Interaction experiment

Czech Technical University, Prague (Centre of Experimental Geotechnics), Czech Geological Survey; UJV Řež, a.s.
A thorough understanding of the interactions between the various materials under real rock environment conditions is essential with respect to the design of the engineered barriers of deep geological repositories (DGR). Thus, the purpose of this project is to verify the behaviour of the bentonite sealing layer influenced by groundwater saturation upon interaction with cement materials while, at the same time, subjected to elevated temperatures.

The project includes the sinking of boreholes, with physical models simulating a waste disposal container located in a DGR.

Each model will simulate a stand-alone disposal system employing different types and forms of materials and differing thermal loads. Czech Ca-Mg bentonite, extracted from the Černý vrch deposit, will be used for the construction of the bentonite layers. The bentonite will take the form of moulded blocks or granulated bentonite (pellets) with differing dry density parameters. Samples containing standard pH concrete and low pH concrete (of a value of around 11) will be emplaced in the boreholes for the study of the various interactions.

Some of the experiments will involve the monitoring of interactions at natural temperatures (“cold” experiments) and the rest will be used for the investigation of interactions at elevated temperatures up to 200°C (“hot” experiments). The experiments will be fitted with sensors for monitoring the development of the saturation of the bentonite barrier and heat dissipation. The figure below provides a schematic overview of the two types of experiment

The results of the experiments will provide for:

  • a detailed description of the chemical and mineralogical processes arising from the interaction of the various materials (bentonite, concrete, rock)
  • a comparison of the various processes dependent on the set conditions in particular boreholes in the environment saturated by groundwater
  • a THM (thermo-hydro-mechanical) mathematical model

The aim of this project is to design, construct and operate a number of physical models. The final “dismantling” phase of the programme  will involve the disassembling of the models and detailed analysis of the extracted samples for evaluation of the observed interactions.