9.3. Effective Stress Behavior

Try these first

1. 1.

   What is effective stress?

   Hint

   Remember the effective stress equation.

2. 2.

   Define hydraulic gradient.

   Hint

   Think of it in terms of water flow direction.

3. 3.

   What is the formula for effective stress?

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

   Hint

   Remember the equation and how each term behaves.

4. 4.

   True or False: An increase in pore water pressure always increases effective stress.

   • True
   • False

   Hint

   Consider the impact of water pressure on soil stability.

5. 5.

   You have a soil layer with a depth of 12 m, total stress of 36 T/m², and pore water pressure of 15 T/m². Calculate the effective stress. Discuss the implications of pore water pressure changes on stability.

   Hint

   Apply the effective stress equation to analyze stability.

6. 6.

   A project involves excavating to a depth of 5 m in an area where the water table is at 3 m. Calculate the effective stress at the bottom of the excavation, and explain what could happen if the water table rises.

   Hint

   Be careful to consider layers above and any changing conditions!