Analysis of tunnel face stability with advanced pipes support

Abstract

To keep the tunnel face stable is very important for tunnel construction. In this paper, the tunnel face stability under the advanced pipe was analyzed using the Winkler foundation model and rigid limit equilibrium. The tunnel face deformation characteristics were also analyzed using the numerical simulation. The influence of parameters on the deflection of the pipe roof and the stability of the tunnel face were discussed. The results show that the tunnel face stability can be improved through increasing the pipe diameter, decreasing the initial displacement at the beginning of the pipe seat, and adopting the short round length and small excavation height. With the increase of tunnel burial depth, the safety factor of tunnel face stability first decreases, then increases, and then remains unchanged. The deformation at the center of the tunnel face is larger than the deformation at the surround sides and at the corner. The horizontal displacement varies little with the increasing of the pipe length. The horizontal displacement at the center of the tunnel face increases with the increase of the pipe ring spacing and the pipe longitudinal spacing. There is an optimum external angle. 保持掌子面稳定是隧道施工的重要内容. 基于温克尔地基模型和刚体极限平衡法, 对超前小导管下的隧道掌子面围岩稳定性进行了分析. 并通过数值模拟, 分析了隧道掌子面变形特征, 进而讨论了各参数对管棚挠度和掌子面稳定性的影响. 结果表明: 增大小导管的管径, 减小小导管支座处的初始位移, 采用短进尺、 小开挖高度可提高掌子面的稳定性. 随着隧道埋深的增加, 掌子面稳定性安全系数先减小后增大, 然后保持不变. 隧道掌子面中心的变形量大于周边和转角处的变形量. 水平位移随管长的增加变化不大. 掌子面中心的水平位移随着管环间距和管长的增大而增大间隔. 超前小导管存在一个最优的外插角度.