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Mechanical Analysis of Soil - Introduction to Sieve Analysis | CIVL 1101, Exams of Civil Engineering

Material Type: Exam; Class: Civl Engr Measurements Lab; Subject: CIVL Civil Engineering; University: University of Memphis; Term: Summer 1991;

Typology: Exams

Pre 2010

Uploaded on 07/28/2009

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Mechanical Analysis of Soil
]Mechanical analysis is the determination of the size
range of particles present in a soil, expressed as a
percentage of the total dry weight.
]There are two methods generally used to find the
particle–size distribution of soil:
\1)
sieve analysis
for particle sizes larger than 0.075 mm in
diameter, and
\(2)
hydrometer analysis
for particle sizes smaller than
0.075 mm in diameter. The basic principles of sieve analysis
and hydrometer ever analysis are briefly described in the
following two sections.
Mechanical Analysis of Soil
Sieve analysis Hydrometer analysis
Sieve Analysis
]Sieve analysis consists of shaking the soil sample
through a set of sieves that have progressively smaller
openings.
Sieve Analysis
Sieve Number Opening (mm)
4 4.750
6 3.350
8 2.360
10 2.000
16 1.180
20 0.850
30 0.600
40 0.425
50 0.300
60 0.250
80 0.180
100 0.150
140 0.106
170 0.088
200 0.075
270 0.053
Sieve Analysis
]First the soil is oven dried and then all lumps are
broken into small particle before they are passed
through the sieves
]After the completion of
the shaking period the
mass of soil retained on
each sieve is determined
Sieve Analysis
]The results of sieve analysis are generally expressed
in terms of the percentage of the total weight of soil
that passed through different sieves
Sieve
#
Diameter
(mm)
Mass of soil
retained
on each sieve
(g)
Percent of
soil
retained on
each sieve (g)
Percent
passing
(%)
10 2.000 0 0 100.00
16 1.180 9.90 2.20 97.80
30 0.600 24.66 5.48 92.32
40 0.425 17.60 3.91 88.41
60 0.250 23.90 5.31 83.10
100 0.150 35.10 7.80 75.30
200 0.075 59.85 13.30 62.00
Pan –– 278.99 62.00 0
CIVL 1101 Introduction to Sieve Analysis 1/6
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Mechanical Analysis of Soil

] Mechanical analysis is the determination of the size

range of particles present in a soil, expressed as a

percentage of the total dry weight.

] There are two methods generally used to find the

particle–size distribution of soil:

\ 1) sieve analysis – for particle sizes larger than 0.075 mm in

diameter, and

\ (2) hydrometer analysis – for particle sizes smaller than

0.075 mm in diameter. The basic principles of sieve analysis

and hydrometer ever analysis are briefly described in the

following two sections.

Mechanical Analysis of Soil

Sieve analysis Hydrometer analysis

Sieve Analysis

] Sieve analysis consists of shaking the soil sample

through a set of sieves that have progressively smaller

openings.

Sieve Analysis

Sieve Number Opening (mm) 4 4. 6 3. 8 2. 10 2. 16 1. 20 0. 30 0. 40 0. 50 0. 60 0. 80 0. 100 0. 140 0. 170 0. 200 0. 270 0.

Sieve Analysis

] First the soil is oven dried and then all lumps are

broken into small particle before they are passed

through the sieves

] After the completion of

the shaking period the

mass of soil retained on

each sieve is determined

Sieve Analysis

] The results of sieve analysis are generally expressed

in terms of the percentage of the total weight of soil

that passed through different sieves

Sieve

Diameter (mm)

Mass of soil retained on each sieve (g)

Percent of soil retained on each sieve (g)

Percent passing (%)

Pan –– 278.99 62.00 0

Sieve Analysis

Sieve

Diameter (mm)

Mass of soil retained on each sieve (g)

Percent of soil retained on each sieve (g)

Percent passing (%)

Pan –– 278.99 62.00 0

] Sieve Analysis (Mass of Dry Soil Sample = 450 g)

Sieve Analysis

Sieve

Diameter (mm)

Mass of soil retained on each sieve (g)

Percent of soil retained on each sieve (g)

Percent passing (%)

Pan –– 278.99 62.00 0

] Sieve Analysis (Mass of Dry Soil Sample = 450 g)

Particle–Size Distribution Curve

] The results of mechanical analysis (sieve and hydrometer

analyses) are generally presented by semi–logarithmic

plots known as particle–size distribution curves.

] The particle diameters are plotted in log scale, and the

corresponding percent finer in arithmetic scale.

