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Geotechnical Engineering Geotechnical Engineering Geotechnical Engineering is a broader term for Soil Mechanics.Geotechnical Engineering is a broader term for Soil Mechanics.

Geotechnical Engineering contains:Geotechnical Engineering contains: Soil Mechanics (Soil Properties and Behavior) Soil Mechanics (Soil Properties and Behavior)

Soil Dynamics (Dynamic Properties of Soils, Earthquake Soil Dynamics (Dynamic Properties of Soils, Earthquake Engineering, Machine Foundation) Engineering, Machine Foundation)

Foundation Engineering (Deep & Shallow Foundation)Foundation Engineering (Deep & Shallow Foundation)

Pavement Engineering (Flexible & Rigid Pavement)Pavement Engineering (Flexible & Rigid Pavement)

Rock Mechanics (Rock Stability and Tunneling)Rock Mechanics (Rock Stability and Tunneling)

Geosynthetics (Soil Improvement)Geosynthetics (Soil Improvement)

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Soil FormationSoil FormationSoil material is the product of rockSoil material is the product of rock

The geological process that produce soil is The geological process that produce soil is

WEATHERINGWEATHERING (Chemical and Physical). (Chemical and Physical).

Variation in particle size and shape depends on: Variation in particle size and shape depends on:

Weathering ProcessWeathering Process

Transportation ProcessTransportation Process

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Type of soils produced by the different weathering & Type of soils produced by the different weathering & transportation process:transportation process:

BouldersBoulders

Gravel Gravel

Sand Sand

Silt Silt

Clay Clay

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All soils consist of a collection of:All soils consist of a collection of:

gravel, gravel,

sand, sand,

silt or silt or

clay particles clay particles

with varying spaces between them which with varying spaces between them which are usually filled with water. are usually filled with water.

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Soils are usually:Soils are usually:cohesionless, cohesionless,

cohesive, or cohesive, or

organic.organic.

Cohesionless soilsCohesionless soils have particles that do have particles that do not tend to stick together.  not tend to stick together.  

Mostly composed of sand, may be some silt.Mostly composed of sand, may be some silt.

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Cohesive soilsCohesive soils are characterized by very are characterized by very small particle sizes where surface small particle sizes where surface chemical effects predominate.  They are chemical effects predominate.  They are both "sticky" and "plastic". CLAYS.both "sticky" and "plastic". CLAYS.

Organic soilsOrganic soils are typically spongy, are typically spongy, crumbly, and compressible.  They are crumbly, and compressible.  They are undesirable for supporting structures. undesirable for supporting structures.

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Important Physical Parameters of SoilsImportant Physical Parameters of Soils

Soils contain three components, which Soils contain three components, which may be characterized as: may be characterized as:

solid, solid,

liquid, and liquid, and

gas. gas.

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The solid components of soils are weathered The solid components of soils are weathered rock and (sometimes) organic matter. rock and (sometimes) organic matter.

The liquid component of soils is almost The liquid component of soils is almost always water (often with dissolved matter), always water (often with dissolved matter), and and

the gas component is air. the gas component is air.

The volume of water and gas is referred to as the void.The volume of water and gas is referred to as the void.

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SOIL PHYSICAL & INDEX PROPERTIESSOIL PHYSICAL & INDEX PROPERTIES 1- Soil Composition1- Soil Composition

SolidsSolids WaterWater AirAir

2- Soil Phases 2- Soil Phases DryDry Fully SaturatedFully Saturated Partially SaturatedPartially Saturated

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3- Analytical Representation of Soil:3- Analytical Representation of Soil:

For the purpose of defining the physical For the purpose of defining the physical and index properties of soil it is more and index properties of soil it is more convenient to represent the soil convenient to represent the soil skeleton by a block diagram or phase skeleton by a block diagram or phase diagram.diagram.

4- Weight - Volume Relationships:4- Weight - Volume Relationships:

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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).

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A graphical presentation of soil propertiesA graphical presentation of soil properties

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Mass Mass

Total mass of soil, M = MTotal mass of soil, M = Mww + M + Mss

Mass of solid, MMass of solid, Mss

Mass of water, MMass of water, Mw w

Weight Weight

Total weight of soil, W = WTotal weight of soil, W = Www + W + Wss

Weight of solid, WWeight of solid, Ws s

Weight of water, WWeight of water, Www

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1. Density of solids, 1. Density of solids, ss

ss= M= Mss/V/Vss or or ss= G= Gss . . ww

2. Specific Gravity, G2. Specific Gravity, Gss

Ratio of the density of solids to the density Ratio of the density of solids to the density of water.of water.

GGss= = ss//ww

GGss= M= Mss/V/Vss

ww

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Specific Gravity, GSpecific Gravity, Gss

For Sand, GFor Sand, Gss= 2.6 – 2.7= 2.6 – 2.7

Clay, GClay, Gs s = 2.65 – 2.80= 2.65 – 2.80

Organic soils, GOrganic soils, Gss= 2.5= 2.5

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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.

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Relative Density, DRelative Density, Drreemaxmax:: max. void ratio for the max. void ratio for the loosest loosest possible possible statestate eeminmin:: min. void ratio for the min. void ratio for the densest densest possible possible statestate eefieldfield: void ratio of the soil for which relative : void ratio of the soil for which relative density is defined.density is defined.

Relative Density, DRelative Density, Dr r is a parameter for is a parameter for granular granular soils.soils.

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Relative Density Relative Density PackingPacking

(%)(%)

0-150-15 Very looseVery loose

15-3515-35 LooseLoose

35-6535-65 MediumMedium

65-8565-85 DenseDense

85-10085-100 Very denseVery dense

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8. Unit Weight8. Unit Weight

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

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Name Equation Description

Void Ratio

Ratio of the void volume to the solid volume.

Porosity

Percent of the total volume that is taken up by the void.

Degree of Saturation

Percent of the void that is taken up by the water.

Water Content

Percent of the weight of water to the weight of solids.

Unit Weight

Total density of the soil. Includes solids and the void.

Dry Unit Weight

Density of the soil when it is completely dried out.

Unit Mass, Dry Unit Mass

Density of the soil and the dry density of the soil.

Specific Gravity of Solids

Ratio of the density of solids to the density of water. Note:

Other Important Relationships: W=Ws+Ww V=Vs+Vv=Vs+Vw+Va

ρw