Evaluating hydro-mechanical interactions of adjacent clay-based sealing materials

• The DBF showed a degree of desaturation in both tests after 1.5 and 3.5 years.
• GF and HCB moved toward EMDD homogeneity due to their similar mineral textures.
• The DBF and HCB after 3 years still have very different EMDD values.
• The DBF and HCB have different mineral textures and compressibility limitations.
• The DBF and HCB are not expected to come to either density or EMDD homogeneity.

Canada’s Nuclear Waste Management Organization (NWMO) is investigating various geological isolation concepts for Canada’s used reactor fuel (NWMO, 2005). These options are all based on the concept of multiple barriers that include Highly Compacted Bentonite (HCB), Dense Backfill (DBF), Light Backfill (LBF), and Gap Fill (GF). The hydraulic, mechanical, and other characteristics of these clay-based sealing materials have been examined previously, but typically in relative isolation (e.g., Dixon, 1999, Blatz, 2000, Siemens, 2006, Stroes-Gascoyne et al., 2006 and Baumgartner et al., 2007). Information on how these clay-based sealing materials interact with each other is needed to understand the evolution and performance of the overall sealing system.A total of twenty-three (23) tests that examine the physical interaction of physically dissimilar clay-based sealing materials were installed and monitored at Atomic Energy of Canada Limited’s (AECL) geotechnical laboratory. This paper describes the process of water uptake, interaction between the components installed, and the role of groundwater salinity on water uptake as interpreted from these tests.