Oedometric and water-retention behaviour of highly compacted unsaturated smectites

This paper summarizes the findings from an experimental program concerning the hydromechanical behavior of two smectite clays tested under high stresses. Increasing axial stress on the smectite samples under controlled relative humidity (suction) leads to collapse in the soil structure and increases the degree of saturation. Irreversible volume change is observed in samples tested under cyclic suction with constant axial load. Water-retention (adsorption and desorption) behavior of the smectite clays tested in this study is affected by particle size, initial void ratio, and confinement conditions during the tests. Laponite, which has a large specific surface area, tends to hold more water than hectorite at a given relative humidity. More water is adsorbed by samples compacted at lower axial stress.