新建盾构隧道近接施工对既有隧道纵向变形影响研究

Research on Effects of Adjacent Construction of New Shield Tunnel on Longitudinal Deformation of Existent Tunnel

基于Mindlin解和Loganathan公式对盾构施工正面附加荷载、侧壁摩擦力及盾尾土体损失作用分别进行数值积分求解,得出土体弹性位移场;借助Pasternak地基模型建立既有隧道受荷变形平衡微分方程,得到既有隧道因新建隧道盾构施工产生的附加位移。应用该解析解计算分析平行、正交以及重叠三种形式盾构隧道施工的影响,并采用有限元软件,考虑开挖卸荷、盾尾注浆及掌子面顶进等施工过程,对上述三种工况进行三维数值模拟。将数值模拟、实测值及理论分析结果对比分析发现,三者整体上吻合较好,验证了本文新建盾构隧道对既有隧道纵向变形理论分析方法的正确性。为快速评估盾构近接施工对既有盾构隧道结构安全的影响提供了新途径。

Based on the Mindlin solution and Loganathan formula, the elastic displacement field of soil caused by bulkhead additive thrust, friction force and ground loss between shield and soil was obtained by using numerical integration. The equilibrium differential equation of the load-induced deformation of existing tunnel was established by means of Pasternak foundation model, to obtain the additional displacement of the existing tunnel caused by the construction of new shield tunnel. The effects of shield tunneling in parallel, undercrossing and overlapping forms were analyzed by above analytical solution, and the adjacent construction of the three forms above was simulated in 3D model by using finite element software with consideration of step excavation, grouting at the tail, and face support process. At last, the comparison and analysis of the results of theoretical analysis, finite element numerical simulation and field monitoring showed good agreement among the three and verified the correctness of this theoretical method, which provides a new way to evaluate the effects of adjacent construction of the new shield tunnel on the safety of existent tunnel.