Experimental and Numerical Investigations on Subgrade Stabilized with Bagasse Ash and Geosynthetics

Abstract: Conventional subgrade soil stabilization agents often come with high costs and pose significant environmental challenges due to their greenhouse gas emissions. This reality highlights the urgent need for sustainable, affordable, and eco-friendly alternatives in civil engineering practices. In Ethiopia, which ranks as the sixth-largest sugar producer in Africa, a pressing issue arises from the vast quantities of sugarcane bagasse ash (SCBA) waste generated by sugar factories. However, this waste also offers a unique opportunity to harness it as an alternative stabilization agent to enhance the properties of weak soils.
This study aims to evaluate the effectiveness of sugarcane bagasse ash (SCBA) in combination with nonwoven geotextile (NWG) for improving the engineering characteristics of high-plasticity subgrade soils. Comprehensive physical, chemical, and mechanical tests were conducted on soil samples collected from Jimma city, providing a robust understanding of the material properties. Additionally, numerical simulations using PLAXIS 2D V20 were conducted to model the deformation characteristics of a pavement constructed on a subgrade stabilized with SCBA-NWG. Nominal and heavy axle loads were applied during these simulations to represent regular and extreme loading conditions.
Laboratory results demonstrated that the strength of plastic clay improved significantly when SCBA and NWG were applied independently. Furthermore, the most remarkable enhancements were observed when these materials were optimally combined, resulting in significant improvements in both the physical and mechanical properties of the soil. The CBR (California Bearing Ration) values of stabilized soils increased by 250%, 350%, and 900% when SCBA, NWG, and a combination of SCBA + NWG were used individually and in combination, respectively. The observed enhancements can be attributed to the combined effects of mechanical and chemical modifications, along with the pozzolanic activity occurring within the matrices of the soil-stabilizing agents.
The finite element analysis results further revealed a notable reduction in vertical surface deformation when SCBA and NWG were incorporated into the subgrade layer. Additionally, variations in the positioning of the NWG within the subgrade exhibited significant differences in stress distributions and settlement magnitudes. The response of the pavement on a stabilized subgrade, with an optimized combination of SCBA and NWG under nominal loads, shows a significant improvement in deformation resistance. Additionally, it demonstrates reasonable effectiveness in resisting extreme load conditions.
By utilizing SCBA, this research contributes to the development of greener road infrastructure, promoting sustainability in pavement engineering. The findings underscore the potential of innovative materials to not only enhance soil properties but also mitigate environmental impacts, paving the way for more eco-friendly construction practices in developing countries.