锦屏二级水电站深埋隧洞施工难点解析

锦屏二级水电站深埋长隧洞群平均埋深达到1 500~2 000 m，地应力高，工程地质条件复杂，超高压大流量地下水、岩爆、围岩大变形是世界性难题。为解决以上问题，对锦屏二级水电站深埋长隧洞群施工难点进行探讨，主要研究内容和结论如下： 1）地下水处理采用“以堵为主、堵排结合”的总体设计原则，采用的处理技术有引流、局部封堵、系统的高压固结灌浆和分流导洞封堵等； 2）从“以防为主”和“以治为主”2个方面讨论岩爆防治方法，重点论述应力解除爆破和TBM掘进的岩爆处理； 3）分析软岩大变形产生的原因及采取的处理措施，重点论述上台阶扩挖洞径的确定和落底开挖前的加强支护措施。

Analysis on Difficulties in Construction of Deep-covered Tunnels:Case Study on Tunnels of Jinping Ⅱ Hydropower Station

The average cover depth of the tunnels of Jinping II Hydropower Station ranges from 1 500 m to 2 000 m. These tunnels have high ground stress and complex engineering geological conditions. Rock burst, groundwater with super high pressure and large flow rate, and large deformation occurring during the construction of these tunnels are worldwide difficult problems. The difficulties in the construction of the deep covered tunnels of Jinping II Hydropower Station are discussed in the paper. The main contents of the study are as follows: 1) The principle of “taking water stopping as the main measure, with water releasing as the assistant measure” is followed. Water coping technologies, such as guided water drainage, local water stopping, high pressure grouting, and water releasing through distributary tunnel, are used. 2) The prevention and control of rock bursts are discussed in terms of “taking prevention as the main measure” and “taking the control as the main measure”. The technology of distress blasting and rock burst prevention in TBM tunneling are discussed with emphasis. 3) The causes and countermeasures for serious deformation of soft rock mass are analyzed. The determination of the diameter the enlarged top heading of the tunnel and the strengthening support made before tunnel bottom excavation are discussed with emphasis. 