Particle–Size Distribution Curve

Silt and clay Sand

Particle diameter (mm)

Percent finer (%)

1. Weigh to 0.1 g each sieve which is to be used

2. Select with care a test sample which is representative

of the soil to be tested

3. Weigh to 0.1 a specimen of approximately 500 g

of oven–dried soil

4. Sieve the soil through a nest of sieves by hand

shaking. At least 10 minutes of hand sieving is

desirable for soils with small particles.

5. Weigh to 0.1 g each sieve and the pan with the soil retained on

them.

6. Subtract the weights obtained in step 1 from those of step 5 to

give the weight of soil retained on each sieve.

The sum of these retained weights should be checked against the

original soil weight.

Recommended Procedure

] Percentage retained on any sieve:

Calculations

100%

weight of soil retained

total soil weight

= ×

] Cumulative percentage retained on any sieve:

= ∑Percentage retained

] Percentage finer than an sieve size:

100%− ∑Percentage retained

Effective Size, Uniformity Coefficient, and

Coefficient of Gradation

] For the particle-size distribution curve we just used,

the values of D 10 , D 30 , and D 60 are:

D 10 = 0.093 mm D 30 = 0.25 mm D 60 = 0.51 mm

u

D C D

=

mm

mm

= =

c

D C D D

= ×

(0.25 )

0.51 0.

mm

mm mm

= = ×

Effective Size, Uniformity Coefficient, and

Coefficient of Gradation

Particle diameter (mm)

Percent finer (%)

] The particle–size distribution curve shows not only the

range of particle sizes present in a soil but also the

type of distribution of various size particles.

Effective Size, Uniformity Coefficient, and

Coefficient of Gradation

Particle diameter (mm)

Percent finer (%)

] This particle-size distribution represents a soil in

which the particles are distributed over a wide range,

termed well graded

Effective Size, Uniformity Coefficient, and

Coefficient of Gradation

Particle diameter (mm)

Percent finer (%)

] This particle-size distribution represents a type of

soil in which most of the soil grains are the same size.

This is called a uniformly graded soil.

Effective Size, Uniformity Coefficient, and

Coefficient of Gradation

Particle diameter (mm)

Percent finer (%)

] This particle-size distribution represents such a soil.

This type of soil is termed gap graded.

Example Sieve Analysis

] From the results of a sieve analysis, shown below,

determine:

(a) the percent finer than each sieve and plot a grain–size

distribution curve,

(b)D 10 ,D 30 ,D 60 from the grain–size distribution curve,

(c) the uniformity coefficient,Cu, and

(d) the coefficient of gradation,Cc.

Sieve Number

Diameter (mm)

Mass of soil retained on each sieve (g) 4 4.750 28 10 2.000 42 20 0.850 48 40 0.425 128 60 0.250 221 100 0.150 86 200 0.075 40 Pan –– 24

Example Sieve Analysis

Sieve

Number

Diameter

(mm)

Mass of soil retained

on each sieve (g)

Pan –– 24

Sieve Number

Mass of soil retained on each sieve (g)

Percent retained on each sieve (%)

Cumulative percent retained on each sieve (%)

Percent finer (%)

Pan 24 3.89 100.00 0 617

Example Sieve Analysis

Sieve Number

Mass of soil retained on each sieve (g)

Percent retained on each sieve (%)

Cumulative percent retained on each sieve (%)

Percent finer (%)

Pan 24 3.89 100.00 0 617

Example Sieve Analysis

Particle diameter (mm)

Percent finer (%)

Example Sieve Analysis

D 30 = 0.27 mm

D 10 = 0.14 mm

D 60 = 0.42 mm

Example Sieve Analysis

] For the particle-size distribution curve we just used,

the values of D 10 , D 30 , and D 60 are:

D 10 = 0.14 mm D 30 = 0.27 mm D 60 = 0.42 mm

u

D C D

=

mm

mm

= =

c

D C D D

= ×

(0.27 )

0.42 0.

mm

mm mm

= = ×

Group Work - Sieve Analysis

] From the results of a sieve analysis, shown below,

determine:

(a) the percent finer than each sieve and plot a grain–size

distribution curve,

(b)D 10 ,D 30 ,D 60 from the grain–size distribution curve,

(c) the uniformity coefficient,Cu, and

(d) the coefficient of gradation,Cc.

Sieve Number

Mass of soil retained on each sieve (g) 4 0 10 40 20 60 40 89 60 140 80 122 100 210 200 56 Pan 12