Recently, permeable geotextile tubes in conjunction with prefabricated horizontal drains (PHDs) have become increasingly popular for dewatering high water content slurries or sludge. However, how to analyze the consolidation process of the sludge in the geotextile tube so as to provide a proper design and prediction becomes a technical challenge. In this paper, we have proposed a two-dimensional plain-strain consolidation model for sludge consolidation in a geotextile tube under combined fill and vacuum preloading. A semi-analytical solution was obtained and validated through experimental observations. A salient finding of this study is the identification of a critical condition at which the optimum consolidation efficiency is achieved. Consolidation efficiency decreases gradually beyond this critical condition, which arrives later as the PHD pave rate and element height to width ratio increase. Furthermore, this analytical method clearly shows how preloading affects the dewatering process and the effect of fill surcharge is more pronounced than that of vacuum preloading of the same magnitude, owing to the vacuum attenuation and leakage.

In land reclamation projects, the vacuum preloading method has been widely used to strengthen dredged fills by removing water. However, during the improvement process, clogging inevitably occurs in the drains and soils, hindering water drainage and causing inhomogeneous consolidation results. Therefore, it is essential to evaluate the effect of clogging on the consolidation behavior of dredged slurry at different radii. In this study, analytical solutions are derived under an uneven strain assumption to calculate the consolidation in the clogging zone and the normal zone, with time-dependent discharge capacity and clogging in the soil considered. Results calculated by the proposed solutions indicated that the clogging effect slows down the development of consolidation, reduces the final consolidation degree, and increases the difference between consolidations at different radii. It is found that the influence of the clogging effect's varies with the speed of the discharge capacity decay, the value of the initial discharge capacity of the drain, the permeability, and the radius of the clogging zone. Finally, a practical application of the proposed solution is discussed, and the proposed solution is suggested for the calculation of consolidation when treating high-water-content slurry.