An assessment of mud consolidation in a marine disposal pit

Contaminated mud dredged from various reclamation and maintenance dredging projects in Hong Kong is disposed of in the pre-formed marine disposal pits at East Sha Chau, Hong Kong. To facilitate allocations of mud disposal volume to the projects, it is essential to know the pit capacity as accurately as possible. In assessing the pit capacity, consolidation of the disposed mud should be counted so as to maximize the disposal volume, and thus optimize the pit usage. In particular, it is important to estimate the amount of consolidation by the time the pit is filled to the design level before capping with a clean mud layer to finish off the pit. An assessment, using one-dimensional consolidation theory, was carried out to evaluate the consolidated volume. A finite difference approach was adopted to predict the excess pore-water pressure dissipation, hence the degree of consolidation at a specific time. Laboratory tests were carried out on mud samples to obtain parameters for the analysis. The theoretical predicted consolidation was compared with the measured value derived from bathymetric survey. The theoretical data matches the measured data well.