9.4.3. Effective stress equation

Try these first

1. 1.

   What is the formula for effective stress?

   Hint

   Remember it involves total stress and pore pressure.

2. 2.

   Define quick sand condition.

   Hint

   Think about how upward water flow affects soil.

3. 3.

   What does effective stress indicate in soil mechanics?

   • Total stress
   • Stress carried by soil particles
   • Pore water pressure

   Hint

   Think about the stress that affects the structural integrity of soil.

4. 4.

   True or False: A rise in groundwater level always increases effective stress.

   • True
   • False

   Hint

   Reflect on how water pressure interacts with total stress.

5. 5.

   A construction site has a clay layer with a total stress of 40 kPa above a sand layer. When the groundwater table rises, the pore water pressure increases to 20 kPa. Evaluate how this affects the effective stress.

   Hint

   Consider what happens to the effective stress when pore water pressure changes.

6. 6.

   In a detailed analysis of soil stability, if soil at a depth of 15 m has a total stress of 50 kPa and pore water pressure is measured at 15 kPa, calculate the effective stress. Discuss the engineering implications.

   Hint

   Refer to the definitions of total and effective stress in your calculations.