高应力软岩隧道超前导洞法应力释放试验研究

Experimental Study of Stress Release Using a Pilot Heading for a Highly Stressed Soft-Rock Tunnel

隧道穿越高地应力软弱围岩时，常常发生大变形地质灾害。隧道大变形灾害危害程度极大，主要表现为处理风险大、整治费用高、工期被延误。预防和治理高应力软岩隧道大变形是隧道工程界的一个重难问题。文章通过在兰渝铁路木寨岭隧道和毛羽山隧道进行超前导洞应力释放试验，得出了超前导洞法应力释放对大变形的控制作用。试验结果表明，在隧道内设置的超前导洞与隧道拱顶及边墙距离约3m左右时，超前导洞一般在3～7d内达到应力释放效果；与不采用超前导洞法相比，正洞扩挖时变形量可减少约30％～40％。

Geological disasters causing large deformations often occur when a tunnel passes through highly stressed soft rock. Such a disaster is greatly harmful to a project in terms of high risk treatments, expensive mainte- nance costs, and a delayed construction time. Therefore, preventing and treating the large deformation of a highly stressed soft-rock tunnel is a key and complex issue in tunnel engineering. Based on tests in the Muzhailing and Maoyushan tunnels on the Lanzhou-Chongqing railway, it was found that stress release by pilot heading can control large deformations. The stress is released within 3-7 days if the pilot tunnel is about 3m away from the tunnel crown and sidewalls. Additionally, the deformation of the main tunnel can be reduced by nearly 30%-40% compared to pro- jects without pilot tunnels during the enlarging excavation.