郑西客专高桥隧道下穿既有铁路设计与施工

郑西客专高桥隧道出口下穿既有南同蒲铁路段集成了特浅埋、大断面、新黄土、小角度下穿等技术难点,由于浅埋、新黄土隧道施工易发生较大变形甚至突然性塌方,为确保下穿段施工安全和既有线运营安全、同时保证隧道建设工期,通过技术经济比选,最终确定采用超前管棚+双层支护+台阶法方案。现场通过地表对既有线进行加固、洞内100 m长管棚超前支护和双层喷锚支护,以及仰拱快速封闭等技术手段,实现了采用台阶法安全、快速下穿通过既有铁路段的目的。文章介绍了方案比选情况和现场施工情况,对试验测试情况进行了总结分析,对大断面黄土隧道下穿既有铁路段采用双层支护台阶法的适用性进行了评价,并提出了其技术关键和相关注意事项,为类似工程提供了一种新的建设思路。

Design and Construction of the Gaoqiao Tunnel on the Zhengzhou-Xi'an Passenger Dedicated Line Passing Under the Existing Railway

The exit section of the Gaoqiao Tunnel on the Zhengzhou-Xi’an Passenger Dedicated Line passing under the existing Nantongpu railway is characterized by the technical difficulties of a super-shallow depth,a large cross-section,new loess geology and a small passing angle.Since the shallow loess tunnel is prone to large deformations and abrupt collapse,a design concept using a pipe roof,double-layer support and bench method was ultimately adopted,ensuring the safety of tunnel construction,continued operation of the existing line,and adherence to the construction schedule.Additionally,such measures as reinforcement of the existing railway from the surface,100m long pipe-roof,double-layer anchor and shotcrete support and rapid invert enclosing were utilized.This paper introduces the scheme comparison and site construction of a large loess tunnel beneath an existing railway,analyzes the testing conditions and evaluates the applicability of the double-layer support and bench method for this type of tunnel and presents relevant technical points.