Geotechnical Characteristics and Behaviour of Kuttanad and Cochin Marine Clays from India: A Comparative Study

This study provides an insight into a comprehensive study on two soft clay deposits namely Kuttanad and Cochin marine clays from the south western state of Kerala, India. These clays are deltaic formations that possess low shear strength and high compressibility characteristics. Many cases of large post construction settlements and failures have been reported from these regions. Additionally, these clays are popular for undergoing irreversible changes in properties on drying and there were many theories associated with this trend for both clays; the significant reasons attributed being the presence of organic matter, the aggregations assisted by the exchangeable di-valent and tri-valent cations and high pore fluid salinity. The question of which was the predominant reason was a point of discussion in the past. In this paper, the similarities and dissimilarities of the two clays have been brought out. The irreversible nature of properties on drying was investigated for both clays using physicochemical techniques and FTIR Spectroscopy. Subsequently, a high energy dispersion tool, generally used for emulsification, was employed in an attempt to reverse the properties of the dried clays. While there was significant reversal of the properties in Cochin marine clay (CMC), it was only about 75 to 80% in Kuttanad clay. A detailed FTIR analysis indicated the presence of strong hydrogen bonds between the interlayer water and basal oxygens of kaolin-like layers in Kuttanad clay that is characteristic of the halloysite mineral. The presence of halloysite, higher salinity and organic matter of Kuttanad clay compared to CMC could be the major factor leading to the incomplete reversal of the properties for Kuttanad clay on drying.