Shangbai tunnel on Datong-Xi'an Passenger Dedicated Railway Line traverses the loess and sand layer boundary strata. The layer is dry, dense, and cohesionless, so it's easy to be in flow state after excavation-disturbance. Consequently, it's prone to lead to large deformation, collapse and so on at primary support step. After analysis of special geology cofferdam, an arch changing technology based on horizontal jet grouting piles cross construction at forward direction and backward direction, is proposed. And this new technology is used on large deformation section (DK596+214~+199) of Shangbai tunnel. The technology solves successfully the problem of deformation treatment of the tunnel in this kind of geology. And it's a good reference to similar geological disaster treatment and construction.% 大西客运专线上白隧道洞身穿越黄土与砂层分界地层中。该砂层干燥、致密，砂粒之间无粘结性，开挖扰动后，易成流动状态，从而导致初期支护易发生较大变形、塌方等事故。经过对该特殊地质围岩的分析，提出了对上白隧道DK596+214~+199大变形段采用正向与反向水平旋喷桩交叉施工进行换拱处理技术，成功的解决了该类地质隧道变形处理难的问题，对同类地质灾害处理和施工具有一定的借鉴意义。
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