Comparative Study for Improving Soft Soil Beneath an Embankment

Earth embankments are often required at construction sites to support roads, networks, and rail systems. Therefore, this paper studies different methods for improving soft soil in order to construct an earth embankment on such soft soil. A numerical analysis was performed using 2D finite element software (Plaxis) to simulate the proposed embankment and the underlying soil. The findings revealed that the soil at the site could not sustain the stresses imposed from the full height of the embankment, leading to shear failure in the soil before establishing the proposed height of the embankment. To tackle this problem, two techniques were considered and a comparative analysis was conducted to assess the effectiveness of these techniques. The first technique involved using lightweight materials, such as soil mixed with sawdust or geo-foam for constructing the embankment. In the second technique variety of replacement techniques, including concrete piles (CP), deep-mixing columns(DMC), stone columns(SC), and sand piles(SP) were employed to improve the bearing capacity of the soft soil layers. Research findings indicate that only 60% of embankment height could be constructed on non-improved soil with acceptable settlement. Using lightweight materials significantly reduces settlement and stress without the need for additional improvement measures. Replacing the weak soil with different materials enhances the soil properties and helps in transferring loads through the soil. Replacing soft soil reduced the settlement by ratio varied between 8.50–75% and the stress by ratios ranging from 30–80%. Importantly, the findings from DMC align with those of CP. Finally, British Standard 8006 (2010) overestimates the loads acting on CP by a ratio varied from 2 to 14. This ratio increases as the pile's material stiffness decreases.