Aperture Back Calibration through DFN for Stochastic Discontinuum Modeling of Groundwater Inflow into Underground Excavations

Prediction and modeling of groundwater inflow into underground excavations is one of the most important and challenging issues faced by hydrogeologists. This paper presents a framework for direct utilization of discrete fracture network (DFN) with calibrated hydraulic aperture for stochastic discontinuum modeling and uncertainty analysis of groundwater inflow into underground excavations. The stochastic discontinuum modeling of groundwater inflow into the underground excavation was performed by FNETF computational code that established for discrete fracture flow analysis. The main input data for stochastic discontinuum modeling of groundwater inflow into underground excavation (i.e. geometrical properties of fractures and groundwater state) were captured from site investigations and measurements in Siah Bisheh pumped storage project at the North of Iran. Detailed measurements of groundwater inflow into powerhouse and transformer caverns (PHC and TC, respectively) provide an opportunity to determine the hydraulic aperture (the remaining input data for performing stochastic discontinuum method) through back calibration. To reach this goal, about 40 different mean hydraulic apertures ranging from 0.04 mm to 0.12 mm were considered in the back calibration procedure. Finally, the validity of calibrated hydraulic aperture was explored by simulation results of the groundwater inflow into TC. The results of this study indicate that the measured groundwater inflow into TC are in the range of calculated mean value plus-minus standard deviation. With regard to this correspondence, it can be concluded that stochastic discontinuum method with DFN realizations including the calibrated hydraulic aperture is suitable to predict the groundwater inflow into the the underground excavations.

کلیدواژه ها:

FNETF ، Discrete Fracture Flow ، Stochastic discontinuum ، DFN application ، Hydraulic aperture back calibration