Expansive soils that consist of swelling clay pose a major challenge to engineers and are considered as geological hazards throughout the world. Determination of swelling pressure is also necessary for designing suitable foundation systems. In this regard, some tests were performed to determine the swelling characteristics of montmorillonite and bentonite clay. With the help of a dew point potentiometer, the suction of these clays was measured. In this study, provide a new approach to apply the methodology to define the swelling pressure of clay. Experiments by three methods to determine the swelling pressure of clays showed that the conventional consolidation test gives an upper bound value, the method of equilibrium void ratios for various consolidation pressures gives the least value, and tests by the constant volume method give intermediate values. However there is no definite relationship between the three methods. The paper also shows that time effects involved in conducting the tests and the effect of stress path are both significant. Time versus swelling, and to a greater extent, time versus pressure relations can be represented by a rectangular hyperbola, which can be used to predict the ultimate swelling and the swelling pressure, respectively. Results show that correlate suction with the swelling pressure and the correlation was validated using data reported in the literature.
