上跨既有铁路线立交桥台后路基开挖设计深度达34.5 m，为降低边侧山体危石对既有运营铁路的安全风险及爆破施工对铁路挡墙稳定性的影响，路堑施工采取“先防后挖”的总体方案。其中，针对山体表层危石灾害，采用柔性主动防护、被动防护网与刚性挡渣墙构建立体式多层防护体系；对于路堑浅部不稳定山体，采用机械破碎锤和静态破碎方式开挖；对于路堑深部岩体，根据《爆破安全规程》关于爆破飞石落距的控制原则，将危石滚落冲击范围划分为0~30 m,30~50 m，大于50 m等不同影响段落，采用浅孔爆破及中孔台阶控制爆破相结合的分区、分层开挖方案，将铁路挡墙振动速度控制在1.5 cm/s内，施工效果表明，该措施有效地控制了施工中山体的位移，保障了铁路行车安全。

The designed cutting depth of a road channel in NingguoJixi section on YangzhouJixi Expressway reaches 34.5 m. The program of “protection before cutting” is adopted for the deep cutting, so as to minimize the influence of rockfalling and blasting on the operation of the adjacent existing railway. For the dangerous rocks on the surface of the mountain, multiple protection system consisting of active flexible protection measures, passive protection net and rigid retaining wall is established; For the unstable strata in the shallow depth of the road channel, mechanical percussive hammers and static fragmentation method are used; For the rock mass in the deep position of the road bed, sectionbysection and layerbylayer cutting based on shallowhole blasting and mediumhole step controlled blasting is carried out. In the end, the blasting vibration velocity of the retaining wall has been controlled at less than 1.5 cm/s, the displacement of the mountain body has been brought under effective control and the safety of the operating railway has been ensured. 