Settling and Consolidation of Soft Mud-Sand Layers

This paper discusses the settling and consolidation of soft mixtures of mud and sand based on experiments in a set of laboratory settling columns of varying lengths in the range of 0.5-3 m. Two types of natural muds with varying percentages of sand were used in the settling columns. In addition, mud-sand mixtures with relatively high percentages of sand were tested. The theory of the hindered settling and consolidation processes is briefly explained, and a relatively simple simulation model is proposed. The model simulation results are compared to the results of two laboratory tests with reasonably good agreement between measured and computed values. A plot of the dry bulk density as a function of the percentage of clay and sand is presented, which can be used to obtain an estimate of the in situ density of muddy layers to be dredged from navigation channels and harbor basins. Furthermore, a plot of the timescale of the primary consolidation process is presented.