Osmotic suction of highly plastic clays

This paper presents a study on osmotic suction of compacted highly plastic clays. Two different types of bentonite (i.e. Calcigel and a bentonite from India called herein as Indian bentonite) were used. Squeezing technique was utilized to obtain soil pore-water of the specimen. Using relationship between electric conductivity and osmotic pressure of salt solution, osmotic suction of soil pore-water was obtained. Additional tests (i.e. total and matric suction using filter paper method and swelling pressure using constant volume swelling pressure test) were performed. The results show that osmotic pressure of soil pore-water obtained decreases by increasing squeezing pressure. Based on experimental result, osmotic suction of the specimen is osmotic pressure of the first drop of extracted soil pore-water. An empirical method was suggested to determine the squeezing pressure in squeezing technique. In addition, roles of osmotic suction in thermo-hydro- mechanical behavior of highly plastic clays were presented and discussed in the paper.