Some aspects of the compaction of raw dredged sediments for a direct reuse as fill material

The management of sediments dredged and deposited on land has been the focus of many recycling studies, especially in laboratories where small quantities of sediments are oven-dried. These investigations have usually concluded that recovery as a material requires stabilization/solidification treatment. Few research studies are available for the sustainable, ecological and direct use of dewatered sediments, particularly on the compaction of raw sediments and the analysis of the different influences related to their texture, composition and drying methods. The present study investigates the compaction of raw dredged sediments for their potential reuse as fill material in the infrastructure projects. A series of 16 types of sediment from various environments, including rivers, dams and harbors, were compacted at an energy equivalent to that of the normal Proctor test. The test used a miniature laboratory version of the conventional Proctor test to estimate optimal compaction parameters. The results show that factors such as particle size, plasticity, specific gravity and organic matter content have a significant influence on optimum compaction values. Four distinct groups of sediments were identified, each with specific characteristics in terms of maximum dry density and optimum moisture content. The analysis first focused on the study of the influence of these factors (geotechnical properties) on the optimum compaction parameters in relation with organic matter content, for which a threshold of 5% made it possible to distinguish between non-organic and organic sediments. Another important result concerns the sediment drying method, which affects an influence on these optimum compaction parameters. While the most common method used in laboratory studies is oven-drying, on-site applications use natural drying using ambient air. The trends observed for these drying methods could be useful to sediment authorities in the case of on-site applications.