扁平率对超宽断面隧道结构受力的影响分析

Analysis of Effect of Flatness Ratio on Stress of Ultra-wide Cross-section Tunnel Structures

摘要:

城市化进程加速背景下，超宽断面隧道因适应交通功能的需求成为地下工程发展的重要方向。因此，对超宽断面隧道的围岩变形及支护受力性能的研究具有重要意义。以广东某暗挖隧道工程为依托，采用有限元软件GTS建立二维有限元模型，通过对周边土体位移以及支护结构受力进行分析，研究不同扁平率下超宽断面隧道的结构受力特点，进而总结出超宽断面隧道最佳扁平率。分析结果表明：（1）隧道拱顶土体竖向位移随着扁平率的增加而降低，在扁平率为0.5~0.6区间降幅较大，0.6~0.7区间降幅较小；（2）整体而言，在扁平率为0.60~0.65区间，隧道初支轴力和弯矩较小；（3）扁平率在0.50~0.55区间时，隧道初支与临时支撑交接处弯矩较大，而在0.60~0.65区间，该处弯矩显著减小；（4）对于强风化花岗岩地层中的超宽断面隧道的建议设计扁平率为0.60~0.65。

Abstract:

With the accelerated urbanization process, the ultra-wide cross-section tunnels have become an important direction for the development of underground engineering due to their adaptation to the demands of transportation functions. Consequently, the research on the deformation of surrounding rock and the mechanical behavior of support for the ultra-wide cross-section tunnels is of paramount importance. Relying on a bored tunnel project in Guangdong, the finite element software GTS is used to establish a 2D finite element model. By analyzing the displacement of surrounding soil and the stress of support structure, the stress characteristics of ultra-wide cross-section tunnel structures under the different flatness ratios are studied so as to summarize the optimal flatness ratio of ultra-wide cross-section tunnel. The analysis results indicate that (1) The vertical displacement of tunnel vault soil reduces with the increase of flatness ratio. The decrease is relatively large in the flatness ratio range of 0.5~0.6, and relatively small in the range of 0.6~0.7. (2) As a whole, in the range of flatness ratio 0.6~0.65, the axial force and bending moment of the initial support of the tunnel are relatively small. (3) When the flatness ratio is within the range of 0.5~0.55, the bending moment at the connection of the initial support and the temporary support of the tunnel is relatively large, and within the range of 0.6~0.65, the bending moment at this location is significantly reduced. (4) The recommended design flatness ratio for ultra-wide cross-section tunnels in strongly weathered granite strata is 0.60~0.65.