Numerical simulation of the change in groundwater level due to construction of the Giheung Tunnel

We performed numerical simulations of the excavation of an underground structure (the Giheung Tunnel) in order to evaluate the rate of groundwater flow into the structure and to estimate the groundwater level around the structure. The tunnel was constructed in Precambrian bedrock in Gyeonggi Province, South Korea. Geological and electrical resistivity data, as well as hydraulic test data, were used for the numerical modeling. The modeling took into account the strike-slip faults that cross the southern part of Giheung Tunnel, as these structures influence the discharge of groundwater into the tunnel. The transient modeling estimated a groundwater flow rate into the tunnel of /day, with a grout efficiency of 40%, yielding good agreement between the calculated change in groundwater level (6.20 m) and that observed (6.30 m) due to tunnel excavation.