Soil Classification 1

8/12/2019 Soil Classification 1

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Standard Practice for Classification of

Soils for Engineering Purposes.

(Unified Soil Classification System)[ASTM:D 248700]

Prepared by: Sitti Aminah


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CONTENT

Scope

Terminology

Significance

Apparatus

Sampling

Examples

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SCOPE

describes a system for classifying mineral and organo-mineral soils

for engineering purposes based on laboratory determination of

particle-size characteristics, liquid limit, and plasticity index and shall

be used when precise classification is required.

The group symbol portion of this system is based on laboratory tests

performed on the portion of a soil sample passing the 3-in. (75-mm)

sieve

This standard is the ASTM version of the Unified Soil Classification

System.

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TERMINOLOGY

Clay

soil passing a No. 200 (75-m) U.S. standard sieve that can be made to exhibit

plasticity (putty-like properties) within a range of water contents and that exhibits

considerable strength when air dry.

Gravel

Particles of rock that will pass a 3-in. (75-mm) sieve and be retained on a No.4

(4.75mm) U.S. standard sieve.

Two types:

> Coarse: passes 3-in. (75-mm) sieve and retained on 34-in. (19-mm)

sieve;

> Fine: passes 34-in. (19-mm) sieve and retained on No. 4 (4.75-mm)

sieve.

Organic

clay

A soil that would be classified as a clay except that its liquid limit value after oven

drying is less than 75 % of its liquid limit value before oven drying.

Organic siltan organic silt is a soil that would be classified as a silt except that its liquid limit value

after oven drying is less than 75 % of its liquid limit value before oven drying.

Peat

a soil composed of vegetable tissue in various stages of decomposition usually with an

organic odor, a dark-brown to black color, a spongy consistency, and a texture ranging

from fibrous to amorphous.

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Sand

Particles of rock that will pass a No.4 (75-mm) sieve and be retained on a

No.200 (75-m) U.S. standard sieve.

Three types:

Coarsepasses No. 4 (4.75-mm) sieve and retained on No.10 (2.00-mm)

sieve,

Mediumpasses No. 10 (2.00-mm) sieve and retained on No. 40 (425-m)

sieve, and

Finepasses No. 40 (425-m) sieve and retained on No. 200 (75-m) sieve.

Silt

a silt is a fine-grained soil, or the fine-grained portion of a soil, with a

plasticity index less than 4 or if the plot of plasticity index versus liquid limit falls

below the A line.

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Soil classification chart5


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SIGNIFICANCE AND USE

classifies soils from any geographic location into categories representing the

results of prescribed laboratory tests to determine the particle-size

characteristics, the liquid limit, and the plasticity index.

The assigning of a group name and symbol(s) can be used to describe a soil

to aid in the evaluation of its significant properties for engineering use. provides a useful first step in any field or laboratory investigation for

geotechnical engineering purposes.

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APPARATUSPlasticity Chart cumulative particle-size distribution

curve

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SAMPLING AND SPECIMEN

Where only the particle-size analysis of the sample is required, specimens

having the following minimum dry weights are required:

*Whenever possible, the field samples should

have weights two to four times larger than

shown.

When the liquid and plastic limit tests must also be performed, additional material

will be required sufficient to provide 150 g to 200 g of soil finer than the No. 40 (425-

m) sieve.8


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Examples

Preliminary classification

Procedure

1)FINE GRAINED:

>= 50% passNo.200 sieve

2) COARSE GRAINED:

> 50% retainedNo. 200 sieve

* In this case, (100-15.2=84.8%),hence >50%retained at No. 200 sieve, COARSE GRAINED

Example 1

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If Coarse- grainedsoil

Retained No 4 (Gravel) = 100 - 76.5= 23.5% of the total

soilor (23.5/84.8)(100) = 27.7%of the coarse-grained soil

Therefore, Sand = 100 - 27.7= 72.3%of the coarse-

grained soil.

Since sand is more than 50% > go to Sands (Primary

letter S)

Sand or gravel?

Check % of fines

(passing No 200)

If % fines < 5% Clean sands

If % fines between 5-12% Dually-

named

If % fines > 12% Sands with fines

*in this case, % fines (passing No 200) = 15.2%, Sands with fines,

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Check Plasticity chart

(type of fines)

* soil is classified as SC(Clayey Sand)

PI = LL- PL = 18, LL = 30

Check plasticity chart CL (clay with low

LL)

Thus, fines are predominantly CLAY

Hence the Secondary letter is C

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Example 2

Given: Sieve Opening (mm) Mass of soil retained on each sieve (kg)4.75 3

2 1

0.425 0.5

0.075 0.3

pan 0.2

Sieve No

Sieve Opening

(mm)

Mass of soil retained on each

sieve (g)

Percent mass

retained

(%)

Cumulative percent

retained % passing

4 4.75 3 60 60 40

9 2 1 20 80 20

35 0.425 0.5 10 90 10

200 0.075 0.3 6 96 4

Pan 0.2 4 100 0

Solution:

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Procedure

1)FINE GRAINED:


2) COARSE GRAINED:


Fineor coarse?

