Bentomap. Survey of bentonite and tunnel backfill knowledge. State-of-the-art

The objective of the state-of-the-art report is to compile the conducted experimental research and THM knowledge for buffer and backfilling materials, bentonite in particular. In addition, the report presents evaluation, scope, limitations and possible deficiencies of the knowledge and creates a wider perspective of the level of the national and international know-how on bentonite and backfilling research. The survey ranges from small scale laboratory tests to the full-scale tests in real deep depository conditions. The focus of the evaluation is on the thermo-hydro-mechanical properties of bentonite and backfill materials. The thermal properties examined are thermal conductivity, specific heat, and the thermal expansion coefficient. The compiled hydraulic property results, on the other hand, pertain to hydraulic conductivity and the water retention curve, and the investigated mechanical properties include strength, deformation, rheological and swelling properties. The presentation of results from the experimental research is followed by discussion and conclusions drawn from both the individual studies and the Bentomap database as a whole. (orig.)