THEMATIC ISSUE Development of approaches for modelling coupled thermal– hydraulic–mechanical–chemical processes in single granite fracture experiments Alexander E. Bond 1 • Ivan Brusky ´ 2 • Neil Chittenden 1 • Xia-Ting Feng 3 • Olaf Kolditz 7 • Philipp Lang 4 • Renchao Lu 7 • Christopher McDermott 5 • Ivars Neretnieks 6 • Peng-Zhi Pan 3 • Jan S ˇ embera 2 • Hua Shao 8 • Hide Yasuhara 9 • Hong Zheng 3 Received: 19 February 2016 / Accepted: 23 September 2016 Ó Springer-Verlag Berlin Heidelberg 2016 Abstract The geological formation immediately sur- rounding a nuclear waste disposal facility has the potential to undergo a complex set of physical and chemical pro- cesses starting from construction and continuing many years after closure. The DECOVALEX project (DEvelop- ment of COupled models and their VALidation against EXperiments) was established and maintained by a variety of waste management organizations, regulators and research organizations to help improve capabilities in experimental interpretation, numerical modelling and blind prediction of complex coupled systems. In the present round of DECOVALEX (D-2015), one component of Task C1 has considered the detailed experimental work of Yasuhara et al. (Appl Geochem 26:2074–2088, 2011), wherein three natural fractures in Mizunami granite are subject to variable fluid flows, mechanical confining pres- sure and different applied temperatures. This paper pre- sents a synthesis of the completed work of six separate research teams, building on work considering a single synthetic fracture in novaculite. A range of approaches are presented including full geochemical reactive transport modelling and 2D and 3D high-resolution coupled thermo– hydro–mechanical–chemical (THMC) models. The work shows that reasonable fits can be obtained to the experi- mental data using a variety of approaches, but considerable uncertainty remains as to the relative importance of com- peting process sets. The work also illustrates that a good understanding of fracture topography, interaction with the granite matrix, a good understanding of the geochemistry and the associated multi-scale THMC process behaviours is a necessary pre-cursor to considering predictive models of such a system. Keywords Fracture Á Fluid flow Á Coupled analysis Á THMC Á Code comparison Á Rock-matrix diffusion Introduction Understanding the likely behaviour of fractured rock under variable chemical (C), hydraulic (H), thermal (T) and mechanical (M) conditions in close proximity to a radioactive waste disposal facility is clearly of interest for safety cases supporting a number of disposal concepts. The This article is part of a Topical Collection in Environmental Earth Sciences on ‘‘DECOVALEX 2015’’, guest edited by Jens T Birkholzer, Alexander E Bond, John A Hudson, Lanru Jing, Hua Shao and Olaf Kolditz. & Alexander E. Bond alexbond@quintessa.org & Peng-Zhi Pan pzpan@whrsm.ac.cn 1 Quintessa Ltd, Henley-on-Thames, UK 2 Technical University of Liberec, Liberec, Czech Republic 3 State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, China 4 Imperial College, London, UK 5 School of Geosciences, University of Edinburgh, Edinburgh, UK 6 Department of Chemical Engineering, Royal Institute of Technology, Stockholm, Sweden 7 Department of Environmental Informatics, Helmholtz Centre for Environmental Research – UFZ, Leipzig, Germany 8 Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany 9 Ehime University, Matsuyama, Japan 123 Environ Earth Sci (2016) 75:1313 DOI 10.1007/s12665-016-6117-0