Constructing and operating a large underground facility for the geological disposal of high-level radioactive waste for decades will cause changes in the geological environment around the underground facility. Since the permeability and heterogeneity of fractured granite in Japan are higher than those in Europe, the disturbance to the groundwater environment due to tunnel excavation is expected to be large and complex. Therefore, modeling of fracture characteristics is important to accurately predict changes in the geological environment due to the construction and after the closure of the underground facility. However, the modeling approach focused on the fractured granite deeper than several hundred meters has not been completely established in Japan. Therefore, in this study, we investigated the methodology of modeling for fractured granite around the drift at a depth of 500 m in the Mizunami Underground Laboratory, Japan as a case study. As a result, we developed the fracture modeling method to estimate not only geological parameters of fractures but also hydraulic parameters based on the reproducibility of trace length distribution of fractures. By applying this modeling method, it was possible to construct a Discrete Fracture Network (DFN) model that can accurately reproduce the statistical characteristics of fractures. Besides, the application of the conditioning method to correct the fracture location and transmissivity to match the observation data to a specific site was demonstrated to enable the evaluation of local fracture characteristics. Furthermore, the relationship between the in-situ investigation and the data required for the modeling of hydrogeological heterogeneity of the fractured granite was clearly described, and the strategy of in-situ investigation, modeling, and disposal panel design for fractured granite using the DFN modeling during the underground facility construction phase as a useful knowledge of the geological disposal project in Japan was proposed.

建设和运行大型地下高放废物地质处置设施数十年，将引起地下设施周围地质环境的变化。由于日本裂隙花岗岩的渗透率和非均质性高于欧洲，预计隧道开挖对地下水环境的干扰较大且复杂。因此，断裂特征的建模准确预测由于施工和地下设施关闭后地质环境的变化是非常重要的。然而，针对深度超过数百米的断裂花岗岩的建模方法在日本尚未完全建立。因此，在本研究中，我们以日本 Mizunami 地下实验室的 500 m 深度漂移周围的断裂花岗岩建模方法作为案例研究。因此，我们开发了裂缝建模方法，不仅可以估计裂缝的地质参数，还可以估计水力参数基于裂缝迹线长度分布的再现性。通过应用这种建模方法，可以构建一个可以准确再现裂缝统计特征的离散裂缝网络（DFN）模型。此外，应用调理方法纠正骨折位置和证明了将观测数据与特定地点相匹配的透射率，以评估局部裂缝特征。此外，清晰地描述了原位调查与断裂花岗岩水文地质非均质性建模所需数据之间的关系，以及使用DFN建模对断裂花岗岩进行原位调查、建模和处置面板设计的策略在地下设施建设阶段，提出了日本地质处置项目的有用知识。