Desk based study and literature review of diapirism in plastic clays and an analysis of the critical state of boom clay

NIRAS/ONDRAF is preparing an initial Safety & Feasibility Case (SFC 1) for high-level and long-lived radioactive waste (to be completed by 2013) to demonstrate that geological disposal in poorly indurated (plastic) clays (using the Boom Clay as reference case and the Ypresian clays as an alternative) is a practical and safe disposal option to allow them to progress towards siting a repository. A significant part of the SFC 1 will be a geosynthesis report (edited by SCK-CEN and NIRAS/ONDRAF) to investigate the long-term stability of the Boom Clay. Beneath the Scheldt River, up-doming of the top of the Boom Clay (only at a few 10's of metres of depth) is observed in geophysical records and has been referred to as a ‘diapiric’ structure. NIRAS/ONDRAF has asked the British Geological Survey (BGS) to undertake an initial desk based study to review the literature on diapirism like processes in plastic clays, including the Scheldt River structure, and to discuss the relevance (or lack thereof) of this process in the context of a clay-based geological disposal system for radioactive waste.