Mizunami Underground Research Laboratory is performing the GREET (Groundwater REcovery Experiment in Tunnel) project for understanding of the post-closure recovery of the geological environment in and around the drift in fractured crystalline rock. In the GREET project, part of a research tunnel at 500m depth is being filled with high pressure groundwater prior to the backfilling test with buffer materials. The intention of Task C is to validate the simulation methodologies used to understand the long-term variation of hydro-mechanical-chemical condition during drift closure and water-filling.
Therefore, the overall the objectives of Task C in DECOVALEX-2019 are the reproduction and quantitative evaluation of interactions between H-M-C phenomena through the modelling of the GREET experiment. This work will improve understanding of such systems as well as lead to development and validation of numerical tools, leading to improved confidence in making predictions of tunnel H-M-C evolution in radioactive waste disposal facilities.
Task C is divided into three steps. The first step involves modelling of the disturbance in the subsurface environment due to the construction of the Closure Test Drift (CTD). The second step is simulation and model calibration versus the available transient data. The final step is estimation of the long-term steady-state H-M-C condition after the drift has been closed.
For the modelling in the first step, preliminary data were collected prior to drift excavation (e.g., geological data such as fracture densities, hydraulic conductivities, physical properties of the rock, groundwater pressure and chemical composition) are available for construction of the first numerical model.
For the second step and the final step, monitoring of rock displacements, groundwater pressures and chemical compositions during and after water-filling test are currently being carried out in and around the CTD in order to understand the recovery process of the geological environment. The data collected through the monitoring will be used as input data for the numerical simulation.
The data set for task C is publically available at: http://www.jaea.go.jp/04/tono/miu/dataset/greet/greet.html
A basic schedule of Task C has been planned along with the expected progress of the GREET experiment. However, as the numerical models are modified as the project progresses, it is recommended that the research teams re-analyse the methodologies applied in earlier steps on a case-by-case basis. The following is the current planned schedule of Task C.
For further information, please contact the task leader, Teruki IWATSUKI.