chapter+2

SOIL SOIL CLASSIFICATIONCLASSIFICATION

CHAPTER 2CHAPTER 2

DEFINISI TANAHDEFINISI TANAH• Tanah merupakan endapan lembut atau

longgar yang wujud secara semulajadi dan menghasilkan kerak bumi.

• Tanah juga terbentuk hasil daripada proses luluhawa sama ada disebabkan oleh batu-bata yang runtuh atau tumbuh-tumbuhan yang reput.

PENGKELASAN PENGKELASAN TANAHTANAH

Pembentukan tanah melalui proses luluhawa ke atas batuan oleh agen-

agen seperti angin, air dan suhu.

Sifat-sifat tanah dari segi:

• Saiz butiran tanah• Kandungan air,

udara dan humus• Keasidan dan

kealkalian

Kategori tanah:• Kerikil• Pasir• Kelodak• Tanah liat atau• Campuran bahan di

atas

JENIS-JENIS TANAHJENIS-JENIS TANAH

Kumpulan Sifat Tanah Saiz Tanah

(mm)

Jenis Tanah

Zarah Kasar Tanah Tak Jelekit

0.06-2.0

2.0-60

Pasir

Kerikil

Zarah Halus Tanah Jelekit <0.002

0.002-0.06

Tanah Liat

Kelodak

Organik Tanah Organik <0.002 Tanah Gambut

Jadual : Kumpulan, sifat dan saiz zarah tanah

SIFAT-SIFAT TANAHSIFAT-SIFAT TANAH

Tanah Berzarah Halus (Tanah Jelekit)

Tanah Berzarah Kasar (Tanah Tak Jelekit)

•Nisbah lompang tinggi

•Terdapat jelekitan antara zarah

•Bersifat plastik

•Mudah mampat

•Berlaku endapan pada kadar perlahan dalam jangkamasa lama

•Hampir tidak boleh telap air

•Nisbah lompang rendah

•Tiada jelekitan antara zarah

•Terdapat geseran antara zarah

•Tidak mudah mampat

•Berlaku endapan serta merta apabila dikenakan beban

•Boleh telap air

JADUAL : PERBANDINGAN SIFAT TANAH JELEKIT – TIDAK JELEKIT

JENIS-JENIS TANAHJENIS-JENIS TANAHBATUAN

IGNEUS METAMORFOSIS ENDAPAN

Tindakan kimia

Tindakan biologi

Kelikir - Kelodak Laterit

Ferum Hidroksida & Aluminium Hidroksida


TANAH TERANGKUT (kelikir, pasir, kelodak & tanah liat)

• Lazimnya diangkut oleh air

• Apabila halaju air berkurngan, zarah tanah akan mendap dimulai zarah yang berat.

• Kelikir dan pasir di hulu sungai

• Kelodak dan tanah liat di hilir sungai


TANAH BAKI (tanah atas, laterit)

• Terbentuk melalui proses luluhawa

• Melalui tindakan kimia dan biologi dalam iklim panas & lembab

TANAH ORGANIK (tanah atas, gambut)• Permukaan bumi mengandungi bahan organik – 500mm• Terbentuk hasil daripada proses pereputan bahan organik,

sisa tumbuh-tumbuhan dan organisma yang reput.• Terhasil daripada pembentukan humus akibat tindakan

bakteria dan kulat yang mereputkan sisa organik.• Humus ialah bahan biokimia yang sebabkan tanah organik

bertukar dari perang ke gelap.• Ketumpatan dan keupayaan galas rendah.• Tanah atas merupakan tanah untuk pertanian dan

menimbulkan masalah kejuruteraan.


PHYSICAL PROPERTIES PHYSICAL PROPERTIES

• Used to describe the soil. They are incorporated with the soil classification systems, and in some cases they are related to the mechanical properties.

