9. Effective stress under Hydrodynamic Conditions

Try these first

1. 1.

   Define effective stress.

   Hint

   What is the formula representing effective stress?

2. 2.

   What happens to effective stress when pore water pressure increases?

   Hint

   Consider the relationship between the components in effective stress calculation.

3. 3.

   What is the formula for calculating effective stress?

   • A) C3' = C3 + u
   • B) C3' = C3 - u
   • C) C3' = u - C3

   Hint

   Remember the definition of effective stress.

4. 4.

   True or False: A decrease in pore water pressure always results in an increase in effective stress.

   • True
   • False

   Hint

   Consider how the components of effective stress interact.

5. 5.

   A soil layer experiences a total stress of 300 kPa at a depth of 5 m. Pore water pressure in this layer is measured at 100 kPa. Calculate the effective stress.at this depth and explain its significance.

   Hint

   Use the effective stress formula.

6. 6.

   In a case of quick sand conditions observed at a construction site, the critical hydraulic gradient for the soil was determined to be 1. If the upward pore water pressure in the soil layer was 110 kPa, what was the total stress causing the quick sand condition to occur?

   Hint

   Reflect on the definition of critical hydraulic gradient.