[1D08-13] Model Validation

[1D10] Case study on the development of methodologies for validation of groundwater flow and mass transport models

(2) Effects of the modeling methods of low permeability fractures on groundwater flow characterization

*Masayuki Ishibashi¹, Hironori Onoe², Taichi Esaki¹, Yoichi Tagawa¹, Kazuto Tabei¹, Tadashi Namikawa¹, Hane Kouji¹, Hiromitsu Saegusa², Keisuke Ishida², Atsushi Sawada³ (1. Kajima Corporation, 2. NUMO, 3. JAEA)

Keywords:Fractured rock, groundwater flow characteristics, uncertainties, DFN model, low permeability fractures

In the previous report, two types of fracture network models were developed using data obtained at the Mizunami Underground Research Laboratory (MIU), taking into account differences in the way low permeability fractures are treated as uncertainties in the modeling process. Specifically, one model assumes that all fractures in the modeling target contribute to groundwater flow (hereinafter referred to as the "threshold resetting model"), and the other model assumes that only highly permeable fractures among the modeling target fractures contribute to groundwater flow (hereinafter referred to as the "cutoff model"). In this report, groundwater flow analysis assuming steady-state conditions at tunnel opening was conducted using both the cutoff model and the threshold resetting model, and the groundwater inflow rate into the entire tunnel and hydraulic head at each monitoring section of the borehole were compared with the measured values. Through these comparisons, the influence of the difference in the modeling method of low permeability fractures on the evaluation indices (tunnel inflow rate and sectional hydraulic head) is discussed.