不同开挖工法下超宽断面隧道结构受力特点分析

Analysis on Mechanical Characteristics of Super-Wide Cross-Section Tunnel Structures under Different Excavation Methods

摘要:

随着经济和社会的发展，为满足城市交通功能的需求，超宽断面隧道逐渐增多。因此，对超宽断面隧道的围岩变形和支护受力性能进行研究具有重要意义。结合广东省某暗挖隧道工程，采用有限元软件GTS建立二维有限元模型，通过对隧道周边土体位移和支护结构受力情况的分析，研究不同开挖工法下超宽断面隧道的结构受力特点。分析结果表明：采用中隔壁法（CD法）施工，土体竖向位移主要发生在右侧导洞施工过程中，而采用双侧壁导坑法施工，土体竖向位移主要发生在中导洞施工过程中；在CD法和双侧壁导坑法施工过程中，由于应力集中，初支与临时支撑交接处的弯矩很大；与CD法相比，双侧壁导坑法在施工中的初支弯矩更小；在CD法施工过程中，右侧导洞土体的开挖会导致临时支撑弯矩迅速增大和内力重新分布，而在双侧壁导坑法的施工过程中，中导洞土体的开挖会导致临时支撑弯矩迅速增大和内力重新分布。

Abstract:

With the development of the economy and society, super-wide cross-section tunnels will increasingly emerge to meet urban transportation demands. Therefore, research on the surrounding soil deformation and mechanical behavior of support structures in such tunnels is of significant importance. Combined with a bored tunnel project in Guangdong, a two-dimensional finite element model is established using the GTS finite element software. By analyzing the displacement of surrounding soil and the mechanical response of support structures, the structural mechanical characteristics of super-wide cross-section tunnels under different excavation methods are studied. The results indicate that the vertical displacement of the soil mainly occurs during the construction of the right pilot tunnel when the central dissepiment (CD) method is adopted, and the vertical displacement of the soil mainly occurs during the construction of the central pilot tunnel when the the double-side drift method is used. The bending moments at the junctions of the initial supports and temporary supports are very large in the construction process by the CD method and double-side drift method due to stress concentration. Compared with the CD method, the double-side drift method results in smaller bending moments in the initial support. In the CD method for construction, the excavation of the right-side pilot tunnel will lead to the rapid increases of bending moments and internal force redistribution of the temporary supports. Similarly, excavation of the central pilot tunnel in the double-side drift method will lead to the analogous effects.