This document discusses soil phases and relationships. It defines the solid, liquid, and gas phases of soil as solid particles, water, and air/vapor respectively. It then discusses various volume and weight relationships used in soil science including void ratio, porosity, degree of saturation, specific gravity, water content, and dry, saturated, total, and submerged density and unit weights. Typical values for these properties are provided for different soil types such as gravel, sand, silt, and clay.

1. Soil Science and
Engineering
S. Satheeshkumar
Assistant Professor
Department of agriculture engineering
Kongunadu college of engineering and technology

2. Unit 3
2

3. 3
The main items in this lecture are:
SOIL PHASES
RELATIONSHIPS
Volume
Relationships
Void Ratio,
e
Porosity, n
Degree of
Saturation,
Sr
Air Content,
Av
Weight
Relationships
Specific
Gravity, Gs
Water
Content, w
Density & Unit
Weight

4. • Solid: rock fragments,
mineral grains or
flakes, organic matter.
• water:, with some
dissolved compounds
(e.g. salts).
• Gas: air or water
vapor.

6. V = Vs + Vw + Va

7. e
e
n


1 n
n
e


1 n
v


1
1
Typical Values
void ratios = 0.3 (for a dense, well graded granular soil)
or = 1.5 (for a soft clay).
For a perfectly dry soil: Sr = 0
For a saturated soil: Sr = 1
For a perfectly dry soil: Av = n
For a saturated soil: Av = 0

9. w
s



Range of Gs for common soils: 2.64-2.72
w .Gs = Sr .e

10. = d(1 + w) and
t = d(1 + w)

11. Total, t = W/V w
s
e
1
e
S
G





 s
e
1
w
1




 w
Gs
e
1
w
1






Saturated, sat w
s
e
1
e
G





Dry, d
e
1
G w
s




Submerged (Buoyant), b = t - w = sub w
s
e
1
1
G






12. Soil type
Saturated soil,
sat, kN/m³
Dry soil, d,
kN/m³
Gravel 20-22 15-17
Sand 18-20 13-16
Silt 18-20 14-18
clay 16-22 14-21
Unit weight ranges are: