浅埋隧道变基床系数下管棚的力学机制分析

Mechanical mechanism of piperoofs with variable coefficient of subgrade reaction in shallow tunnels

针对管棚法施工中常基床系数下管棚弹性地基梁模型的缺陷,分析了掌子面前方岩土体基床系数分布规律,建立了变基床系数下管棚的地基梁模型,该模型可考虑掌子面水平位移的影响。并用有限差分法对该模型进行了计算,深入分析了开挖过程中管棚的受力和变形。结果表明:考虑掌子面水平位移影响是非常必要的,做好掌子面加固工作对减小管棚的变形较为有效。同时,管棚力学行为与开挖面位置、开挖进尺及岩体泊松比等因素有很密切的关系,可为管棚的优化设计及施工方案的合理选择提供一定的理论基础。

In order to improve the elastic foundation beam model for piperoofs with constant coefficient of subgrade reaction, the distribution law of coefficient of subgrade reaction in front of the excavation face is discussed. Furthermore, the new elastic foundation beam model with variable coefficients of subgrade reaction is established, in which the lateral deformation effect of the excavation face is taken into account. And it is calculated by finite difference method. The forces and deformations of piperoofs are compared under different conditions. The results show that it is necessary to take the lateral deformation effect of excavation face into account during the analysis, and that the deflection deformation of piperoofs can be effectively reduced by reinforcing the excavation face. Simultaneously, the results also indicate that mechanical behaviors of piperoofs colsely relate to the location of the excavation face, the footage of the tunnelling cycle and the Poisson＇s ratio. The conclusions can be reference for the design parameter optimization and the construction scheme selection of piperoofs.