Qilian Mountain Tunnel is located in the strata with developing underground water and weak broken rock, and the tunnel portal passes through F6 and F7 regional faults with the geological phenomenon of clastic flow. Because of the possibility of large deformation, quick deformation speed, unstable surrounding rocks during excavation, the construction risk of Qilian Mountain Tunnel is very high. This paper carried out design and research on the clastic strata of the portal of Qilian Mountain Tunnel, presented an integrated design scheme based on the pre-strengthening, double-layer supporting and the heat insulation technology. In addition, three-bench seven-step method was adopted at the part of the tunnel portal where the geological condition was relatively good and the water is less; three-bench with temporary inverted arch method was adopted at the part with weak broken rocks and rich underground water. The results of construction monitoring show that the maximum deformation of surrounding rocks is 197 mm within the allowable range, so the design and construction measures are reasonable and feasible.%祁连山隧道地下水发育,岩体软弱破碎,进口段穿越F6、F7区域性断裂,存在碎屑流地质现象,隧道开挖后变形大、变形速度快,易造成围岩失稳,施工风险大.通过祁连山隧道进口碎屑地层的设计研究,提出了以“预加固+双层支护结构+隔热保温技术”为主的综合设计方案.对地质相对较好、水量较小的地段采用三台阶七步法；岩体软弱破碎、水量大的地段采用三台阶临时仰拱法.根据施工监测结果,围岩最大变形为197mm,在设计容许范围之内,设计及施工措施合理可行.
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