basis physical property

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SOIL COMPOSITION

SOIL COMPOSITION
Generally soil can be divided to three components in natural occurrence
This separation know as three phase systems or three phase diagram
It consists of soil solids, water and air

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Soil components in natural occurrence

Volume-Weight relationships
As a result from 3 phase diagram several relationship were produce
This relationship known as volume weight relationships. Refer to 3 phase diagram

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Relationship equations
V = Vs +Vv
( eq. 1)
= Vs + Vw + Va where Vs = volume of soil solids
Vv = volume of voids
Vw = volume of water in the voids Va = volume of air in voids

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Relationship equations
W = Ws + Ww where, Ws =
Ww=
Wa =

( eq. 2)

weight of soil solid weight of water zero (negligible)

Water content@ Moisture content

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Void ratio

The ratio of the volume of voids Vv to the volume of soil solid Vs

Porosity

The ratio of the volume of voids, Vv to total volume, V expressed as either a decimal or a percentage. 5

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Relationship between void ratio and porosity e = Vv = Vv
= (Vv/V ) = n
Vs
V – Vv 1 – (Vv/V)
1- n

n=

e
1+e

Degree of saturation

The ratio of the volume of water, Vw to the volume of voids, Vv. It’s commonly in percentage

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Unit weight

The weight of soil per unit volume
Moist unit weight

Dry unit weight

Relationship between dry unit and bulk unit weight

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Derivation –cont’d

So what is the different between unit weight and density? Unit Weight is influence by gravity forces while mass isn’t (Unit Weight=Weight/ Volume while Density=
Mass/Volume)- Weight = Mass x Gravity acceleration
So we can use the similar equations on related calculation if there is only density

Specific Gravity

Specific gravity can be determined as a ratio of the unit weight of the soil material to the