Some Dafination about soil Mechanics

Unit Weight:

Total unit weight: Cumulative weight of the solid particles, water and air in the material per unit volume. Note that the air phase is often assumed to be weightless.

Porosity:

Ratio of the volume of voids (containing air, water, or other fluids) in a soil to the total volume of the soil.

Void ratio:

is the ratio of the volume of voids to the volume of solid particles in a soil. Void ratio is mathematically related to the porosity.

Permeability:

A measure of the ability of water to flow through the soil, expressed in units of velocity.

Compressibility:

The rate of change of volume with effective stress. If the pores are filled with water, then the water must be squeezed out of the pores to allow volumetric compression of the soil; this process is called consolidation.

Shear strength:

The shear stress that will cause shear failure.

Atterberg Limits

Liquid limit, plastic limit, and shrinkage limit. These indices are used for estimation of other engineering properties and for soil classification.