Three phase diagrams in Geotechnical engineering

Soil is defined as a three-phase system consisting of solid, water and air which are intermixed with each other and whose relative proportion decides the property of soil.

Three Phase Diagram of Soil

Here,

W = total weight of soil mass
Wa = weight of air
Ww = weight of water
Ws = weight of soil
V = total soil mass volume
Va = volume of air
Vw = volume of water
Vv = volume of voids
Vs = volume of solids

Types of Conditions in Three Phase System of Soil:

Dry Condition :

This type of condition is also called as 2 phase system of dry soil. In this condition the combination of air and solid particles takes place.

Generally when the soil mass gets completely dry then the free spaces or voids in between are filled only with air (gaseous). In this case liquid phase remains absent.

Here,

Saturated Condition :

Now in this 2 phase system of saturated soil the voids are only filled with water.

Here,

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