Influence of gradation and proportion of sand on stress–strain behavior of clay–sand mixtures

Abstract

To investigate the influence of proportion of sand as well as its gradation on the undrained strength behavior of soils, undrained tests on statically compacted specimens of clay–sand mixtures were carried, with two extreme clay minerals, namely commercially available kaolinite and bentonite mixed with specimens of three grades of sand fractions, and also varying their proportion from 10 to 80%. This work was extended to two natural soils, viz., Red earth (kaolinitic type) and B.C. soil (montmorillitic type) by using fractionized fine portion from these soils obtained by sedimentation process, and later mixed with different proportions and grades of sand fractions. Results from this experimental investigation reveals that, at optimum sand content in clay–sand mixtures, use of medium sand fractions is more beneficial to improve the undrained strength of the mixtures irrespective of the clay mineral type being present in the mixture. It thus implies that proper selection of grade of sand is also important along with the optimum content to obtain higher strength of a clay–sand mixture. This has practical implications in understanding the performance of embankments or any ground improvement applications involving strength of clayey natural soils for better load carrying capacity, stability, and good performance of the structure supported by soil. It is also very useful in the geo-environmental applications like proper selection of proper grade of clay–sand mixtures as liners for better performance.