Which material swells more from its natural state (bank) to compacted state (placement in an embankment)?

Which material swells more from its natural state (bank) to compacted state (placement in an embankment)?

• A. Cohesive soils
• B. Solid rock
• C. Sand
• D. Bedrock

Answer: (B)

Swelling a material experiences when moving from its natural bank into a compacted embankment is highest for cohesive soils. These clays have fine particles with high plasticity and a strong tendency to absorb moisture, causing significant volume expansion when disturbed or wetted. That expansive behavior means their volume can increase notably during excavation and subsequent placement and compaction. In contrast, solid rock and bedrock are essentially incompressible and show negligible swelling. Sand is granular and non-expansive; it tends to densify and reduce voids under compaction rather than swell. So, cohesive soils swell the most when transitioning from natural bank to compacted fill.

Swelling a material experiences when moving from its natural bank into a compacted embankment is highest for cohesive soils. These clays have fine particles with high plasticity and a strong tendency to absorb moisture, causing significant volume expansion when disturbed or wetted. That expansive behavior means their volume can increase notably during excavation and subsequent placement and compaction.

In contrast, solid rock and bedrock are essentially incompressible and show negligible swelling. Sand is granular and non-expansive; it tends to densify and reduce voids under compaction rather than swell.

So, cohesive soils swell the most when transitioning from natural bank to compacted fill.