Advances in hydro-mechanical behaviors of buffer materials under effect of technological gaps

The self-sealing and self-healing behaviors of technological gaps in a high-level radioactive waste repository are analyzed. The systematical findings are summarized based on the previous studies on the effects of technological gaps on the swelling pressure, permeability, fracturing pressure and self-sealing properties. The results indicate that the presence of technological gaps strongly weakens the swelling potential and water tightness of buffer materials. At the early stage of a real repository development, hydraulic fracturing is likely to be induced along these interfaces under high water pressure. Generally available achievements in this area are quite limited. In the tests, the total average methods are employed to study the mean swelling pressure and permeability of buffer materials. However, the hydro-mechanical behaviors of bentonite within gaps cannot be characterized. Several testing devices are specially designed to monitor the total pressure along the interface, except that the effective swelling pressure and pore water pressure cannot be distinguished. These disadvantages result in great difficulties in mechanism analysis of sealing and healing behaviors of technological gaps. Finally, some suggestions are proposed for further researches.