依托在建国道317 线岗托隧道工程,结合细砂-卵砾石土互层围岩的特点,对双层小导管支护、大管棚支护、水平旋喷支护、大管棚配合水平旋喷支护4种支护方案进行了分析,比选出大管棚配合水平旋喷支护为较优方案,并对其支护效果进行了现场测试.结果表明:施工中拱顶处卵砾石土层断裂,细砂下漏导致隧道发生漏砂、坍塌、冒顶等事故,施工中应加强对地表处理、掌子面反压回填等4个关键工序的控制.经现场测试,大管棚配合水平旋喷形成的壳支护能够承受上方土体和交通荷载,并能有效阻止漏砂.%Based on Gangtuo tunnel project construction in No.317 national highway,four support schemes including double-deck small pipe support,pipe roof support,horizontal rotary jet grouting pile support and pipe roof support with horizontal rotary jet grouting pile were analyzed by combining with the surrounding rock characteristics of the fine sand-gravel soil inter-bedded stratum,and the pipe roof support with horizontal rotary jet grouting pile was selected as the best scheme,the support effect of which was tested on the spot.The results show that there are fractures of gravel soil layer in vault during construction,fine sand leakage leads to accidents of sand leakage,collapse and roof caving in the tunnel,control methods for the 4 key processes such as the surface treatment,the tunnel face back pressure and back fill,and so on should be strengthened in construction.The field test result show that the shell support system of the pipe roof with horizontal rotary jet grouting pile could bear the soil and traffic loads above the tunnel,which could effectively prevent the sand leakage.
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