<p>In geotechnical engineering, soil stability is crucial because it guarantees that the soil can sustain structures, restrict water penetration, and withstand deformation in a variety of scenarios. This study focuses on two easily accessible waste items that show promise as stabilizing agents for poorly graded clayey soil: pine needles (PN) and marble dust (MD). The Modified Proctor Test, Unconfined Compression Test (UCT), Falling Head Permeability Test, California Bearing Ratio (CBR) Test, and Swelling Test were among the laboratory tests conducted to investigate the impact of these additions on the engineering properties of clayey soil. According to the study, applying PN and MD together improved the soil's mechanical strength, decreased permeability, and controlled its tendency to swell. Density and moisture content both improved, and the stabilization process increased the soil's ability to support weight and its resistance to water flow. These results show that PN and MD have the potential to be economical and environmentally friendly substitutes for soil stabilization. This strategy promotes ecologically friendly construction and geotechnical application methods by using waste resources, which helps to create more sustainable infrastructure. Further field tests and improved models will confirm these eco-friendly soil stabilization gains too. Additionally, it has been demonstrated that adding these elements improves soil performance overall while lowering environmental impact and construction costs. The enhanced soil behavior observed in this study offers a strong basis for further investigation and real-world implementation in sustainable civil engineering projects, supporting sustainable construction methods and effective resource management.</p>