Abstract: The deephole drilling results of the BadongXiangluping tunnel group on the ZhengzhouWanzhou railway crossing karst area revealed multiple adverse geological conditions, including waterflow sound, cold wind leakage, and giant haftfilled karst with a diameter exceeding 80 m. Thus, a regional hydrogeological survey and systematic groundwater hydrodynamic analysis are conducted. The findings indicate that the karst cave bottom is an underground river. Consequently, the existing tunnel route scheme for the preliminary design phase is improved in the construction drawing. Due to the control of station location, elevation, and longitudinal slope of the route, it is impossible to conduct wideranging adjustments on threedimensional space. For that reason, five route schemes are proposed for the plane. Finally, a thorough comparison and selection of main adverse geologies, karst development degree, surrounding rock grade, auxiliary tunnel, construction risk, and project investment are carried out. Considering construction risk and relative investment, the D8K route scheme that avoids the underground river is recommended. Overall, the construction excavation results show a successful route selection.

Key words: railway tunnel, unfavorable geology, karst, geological route selection, line relocation, scheme comparison and selection