physical properties of soil

Physical Properties of Soil ©engineeringmasters

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Physical Properties of soil

Important Constituents of soil

A soil Mass consists of solid Particles, water and air. The solid particles are called soil grains. The Void Space between the soil grains is partly filled with water and partly with air. Thus soil Consists of three major Constituents Named as

Soild Particles Air Water

All these three are blended together to form a complex material.

Note: For dry soil mass, the voids are filled with air only For perfectly saturated soil the voids are filled completely with water

Difference between Three phase Diagram and Two phase Diagram

Three Phase Diagram: The diagram which represents the three constituents of soil i.e. Soilds, air and water is known as three phase diagram.

But in following in two cases a three phase system can becomes a two phase system.

(1) Soil is absolutely dry: in this case soil mass consists only soil grains and air. (2) Soil is fully saturated: in this case Soil mass consists only soil grains and water.

Two Phase Diagram: The diagram which represents the two constituent of soil is known as two phase diagram.

Inter Relationships of various terms three phase diagram.

For engineering analysis and design, it is necessary to express relations between the weights and the volumes of the three phases.




The various relations can be grouped into:

(1) Volume relations (2) Weight relations

(1) Volume Relations

Accordingly, V = Vv + Vs Where Vs = volume of Solids (Soil grains) Vv = Volume of Voids Fur ther Vv = Va + Vw Where Va = volume of air & Vw = volume of water Therefore, V = Va + Vw + Vs

(2) Weight Relations : Similarly = Ws +Ww+ Ws

Where Wa = Weight of air (very small say, negligible) =0 Ww= Weight of water Ws = weight of solids Therefore W = Ww + Ws

Important Soil Properties and Their Interrelationship: The important physical properties of soil widely used in soil engineering are discussed below: (1) Void Ratio: it is defined as the ratio of volume of voids to the volume of solids in a

given soil mass. It is denoted by ‘e’. e = Vv / Vs

Where Vv = Volume of voids Vs = Volume of solids Note:

Void ratio has no unit. The value may even be greater than unity. Void ratio is greater than unity than soil is weak, compressible & pervious.

(2) Porosity: it is defined as the ratio of volume of voids to the total volume of a given soil

mass. it is denoted by ‘n’. n = Vv/ V




Where, Vv = Volume of voids V = Total Volume Note:

It has no unit. It is generally expressed as a percentage. Therefore it is also known as ‘‘percentage

Voids’’ As the Soil becomes dense, the value of void ratio and porosity decreases.

(3) Degree of Saturation: It is defined as the ratio of volume of water to the volume of Voids.

It is denoted by‘s’. S = Vw/Vv Where’Vw = Volume of water Vv = Volume of voids. Note:

Degree of Saturation is dimensionless. It is generally expressed as percentage, therefore known as ‘‘percentage saturation.’’ For dry soil,Vw = 0, S =0% For fully saturated soil,Vv = Vw , S = 100%

(4) Water Content: it is defined as the ratio of the weight to the weight of solids. it is denoted by ‘W’.

w = Ww/ Ws Where, Ww = Weight of Water Ws = Weight of solids Note:

it has no dimension. It is also defined as ‘‘the mass of water which can be removed from a soil, usually by

heating at a temperature of 105° - 110° C, and expressed as percentage of dry mass.’’

physical properties of soil

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