深埋水工隧洞衬砌渗透压力控制措施研究

Seepage pressure control measures for lining of deep buried hydraulic tunnels

我国西部高山峡谷地区水电站工程地下水位高,深埋水工隧洞衬砌外水压力大,防渗排水措施要求高。为减小作用于衬砌上的外水压力,提高衬砌结构的安全性和经济性,同时减小排水对地下环境的影响,需要采取合理的围岩防渗排水措施。结合某在建水电站工程,拟采用固结灌浆、排水孔等防渗排水措施,建立泄洪洞的三维有限元模型,精细模拟固结灌浆和排水孔作用,研究不同方案下隧洞围岩浸润面变化和衬砌所受渗透压力分布规律。结果表明:泄洪洞深部固结灌浆可大幅减少围岩地下水内渗,有效降低对地下水位的影响,有利于生态环境保护;排水孔的排水降压作用显著,可有效减小衬砌所受外水压力。若需兼顾考虑地下水环境影响及有效减小衬砌所受外水压力时,可采用深固结灌浆联合浅排水孔的处理方案,且建议固结灌浆范围为5~8 m,排水孔深度1~2 m。

Groundwater levels of hydropower stations are relatively high in the western alpine gorge area.The external water pressure on the lining of deep buried hydraulic tunnel is larger.So the anti?seepage and drainage measures should be demanded strictly.In order to reduce the seepage pressure and the drainage effect on the underground environment as well as to improve the safety and economy of lining structures,it is necessary to take some effective anti?seepage and drainage measures for surrounding rocks.For a hydropower station under construction,the consolidation grouting and the drainage hole are considered as the anti?seepage and drainage measures respectively.Then,a three?dimensional finite element model of spillway tunnel is established,which can finely simulate the consolidation grouting and the drainage hole.The phreatic surface changing rule of surrounding rocks for the tunnel and the seepage pressure distribution of the lining structure are analyzed.Results show that the seepage discharge from wall rock to tunnel and the influence of drainage on underground water level would decrease if the consolidation grouting is adopted.The consolidation grouting is beneficial for to the environmental protection.In addition,the effects of drainage hole can reduce the seepage pressure on the tunnel lining remarkably.When the influence of drainage on the groundwater environment and the effect of the drainage hole are both taken into account,the treatment scheme combined with deep consolidation grouting and shallow drain holes is proposed,meanwhile the consolidated grouting area and the drain depth are suggested to be5~8m and1~2m respectively.