Behavior of an Embankment on Soft Ground Improved with Soil–Geopolymer Deep Mix Columns under Static and Cyclic Loadings

The soil–cement deep soil mixing (DSM) technique has been widely used to improve the bearing capacity of the soft soil under embankment loading. However, utilizing ordinary portland cement (OPC) releases a tremendous carbon footprint. Industrial waste–based geopolymer has emerged as a sustainable and environmentally friendly solution for stabilizing soft soils. This work investigates the behavior of embankment models constructed on geopolymer-stabilized soil columns (GPSCs) under static and cyclic loading conditions similar to transportation routes. A series of static and cyclic loading tests were carried out on the reduced-scale designed embankment model resting on soft soil (cus = 5 kPa) reinforced with end-bearing (l/h = 1) and floating (l/h = 0.75) GPSCs with area replacement ratios (Ar) of 12.7%, 17%, and 21.2% to analyze the vertical stress–settlement behavior of the improved ground. Earth pressure cells were used to measure the vertical stress on the column and the adjacent surrounding soil under static and cyclic embankment loading. A pore-pressure transducer was used to monitor the excess pore-water pressure generated during the loading process. The results indicate that the ultimate bearing capacity (qult) improvement for end-bearing GPSCs was 246.92%, 344.56%, and 418.8%, whereas the improvement for floating GPSCs was 126.9%, 151%, and 181.64% for Ar values of 12.7%, 17%, and 21.2%, respectively. Furthermore, the stress concentration ratio increases and excess pore-water pressure decreases with increasing Ar and l/h ratios. A mathematical equation was also derived to determine the qult value with Ar and l/h ratios. End-bearing GPSCs were more effective than floating GPSCs at the same Ar under static and cyclic loading. For installing floating GPSCs, a higher area replacement ratio is required for better load bearing under static and cyclic loading. In addition, a life cycle assessment of the geopolymer compared to OPC was performed, showing that the geopolymer is a sustainable and eco-friendly construction material.