Soil qualities need to be improved to address numerous geotechnical engineering issues. Improvements are needed in areas where soil cannot support loads. Soil improvement is essential in areas where the existing ground cannot support structural loads, particularly in problematic soils characterized by high water content, high compressibility, and low shear strength. This study evaluates the geotechnical performance of clayey soil stabilized with waste palm fiber (PF) and tire ash (TA). Soil samples made from clayey soil were used for these studies; four percentages (0.2, 0.4, 0.6, and 0.8%) of palm fiber and three percentages (1, 3, and 5%) of tire ash were employed. The test findings show that increasing the content of palm fiber in clayey soil increases the plastic limit value while decreasing the liquid limit and plasticity index values. Additionally, the liquid limit and clay plasticity index decrease when tire ash is added to mixed soil with the optimum percentage of palm fiber (0.8%). As the amount of palm fiber increases, the optimum moisture content increased while the maximum dry density decreased. By adding more tire ash, the maximum dry density rises. The optimum moisture content of clayey soil continues to decline as the amount of tire ash increases. The treated clay’s unconfined compression strength gradually improved as the amount of palm fiber increased, the UCS increased from 60 kPa for untreated clay to 83 kPa representing an increase of 38.33%. Additionally, compared to untreated specimens, the addition of tire ash and the optimum dosage of palm fiber resulted in an extra improvement strength; with 0.8% palm fiber and 5% tire ash, the UCS reached 170 kPa, corresponding to a 183.33% increase relative to untreated soil.
