The influence of different proportions of clay minerals on the moisture density relationship and index properties of clay soils are not clearly understood because of the different factors that come into play in natural soil formation. This study used 11 different remolded samples prepared by combining double mixtures of commercially available powdered kaolinite, montmorillonite and quartz in proportions of 30%, 50%, 70% and 100% based on dry unit weight to investigate the relationship between different proportions of clay minerals with index properties and compaction characteristics of clay soils. The results described the influence of different proportions of clay minerals on the liquid limit, plastic limit and plasticity index measured using the fall cone penetration test. Also, the variation of maximum dry density and optimum moisture content with different clay mineral proportions has been analyzed. In addition, equations are presented with significant correlations to show the relationship between Atterberg limits, compaction parameters and the proportion of clay minerals. Knowledge on the effect of the different clay minerals on the moisture density relationship and index properties can be used to predict the behavior of compacted clay soils encountered in engineering practices and reduce the time and effort needed for assessing the suitability of clay soils and clay liners for engineering use.

The behaviors of high‐plasticity clays depend largely on the clay mineral content. Recently, it has been observed that sudden slope failures of most clay slopes occur in regions pronounced with repeated rainfall and sunny climate. The reason for this is still unclear. Examining the effect of clay minerals and drastic weather changes on shear strength will be useful in predicting the performance of structures built in such soils and to take precautionary measures to improve the properties before failure. Therefore, a series of quick direct shearing tests were conducted on 11 artificial clay mixtures. The cohesion and frictional strength properties were determined and linked to the proportion of clay minerals and the number of wetting and drying cycles. The results show a significant reduction in shear strength after exposure to wetting and drying. Generally, montmorillonite‐dominated mixtures were less susceptible to the changes in cohesion strength than kaolin‐dominated mixtures, and the reduction in frictional strength was relatively insignificant.