浅埋双连拱隧道进洞口管棚预支护参数分析

Analysis on Parameters of Pipe Roof Advance Support Installed in Portal Sections of Shallow-buried Double-arched Tunnels

复杂地质条件下浅埋双连拱隧道围岩压力通常是不对称的,特别是隧道围岩十分软弱时更为明显。偏压作用对于围岩的稳定性产生较大影响。采用三维弹塑性有限差分方法分析偏压双连拱隧道的管棚预支护作用。管棚效能的发挥不仅与其自身的参数设计及选择有根本关系,而且也与地层参数和隧道结构参数密不可分。针对该隧道的地质条件和管棚设计要求,对钢管环向间距、钢管直径、管棚在围岩中的剩余长度、管棚力学模型、开挖进尺长度5个方面影响因素进行分析,得出偏压双连拱隧道管棚应采用不平衡设计的结论。

Under complex geological conditions, the loading on the surrounding rock mass of shallow-buried double- arched tunnels is usually asymmetrical and it is particular the case when the surrounding rock mass of the tunnel is very weak. The asymmetrical loading has serious influence on the stability of the surrounding rock mass. In the paper, the advance support effect of the pipe roofs of asymmetrical-loaded double-arched tunnels is analyzed by three dimensional elastic-plastic finite difference method. The effect of pipe roofs not only depends on their own parameters, but also depends on the parameters of the ground and the tunnel structure. In the paper, analysis is made on the perimeter spacing, diameter, length remaining in the surrounding rock mass and mechanical model of the steel pipes of the pipe roofs, as well as on the excavation advance rate of the tunnel on basis of the geological conditions of the tunnel and the design requirements of the pipe roofs and conclusion is drawn that unbalanced design should be adopted for the pipe roofs of asymmetrical loaded double-arched tunnels.