1.3. Effective Stress Principle

Try these first

1. 1.

   What is the formula for calculating total stress at a given depth?

   Hint

   Think about the weight of the soil above.

2. 2.

   Define pore water pressure.

   Hint

   Consider what happens in saturated soil conditions.

3. 3.

   What is the formula for effective stress?

   • σ' = σ + u
   • σ' = σ - u
   • σ' = σ * u

   Hint

   Recall the main equation of the Effective Stress Principle.

4. 4.

   The pore water pressure at the water table is:

   • True
   • False

   Hint

   Think about the definition of the water table.

5. 5.

   Given a soil layer with a total stress of 150 kPa and pore water pressure of 50 kPa, if the water table rises by 1 meter causing an additional 5 kPa of pore water pressure, what will the effective stress be after this increase?

   Hint

   Don't forget to recompute pore water pressure after the water table rises.

6. 6.

   In practicing geotechnical exercises, a soil profile has an initial effective stress of 80 kPa. If a construction adds 40 kPa of load, calculate the changes in stress if the initial pore water pressure is 20 kPa. Additionally, explain why maintaining effective stress is essential during this operation.

   Hint

   Look at effective stress's role when loads are applied to soil.