Soil
OUTLINE
• Introduction and Terminology
Advanced
Advanced Soil Mechanics &
Foundation Design
UNSATURATED SOIL
MECHANICS
A/Prof Hadi Khabbaz
Email: hadi.khabbaz@uts.edu.au
• Suction and Measurement Methods
• Effective Stress Concept for Unsaturated
Soils
• Soil Water Characteristic Curve (SWCC)
Ch
(SWCC)
• Permeability of Unsaturated Soils
• Shear strength of Unsaturated Soils
• Examples
• Conclusions
Room 2.511B
Introduction
&
Terminology
State whether the following statements are True or False
1. Soils below water tables are fully saturated.
Soils belo tables are sat 2. All soils above water table are unsaturated.
3. Compacted soils are generally unsaturated soils.
4. Shear strength of a saturated clayey sand is greater than its unsaturated shear strength.
Why do we need to understand
Unsaturated Soil
Mechanics?
Most of the natural soil systems are in arid and semiarid regions and soils subjected to seasonal moisture deficits are in an unsaturated state.
Who needs unsaturated soil mechanics?
Every geotechnical engineer needs to be aware of the th role played by the portion of soil with negative porepressure (i.e. generally the portion above the water table). Many present solutions in soil mechanics and foundation design are quite approximate and based on saturated soils. More research is still required.
1
Stress Distribution during the desiccation of a soil
Stress Distribution during the desiccation of a soil
Certainly there is a need for an appropriate technology for unsaturated
soil behaviour.
Such technology must:
1. Be practical
2. Not be too costly to employ
3. Have a sound theoretical basis
4. Run parallel in concept of conventional soil mechanics
2
Basic Differences between Saturated and
Unsaturated Soils
Nature
Existing of Air
Engineering Behaviour
Negative Pore Water
Pressure
Air
Water
Solid Particles
Compression?
1/P
Compression?
Cf
• Introduction and Terminology
Advanced
Advanced Soil Mechanics &
Foundation Design
UNSATURATED SOIL
MECHANICS
A/Prof Hadi Khabbaz
Email: hadi.khabbaz@uts.edu.au
• Suction and Measurement Methods
• Effective Stress Concept for Unsaturated
Soils
• Soil Water Characteristic Curve (SWCC)
Ch
(SWCC)
• Permeability of Unsaturated Soils
• Shear strength of Unsaturated Soils
• Examples
• Conclusions
Room 2.511B
Introduction
&
Terminology
State whether the following statements are True or False
1. Soils below water tables are fully saturated.
Soils belo tables are sat 2. All soils above water table are unsaturated.
3. Compacted soils are generally unsaturated soils.
4. Shear strength of a saturated clayey sand is greater than its unsaturated shear strength.
Why do we need to understand
Unsaturated Soil
Mechanics?
Most of the natural soil systems are in arid and semiarid regions and soils subjected to seasonal moisture deficits are in an unsaturated state.
Who needs unsaturated soil mechanics?
Every geotechnical engineer needs to be aware of the th role played by the portion of soil with negative porepressure (i.e. generally the portion above the water table). Many present solutions in soil mechanics and foundation design are quite approximate and based on saturated soils. More research is still required.
1
Stress Distribution during the desiccation of a soil
Stress Distribution during the desiccation of a soil
Certainly there is a need for an appropriate technology for unsaturated
soil behaviour.
Such technology must:
1. Be practical
2. Not be too costly to employ
3. Have a sound theoretical basis
4. Run parallel in concept of conventional soil mechanics
2
Basic Differences between Saturated and
Unsaturated Soils
Nature
Existing of Air
Engineering Behaviour
Negative Pore Water
Pressure
Air
Water
Solid Particles
Compression?
1/P
Compression?
Cf