为研究隧道双层初期支护中第2层支护的钢拱架设置方式和施作时机,结合成兰铁路云屯堡隧道高地应力软岩隧道工程,对 高地应力软岩大变形隧道双层初期支护中内、外2层钢拱架的布设方式和第2层初期支护的施作时机进行分析和研究。 由研究结 果可知: 1)双层初期支护中钢拱架采取交错的布置方式更有利于初期支护结构受力和围岩变形控制; 2)第2层初期支护应在第1 层初期支护结构不被破坏前及时施作,对于云屯堡隧道来说,第2层初期支护施作滞后掌子面的距离在7 m内较好。

The setting mode and construction time of the second layer steel arch support in double primary support are of great importance. As a result, the layout mode of inner and outer layers of steel arch and the construction time of the second layer of primary support for the double primary support of high geostress soft rock tunnel with large deformation are analyzed and studied by taking Yuntunbao Tunnel on Chengdu-Lanzhou Railway for example. The study results show that: (1) The staggered arrangement of the steel arch in the double primary support is more beneficial to the control of the primary support structure stress and surrounding rock deformation. (2) The second layer of primary support should be carried out before damage of the first layer of primary support; as for Yuntunbao Tunnel, the distance between the second layer of primary support and the tunnel face should be within 7 m.