Effect of polypropylene fibers on internal erosional behavior of poorly graded sandy soil stabilized with the binary mixtures of clay and polyvinyl acetate

Internal erosion refers to the mechanism of separation and movement of soil grains owing to water flow from a porous environment that may cause significant damage to the structures involved. In the present research, an environmentally friendly approach was used to improve the mechanical strength and erosion resistance of a poorly graded problematic sandy soil (SP) sample with a high degree of erodibility and negligible strength. For this purpose, polypropylene fibers (PP) (0, 0.35, 0.5 and 1%) were added to the studied sandy soil stabilized with different contents of clay (0, 5, 10 and 20%) and polyvinyl acetate (PVAc) resins (0, 1.2, 1.5 and 2%). The main goal of this study was to fully replace traditional stabilizers such as cement with durable and sustainable substitutes. The results revealed that the development in the strength of the samples by increasing the curing times was attributed to the time-dependent performance of PVAc content. Furthermore, the poorly graded sandy soil (PGSS) treated with PVAc and clay showed the highest mechanical strength equal to 2580 kPa after 28 days of curing. In terms of the Erosion Rate Index (ERI), the combination of 20% clay and 0.5% fiber along with 1.2% PVAc had the best performance, which was reported as 4.28 after 28 days. Among different samples reinforced by fiber, the highest ERI is related to the samples with 0.5% fibers at the 28-day curing time. The strength of the samples with clay inclusion was significantly higher than that of the samples with either PP fiber or PVAc inclusion, indicating the high potential of clay addition in developing the strength of the poorly graded sandy samples as confirmed by Scanning Electron Microscopy (SEM) analysis. SEM observations revealed that the treated sand sample became denser as the content of the amendments increased.