1. Geotechnical Engineering
Geotechnical Engineering is a broader term for Soil Mechanics.
Geotechnical Engineering contains:
Soil Mechanics (Soil Properties and Behavior)
Soil Dynamics (Dynamic Properties of Soils, Earthquake Engineering, Machine Foundation)
Foundation Engineering (Deep & Shallow Foundation)
Pavement Engineering (Flexible & Rigid Pavement)
Rock Mechanics (Rock Stability and Tunneling)
Geosynthetics (Soil Improvement)

2. Soil Formation Soil material is the product of rock
The geological process that produce soil is
WEATHERING (Chemical and Physical).
Variation in particle size and shape depends on:
Weathering Process
Transportation Process

3. Boulders Gravel Sand Silt Clay
Type of soils produced by the different weathering & transportation process:
Boulders
Gravel
Sand
Silt
Clay

4. All soils consist of a collection of:
gravel,
sand,
silt or
clay particles
with varying spaces between them which are usually filled with water.

5. Soils are usually: cohesionless, cohesive, or organic.
Cohesionless soils have particles that do not tend to stick together.  
Mostly composed of sand, may be some silt.

6. Cohesive soils are characterized by very small particle sizes where surface chemical effects predominate.  They are both "sticky" and "plastic". CLAYS.
Organic soils are typically spongy, crumbly, and compressible.  They are undesirable for supporting structures.

7. Important Physical Parameters of Soils
Soils contain three components, which may be characterized as:
solid,
liquid, and
gas.

8. the gas component is air.
The solid components of soils are weathered rock and (sometimes) organic matter.
The liquid component of soils is almost always water (often with dissolved matter), and
the gas component is air.
The volume of water and gas is referred to as the void.

9. SOIL PHYSICAL & INDEX PROPERTIES
1- Soil Composition
Solids
Water
Air
2- Soil Phases
Dry
Fully Saturated
Partially Saturated

10. 3- Analytical Representation of Soil:
For the purpose of defining the physical and index properties of soil it is more convenient to represent the soil skeleton by a block diagram or phase diagram.
4- Weight - Volume Relationships:

12. The following are important relationships between these quantities.
The notation will follow:
Total volume of soil V= Vv + Vs = Va + Vw + Vs
Volume of air, Va,
Volume of water, Vw
Volume of solid, Vs and
Volume of void, Vv= Va + Vw
The same notation is used for W (weight) and M (mass).

13. A graphical presentation of soil properties

14. Mass
Total mass of soil, M = Mw + Ms
Mass of solid, Ms
Mass of water, Mw
Weight
Total weight of soil, W = Ww + Ws
Weight of solid, Ws
Weight of water, Ww

15. 1. Density of solids, s s= Ms/Vs or s= Gs . w
2. Specific Gravity, Gs
Ratio of the density of solids to the density of water.
Gs= s/w
Gs= Ms/Vs w

16. Specific Gravity, Gs For Sand, Gs= 2.6 – 2.7 Clay, Gs = 2.65 – 2.80
Organic soils, Gs= 2.5

18. The degree of saturation can range between the limits of zero for a completely dry soil and 1 (or 100%) for a fully saturated soil.

19. Relative Density, Dr emax: max. void ratio for the loosest possible
state
emin: min. void ratio for the densest possible
efield: void ratio of the soil for which relative
density is defined.
Relative Density, Dr is a parameter for granular soils.

20. Relative Density Packing
(%)
Very loose
Loose
Medium
Dense
Very dense

21. 9. Dry Unit Weight, d= Weight of solid/Total volume
Also known as Bulk Unit Weight
9. Dry Unit Weight, d= Weight of solid/Total volume
10. Air content, A= Volume of air, Va/ Volume of soil, V
Va = Vv-Vw

22. ρw