Large-strain nonlinear consolidation of dredged sludge yards with PHDs

Engineering practices and indoor model tests indicate that laying prefabricated horizontal drains (PHDs) can effectively accelerate the consolidation of dredged sludge yards. However, the large-strain self-weighted consolidation theory of dredged sludge yards with PHDs, in which the characteristics of dredged sludge can be fully considered, lacks systematic researches. In this study, based on the Gibson's large-strain consolidation theory and considering the nonlinear compressibility and permeability of dredged sludge, a large-strain nonlinear consolidation model for PHD-treated sludge yards with planar seepage and vertical strain is established, and the solution for this model is obtained by the finite difference method. The reliability of the large-strain nonlinear consolidation model and its solution for the PHD-treated sludge yards is verified by comparing with that for the large-strain self-weighted consolidation of dredged sludge yards without PHDs. On this basis, the influences of different factors on large-strain consolidation behaviors of dredged sludge yards are investigated. The results show that: (1) The consolidation rate can be achieved at the same level as the fully permeable boundary at the bottom once the rate of laying PHDs reaches a certain value, and the optimal rate of laying PHDs decreases with the increase of the stacking height of dredged sludge yards. (2) The optimal rates of laying PHDs are 50% and 27% for stacking heights of 1 and 5 m, respectively. (3) The stacking height has a great influence on the consolidation rate of yards treated with PHDs, and the consolidation rate of yards can be accelerated by increasing the number of PHD layers. (4) The consolidation rate increases with the increase of the permeability index when the compression index keeps fixed. (5) The consolidation rate decreases with the increase of the compression index when the permeability index remains constant.