平行盾构隧道施工对既有隧道影响的数值分析

采用三维有限元方法对平行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相互作用,管片衬砌结构的横观各向同性性质。计算结果表明,既有隧道在盾构机附近主要产生纵向上的不均匀沉降和侧移,在盾构机后方主要产生横断面内的旋转。新隧道的修建还将使既有隧道受到“侧向加载”效应,使其横断面内的弯矩减小,轴力增大,且左、右侧受力不再对称。既有隧道纵向受力出现先受压、后受拉的特征,且在远离新隧道侧将出现最不利应力状态。分析表明盾构机顶进力、注浆压力和地层损失对既有隧道的影响较大,施工中应严格控制,而顶进反力的影响相对较小。该工作为类似工程的施工提供参考。

Numerical analysis of effects of parallel shield tunneling on existent tunnel

3D-FEM is applied to simulate the construction of parallel shield tunnels, and the laws of displacement, deformation and internal force of the old tunnel are analyzed along with the dynamic driving of the new one. In analyzing the interaction between shield machine and lining structure is taken into consideration in the model, as well as the transverse isotropy of lining structure. The results show that in the existent tunnel longitudinal nonuniform settlement and lateral displacement appear around the shield machine, and traverse torsion occurs behind the shield machine. The construction of new tunnel will apply the “lateral loading” effects to the old one, decrease the moment and increase the axial force in the traverse section, and make the internal force state of left and right sides to be not symmetrical any more. The longitudinal force-bearing state of the existent tunnel experiences a process of first compression followed by tension, and the most unfavorable stress state appears in its side far away from the new one. The thrust force, grouting pressure, and stratum loss, which should be controlled strictly, have great effects on the old tunnel; and the counterforce of thrust has a minor effect comparatively. This work offers references for the construction of similar engineering.