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)

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

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

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

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.

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.

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

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.

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

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:

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).

A graphical presentation of soil properties

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

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

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

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.

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.

Relative Density Packing (%) 0-15 Very loose 15-35 Loose 35-65 Medium 65-85 Dense 85-100 Very dense

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

ρw