Stability Analysis of Colombo–Katunayake Expressway Embankment Using Fly Ash-Stabilized Soil as the Embankment Material

Abstract

AbstractThere is a huge scarcity in good-quality embankment materials in Sri Lanka with the rapid development of highway construction in the country. On the other hand, huge amount of fly ash (FA) is produced at Lakvijaya coal power plant and bulk of the FA produced ends up in landfills causing adverse environmental impacts. Therefore, this research aims to predict the feasibility of using FA-stabilized marginal soil (the soil that does satisfy the Road Development Authority requirements for embankment material) as an embankment material by analyzing the stability and deformation of the embankment constructed using FA-stabilized marginal soil. For this purpose, two selected embankment sections at Colombo–Katunayake Expressway (CKE) were analyzed numerically using PLAXIS 2D and SLOPE/W software. FA percentages of 0, 10, 20, 30, and 40% (by weight) were considered for the stabilization, and the soil properties of the marginal soil and the FA-stabilized soil were obtained from relevant literature. First, model was validated using PLAXIS by analyzing various material model combinations (Mohr coulomb (MC), soft soil (SS) and soft soil creep (SSC)) for different soil layers, and the model combination providing consistent settlement results with the field observation was selected for further analysis. Based on the selected model, analyses were conducted to predict the optimum FA content and long-term settlement behavior of the FA-stabilized embankment. Results revealed that MC-SS-SSC (SS for soft soil, SSC for peat, and MC for to other soil type) is the most reliable model to predict the field settlement accurately. The optimum FA content is 30% FA (by weight) for better performance in terms of both deformation and stability behavior. Long-term analysis revealed that there is a significant reduction in vertical settlement, lateral deformation, and improvement in factor of safety (FOS) of FA-stabilized embankment compared to nonstabilized embankment.KeywordsEmbankment fillFinite-element methodFly ashMarginal soilSettlement