• - Color- Odor- Grain Size- Grain Shape- Specific Gravity- Unit Weight- Water Content- Void Ratio- Degree of Saturation- Porosity

PHASE DIAGRAMPHASE DIAGRAM

• Soil is a three phase system consisting of

- Solids- Water- Air

HUBUNGAN FASAHUBUNGAN FASA

T A N A HZARAH2;

•Pepejal

•Air

•udaraTanah Kering

Zarah Pepejal

& Udara

Tanah Tepu

Zarah Pepejal

& Air Liang

Tanah Separa Tepu

Zarah Pepejal, Air & Udara

KOMPONEN TANAHKOMPONEN TANAH

V=volume of soil sample at natural state (isipadu contoh tanah dalam keadaan asal)

Vv=volume of void(isipadu liang)

Vs=volume of soil particles (isipadu zarah tanah)

Va= volume of air (isipadu udara)

Vw=volume of water (isipadu air)

PHASE DIAGRAMPHASE DIAGRAM

EXAMPLE 1EXAMPLE 1

9.8

2.68

0.78

= 2.68 x 9.8

1 + 0.78

= …………………

EXAMPLE 2EXAMPLE 2

EXAMPLE 3EXAMPLE 3

A soil sample has a void ratio of 0.78,

water content 12% & specific gravity 2.68.

Calculate :

a) Bulk unit weight,

b) Dry unit weight,

c) Degree of saturation, (Sr)

d) Porosity, (n)

Example 4Example 4

A soil test carried out a sample of soil 1.75kg and a volume of 0.001m3. Determined the specific gravity of the solids was 2.68 and the dry density of the soil was 1500kg/m3. Find;– Moisture content of soil– Void ratio– Porosity– Saturated density– Degree of saturation

Example 5Example 5

A 30.5kg of sample soil had a volume of 0.0184m3. When dried out in an oven its weight was reduced to 27.3kg. The specific gravity of the solids was found to be 2.67. Determine the :

• Bulk density• Dry density• Dry unit weight• Percentage of moisture content• Saturated density• Void ratio • Porosity• Degree of saturation

SOLUTIONSOLUTION

a) (1+ 0.12) x 2.68 x 9.8 / (1+0.78) = 16.53 kN/m3

b) 16.53 / (1+0.12) = 14.76 kN/m3

c) (0.12 x 2.68) / 0.78 = 41.23 %

d) 0.78 / (1+0.78) = 0.44

• Used to classify the soil or to correlate with the mechanical properties.

- Atterberg Limits or Consistency Limits- Moisture Content-Unit Weight Relationship- Grain Size Distribution- Relative Density Dr- CBR

- LBR

INDEX PROPERTIESINDEX PROPERTIES


• Consistency of Soil • Basic States: * Depending on the moisture content, soil

behaves like: a- Solidb- Semisolidc- Plasticd- Liquid

FIGURE : FIGURE : SOIL SOIL CLASSIFICATION CLASSIFICATION

Basic StatesBasic States

• Atterberg Limits or Consistency Limits:

a-The moisture content (wc) at which the transition from one state to another is defined as: a- Shrinkage Limit (SL) from Solid to Semisolid.

b- Plastic Limit (PL) from Semisolid to Plastic.

c- Liquid Limit (LL) from Plastic to Liquid.


LIQUID LIMIT:

• It is the water content at 25 blows and can be determined by using Casagrande Cup. The slope of the line is defined as the flow index.


Liquid Limit TestLiquid Limit Test

PLASTIC LIMIT

• Is the moisture content at which the soil crumbles when rolled into threads of 1/8 in. in diameter.



• PLASTICITY INDEXPI = LL – PL (BS 5930:1981)

• PLASTICITY CHARTPI vs. LL.* Line A differentiates between the silt and the clay

• SHRINKAGE LIMIT • LIQUIDITY INDEX

SOIL CLASSIFICATION SOIL CLASSIFICATION SYSTEMSSYSTEMS

• Why do we need to classify soils ?

