Unsaturated Soil Concepts and Their Application in Geotechnical Practice

model. They conclude that the models using three fitting parameters provide the best fit over a wide range of suctions. Models for soil-water characteristic curves are only useful if we have experimental data on which to base them. Agus, Leong and Rahardjo (Singapore) present a large number of experimental soil-water characteristic curves determined for two types of residual soil from Sigapore. They present data for eight different sites. This data set allows them to relate the parameters of the soil-water characteristic curves to index properties. They conclude that the relationships derived are suitable to pro­ vide a quick preliminary estimate of a soil-water characteristic curve. The importance of soil-water characteristic curves is emphasized by another con­ tribution dealing with this topic. Aung, Rahardjo, Leong and Toll (Singapore) inves­ tigate the relationship between mercury intrusion porosimetry measurements and soil-water characteristic curves. The porosimetry measurements are presented as soil-air characteristic curves. The slopes of the soil-air characteristic curves are found to be similar to the slopes of the soil-water characteristic curves. The equiv­ alent pore diameters calculated from the mercury entry value and the air entry value appear to be related. Therefore, it is suggested that porosimetry data can be used to construct an estimate of the soil-water characteristic curve.