VERIFICATION OF THE EXISTING HYDROGEOLOGICAL MODEL USING HYDRAULIC PRESSURE MONITORING DATA DURING LONG-TERM DRAINAGE FROM THE HORONOBE URL AND PREDICTION OF THE HYDRAULIC RESPONSE TO NEW EXCAVATION OF UP TO A 500-M DEPTH

Abstract

This study simulated the long-term monitoring data of the hydraulic head around the Horonobe Underground Research Laboratory (URL) during the construction and operation to validate the hydrogeological model developed by the previous study. Compared to the previous study, the longer-term simulation and the additional information on the groundwater flow by the excavation progress during the simulation period enabled the reliable evaluation of the effective hydraulic conductivity of low permeable domain in the deep subsurface around the URL. The coverage of the ranges or reproduction of the trends of the longer-term monitoring data by simulation in this study validated the hydraulic conductivity model developed by the previous study. In addition to the validation of the model, the predictive simulation was also the scope of this study for the planned excavation of the URL to 500 m. The hydraulic head above the depth of 400 m was estimated to already reach the steady state now, whereas the hydraulic head below the depth would continue to decrease slightly. The inflow into the shaft was also estimated to reach the steady state now. These simulation results and the theoretical consideration of the observed hydraulic features in the field predicted that the significant change in the hydraulic head and the increase of the long-term inflow would not occur by the further excavation of the URL.