• To describe various soil types encountered in the nature in a systematic way and gathering soils that have distinct physical properties in groups and units.

Various Soil Classification Various Soil Classification Systems:Systems:

• USDA- United State Department of Agriculture (Jabatan Pertanian Amerika Syarikat)

• USCS- Unified Soil Classification System (Sistem Pengkelasan Tanah Bersekutu)

• AASHTO-American Association of State Highway Transportation Officials System

SIEVE ANALYSISSIEVE ANALYSIS

1- PARTICLE SIZE DISTRIBUTION • The particle size of coarse-grained soils is

determined by passing a known weight of soil through a nest of sieves.

• The mesh of sieve is a square grid. Each sieve is label with a number and the size of the grid.

• Typically a stack of sieves will consist of the following from top to bottom.

• Fine-grained soils (silt and clay) are retained on the pan.

Sieve No Opening (mm)

4 4.75

10 2.0

20 0.85

40 0.425

100 0.15

200 0.075


Cumulative Curve: • A linear scale is not convenient to use to size all the soil particles

from 60 mm to 0.002 mm. • Logarithmic Scale is usually used to draw the relationship

between the % Passing and the Particle size.

Grading Characteristics

• Parameters Obtained From Grain Size Distribution Curve:• D10 , Effective Size (saiz Berkesan) • Cu, Uniformity Coefficient (Pekali Keseragaman)

Cu = D60/D10 • Cu < 4 ----- Uniform soil (Tanah Seragam)• Cu > 4 ----- Well graded soil (Tanah Bergred Baik)• Cu > 6 ----- Sand (Berpasir)


• Cc, Coefficient of Curvature (Pekali Kelengkungan)

Cc = (D30)2/ D60 x D10 • Cc from 1 to 3 ------- well graded soil• Cc < 1 (Not well graded)

Cu and Cc are acctually used in USCS (United Soil Classification System)


EXAMPLE : PARTICLE SIZE EXAMPLE : PARTICLE SIZE DISTRIBUTION CURVEDISTRIBUTION CURVE

Grading curvesGrading curves

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

W Well graded

Grading curvesGrading curves

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

W Well graded

U Uniform

Grading curves

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

W Well graded

U Uniform

P Poorly graded

Grading curves

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

W Well graded

U Uniform

P Poorly graded

C Well graded with some clay

Grading curves

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

W Well graded

U Uniform

P Poorly graded

C Well graded with some clay

F Well graded with an excess of fines

Unified Soil ClassificationUnified Soil ClassificationTo determine W or P, calculate Cu and Cc

CD

Du 60

10

CD

D Dc 302

60 10( )

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

D90 = 3 mm

x% of the soil has particles smaller than Dx

ExampleExample

0.0001 0.001 0.01 0.1 1 10 1000

20

40

60

80

100

Particle size (mm)

% F

iner

• %fines (% finer than 75 m) = 11% - Dual symbols required

• D10 = 0.06 mm, D30 = 0.25 mm, D60 = 0.75 mm

1009080706050403020100

100

90

80

70

60

50

40

30

20

10

0100

90

80

70

60

50

40

30

20

10

0

SiltSizes(%)

SandSiltySand SandySilt

Clay-Sand Clay-Silt

SandyClay SiltyClay

Clay

LOWERMISSISSIPPIVALLEYDIVISION,U.S.ENGINEERDEPT.

Simple ClassificationSimple Classification• In general soils contain a wide range of particle sizes

• Some means of describing the characteristics of soils with different proportions of sand/silt/clay is required.

Simple ClassificationSimple Classification• In general soils contain a wide range of particle sizes

• Some means of describing the characteristics of soils with different proportions of sand/silt/clay is required.

