The three constituen ts are blended together to form a complex material. It is also known as block diagram. D ry soil and saturated soil is known as two ph ase diagram.

**Soil Mechanics: Phases Relationship**

**Phases Relationship**

The three constituen ts are
blended together to form a complex material. It is also known as block diagram.
D ry soil and saturated soil is known as two ph ase diagram.

**Weight**

Wt = Ww + Ws + Wg

**Volume**

Vt = Vv + Vs = Va + Vw + Vs + Vg

**1. Volumetric Relation ships **

**i) Void ratio**

It is
defined as the ratio of volume of voids to the volume of soli ds.

**e = Vv/Vs**; the
void ratio is expressed in decimal.** **

**ii) Porosity (n) or Percentage of
voids**

It is
defined as the ratio of the volume of voids to the total volum e.

n = Vv/V; Porosity is expre ssed as percentage & it is not
exceed 100%.

**n = e/1+e; e = n/n-1**

**iii) Degree of Saturation (S)**

The degree of saturation (s) is the ratio of the volume of
water to the volume of

voids.

**S = Vw/Vv; **The
degree of saturation is generally as a percentage . It is equal to zero** **when
the soil is absolutely dry & 100 % when the soil is fully saturated.

**iv) Percentage of air voids (na)**

It is defined a s the ratio of the volume of air to the total
v olum, .**na = Va/V** (it is represented as(%)

**v) Air Content (ac)**

It is
defined as the ratio of the volume of air to the volume of voids, .ac = Va/Ve,

Air Content is usually expressed
as percentage. Air Content and percentage of air voids are zero when the soil
is saturated.(Va=0)

na = Va/V = Va/Vv .Vv/V

**na = n.ac**

**vi) Water content (w)**

The water content (w) is defined as the ratio of the mass of
water to mass of solids.

**w = Mw/Ms**. It is
also known as moisture content (m); it is expressed as percentage but used** **as
a decimal computation.

**2. Volume Mass Relationships**

**i) Bulk density (****?)**

The bulk mass density (?) is defined
as the total mass (m) per unit total volume (v)

? = m/v.It is also known as Bulk mass
density, Bulk density, Wet mass density and density.

It is expressed as kg/m3 , gm/ml (or)
mg/m3

**ii) Dry mass density (?d)**

The dry density (?d) is defined as
the mass of solids per unit total volume.

?d
=Ms/V

**iii)Saturated density(?sat) **

Saturated density the bulk mass density of the soil when it is fully
saturated.

?sat=Msat/V

**iv)Submerged density**

When the soil exists below water
it is submerged conditions. When a volume of v of soil is submerged in water,
it displaces an equal volume of water.

**v)Density
of solids **

Density of solids is equal to the
ratio of the mass of solids to the volume of solids.

Rs=Ws/Vs

**3. Volume-Weight Relationships**

**i)Bulk unit weight (?)**

Bulk unit weight is defined as
total weight per unit total volume.

**? =W/V**

**ii) Dry unit weight (****?d)**

It is defined as the weight of
soil solids per unit total volume. **?d= Ws/V**

**iii) Saturated unit weight**

The saturated unit
weight is bulk unit weight when the soil is fully saturated. It is defined as weight of saturated soil solids to
the unit total volume. **?sat=Wsat/V**

**iv) Submerged unit
weight (?')**

It is defined as the submerged weight per unit of total
volume.

?? = Wsub/V; ?sat = Wsub-?w

**v) Unit weight of soil
solids (?s) **

The unit weight of solids (?s) is equal to the ratio of the
weight of solids to the total volume of solids. = ?s= Ws/Vs

**4
Specific gravity of solids (G)**

**i)
The specific gravity of solid particles** is defined as the
ratio of the mass of a given volume of solids to the mass of an equal volume of
water @ 4 o C. = G =ps/pw

The specific gravity of
solids for most natural soils is range of 2.65 to 2.80.

**ii)
Mass specific gravity** (or) apparent specific gravity (or)
Bulk specific gravity

It is defined as the
ratio of the mass density of the soil to the mass density of water.

Gn=p/pw

**iii)
Absolute specific gravity (or) True specific gravity**

If all the internal
voids of the particles are exclude from the determination the true volume of
solids, then the specific gravity is called as Absolute (or) True specific
gravity.

Ga=(ps)/pw

**5.
Density Index (ID)**

Relative compactness of
natural soil.

It is varies from 0 to
1

ID= emax - e / emax-emin

. e max = voids ratio
in loosest state ;e min = voids ratio in densest state.

e = natural voids ratio
of deposits; When the natural state of cohesion less soil in the densest form e
= e min, ID = 1.

**Relative
Density Density Description**

0-15 Very loose

15-35 Loose

35-65 Medium

65-85 Dense

85-100 Very dense

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