Compressibility of Compacted Clays Mixed with a Wide Range of Bentonite for Engineered Barriers

Compacted clay–bentonite mixtures are often used as compacted blocks and landfills in high-level radioactive waste repositories and clay liners, respectively. A better understanding of their compressibility behaviour is essential to guarantee the disposal safety. In this study, mixtures of clays and bentonite are used to investigate the compressibility and compaction behaviour. Three natural clays were selected with different physical characteristics, and clay–bentonite mixtures were prepared by mixing the bentonite content up to 50%. A series of standard compaction tests and consolidation tests were performed in the laboratory; the samples for the consolidation test were prepared at the optimum moisture contents and maximum dry unit weights. With increasing bentonite content, the liquid limit, plasticity index, optimum moisture content, initial void ratio and compression index of natural clays increase and maximum dry unit weight and yield stress decrease. It was observed that the effect of bentonite on geotechnical characteristics pronounced when bentonite content exceeded 10%. Correlations were also proposed to estimate the compression characteristics and compression curves of compacted clays using three physical parameters such as the initial void ratio, optimum moisture content and maximum dry unit weight.