• Note the importance of clay - Finest 20% control behaviour1009080706050403020100

100

90

80

70

60

50

40

30

20

10

0100

90

80

70

60

50

40

30

20

10

0

SiltSizes(%)

SandSiltySand SandySilt

Clay-Sand Clay-Silt

SandyClay SiltyClay

Clay

LOWERMISSISSIPPIVALLEYDIVISION,U.S.ENGINEERDEPT.

Example: equal amounts sand/silt/clayExample: equal amounts sand/silt/clay

Give typical names: indicate ap-proximate percentages of sandand gravel: maximum size:angularity, surface condition,and hardness of the coarsegrains: local or geological nameand other pertinent descriptiveinformation and symbol inparentheses.

For undisturbed soils add infor-mation on stratification, degreeof compactness, cementation,moisture conditions and drain-age characteristics.

Example:

Well graded gravels, gravel-sand mixtures, little or nofines

Poorly graded gravels, gravel-sand mixtures, little or nofines

Silty gravels, poorlygraded gravel-sand-silt mixtures

Clayey gravels, poorly gradedgravel-sand-clay mixtures

Well graded sands, gravellysands, little or no fines

Poorly graded sands, gravellysands, little or no fines

Silty sands, poorly gradedsand-silt mixtures

Clayey sands, poorly gradedsand-clay mixtures

GW

GP

GM

GC

SW

SP

SM

SC

Wide range of grain size and substantialamounts of all intermediate particlesizesPredominantly one size or a range ofsizes with some intermediate sizesmissing

Non-plastic fines (for identificationprocedures see ML below)

Plastic fines (for identification pro-cedures see CL below)

Wide range in grain sizes and sub-stantial amounts of all intermediateparticle sizes

Predominantely one size or a range ofsizes with some intermediate sizes missing

Non-plastic fines (for identification pro-cedures, see ML below)

Plastic fines (for identification pro-cedures, see CL below)

ML

CL,CI

OL

MH

CH

OH

Pt

Dry strengthcrushingcharacter-

istics

None toslight

Medium tohigh

Slight tomedium

Slight tomedium

High to veryhigh

Medium tohigh

Readily identified by colour, odourspongy feel and frequently by fibroustexture

Dilatency(reactionto shaking)

Quick toslow

None to veryslow

Slow

Slow tonone

None

None to veryhigh

Toughness(consistencynear plastic

limit)

None

Medium

Slight

Slight tomedium

High

Slight tomedium

Inorganic silts and very fine sands,rock flour, silty or clayeyfine sands with slight plasticityInorganic clays of low to mediumplasticity, gravelly clays, sandyclays, silty clays, lean clays

Organic silts and organic silt-clays of low plasticity

inorganic silts, micaceous ordictomaceous fine sandy orsilty soils, elastic silts

Inorganic clays of highplasticity, fat clays

Organic clays of medium tohigh plasticity

Peat and other highly organic soils

Give typical name; indicate degreeand character of plasticity,amount and maximum size ofcoarse grains: colour in wet con-dition, odour if any, local orgeological name, and other pert-inent descriptive information, andsymbol in parentheses

For undisturbed soils add infor-mation on structure, stratif-ication, consistency and undis-turbed and remoulded states,moisture and drainage conditions

ExampleClayey silt, brown: slightly plastic:small percentage of fine sand:numerous vertical root holes: firmand dry in places; loess; (ML)

Field identification procedures(Excluding particles larger than 75mm and basing fractions on

estimated weights)

Groupsymbols

1Typical names Information required for

describing soilsLaboratory classification

criteria

C = Greater than 4DD----60

10U

C = Between 1 and 3(D )

D x D----------------------30

10c

2

60

Not meeting all gradation requirements for GW

Atterberg limits below"A" line or PI less than 4

Atterberg limits above "A"line with PI greater than 7

Above "A" line withPI between 4 and 7are borderline casesrequiring use of dualsymbols

Not meeting all gradation requirements for SW

C = Greater than 6DD----60

10U

C = Between 1 and 3(D )

