Basics of Soil Mechanics- Principle of effective stress

Question 1

What are saturated soils composed of?

(2)

Answer 1

1) Grains with different shapes and sizes
2) Water

Question 2

What do the soil grains contribute towards?

Answer 2

The main structure of the soils skeleton

Question 3

What is the formula to calculate the degree of saturation?

Answer 3

Sr = Vw/Vv

• Sr- Degree of saturation
• Vw- Volume of water
• Vv- Volume of voids

Question 4

What is the formula for Terzaghi’s Principle?

Answer 4

σ = σ’ + u

• σ = Total Stress (external actions)
• σ’ = Effective Stress (actions on solid skeleton)
• u = Pore Water Pressure (pressure of interstitial fluid)

Question 5

What is interstitial fluid pressure?

Answer 5

Pressure of the fluid between grains

Question 6

How can we model a specimen of saturated soil?

Answer 6

σ = Normal stress applied on top of the soil

Opening = soil permeability

Spring = Soil grains

Question 7

What is the physical meaning of the opening in the saturated soil model?

Answer 7

Soil Permeability (m/s)

• Measures the speed of water that flows through a given thickness of soil
• It can greatly change depending on the soil
• It influences the mechanical behaviour of soils