Which of the following methods is NOT used to improve soft soils?

• A. Pre-compression
• B. Vertical drains
• C. Dredging
• D. In-situ densification

Answer: (C)

Dredging is not a method typically used to improve soft soils. Instead, dredging is a process primarily used for removing sediment from the bottom of bodies of water, such as rivers or lakes, to deepen them or remove accumulated materials. While dredging may alter the conditions of the environment or prepare sites for construction, it does not specifically address the challenges posed by soft soils in the context of soil improvement.

In contrast, pre-compression is a technique that involves applying a surcharge load to the soil to expedite consolidation and enhance its load-bearing capacity. Vertical drains are installed to reduce pore water pressure and accelerate consolidation in soft, saturated soils. In-situ densification involves the mechanical compaction of soil to increase its density and strength without removing it from its location. Each of these methods directly targets the characteristics of soft soils to improve stability and support for structures, making them suitable for soil improvement projects.