Abstract：The groundwater inflow into a tunnel affects not only the construction schedule，cost，stability and safety，but also the groundwater level. Because of the increasing public concern regarding the impact of tunneling on surrounding environments，the control of groundwater has become an essential part of the planning，design and construction of a tunneling project. The impact on groundwater table due to groundwater inflow into Shinkansen (high speed trains) Chikushi Tunnel in Japan is analyzed by coupling geographic information systems(GIS) and FLAC3D. Firstly，the area around Shinkansen Chikushi Tunnel is drawn into watersheds using the hydrologic- analysis of ArcGIS；and tank model，which is a method for hydrologic balance analysis of precipitation，evaporation，water flow and infiltration，is used for calculating the rainfall infiltration. All the data，such as the geological data，three-dimensional terrain and rainfall，are processed using GIS. Then，a three-dimensional groundwater flow numerical model is used to predict the groundwater inflow into tunnel and the drop of groundwater level around the tunnel. Based on the 3D numerical model，considering the rainfall infiltration and the tunnel excavation sequences，a time-spatial simulation of the groundwater inflow and its influence on the groundwater level of Shinkansen Chikushi Tunnel are presented.
