Influence of Clay Content and Montmorillonite Content on Swelling Behavior of Expansive Soils

Swelling behavior of an expansive soil is principally governed by the contents of montmorillonite mineral and clay present in it. Studies attributing the swelling behavior to the presence of montmorillonite mineral are numerous, but defining an intricate relationship between clay and montmorillonite contents is almost nil. Thus, a comprehensive study is undertaken in this technical note that can aid in quantifying the exact influence of clay content (CC) and/or montmorillonite content in clay content (MCCC) on the swelling behavior. Interrelating CC and MCCC parameters is also another objective of the paper. Several numbers of different expansive soils were collected from different regions of India and experiments were conducted to quantify free swell index (FSI), CC, and MCCC. The results demonstrate that it is not only CC, but also MCCC has a remarkable influence on the swelling behavior. It has, particularly, been noticed from the interpretation of results that the role of mixed clay minerals, which is contrasting to a common belief that it is only MCCC primarily contributes to the swelling phenomenon and is least attempted by research fraternity, cannot be subdued. The study finds that between MCCC and CC, the former parameter seems to be more reliable for accurate prediction of swelling potential. The relationship between CC and MCCC seems to be linear up to MCCC of 40%. Beyond MCCC of 40%, CC apparently clustered between 30 and 60% only. MCCC, even though, found in minor quantity, exhibited significant influence on the FSI. The results presented in the study bear a practical significance for the safe design of foundation systems, buried pipelines, etc., in/on the expansive soils.