Environment-vulnerability evaluation of a high-speed railway line in Korea using a groundwater-anomaly method

The Republic of Korea completed the first phase of the Honam high-speed railway from Seoul to Gwangju in 2014, and the second phase from Gwangju to Mokpo will be completed in 2025. This study evaluates the vulnerability of the groundwater environment in the Cheonan-Iksan zone, which passes through three preliminary lines (the Cheonan-Daejeon-Iksan line, Cheonan-Gongju- Iksan line, and Cheonan-Osong-Iksan line) of the Honam high-speed railway, to determine the most suitable line. The groundwater-level anomaly is evaluated along the three lines of the high-speed railway. The depth to water ranged from 0.03 to 21.1 m and from 0.17 to 227.95 m (AMSL). To determine a suitable line for the high-speed railway, a groundwater-level anomaly (GLA) grade is used, which considers the spatial distributions of the depth to water and groundwater elevation. Based on the GLA evaluation index, the Cheonan-Daejeon-Iksan (CDI) line exhibited the highest vulnerability (85.39), while the Cheonan-Osong-Iksan (COI) line had the lowest vulnerability (47.41). Vulnerable geological engineering, which is indicated by a discharge-estimation (DE) grade higher than 4, occurred in a section of the CDI line with a DE grade of 9, suggesting that attention should be directed to the discharge of groundwater during tunnel excavation.