Understanding evolution of groundwater hydraulic and chemical conditions is important for safety assessment of radioactive waste disposal. Perturbations to groundwater can occur due to the construction and operation of the underground facility. The initial perturbations and their recovery after the tunnel closure were observed in the Groundwater REcovery Experiment in Tunnel (GREET) in Mizunami, Japan, at 500-m depth in granite. In a 100-m-long tunnel, 50 m was isolated by building a plug. Aside from other measurement and exploration data, groundwater pressures and chemical composition were monitored in boreholes with 24 packer sections. This work used numerical modelling to better understand and be able to predict the observed water flow and solute transport phenomena. The model covered 100-m scale around the tunnel and was divided into a continuum far-field domain and a near-field domain with deterministic discrete fractures and matrix blocks. A mixed-hybrid finite element solution was used with independent degrees of freedom for 3D and 2D elements. Modelling started with a blind prediction followed by a calibration (inverse model) for drainage and flooding experiment phases. The inverse hydraulic model fitted the more/less communicating sections and estimated transmissivity and conductivity parameters that are consistent for the two phases. The model sensitivity on transport parameters was insufficient for the inverse model, which can use only simplified measured evolution to avoid noisy data.

了解地下水水力和化学条件的演变对于放射性废物处置的安全评估很重要。由于地下设施的建设和运营，可能会对地下水产生扰动。在日本 Mizunami 500 米深的花岗岩隧道地下水回收实验 (GREET) 中观察到了隧道关闭后的初始扰动及其恢复。在一条100米长的隧道中，50米是通过建塞隔离的。除了其他测量和勘探数据外，还使用 24 个封隔器段对钻孔中的地下水压力和化学成分进行了监测。这项工作使用数值模型来更好地理解并能够预测观察到的水流和溶质运移现象。该模型覆盖了隧道周围 100 米的尺度，分为连续的远场域和具有确定性离散裂缝和基质块的近场域。混合混合有限元解决方案用于 3D 和 2D 元素的独立自由度。建模从盲预测开始，然后是排水和洪水实验阶段的校准（逆模型）。逆水力模型拟合了更多/更少的连通部分和估计的两相一致的透射率和导电率参数。模型对输运参数的敏感性对于逆模型来说是不够的，它只能使用简化的测量演化来避免噪声数据。