盾构法修建正交下穿地铁隧道对上覆隧道的影响分析

在地铁工程中,常采用盾构法修建正交下穿隧道,新隧道的掘进不可避免地对既有隧道产生影响。采用三维有限元方法对正交下穿盾构隧道施工进行模拟,分析新隧道动态掘进时既有隧道位移、变形和内力的变化规律。模型中考虑了盾构机与管片衬砌的相互作用,以及管片衬砌结构的横观各向同性性质。计算结果表明,新隧道施工时既有隧道将产生不均匀沉降、不均匀侧移和扭转,且在对称面上出现最大值。对称面上管片的变形与受力出现先“加载”、后"卸载"、再“加载”的特点,同时该处的纵向弯矩不断增大,并在隧道底部产生较大拉应力。本文所研究的内容可为类似工程的施工提供参考。

Analysis of Influence of Undercrossing Subway Shield Tunneling Construction on the Overlying Tunnel

Undercrossing tunnels are frequently constructed by the shield-driven method in metro projects.Shield tunneling affects the existing tunnel inevitably.By means of 3D-FEM,the process of undercrossing shield tunnel construction is simulated and the changing laws of displacement,deformation and internal forces of the existing tunnel are analyzed.The interaction between the shield and segments and transverse isotropic characteristics of the segment structure are taken into consideration in the model.The results show that there appear in the existing tunnel differential settlement,and nonuniform lateral displacement and torsion,and they reach their peak values on the plane of symmetry.On the symmetrical plane,the deformation and internal force of the segments experience a sequence of loading,unloading and reloading.At the same time,longitudinal moments grow up continuously in the same places and great tensile stresses appear at the bottom of the existing tunnel.This paper offers references for the construction of similar projects.