Stabilization of Subgrade Soil Using Sugarcane Fiber

Abstract: Pavements are designed to provide smooth, stable, and safe transportation to vehicles and pedestrians. The traffic load is distributed through each pavement layer and transferred to the underlying subgrade soil. The subgrade soil may not always be durable enough to support the pavement structure. Therefore, the subgrade soil is generally stabilized to improve soil properties using methods like mechanical compaction, chemical additives (lime, cement), or geosynthetics. This enhances the soil’s load-bearing capacity, reduces settlement, and increases durability, making it suitable for construction projects. All these soil stabilization methods have some limitations, such as cost, environmental impacts, ease of application, etc.
India is a developing country with a total road infrastructure of 6.3 million kilometers. Using typical soil stabilization techniques is not always feasible for such a vast road network and budget limitations. Several researchers have used natural fibers, such as coconut fiber, rice husk, etc., to encounter all these issues. Soil stabilization using natural fibers is an ancient technique with advantages over other popular methods. This study used sugarcane fiber (after the juice had been removed) for subgrade soil stabilization using soil samples from Chennai, India. The aim is to determine the extent of soil strength improvement and different trends in engineering properties by adding different percentages (by weight) of sugarcane fiber. Sugarcane is readily available in all parts of India, is exceptionally cheap, easy to handle, and poses no environmental risks. The sugarcane fiber sample was prepared by sun drying and oven drying the sugarcane's outer shell for 48 hours and manually chopping it into 8 to 12 mm pieces with a length-to-diameter ratio ranging between 4 and 24. The soil sample was collected from an excavated site at a depth of 600 mm from the surface. The soil sample was initially tested for the soil type using the grain size distribution and Atterberg’s limits. Then, the unconfined compressive strength (UCS), California bearing ratio (CBR), and proctor compaction test were performed on the soil samples without added fiber and with varying amounts of added fiber.
The results show that the soil was a well-graded sand (SW), as per the Unified Soil Classification System (USCS). The optimum moisture content increased, whereas the maximum dry density decreased by increasing the percentage of fiber dosage. The strength (UCS and CBR values) initially increases and then decreases as the percentage of sugarcane fiber increases, with maximum strength at 2% fiber content. The CBR and UCS values increased by 2.12 and 2.40 times, respectively, at the optimum fiber content compared to the original soil sample. Overall, this study shows the applicability of sugarcane fiber in enhancing the subgrade soil strength.