Soil is laid down by sedimentation through water, passing through the phases of a fluid supported suspension, through a loose structure to a soft soil, the stiffness of which then gradually increases under additional load. Consolidation is caused by the self-weight of the soil and, while the sediment is soft, is accompanied by large strains. To predict magnitudes and rates of movement, the physical processes must be understood and used as the basis of a theoretical model. This Paper describes laboratory experiments on the development and consolidation of a soft soil in settling columns, with measurement of density (using an accurate, non-destructive X-ray technique), total stress, pore pressure and settlement. The results are compared with an earlier theoretical model. Modifications made to the model in the light of observed experimental features allow it to be used to predict the laboratory consolidation. Le sol est depose par sedimentation a travers l'eau; il a d'abord la forme d'une suspension soutenue...