The Decovalex project: studies of coupled THM experiments and lessons learned

Initiated in 1992, the DECOVALEX project is an international collaboration for advancing the understanding and modelling of coupled thermo-hydro-mechanical (THM) processes in geologic systems. The project has progressed successfully through three stages. It has played a key role in the development of the field of mathematical modelling and in-situ testing of coupled THM processes in fractured rock and buffer/backfill materials, a subject of importance to performance assessment of a radioactive waste geologic repository. This paper summarizes studies of field experiments and bench mark tests under the most recent stage of the project, DECOVALEX III (2000-2003). The field experiments are the FEBEX experiment at Grimsel, Switzerland, investigating coupled THM processes in crystalline rock-bentonite system, and the Drift Scale Test (DST) experiment at Yucca Mountain, Nevada, investigating coupled THM processes in unsaturated tuff. These are two of the largest multi-year heater tests undertaken to date for the study of coupled THM processes in geological systems. Within the DECOVALEX project, multiple research teams studied data from these two sites, using multiple approaches and different computer codes. Comparisons of results have provided insight into coupled THM processes and to the state of the art regarding modeling capabilities. Lessons learned from these studies are discussed. The scientific advances and enhanced insight gained through this kind of international cooperation illustrate the effectiveness of the DECOVALEX project. (authors)