Introduction

DECOVALEX-2011 was the fifth phase of the DECOVALEX-2011 project, running from 2008 though to 2011. This phase extended the traditional thermal-hydrological-mechanical focus of DECOVALEX research into new challenging research topics of scientific originality: (1) the coupled hydro-mechanical-chemical (HMC) behaviour of argillaceous clay rocks, a major step forward in relation to improved performance and safety assessments for radioactive waste repositories in different rocks, (2) the spalling of crystalline rocks under combined thermo-mechanical loading conditions, and (3) the impact of stress/deformation on contaminat transport in fractured rocks. Within this context, the general objectives of the research performed in the D-2011 phase were to characterise and evaluate the impact of coupled THMC processes, i.e. adding chemical effects, on the performance and safety assessments for a geological repository, with considerations of:

• increasing the basic understanding of coupled THMC processes in fractured rocks (crystalline and argillaceous) and buffer materials;
• investigating the predictive capabilities of different codes for field experiments and to perform verification of codes;
• exchanging experimental data, and improving the understanding of the constitutive behaviour of crystalline and argillaceous rock masses and buffer materials;
• performing THMC calculations in a performance assessment context; and
• reviewing the state-of-the art in coupled THMC issues in performance assessment.

The project involved a large number of research teams supported by radioactive waste management agencies and governmental regulatory bodies in China, Finland, France, Korea Republic, Japan, Sweden and the UK, who conducted advanced studies and numerical modelling of coupled THMC processes under three tasks:

• Task A: HM-C processes in argillaceous rocks;
• Task B: TM modelling of fracture initiation and propagation, and rock spalling in rock openings and its consequences;
• Task C: Assessment of coupled THMC processes in single fractures and fractured rocks.

The work defined in these three Tasks was divided into different phases or steps so that the progress could be monitored and the achievements documented in project reports and other publications.The following four final reports listed below were generated after the completion of the Decovalex-2011 project:

• J. A. Hudson and L. Jing, 2012. DECOVALEX-2011 Project: Executive summary. School of Achitecture and Built Environment, Royal Institute of Technology, Stockholm, Swedem. TRITA-LWR. Report 3017, ISSN 1650-8610, ISRN KTH/LWR/REPORT 3017-SE (pdf);
• B. Garitte, 2012. DECOVALEX-2011 project: Final report of Task A. School of Achitecture and Built Environment, Royal Institute of Technology, Stockholm, Swedem. TRITA-LWR. Report 3034, ISSN 1650-8610, ISRN KTH/LWR/REPORT 3034-SE (pdf);
• C. Andersson. DECOVALEX-2011 project: Final report of Task B. School of Achitecture and Built Environment, Royal Institute of Technology, Stockholm, Swedem. TRITA-LWR. Report 3035, ISSN 1650-8610, ISRN KTH/LWR/REPORT 3035-SE (pdf);
• J. A. Hudson and L. Jing, 2012. DECOVALEX-2011 Project: Final Report of Task C. School of Achitecture and Built Environment, Royal Institute of Technology, Stockholm, Swedem. TRITA-LWR. Report 3036, ISSN 1650-8610, ISRN KTH/LWR/REPORT 3036-SE (pdf).

The Funding Organisations of the DECOVALEX-2011 project were as follows: Institute of Rock and Soil Mechanics, Chinese Academy of Sciences (CAS), China; Institute for Protection and Nuclear Safety (IRSN), France; Japanese Atomic Energy Agency (JAEA), Japan; Korean Atomic Energy Research Institute (KAERI), Korea; Radioactive Waste Management (RWM), UK ; Posiva Oy (Posiva), Finland; Radioactive Waste Repository Authority (SURAO), Czech Republic; Swedish Nuclear Fuel and Waste Management Co. (SKB), Sweden; and Wuhan University (WHU), China.