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大西铁路客运专线上白隧道全长1717m,最大开挖断面187.08m2,最大开挖跨度16.4m.该隧道最大特点为全隧均穿越水平干燥粉细砂地层,由于施工难度大、安全风险高,于2011年被原铁道部列为极高风险隧道.其中出口正洞掌子面在前期对各种处理措施采用试验性施工阶段发生了初期支护大变形,上白隧道出口开挖过程中由于漏砂导致初期支护发生沉降大变形,最大沉降量67cm,平均沉降量49cm,19m范围的初期支护拱架侵限需要进行换拱处理.在采用传统注浆先加固后换拱的处理方案未能成功后,利用以反向施做旋喷咬合桩为核心的综合施工技术,成功解决了干燥粉细砂层等不良地质大断面隧道发生初期支护大变形后的换拱施工技术难题,取得了良好的经济效益及社会效益,颇值类似工程借鉴.“,”Shang-bai tunnel of Datong-Xi'an High-speed Railway have length of 1 717m, the largest excavation section is 187.08m2, and the largest excavation span is 16.4m. The most important feature of the tunnel for the whole tunnel through the level of dry powder fine sand strata in 2011 due to the difficulty of construction, high security risks, classified as high risk by the former Ministry of Railways tunnel. Which exports hole on white tunnel exit during the excavation of tunnel face using a variety of measures in the early the experimental construction phase large deformation of the initial support, the initial support settlement of large deformation occurs due to sand leakage, the maximum settlement amount 67cm, the average settlement 49cm, 19m range of initial support gantry intrude limit the need for change arch. Adverse geological section tunnel using traditional grouting reinforced after successful treatment program has failed to change the arch churning do to reverse measures bite pile construction technology as the core, successfully resolved the dry powder fine sand layer the initial support construction of large deformation change arch technical problems, and achieved good economic and social benefits, quite a value similar projects.