6.1. Fine-grained soils

Try these first

1. 1.

   Define fine-grained soils.

   Hint

   Recall the particle size criteria.

2. 2.

   What does the plasticity index measure?

   Hint

   Think about the transition states of soil.

3. 3.

   What percentage of particles must be smaller than 0.075 mm to classify soil as fine-grained?

   • 30%
   • 50%
   • 60%

   Hint

   Think about what 'fine-grained' means.

4. 4.

   True or False: The liquidity index is a measure of soil plasticity.

   • True
   • False

   Hint

   Consider how liquidity relates to soil states.

5. 5.

   A soil sample has W_L = 70%, W_P = 36%. It contains 40% clay. Calculate its plasticity index, activity, and liquidity index. Discuss its construction suitability.

   Hint

   Make sure to substitute the correct values into the formulas.

6. 6.

   A construction site requires a soil that can handle rapid moisture changes. If you have two samples—Sample A with W_L = 45% and PI = 15%, and Sample B with W_L = 60% and PI = 35%—which do you choose and why?

   Hint

   Evaluate the plasticity of each sample based on their PI.