基坑开挖对临近地铁隧道力学性状的影响研究

Influence of Excavation on Adjacent Metro Tunnel Mechanics Properties

基坑开挖对临近既有隧道影响的计算与评价是基坑工程实施过程中必须考虑的关键问题之一,以某基坑开挖为算例,按照隧道-土体-基坑围护结构共同作用,建立了三维非线性有限元模型。计算了基坑边线与隧道轴线成0°、30°、60°和90°夹角的4种工况,分析基坑与隧道轴线不同交角条件下,基坑开挖对隧道结构变形和内力的影响。结果表明:随着基坑开挖深度的增加,基坑开挖引起隧道结构变形和内力的改变更加明显;随着与基坑距离的增大,隧道结构受基坑开挖的影响逐渐减弱;隧道与基坑的相对位置不同,基坑开挖引起隧道结构的受力变形差异明显,随着二者交角的增大,隧道结构的竖向变形逐渐增大,侧向变形逐渐减小,而轴力和弯矩变化较为复杂。

The influence of excavation on adjacent existing tunnel is one of the key issues that must be considered during pit excavation process. Taking a pit excavation for example,a 3D nonlinear constitutive model that consists of the tunnels,surrounding soils and foundation pit support structure is established. The four conditions of the angle which includes 0°,30°,60°and 90°between tunnel axis and the pit sideline have been calculated,the regularities distribution of tunnel structure deformation and internal force due to excavation under different angles have been analyzed. The results show that the deformation and internal force of tunnel structure have more obvious changes induced by excavation with the increase of excavation depth. With the increase of the distance between tunnel and foundation pit,the influence gradually weakened. There are obvious differences on the distribution of deformation and stress of tunnel structure under different positions. With the increase of crossing angle,the tunnel structure vertical deformation increases,lateral deformation decreases,while the axial force and bending moment changes are complicated.