p.3
Total, Neutral, and Effective Pressure
What is the relationship between Total Pressure, Effective Pressure, and Neutral Pressure?
Total Pressure (σ) equals Effective Pressure (σ') plus Neutral Pressure (u).
p.3
Examples of Pressure Calculations
What is the Total Pressure at a depth of 1 m?
Total Pressure = 16.7 kPa.
p.8
Effective Stress in Soil Mechanics
What density should be used when calculating pressures in nearly fully saturated silts and clays?
ρ sat (saturated density).
p.10
Effective Stress in Soil Mechanics
What is the effective vertical stress at the top of a clay layer that is 4 m thick with a saturated density of 2.00 t/m³, when the water table is 2 m below ground level?
At the top of the clay layer, σ' = (4 m * 2.00 t/m³) - (2 m * 9.81 kN/m³) = 8 t/m² - 19.62 kN/m².
p.9
Self-Assessment Questions on Soil Pressure
What are the three types of vertical stress to calculate for the soil profile?
Total, neutral, and effective vertical stress.
p.2
Total, Neutral, and Effective Pressure
What is the general form of the total pressure equation?
σ = σ' + u, where σ' is the effective pressure and u is the neutral pressure.
p.3
Examples of Pressure Calculations
What is the Effective Pressure at a depth of 3 m?
Effective Pressure = 34.4 kPa.
p.2
Total, Neutral, and Effective Pressure
What does the vertical stress equation represent?
Vertical Stress = Mass Density × g × Depth.
p.4
Effective Stress in Soil Mechanics
Does the distributed load change the water pressure in the sand?
No, it does not change the water pressure.
p.9
Self-Assessment Questions on Soil Pressure
What is the effective vertical stress (σ') at the top of the clay in a dam with a base of sand (ρ_sat = 1.85 t/m³) and clay (ρ_sat = 2.12 t/m³)?
To be calculated based on the given parameters.
p.3
Total, Neutral, and Effective Pressure
What is the significance of the equation σ = σ' + u in soil mechanics?
It is the most important equation in soil mechanics, relating Total Pressure, Effective Pressure, and Neutral Pressure.
p.2
Total, Neutral, and Effective Pressure
How is water pressure on the base calculated?
Water pressure (u) = ρw × g × h (in kPa).
p.2
Total, Neutral, and Effective Pressure
What does σ represent in the pressure equations?
σ represents the total pressure.
p.1
Total, Neutral, and Effective Pressure
What does the total mass of the contents in a container filled with gravel depend on?
The mass density of the saturated gravel and the volume (Area × Height).
p.4
Pressure Calculation in Soil Layers
How is water pressure (u) calculated in the example?
u = ρw ghw = 1.0 × g × 5 = 49.1 kPa.
p.2
Total, Neutral, and Effective Pressure
What is the relationship between total pressure, soil pressure, and water pressure?
Total Pressure = Soil Pressure + Water Pressure.
p.3
Effective Stress in Soil Mechanics
What does the term 'Effective Pressure' refer to in soil mechanics?
It refers to the soil pressure that contributes to shear strength, while water pressure contributes nothing to strength.
p.9
Self-Assessment Questions on Soil Pressure
What is the vertical stress (σ) at the top of the sand in a dam with a base of sand (ρ_sat = 1.85 t/m³) and water level of 4 m?
To be calculated based on the given parameters.
p.3
Examples of Pressure Calculations
What is the Effective Pressure at a depth of 1 m?
Effective Pressure = 16.7 kPa.
p.9
Self-Assessment Questions on Soil Pressure
What is the effective vertical stress 5 m below the top of the sand in a river that is 2 m deep with ρ_sat = 2.05 t/m³?
To be calculated based on the given parameters.
p.8
Effective Stress in Soil Mechanics
What happens to the pressure within the water above the water table?
It is below atmospheric pressure, resulting in negative pressure.
p.10
Effective Stress in Soil Mechanics
What happens to the effective stress (σ') at the base of the soil stratum when groundwater is lowered to 3 m below ground level?
