1.1. Total Stress

Try these first

1. 1.

   Define total stress in soil mechanics.

   Hint

   Think about what contributes to the pressure at a depth.

2. 2.

   What is the formula for calculating total stress?

   Hint

   Remember the elements involved in the formula.

3. 3.

   What is total stress defined by?

   • Weight of soil above
   • Weight of water only
   • Weight of air only

   Hint

   Think about what contributes to the pressure in the ground.

4. 4.

   True or False: Pore water pressure increases when the water table rises.

   • True
   • False

   Hint

   Recall the relationship between water table height and pore pressure.

5. 5.

   A construction site is excavating down to 10 meters in saturated clay with a unit weight of 20 kN/m³. If the water table is at 5 meters, calculate the expected total stress at the depth of 10 meters. Discuss the implications on effective stress if pore water pressure is also identified.

   Hint

   Consider both the weight of the soil and the water when calculating total stress.

6. 6.

   Explain how changes in water table levels during heavy rainfall could impact the stability of a retaining wall constructed in sandy soil. Include calculations for how much the pore water pressure changes with a water table rise of 2 meters.

   Hint

   Evaluate how changes in pore water pressure influence effective stress and subsequently wall stability.