Laboratory Evaluation of Lateral Swelling Pressure

A laboratory technique for the determination of the lateral swelling pressure of expansive clays is described. The method uses a hydraulic triaxial cell fitted with a lateral strain belt, and is based on the ``Method of Equilibrium Void Ratios'' (Sridharan et al). Comparative tests on a high-plasticity clay from southeast Queensland, Australia, using a conventional oedometer cell indicate that the lateral swelling pressure may be more than twice the vertical value. The method has the advantage that a constant vertical stress similar to field conditions may be imposed on the soil sample. Furthermore, lateral strains are measured directly, thus obviating the need for inferring them from measurements of axial and volumetric strain. The method enables the lateral swelling pressure under conditions of some known, finite value of lateral strain to be estimated, which is useful for applications such as retaining walls where finite deflections are inevitable. A disadvantage of the method is the time required to conduct sufficient tests to accurately define the swelling pressure.