Abstract

Interest in the behaviour of naturally consolidated soils stems from the relevance of these materials to the dredging industry, and the environmental impact of dredging and the dumping of pollutants at sea above soft cohesive sediment beds. Since these soils are compositionally and behaviourally complex, there is a need to characterize their properties in a non-destructive manner. This paper presents the seismo-acoustic behaviour of a number of these soft soils as studied in the laboratory. It is shown that the changing behaviour of the sediment, as it consolidates, and as the soil structure develops, has a considerable influence on its stiffness characteristics. Shear modulus is determined using shear wave velocity and bulk density measurements which were found to range between zero and 160 kPa during the course of the experiments. Estimation of soil shear stiffness in this manner would be a parameter of interest to the dredging industry in defining navigable depth. In terms of environmental matters, such estimates of marine soil shear stiffness may be of use in quantifying the erodibility of the sea bed; this is of particular significance where sediments are contaminated by pollutants.