The placement of filtered tailings over hydraulic deposits creates a geotechnical condition in which a stiff, partially unsaturated engineered fill is constructed over a soft, compressible, saturation controlled foundation. Hydraulic tailings from past operations often exhibit loose structures, high void ratios, and stratified fabrics that may lie near or above their critical state line under modest loading. These characteristics make the foundation response highly sensitive to stress path, pore pressure generation, and strain accumulation during sequential stacking. This study develops an integrated stability assessment focused on controlling critical state tendencies, tracking pore pressure evolution, and predicting deformations during embankment construction. Field and laboratory testing on representative hydraulic tailings indicate contractive behaviour within operational stress ranges, low initial stiffness, and high susceptibility to rapid pore pressure buildup under undrained loading. Critical state parameters were incorporated into numerical models to simulate stress paths during staged deposition. Coupled stress deformation and transient seepage analyses indicate that, as filtered tailings are placed, excess pore pressures concentrate near depositional interfaces and within low-permeability laminae inherited from hydraulic sedimentation. Without drainage enhancement, these pressures reduce effective stress and may shift portions of the foundation toward the critical state surface, promoting localised softening or delayed settlement. Conversely, basal drains, relief wells, and engineered drainage corridors accelerate dissipation and maintain effective stress trajectories within stable domains. Results also show that controlled compaction of filtered tailings improves load distribution and limits the propagation of shear strains into weaker hydraulic layers. Monitoring settlement and lateral displacement is essential to detect transitions toward the critical state. Seasonal infiltration modelling suggests that transient wetting may reduce suction in filtered layers but does not compromise stability when drainage pathways remain functional. Overall, safe stacking on hydraulic foundations is feasible when design explicitly manages state parameter evolution, pore pressure dissipation, and deformation control, ensuring the long-term stability of the combined system.