Abstract
This study investigated the effect of two types of fibers (natural and synthetic) on the swelling properties of clayey soils. Nylon and palmyra fibers with different aspect ratios (L/d) were mixed with three types of expansive soils that had different physical properties. Four aspect ratios (25, 50, 75, and 100) and five different amounts of fiber (1, 2, 3, 4, and 5%) were used in the study and both swelling pressure and swell potential were evaluated for each combination. The results of the study showed that an increase in the percentage of both types of fiber reduced the swelling pressure and swell potential of the clayey soils significantly. It was also noted that the palmyra fibers had a greater effect than the nylon fibers in reducing the swelling pressure of the expansive soils that included the same amount of the fiber. The lower aspect ratio (L/d) appeared to have a greater effect in reducing the swelling pressure for the two types of fibers. The impact of mixing the fibers with the clayey soils increased as the clay fraction increased.