Permeability FEBEX test

First, we identified the input parameter for THAMES on properties of FEBEX bentonite, because the fundamental properties of FEBEX bentonite had been obtained by various laboratory tests to identify the input data for the numerical code CODE BRIGHT (enresa (1998)). After calibrations of the all required parameters for THAMES, such as thermal vapour flow diffusivity and intrinsic permeability, the coupled THM simulations were carried out. 

The numerical model ROCMAS was applied to predict coupled THM processes in a bentonite barrier at the FEBEX in situ test. The results indicate that numerical modeling can provide highly reliable predictions for temperature distribution, and reasonably reliable predictions for moisture flow and stress in a bentonite barrier. Moreover, field observations and modeling shows that resaturation of the buffer was controlled by the properties of the bentonite barrier whereas the permeability of the rock was sufficiently high to act as an unrestriced water source. Therefore, the wetting of the bentonite took place uniformly from the rock and was not impacted by the permeability difference between the Lamprophyres dykes and surrounding rock. 

In the FEBEX project blocks made of Ca-bentonite are tested for their suitability in radioactive waste isolation. This material has been tested in various laboratory experiment to identify the material parameters. The modelling of gas and water flow in engineered barriers demands beneath the intrinsic permeability and porosity constitutive equations for capillary pressure and relative permeabilities. 

This test has been modeled with RockFlow/ RockMech in ID to check the chosen hydraulic parameters for the modeling of the FEBEX in situ experiment. The capillary pressure curve has been set as shown in Figure 3. Relative permeability for gas has been developed from the experimental results shown in Figure 4. Relative permeability for water has been assembled from the dependency on saturation and swelling pressure and an additional factor c. 

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