基坑开挖引起邻近盾构隧道转动与错台变形计算

基坑开挖会对邻近盾构隧道的变形产生显著影响。考虑基坑开挖时卸载在隧道轴线处产生的附加应力,建立了综合考虑剪切错台变形和刚体转动变形的隧道变形计算模型,结合最小势能原理推导出隧道的纵向变形量、环间错台量、环间转角和环间剪切力的计算公式。选取两组工程实例进行分析,将计算结果与实测数据进行比较。研究结果表明:邻近并平行于盾构隧道的基坑侧壁的卸荷效应对旁边隧道的影响最大;隧道水平位移最大值附近的管片基本不发生错台变形和刚体转动变形,环间剪切力值也很小;而在隧道水平位移曲线的反弯点处,隧道的剪切错台量、环间转角和环间剪切力值达到最大;在基坑开挖工况下,邻近隧道的水平位移变形模式以剪切错台为主,刚体转动为辅。

Calculation of rigid body rotation and shearing dislocation deformation of adjacent shield tunnels due to excavation of foundation pits

Excavation of foundation pits has a significant impact on the deformation of the adjacent shield tunnels. Considering the additional stress at the tunnel axis due to the soil unloading during excavation, a tunnel deformation model combining the shear-dislocation and rigid-body rotation is established. The formulas for the longitudinal deformation, segment-joint dislocation displacement, rotation angle and segment-joint shear force of the tunnel are deduced based on the principle of the minimum potential energy. Two engineering cases are selected for analysis, and the calculated results are compared with the measured data. The results show that: the soil unloading stress of the adjacent parallel surrounding wall has the largest effect on the tunnel when the foundation pit is beside the tunnels. On the location of the maximum tunnel horizontal deformation, the dislocation and rigid-body rotation of tunnel segments are close to zero, and the segment-joint shear force is also very small. At the inflection point of the horizontal displacement curve, the segment-joint rotation angle and segment-joint shear force of the tunnel both reach the maximum. Under the excavation of the foundation pit, the tunnel deformation model is mainly composed of shear dislocation and complemented by rigid body rotation.