Experimental characterization and numerical modeling of the self-weight consolidation of a dredged mud

Abstract

The kinetics of one-dimensional self-weight consolidation of dredged mud depends on the permeability and the compressibility of the mud, in addition to the height of the mud and the drainage conditions at the boundaries. The process is highly non-linear because of the drastic variation of permeability and compressibility during the densification of the mud. In this work, we investigate the self-weight consolidation of a mixed sediments, dredged from the Belgian rivers and channels and discharged in disposal siteFirst of all, this study proposes two original experiments, the hydraulic column and the kinematic permeameter, to determine the two constitutive relations governing this self-weight consolidation. A power law is used to relate the permeability with the void ratio of the mud, while a hyperbolic function is preferred for the relation between void ratio and vertical effective stress. Additionally, self-weight consolidation tests of dredged mud are performed in plexiglass column, drained at the base through a layer of sand. The settlement of the mud–water interface and the excess pore water pressure profile are monitored during the tests.In addition to this experimental characterization, the Gibson’s large strain consolidation equation is solved through a finite difference method to evaluate the ability of the constitutive relations to reproduce the kinetics of self-weight consolidation observed in the consolidation column. Finally, sensitivity analysis of the constitutive relations of the mud is carried out. The model reproduces quite well the evolution of the excess pore water pressure profile in the mud, while the rate of settlement of the mud–water interface is overestimated by the model at very short term. Also, it is observed that the draining sand at the base plays an insignificant role on the speed of consolidation if the permeability of this sand remains lower that the permeability of the mud at the densified state.