Abstract: In karst areas, groundwater is abundant, and the construction of tunnels and other underground projects often causes environmental problems, including groundwater leakage and depletion. To address these problems, route selection is investigated from an environmental geology perspective in the karst development area along the Xi’an-Shiyan High-speed Railway across the Qinling Mountains. Following the principle of protecting groundwater sources used for drinking in karst areas, the environmental geological impacts of alternative tunnel routes are assessed and route selection is evaluated based on the investigated characteristics of karst development and karst groundwater along the railway. The following conclusions are drawn: (1) Karst in the study area is weakly to moderately developed, with individual karst features consisting mainly of small caves and pores. The karst water system primarily comprises a karst fissure water system and is discharged mainly into branch gullies through descending springs associated with surface karst fissures. Cave-fissure water systems develop locally within karst-tectonic superposition zones, whereas underground rivers do not develop. The water is characterized by low TDS, high hardness, and good water quality, making it the primary source of drinking water for local residents. (2) Among the tunnel alternatives, the straightening scheme provides better tunnel surrounding rock conditions but poses a greater risk of groundwater leakage and depletion. Although the detour scheme has poorer surrounding rock conditions, it substantially reduces the environmental geological risk of groundwater leakage and depletion. Thus, the detour scheme is selected for construction, which proves to be reasonable and feasible in practice. (3) Environmental geology should be an important consideration during the planning and route selection of tunnels in karst areas.

Key words: Xi’an-Shiyan High-speed Railway, karst tunnel, groundwater leakage and depletion, environmental geological route selection