Purpose <p>Long-term mining operations in the mining area have caused severe Cd-contaminated soil, posing significant threats to plant growth, human health, and slope ecological stability. Current remediation technologies struggle to simultaneously achieve multiple objectives, including efficient cadmium immobilization, ecological restoration, and slope stabilization to improve shear strength.</p> Materials and methods <p>This study combines cement, Biochar, and ryegrass to establish a ternary synergistic remediation system integrating immobilization, stabilization, and ecological restoration. Through experiments with varying ratios, the system’s mechanical enhancement effects on Cd-contaminated soil, pollutant immobilization efficiency, and plant physiological responses were systematically evaluated.</p> Results and discussion <p>Results indicate optimal comprehensive performance at a cement content of 3% and Biochar content of 10%. At this ratio, the cohesion of the root-soil complex increased by 237% compared to contaminated soil. Cd immobilization rate reached 96.8%, and the proportion of stable Cd in soil increased from 10.0% to 76.8%. Simultaneously, ryegrass exhibited robust growth under this formulation, with its transport coefficient stabilizing at a low level of 0.08–0.11. Cd content in stems/leaves and roots decreased by 92.1% and 84.8%, respectively, compared to the control group.</p> Conclusions <p>Mechanistic analysis indicates that this system achieves an organic integration of mechanical reinforcement, pollution stabilization, and ecological restoration through the synergistic interaction of multiple mechanisms, including cadmium adsorption, immobilization, and plant bioaccumulation. This study provides a theoretical basis for the synergistic remediation of cadmium-contaminated soils and vegetation degradation in mining areas.</p> Graphical abstract <p></p>