Abstract: 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.

Key words: underpass railway subgrade, large crosssection tunnel, pipecurtain method