李家峡水电站导流洞进口，地势陡峭，坡面自然高度达２００余ｍ。高程２１３０ｍ平台以下为８５ｍ高的洞脸边坡，该部分坡积物清除完后，意外地出现了ＮＳ向及ＮＥ向两组密集度很高的构造裂隙。这两组裂隙与岩层相互切割形成的不稳定体导致提前进洞失败。因此，如何在裂隙极为发育的薄层混合岩边坡上成洞便成了工程前期的头号技术难题。 Lijiaxia Hydropower Station diversion tunnel imports, steep terrain, the natural slope of more than 200 m. Elevation 2130m Below the 85m-high cave face slope, after the clearance of this part of slope, the two groups of high-intensity structural fractures, NS and NE, unexpectedly appeared. The instability created by the mutual cleavage of these two sets of fractures with the formation led to the failure of advancement of the hole. Therefore, how to make holes in thin-bedded mixed rock slopes with extremely developed fractures becomes the number one technical problem in the early stage of engineering.