6.8. Worked Example

Try these first

1. 1.

   What is the formula for calculating the plasticity index?

   Hint

   Think about the difference between two limits.

2. 2.

   How would you classify soil with a plasticity index of 22%?

   Hint

   Check the plasticity chart.

3. 3.

   What does the plasticity index measure?

   • Soil consistency
   • Plasticity of soil
   • Soil grain size

   Hint

   Think about what aspect of soil we are measuring.

4. 4.

   True or False: The liquidity index indicates whether soil is liquid, soft, or stiff.

   • True
   • False

   Hint

   Remember how liquidity relates to soil states.

5. 5.

   Given a soil with a liquid limit of 55%, plastic limit of 30%, and clay content of 80%, determine the plasticity index, liquidity index, and classify the soil.

   Hint

   Use the formulas given in the example.

6. 6.

   Assess a soil sample with a plasticity index of 15% and clay content of 50%. What activity classification does the soil fall into?

   Hint

   Calculate using the activity formula.