1.5. Conducting Tests on Unsaturated Soils

Try these first

1. 1.

   What is the unconfined compressive strength called?

   Hint

   Identify the term we use to represent maximum axial stress in an unconfined test.

2. 2.

   What is the confining pressure (σ3) during the unconfined compression test?

   Hint

   Think about what 'unconfined' means in terms of pressure.

3. 3.

   What does unsaturated refer to in unsaturated soils?

   • Fully water-saturated
   • Partially water-saturated
   • No water at all

   Hint

   Consider what 'unsaturated' means in terms of water content.

4. 4.

   The unconfined compressive strength qu is equal to what during the test?

   • True
   • False

   Hint

   Remember the definition of qu in the context of this test.

5. 5.

   A soil sample shows an unconfined compressive strength of 150 kPa and is tested under increasing levels of saturation. If the saturation increases to 80%, what would you predict occurs to the strength? Explain your reasoning.

   Hint

   Recall the relationship between water content and soil stability.

6. 6.

   In a field study, a retaining wall is constructed on a saturated clay layer. Using the knowledge from the unconfined compression test, outline how you would evaluate its integrity following heavy rainfall.

   Hint

   Investigate how the test may reveal changes in soil properties post-rainfall.