The paper presents the results of an experimental study of the influence of clay content (in silt-clay and sand-clay mixtures) on liquefaction beneath progressive waves. The experiments showed that the influence of clay content is very significant. Susceptibility of silt to liquefaction is increased with increasing clay content, up to 30%, beyond which the mixture of silt and clay is not liquefied. Sand may become prone to liquefaction with the introduction of clay, contrary to the general perception that this
type of sediment is normally liquefaction resistant under waves.