With groundwater lowered, u = 3 m * 9.81 kN/m³ = 29.43 kN/m². Total stress remains 30 t/m², so σ' = 30 t/m² - 29.43 kN/m² = 0.57 t/m².
p.2
Effective Stress in Soil Mechanics
What is the significance of the contact area between gravel and the base?
The contact area is extremely small and can be neglected.
p.3
Examples of Pressure Calculations
At a depth of 0 m, what are the vertical pressures?
All vertical pressures = 0 kPa.
p.3
Examples of Pressure Calculations
At a depth of 3 m, what is the Total Pressure calculated?
Total Pressure = 54.0 kPa.
p.8
Total, Neutral, and Effective Pressure
What is the relationship between effective stress and total stress in the example provided?
Effective stress equals total stress.
p.8
Capillary Rise of Water in Soils
What phenomenon occurs in soils similar to capillary rise in a tube?
Capillary rise of water in soils.
p.5
Total, Neutral, and Effective Pressure
How is effective pressure calculated at a depth of 2 m?
Effective Pressure (σ') = Total Pressure (σ) - Water Pressure (u) = 35.3 kPa - 0 kPa = 35.3 kPa.
p.7
Effective Stress in Soil Mechanics
What is the required downward pressure to achieve a Factor of Safety of 1.3?
1.3 times the upward pressure of the water.
p.9
Self-Assessment Questions on Soil Pressure
What is the effective vertical stress 5 m below the top of the saturated sand at the base of the Coral Sea, which is 200 m below the water surface?
To be calculated based on the given parameters.
p.10
Effective Stress in Soil Mechanics
What is the effective stress (σ') at the base of a 15 m thick soil stratum with ρ = 1.65 t/m³ and ρ_sat = 2.00 t/m³ when groundwater is at ground level?
To calculate effective stress, use σ' = σ - u, where σ is total stress and u is pore water pressure. At 15 m depth, σ = 15 m * 2.00 t/m³ = 30 t/m², and u = 0 (groundwater at surface), so σ' = 30 t/m².
p.10
Effective Stress in Soil Mechanics
If dry sand is excavated, at what depth does the effective stress at the bottom of the clay layer become zero?
Effective stress becomes zero when the total stress equals the pore water pressure, which can be calculated based on the depth of excavation.
p.1
Definitions of Mass and Weight
What is the definition of a Newton?
The force which, when it acts on a body of 1 kg mass, will give or tend to give it an acceleration of 1 m/s².
p.4
Effective Stress in Soil Mechanics
What does the distributed load of 30 kPa do to the total stress?
It causes an increase in total stress of 30 kPa.
p.8
Total, Neutral, and Effective Pressure
How is total stress calculated in a silt layer at 2 m depth?
Total stress = 1.95 × 9.8 × 2 = 38.3 kPa.
p.10
Effective Stress in Soil Mechanics
What is the effective vertical stress at a depth of 8 m and 12 m below ground level before and after a water table rise of 3 m?
Before the rise, calculate total stress and pore water pressure at both depths. After the rise, recalculate pore water pressure and adjust effective stress accordingly.
p.2
Pressure Calculation in Soil Layers
What is the formula for calculating force in kN?
Force (F) = Mass (m) × Acceleration (g).
p.1
Pressure Calculation in Soil Layers
How do you calculate the pressure exerted by a mass?
Pressure = Downward force / Area.
p.1
Total, Neutral, and Effective Pressure
What is the formula for total force on the base of a container filled with saturated gravel?
Total force = Density × Volume.
p.8
Capillary Rise of Water in Soils
Why are the rises in gravel and sand considered negligible?
Because the values are very low compared to silts and clays.
p.3
Examples of Pressure Calculations
What is the Water Pressure at a depth of 3 m?
Water Pressure = 19.6 kPa.
p.10
Effective Stress in Soil Mechanics
How do you calculate effective vertical stresses at the top and base of a clay layer overlain by sand?
Effective vertical stress is calculated using σ' = σ - u, where σ is the total vertical stress from the weight of the overlying material and u is the pore water pressure.
