The “method of overlap” replaces traditional welding to solve the problem of how the geosynthetic-encased stone column is limited by the welding frame during site construction, making the site construction simplified and economical, but its bearing mechanism is not clear. Therefore, the bearing mechanism and failure mode of the stone column was studied through the compression test of the multi-layer geosynthetic-encased stone column under dynamic and static loading. The research shows that the multi-layer encasement improves the modulus and lateral restraint of the stone column, which increases the stress transfer rate and reduces the damage degree of the stone column. The vertical ultimate bearing capacity increase in multi-layer geosynthetic-encased stone columns under dynamic and static loading is significantly different, and the difference can be up to 47.1%; the corresponding number of encasement layers should be selected according to the actual situation. The influence of the difference between dynamic and static loading on the location of the main radial strain of the stone column can be ignored, but the lateral restraint of the stone column under dynamic loading is weakened, the stress transfer rate is reduced, and the radial strain is reduced and more uniform along the stone column height. The vertical ultimate bearing capacity of the one- and two-layer geogrid-encased stone column under dynamic loading is lower than that of static loading. When treating soft foundations, the influence of traffic loads should be considered, and the bearing capacity of the geosynthetic-encased stone column should be appropriately increased in design value.

To address the critical limitations of conventional parallel double-anchor support systems, including coplanar load imbalance, critical spacing risks, deviations from theoretical designs, and maintenance difficulties, this study proposes an innovative multi-anchored sheet pile reinforcement method. Centrifuge model tests incorporating digital image correlation (DIC) techniques were systematically conducted to investigate the anchoring mechanism of the novel system in port basin bulkhead reinforcement, with a particular emphasis on parameter optimization. The results indicate that the excavation depth predominantly governs the mechanical response of quay walls (sensitivity coefficient 2.3), necessitating phased excavation protocols for deformation control. In contrast, tie-rod horizontal spacing demonstrates low sensitivity (0.018), enabling displacement-controlled dynamic optimization to balance safety and cost-effectiveness. Further, strategic anchor rod installation restructures stress transmission paths, effectively suppressing the shear deformation of shallow soil. The synergistic interaction between prestress application and soil–anchor load transfer mechanisms induces potential migration of the slip surface toward reinforced zones, enhancing stability by 34–41% compared to conventional systems. The developed composite prestressed anchor system achieves a 71.9–77.3% reduction in sheet pile bending moments through stiffness enhancement–stress redistribution coupling effects, establishing a new paradigm for high-performance port infrastructure.