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为了解决浅埋大跨小间距黄土隧道的设计、施工等技术难题,以桃花峪隧道工程为背景,开展了隧道合理支护体系及施工技术的研究。采用隧道现场对比试验方法,设置了小间距隧道相互影响分析试验段、不同隧道开挖方法对比试验段、型钢钢架支护体系与格栅钢架支护体系对比试验段、有系统锚杆与无系统锚杆对比试验段,在试验段内测试了隧道拱顶沉降、水平收敛、围岩压力、支护结构内力等,并对测试数据进行了综合对比分析。结果表明:在两隧道间距5m,且均采用CD法施工的条件下,后行隧道施工对先行隧道的影响较小;在喷射混凝土早期强度满足要求的条件下,型钢钢架与格栅钢架支护体系的控制变形及承载能力相当,均可适用于大跨小间距黄土隧道;在大跨小间距黄土隧道中系统锚杆作用效果不明显,可以取消,取消后可加快断面及早闭合,更有利于控制支护变形;直立中隔壁CD法更有利于控制拱顶沉降;在桃花峪隧道施工中,全隧成功采用格栅+喷射混凝土支护体系,并全部取消系统锚杆,施工采用直立中隔壁CD法,确保了施工安全,并节省了大量工程投资。
In order to solve the technical problems such as the design and construction of shallow long-span and small-span loess tunnels, the research on the reasonable support system and construction technology of tunnels is carried out under the background of Taohuayu Tunnel Project. The tunnel cross-section test method was used to set up the experimental section of interaction between small spacing tunnels, the comparative test section of different tunnel excavation methods, the comparative test section of the support system of steel frame and the steel grid support system, In the comparative test section without system anchor rod, the settlement of tunnel vault, horizontal convergence, pressure of surrounding rock and internal force of supporting structure were tested in the test section. The test data were compared and analyzed comprehensively. The results show that under the condition of 5m distance between two tunnels and using CD method, the effect of the tunnel construction on the tunnel ahead is small. When the early strength of the shotcrete meets the requirements, The control deformation and bearing capacity of the supporting system are quite comparable, which can be applied to large-span and small-pitch loess tunnels. The effect of system anchors in the long-span and small-pitch loess tunnels is not obvious and can be canceled. It is more conducive to controlling the deformation of the support; CD method of the upright middle partition wall is more conducive to controlling the vault settlement; in the construction of Taohuayu tunnel, the grid is fully supported by the grid + sprayed concrete support system and all the system bolts are canceled, In the next CD method, to ensure the construction safety, and save a lot of engineering investment.