Consolidation and swelling behavior of major clay minerals and their mixtures

One of the most important geotechnical properties of a soil mass is compressibility. Compressibility is widely used in the design of the geotechnical structures including but not limited to foundations, embankments, dams and landfills. Previously, various researchers proposed numerous equations to estimate the compression index of a soil mass with other soil properties such as liquid limit, initial void ratio, void ratio at liquid limit, specific gravity or a combination of the above parameters. Almost every article in the literature concluded that the mineral composition and initial moisture content greatly influence the compression index of a soil mass. However, little research has been done on the compression index under an environment of controlled mineralogy and initial moisture content. Fifty-five different soil specimens composed of mixtures of montmorillonite, kaolinite, illite and quartz were prepared in the laboratory at an initial moisture content equal to their corresponding liquid limits. The results showed that the Intrinsic Compression Line (ICL) was unique for each dominating clay mineral. Furthermore, the compression index and swelling index exhibited good correlations with the initial void ratio, the liquid limit, and the plasticity index. Equations were proposed to estimate the compression and the swelling index of a soil mass using the liquid limit. The compression and the swelling indices for eighty-two natural specimens were estimated using the proposed equations and were found to be similar to the measured values. Moreover, triangular correlation charts relating the mineral composition to the compression index as well as the swelling index were developed to estimate the compression and the swelling indices of a soil mass.