关键词: 衬砌结构;围岩灌浆;排水孔;外水压力;渗透系数;秦岭隧洞;引汉济渭工程;

Abstract: Aiming at high groundwater head exerted on Qinling tunnel in Hanjiang-to-Weihe River Valley Water Diversion Project, three types of linings, totally impermeable lining, low permeable lining, ling with drainage holes, were studied by numerical calculation considering without and with grouting layer. The variation of external water pressure on lining is analyzed under different working conditions, and the validity of drainage hole design is proved through typical tunnel section. The results show that the external water pressure on secondary lining decreases gradually with enhancement of lining’s permeability. When the lining is permeable partly and without drainage holes, the smaller the permeability coefficient of grouting layer is, the smaller the external water pressure on lining is, and the external water pressure and seepage flow on lining decreases with the increasing thickness of the grouting layer. However, when the thickness of the grouting layer reaches a certain level, the external water pressure on lining still decreases but with a mild reducing amplitude. The application of surrounding rock grouting and drainage holes can greatly reduce the external water pressure on secondary lining and reduce the seepage flow effectively. It is concluded that the surrounding rock grouting plus drainage holes has good effect, which could reduce groundwater pressure head on the second lining to nearly 0.

Key words: lining structure; surrounding rock grouting; drainage hole; external water pressure; permeability coefficient