Soil mechanics

• Basic mechanics of soils
• Description and classification
• Effective stress
• Volume change
• Shear strength

To design of structures in the ground we need to describe

• soil strength
• soil compressibility and stiffness
• seepage

• friction
• logarithmic compression
• plasticity
• Darcy seepage

 

 

 

 

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Volume change

Back to Soil mechanics

• Compression and swelling
• Consolidation
• Compaction
Saturated soil contains only mineral grains and water. Both are relatively incompressible so the volume can only change if water can drain out. In unsaturated soil volume changes can occur as air compresses or bleeds out. In both cases loading will bring the grains closer together and the specific volume will reduce.
1. Reduction in volume leads to
2. increase in strength
3. increase in stiffness
4. settlement of foundations


If soil is unloaded it will swell as the grains move apart. Swelling leads to reduction in strength and stiffness and heave of excavations.