究

Study on the Influence of Foundation Excavation on Existing Shield Tunnel

为分析基坑开挖对既有盾构隧道的影响,通过数值计算软件模拟盾构隧道施工过程,得到基坑开挖前盾构隧道的应力状态;并以此为基础,进行基坑开挖对盾构管片变形与应力影响的全过程研究。结果表明,双排桩支护方式下,基坑开挖至坑底时,区间隧道距坑底最近的拱肩位置处变形最大,以水平位移为主,最大达6. 77 mm;管片竖向隆起量较小,最大值为1. 31 mm,管片拱肩部位存在一定的应力集中,最大应力达3. 52 MPa;管片拱腰部位X向应力较小,最大值为0. 3 MPa。随基坑内部结构的施工,盾构管片变形逐渐减小。依据变形、应力等控制指标,对最不利条件下管片位移、应力及曲率半径等参数进行安全影响评估,认为该工程条件下,基坑开挖对区间隧道影响较小。

In order to analyze the influence of adjacent foundation pit excavation on the existing shield tunnel, the numerical simulation is used to simulate the construction process of the shield tunnel, and the stress state of the shield tunnel before the excavation is obtained. Based on this, the influence of foundation pit excavation on deformation and stress of shield segment in the whole process has been studied. The results show that under the double-row pile support mode, when the foundation pit is excavated to the bottom of the pit, the maximum deformation appears at the spandrel of interval tunnel closest to the bottom of the tunnel, which is mainly horizontal displacement, up to 6.77 mm;vertical uplift of the segment is smaller, with a maximum value of 1.31 mm, while there is a certain stress concentration in the section of the arched shoulder, with a maximum stress of 3.52 MPa;the X-direction stress of the segment hance is small, and the maximum value is 0.3 MPa. With the construction of the internal structure of the foundation pit, the deformation of the shield segment is gradually reduced. According to the control indexes such as deformation and stress, the safety impact assessment of the displacement, stress and radius of curvature of the segment under the most unfavorable conditions is carried out. It is considered that under the engineering conditions, the foundation pit excavation has less influence on the interval tunnel.