Grain, Soil and Water Pressure: Effective Stress & Vertical Soil Stress Flashcards
1
Q
What is effective stress in soil mechanics?
A
Effective stress is the stress carried by soil grains, influencing strength and stability.
2
Q
Why is effective stress important?
A
It determines the strength, consolidation, and shear resistance of soil, as water pressure does not contribute to soil structure.
3
Q
What is the formula for vertical soil stress?
A
σ_v = σ_v’ + σ_w
Where:
σ_v = Total vertical soil stress
σ_v’ = Vertical effective stress
σ_w = Water pressure
4
Q
How is vertical soil stress calculated in a dry condition (no groundwater)?
A
σ_v = h × γ_soil
Where:
h = Depth (m)
γ_soil = Unit weight of soil (kN/m³)
5
Q
What happens to total soil stress when groundwater is present?
A
Water pressure reduces effective stress, meaning:
σ_v ≠ σ_v’
