平行隧道开挖引起上方既有隧道的纵向变形研究

城市地铁隧道大多数采用平行双洞的布置形式作为隧道设计施工方案，根据不同的地层条件等因素采用盾构法或暗挖法施工。由于城市地下空间变的越来越拥挤，研究新建平行双洞隧道施工过程中对邻近既有隧道的影响程度问题显得尤为重要。本文基于两阶段分析方法研究预测平行双洞隧道开挖引起上方已建隧道的纵向变形的简化解析方法。首先，采用两高斯曲线叠加，计算新建平行双洞隧道施工引起的作用在既有隧道上的附加荷载。然后，将既有隧道考虑为Winkler 地基上的Timoshenko梁，建立既有隧道纵向变形的基本微分方程，并基于Galerkin 法进行求解。将本文提出的简化解析方法得到的结果与工程沉降实测数据进行对比以验证本文提出的预测方法的合理性。最后，进行了参数敏感性分析，研究了不同隧道相互位置、地层损失率、相对抗弯刚度和地层土性参数等对结果的影响规律。

Longitudinal deformation of existing tunnel due to underlying twin-parallel tunnels excavation

Most urban subway tunnel use parallel form as the tunnel design and construction scheme. And the construction methods are divided into shield method or subsurface excavation method according to different factors such as the geological conditions. Because the urban underground space has become more and more crowded, the study on the influence degree of the existing tunnel due to underlying twin-parallel tunnels excavation is particularly important. In this paper, the simplified analytical method is proposed baesd on the two-stage method to obtained the longitudinal deformation of existing tunnel due to underlying twin-parallel tunnels excavation. In first stage, the impact of twin underlying tunneling on the existing tunnel is taken as the superposition of two separate modified Gauss-distributed loading induced by each twin tunnels. In second stage, the existing tunnel is simplified as Timoshenko beam on Winkler foundation. Then the problem was analytically solved accordingly by using Galerkin method. The proposed prediction method is verified with the practical tunnel engineering. Finally, the parametric studies including different tunnel location, formation loss rate and relative bending stiffness and mechanics parameters of soils are presented to investigate the influence rules on longitudinal deformation of metro tunnels.