Chapter 2 Lecture - Mechanical Analysis of Soil Content

7/29/2019 Chapter 2 Lecture - Mechanical Analysis of Soil Content

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Unfortunately, soils are made by nature and not by

man, and the products of nature are always

complex.Karl von Terzaghi, 1936

Soil properties control their

mechanical behaviour


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From an engineering perspective

Study of soil focuses on:

characteristics of soils as const ruct ion

materials.

suitability of soils to withstand the load

app l ied by structu res.


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SOILS PARTICLE SIZE

Gravel (2 mm - 76.2 mm)

Sand (0.075 mm 2 mm)

Gravel and sand can be classified according to

particle size by sieve analysis. Silt (0.002 mm 0.075 mm)

Clay (Smaller than 0.002 mm)

Particle size may be determined by observingsettling velocities of the particles in a watermixture.


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SOILS BY PROPERTIES

Granular( or cohesionless) Soils

Soil particles do not tend to stick together

Gravel

Sand

Silt

Cohesive Soils

Soil particles tend to stick together.

Clay Organic Soils

Spongy, crumbly, and compressible

Undesirable for use in supporting structures


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Unfortunately, soils are made by nature and not by

man, and the products of nature are always

complex.

Karl von Terzaghi, 19362.6 Specific Gravity (Gs)

It is defined as the ratio of the unit weight of a givenmaterial to the unit weight of water.

Needed for various calculations in soil mechanics

like the volume of solids in a sample

For example: A material with SG of 2 is twice as heavy as

water (2x 62.4 lbs/ft3

) = 124.8 lbs/ft3

This number indicates how much heavier/lighter a material is than water.


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General Ranges of SG For Soils

Sand 2.63 2.67

Silt 2.65-2.7

Clay & Silty Clay 2.67-2.9

Organic Soils


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2.7 Mechanical Analysis of Soil

It is the determination of the size range of particles

present in a soil, expressed as a percentage of the

total dry weight.

Coarse-grained soils:

Gravel Sand

Fine-grained soils:

Silt Clay

NO.2000.075mm

NO. 4

4.75 mm


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The texture of a soil is its appearance, itdepends on the relative sizes and shapes of the

particles as well as the range or distribution of

those sizes.

Two methods are used to find the particle-size

distribution of soil:

Sieve Analysis

Hydrometer Analysis

Mechanical Analysis of Soil Cont.

Experiment


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Coarse-grained soils:

Gravel Sand

Fine-grained soils:

Silt Clay

0.075 mm

Sieve analysis Hydrometer analysis



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Sieve Analysis

For particle sizeslarger than

0.075 mm

in diameter

Hydrometer Analysis

For particle sizessmaller than

0.075 mm

in diameter


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Engineering applications

It will be used for the soil classification (next topic).

It can be used to define the grading specification

of a drainage filter.

It can be a criterion for selecting fill materials ofembankments and earth dams, road sub-base

materials, and concrete aggregates.

It can be used to estimate the results of grouting

and chemical injection, and dynamic compaction.



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Sieve Analysis Cont.

http://www.youtube.com/watch?v=j5_6lXOwmv0
http://www.youtube.com/watch?v=j5_6lXOwmv0http://youtu.be/j5_6lXOwmv0http://www.youtube.com/watch?v=j5_6lXOwmv0http://www.youtube.com/watch?v=j5_6lXOwmv0http://www.youtube.com/watch?v=j5_6lXOwmv0http://www.youtube.com/watch?v=j5_6lXOwmv0http://www.youtube.com/watch?v=j5_6lXOwmv0http://www.youtube.com/watch?v=j5_6lXOwmv0


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ASTM 500 g/oven dried (Temp 105C)

September 16, 2013



Pan

200

100

80

40

40

10

4

0

Shaking time 5 min. to 10 min.


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+

Mechanical Analysis of Soil Cont


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B. Hydrometer Analysis

http://www.youtube.com/watch?v=n8rntKMeOwY

http://www.youtube.com/watch?v=n8rntKMeOwYhttp://www.youtube.com/watch?v=n8rntKMeOwYhttp://www.youtube.com/watch?v=n8rntKMeOwYhttp://www.youtube.com/watch?v=n8rntKMeOwYhttp://www.youtube.com/watch?v=n8rntKMeOwY


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Mechanical Analysis of Soil Cont Hydrometer Analysis Cont


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velocity of the sphere in a fluid

diameter of soil sphere

density of soil particles

density of water

viscosity of water

Stokes Law (law of sedimentation in the water)

is used to express the velocity of soil particle.

Mechanical Analysis of Soil Cont. HydrometerAnalysis Cont.

HydrometerAnalysis utilizes the relationship between:

Hydrometer Analysis ContMechanical Analysis of Soil Cont


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HydrometerAnalysis Cont.Mechanical Analysis of Soil Cont.


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http://www.youtube.com/watch?v=n8rntKMeOwY


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Particle-Size Distribution Curve Cont


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Mechanical Analysis of Soil Cont.Particle Size Distribution Curve Cont.

Mechanical Analysis of Soil Cont. Particle-Size Distribution Curve Cont


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Mechanical Analysis of Soil Cont. Particle Size Distribution Curve Cont.

Mechanical Analysis of Soil Cont. Particle-Size Distribution Curve Cont.


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Mechanical Analysis of Soil Cont Particle-Size Distribution Curve Cont.


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Mechanical Analysis of Soil Cont. Particle-Size Distribution Curve Cont.


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The Particle-size distribution curve shows:

The range of particle sizes present in a soil

Type of distribution of various-size particles

y Particle Size Distribution Curve Cont.

Well-graded = contains a variety of sizes

(gradient of curve constant over large grain

size range)

Poorly-graded = narrow range of sizes

Mechanical Analysis of Soil Cont Particle-Size Distribution Curve Cont.


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Mechanical Analysis of Soil Cont. a t c e S e st but o Cu e Co t

Mechanical Analysis of Soil Cont Example 2.1


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Mechanical Analysis of Soil Cont. p

Mechanical Analysis of Soil Cont Example 2.2


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Mechanical Analysis of Soil Cont. p

Mechanical Analysis of Soil Cont


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Mechanical Analysis of Soil Cont Particle Shape


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Mechanical Analysis of Soil Cont. Particle Shape

Mechanical Analysis of Soil Cont Particle Shape


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Mechanical Analysis of Soil Cont. Particle Shape

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Chapter 2 Lecture - Mechanical Analysis of Soil Content