考虑拱效应的隧道管棚力学模型与参数分析

为了更好地研究隧道管棚的实际受力状态,根据隧道施工工序和施工影响,将隧道管棚划分为二衬段、初支段、开挖段以及掌子面前方的扰动段和未扰动段等五段,考虑管棚注浆后形成整体管棚拱的拱效应,建立了五段式隧道管棚的Winkler弹性地基梁新模型,推导了五段式隧道管棚模型的挠度和内力计算公式,并与既有工程案例进行对比分析,同时对不同的开挖进尺、管棚直径和加固区弹性模量进行了分析。结果表明:新模型得到的管棚挠度最大值和挠度最大值对应的位置与现场监测结果更为接近,能够解决已有管棚模型因边界条件设置不合理而造成的管棚变形在扰动段的末端出现的上拱现象,更符合管棚实际的变形情况;改变开挖进尺对管棚的挠度影响更大,管棚钢管直径为108 mm和114 mm时,其管棚支护效果相差不大;当E_c(加固区弹性模量)＞40.0 E_g(围岩弹性模量)时,开挖进尺和钢管直径对管棚的挠度和弯矩的影响不大,因此,提高加固区的弹性模量是减小管棚挠度和内力最有效的方法。

A Mechanical Model and Parameter Analysis for Pipe-RoofConsidering the Arch Effect

In order to better study the actual stress state of the tunnel pipe-roof, according to the tunnel construction process and construction influence, the lining segment of the pipe roof tunnel was divided into five segments: the second lining section, the primary support section, the excavation section, and the disturbed and undisturbed section in front of the palm face. Considering the whole pipe-roof arch effect formed after pipe-roof grouting, a Winkler elastic foundation beam model of the five-sections tunnel pipe-roof is established. The flexure and internal force calculation formula of the five-paragraph tunnel pipe-roof model are deduced and compared with existing engineering cases. At the same time, different excavation footage, pipe diameters and elastic modulus of reinforced area are analyzed. The results show that: The maximum deflection of the pipe-roof obtained by the new model and the corresponding position are closer to the on-site monitoring results, which can solve the problem of pipe-roof deformation in the disturbance section caused by the unreasonable setting of boundary conditions in the existing pipe-roof model. The arching phenomenon at the end is more in line with the actual deformation of the pipe-roof. Changing the excavation footage has a greater impact on the deflection of the pipe-roof. When the diameter of steel pipe is 108 mm and 114 mm, the pipe-roof support effect are similar; when E_c (elastic modulus of converging) is greater than 40.0 E_g (elastic modulus of ground rock), the excavation footage and the diameter of the steel pipe have little effect on the deflection and bending moment of the pipe-roof. Therefore, increasing the elastic modulus of the reinforced area is the most effective method for reducing pipe-roof deflection and internal force.