Construction on soft cohesive soils presents significant engineering challenges due to low shear strength and high compressibility, leading to excessive long-term consolidation settlement. This paper investigates the efficacy of three primary ground improvement techniques: Preloading with Prefabricated Vertical Drains (PVDs), Stone Columns (Granular Piles), and Deep Soil Mixing (DSM). Using PLAXIS 2D/3D numerical modeling and field data from infrastructure projects in coastal regions, this study quantifies settlement reduction ratios. Results indicate that while PVDs accelerate consolidation, DSM columns provide the highest immediate stiffness, reducing total settlement by up to 75% compared to untreated ground. Soft cohesive soils are often characterized by their high void ratio (e) and secondary compression index. "excessive long-term consolidation settlement" isn't just a physical change; it’s a time-dependent threat to infrastructure integrity. The Stochastic Nature: Unlike sands, soft clays have a "memory" (Over-consolidation Ratio or OCR). Your paper elaborates on how these improvement techniques reset or bypass the soil's natural consolidation path, forcing it to reach an "end-of-primary" state much faster or with less overall deformation. PVDs do not technically "strengthen" the soil instantly; they provide a geometric shortcut. Radial Consolidation: By replacing vertical drainage (long path) with radial drainage (short path to the drain), you are utilizing Barron’s Theory. Reinforcement: They introduce a stiffer material into the soil matrix, creating a "Composite Ground. “Drainage: Like PVDs, they provide a path for pore water, but their primary value is their load-bearing capacity. The "Bulging" Mechanism: Your paper should elaborate on how the lateral confining pressure of the surrounding soft soil is what actually keeps the stone column from failing. DSM is the most aggressive and effective of the three. Pozzolanic Reactions: Elaboration here focuses on the chemical change. When cement/lime is mixed with clay, it creates Calcium Silicate Hydrate (CSH) bonds. Rigid Inclusion: Instead of helping the soil "settle faster, " DSM creates columns that are so stiff they carry 80–90% of the total embankment load, effectively "shielding" the soft soil from stress. This is why you observed a 75% reduction in settlement.
Chaudhary et al. (Tue,) studied this question.