* In this case, (100-4=96%),hence >50% retained at No. 200 sieve, COARSE GRAINED

Sand or gravel?

Retained No 4 (Gravel) = 60% of the total soilor

(60/96)(100) = 63%of the coarse-grained soil

Therefore, Sand = 100 - 63= 37%of the coarse-grained

soil.

Since gravelis more than 50% > go to Gravel (Primary

letter G)

Check % of fines

(passing No 200)

If % fines < 5% Clean gravel


named

If % fines > 12% Gravel with fines

*in this case, % fines (passing No 200) = 4%, Clean g ravel

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Well Graded (W) or

Poorly Graded (P)?Plot the distribution curve, determine

Cuand Cc

Grained-size distribution curve

0

5

10

15

20

25

30

35

40

45

0.010.1110

Grain Diameter (mm)

(Log Scale)

%P

assing

Find D60, D30, D10,then determine the Cuand Cc

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*D10, D30, and D60= the particle-size diameters corresponding

to 10, 30, and 60 %, respectively, passing on the cumulative

particle-size distribution curve.

Well-graded gravelmust conforming to following conditions:

*For this case, Cu = 2.3, Cc =1.3, Poorly graded gravel GP

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Example 3

Sieve No Mass of soil retained on each sieve

4 2

9 2

35 3

200 2

Pan 1

Given:

Solution:

Sieve No Sieve Opening

Mass of soil retained on

each sieve

Percent mass

retained

Cumulative percent

retained

%

passing

4 4.75 2 20 20 80

9 2 2 20 40 60

35 0.425 3 30 70 30

200 0.075 2 20 90 10

Pan 1 10 100 0

PL =21, LL = 35

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Procedure

1)FINE GRAINED:


2) COARSE GRAINED:


Fineor coarse?


Sand or gravel?

Retained No 4 (Gravel) = 20% of the total soilor

(20/90)(100) = 22%of the coarse-grained soil


soil.

Since gravelis more than 50% > go to Sand (Primary

letter S)

Check % of fines

(passing No 200)

If % fines < 5% Clean sand


named

If % fines > 12% sand with fines

*in this case, % fines (passing No 200) = 10%, Dual ly n amed

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Well Graded (W) or


Cuand Cc


Grain size distribution curve

0

10

20

30

40

50

60

70

80

90

0.010.1110

Grain diameter (mm)

(Log scale)

%p

assing

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*For this case, Cu = 2.8, Cc =1.3, Poorly- graded sand SP

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Therefore, the first halfof the dual name is SP-SX

Check plasticity chart for the x

LL =35, PI = 35-21 = 14

From the plasticity chart,

xlocated at CL. Hence,

the soil is classified asSP-SC(Poorly Graded

sand with clay).

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Example 4

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Procedure

1)FINE GRAINED:


2) COARSE GRAINED:


Fineor coarse?


Sand or gravel?

Retained No 4 (Gravel) = (100-48)=52% of the total soilor(52/98)(100) = 53%of the coarse-grained soil


soil.

Since gravelis > 50% go to Gravel (Primary letter

G)

Check % of fines

(passing No 200)

If % fines < 5% Clean gravel


named

If % fines > 12% gravel with fines

*in this case, % fines (passing No 200) = 2%, Clean gravel

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Well Graded (W) or


Cuand Cc


Grain size distribution curve

0

10

20

30

40

50

60

70

80

90

0.010.1110

Grain diameter (mm)

(Log scale)

%p

assing

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*For this case, Cu = 4.8, Cc =2.2, Well- graded gravel GP

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Example 5Sieve Opening Mass of soil retained on each sieve

4.75 3

2 1

0.425 0.1

0.075 0.2

0.7

LL = 62, PL= 44

Sieve No Sieve Opening

Mass of soil retained on each

sieve

Percent mass

retained

Cumulative percent

retained % passing

4 4.75 3 60 60 40

10 2 1 20 80 20

40 0.425 0.1 2 82 18

200 0.075 0.2 4 86 14

Pan 0.7 14 100 0

25

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% passing No. 200 = 14%

LL = 62, PI = 62 -44 = 18, MH.

Hence, GM Silty Gravel

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Example 6

PI= 4216 = 36;

PI plotted above A

line with LL


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Example 7

PI= 6338 = 25;

PI plotted above A

line with LL >50,

MH (Elastic silt)

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Example 8

PI= 7025 = 45;

PI plotted above A

line with LL >50,

CH (Fat Clay)

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Example 9

PI= 2822 = 6;

PI plotted below A

line with LL


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Example 10

PI= 4643 = 3

(less than 4)

PI plotted below A line

with LL


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Thank you

Documents

Soil Classification 1