Consolidation Characteristics of Artificially Structured Kaolin-Bentonite Mixtures with Different Pore Fluids

The consolidation characteristics of kaolin, bentonite, their mixtures, and natural clays have been widely evaluated. However, the effect of pore fluid on the consolidation characteristics of artificially structured kaolin-bentonite mixtures should be more investigated. In this study, the oedometer tests were carried out on mixtures of kaolin with 10%, 20%, and 30% bentonite reconstituted with distilled water and 1 M NaCl. The testing samples with an “artificial structure” were prepared using the preconsolidation procedure. The test results show that bentonite greatly affects the consolidation behavior of mixture samples, especially when the pore fluid is distilled water. In the case of distilled water, the addition of bentonite to kaolin clay significantly increased the compression index (Cc), swelling index (Cs), and coefficient of volume change ( ). In this case, the of mixture samples increased significantly at low effective axial stress (σ′a) levels (less than the preconsolidation pressure) and then decreased as the σ′a further increased. In the case of 1 M NaCl as the pore fluid, the Cc, Cs, and slightly changed with the increase of bentonite content. The research results also confirmed that the effect of saline water on the compression index was noticeable when the liquid limit of soil with distilled water was higher than 110%, and the compression index of soil with distilled water was higher than 1. Regarding the coefficient of consolidation ( ), the of kaolin sample increased as the σ′a increased, and this trend was independent of the pore fluid chemistry. By contrast, the  − σ′a trend of mixture samples depended not only on the pore fluids but also on the stress level.