In order to evaluate the shaft excavation effect on groundwater flow, Power Reactor and Nuclear Fuel Development Corporation has been excavating the test shaft 6 meter in diameter and 150 meter in depth at the Tono Uranium Mine, Central Japan.
In this project, a hydrological evaluation system was set up to understand the shaft excavation effect on groundwater flow. This system consists of groundwater investigation, hydrogeological modeling, predictive simulation and long term observations of the groundwater flow.
The results are as follows;
(1) From the hydrological observation during a year, the recharge rate from the unconsolidated formation situated in subsurface zone into the rock mass was calculated to be 0.57 mm /day.
(2) The hydrogeological model was devided into 12 layers from the results of geological survey, geophysical logging and in-situ hydraulic tests.
(3) From the results of the predictive simulation and observation, the area where pore pressure was changed by the excavation was within 100 meter around the shaft and it was proved that the inflow into the existing shaft and drift was not affected by the excavation.
(4) The predictive simulation and measured data show good agreement.
(5) The availability of the modeling and the simulation, and the efficiency of the hydrological evaluation system have been confirmed.
