为有效保障既有铁路运营安全和解决新建隧道施工安全难题，依托新建隧道洞口段下穿铁路路基特殊工况，采用工程类比法提出一种管幕施工下穿铁路路基施工工法，主要涉及管幕施作、隧道开挖2个工艺，简单介绍基坑开挖、反力墙和导向墙施作、掌子面超前支护等该工法的前期工作，并深入分析探讨了管幕施作流程、精确顶进、管内注浆、隧道开挖、隧道支护等重点工序和关键技术。最后分析总结监测结果，认为该下穿施工工法具有安全实用性： 地表累计沉降最大值为19.2 mm，新建隧道下穿段拱顶沉降最大值25.61 mm，最大水平收敛17.5 mm，实现零预警施工开挖，隧道开挖面安全快速通过下穿段，保证了运营线的安全运营和隧道结构稳定，还解决了施工进度和安全的矛盾。

To guarantee the operation safety of the existing railway and the construction safety of newlybuilt tunnel, a pipecurtain method is proposed for the newlybuilt tunnel when crossing underneath existing railway subgrade using engineering analogy method. The technology includes pipecurtain construction and tunnel construction. The preliminary works of foundation pit excavation, reaction wall and guide wall construction, and advance support of the tunnel face are introduced, and indepth analysis and discussion is conducted on key procedures and technologies such as pipe curtain construction process, precise jacking, grouting in pipe, tunnel excavation, tunnel support, etc. Finally, the monitoring results are analyzed, and the results show that the pipecurtain method adopted in underpass construction is safe and practical, the maximum cumulative settlement of the surface is 19.2 mm, the maximum settlement of the tunnel crown at underpass section is 25.61 mm, and the maximum horizontal convergence is 17.5 mm, realizing zerowarning construction. The safe operation of the existing railway and the construction of newlybuilt tunnel have been guaranteed, and the construction schedule has been reduced.