D x D----------------------30

10c

2

60

Atterberg limits below"A" line or PI less than 4

Atterberg limits above "A"line with PI greater than 7

Above "A" line withPI between 4 and 7are borderline casesrequiring use of dualsymbolsD

eter

min

epe

rcen

tage

sof

grav

elan

dsa

ndfr

omgr

ain

size

curv

e

Use

grai

nsi

zecu

rve

inid

enti

fyin

gth

efr

actio

nsas

give

nun

der

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did

entif

icat

ion

Dep

endi

ngon

perc

enta

ges

offi

nes

(fra

ctio

nsm

alle

rth

an.0

75m

msi

eve

size

)co

arse

grai

ned

soils

are

clas

sifi

edas

foll

ows

Les

sth

an5%

Mor

eth

an12

%5%

to12

%

GW

,GP,

SW

,SP

GM

,GC

,SM

,SC

Bor

deli

neca

sere

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ing

use

ofdu

alsy

mbo

ls

The

.075

mm

siev

esi

zeis

abou

tthe

smal

lest

part

icle

visi

ble

toth

ena

ked

eye

Finegraine

dsoils

Morethan

halfof

materialissm

allerthan

.075

mm

sievesize

Coa

rsegrainedsoils

Morethan

halfof

materialislarger

than

.075

mm

sievesize

Siltsan

dclay

sliq

uidlim

itgreaterthan

50

Siltsan

dclay

sliq

uidlim

itless

than

50

Sand

sMorethan

halfof

coarse

fractio

nis

smallerthan

2.36

mm

Gravels

Morethan

halfof

coarse

frac

tionislarger

than

2.36

mm

Sand

swith

fines

(app

reciab

leam

ount

offin

es)

Clean

sand

s(little

orno

fines)

Gravelswith

fines

(apreciable

amou

ntof

fines)

Clean

gravels

(little

orno

fines)

Identification procedure on fraction smaller than .425mmsieve size

Highly organic soils

Unified soil classification (including identification and description)

Silty sand, gravelly; about 20%hard angular gravel particles12.5mm maximum size; roundedand subangular sand grainscoarse to fine, about 15% non-plastic lines with low drystrength; well compacted andmoist in places; alluvial sand;(SM)

0 10 20 30 40 50 60 70 80 90 100Liquid limit

0

10

20

30

40

50

60

Plas

tici

tyin

dex

CH

OH

or

MHOL

MLor

CL

Comparing soils at equal liquid limit

Toughness and dry strength increase

with increasing plasticity index

Plasticity chartfor laboratory classification of fine grained soils

CI

CL-MLCL-ML

Activity 1 : Activity 1 :

The results of sieve analysis of a soil specimen are shown in Table below :Given total weight of soil = 197.7 g , Test Duration = 3 minutes

Sieve Size (mm)

Weight Retained (g)

Weight Passed (g)

% Retained % Passing

4.750 1.4 ? 0.71 99.29

2.360 9.1 187.2 4.60 ?

1.180 9.3 ? 4.7 ?

0.600 50.0 ? 25.29 ?

0.300 66.5 61.4 33.64 31.05

0.212 38.5 22.9 ? 11.58

0.150 13.3 9.6 ? 4.86

0.075 7.3 2.3 3.69 1.17

Retained 2.3 0.0 - -

Activity 1Activity 1

1) Plot the particle-size distribution graph.

2) Find D10, D30 and D60

3) Find the coefficient of uniformity, Cu

4) Find the coefficient of Curvature, Cc

Answer :Answer :

Sieve Size (mm)

Weight Retained (g)

Weight Passed (g)

% Retained % Passing

4.750 1.4 196.3 0.71 99.29

2.360 9.1 187.2 4.60 94.69

1.180 9.3 177.9 4.7 89.98

0.600 50.0 127.9 25.29 64.69

0.300 66.5 61.4 33.64 31.05

0.212 38.5 22.9 19.47 11.58

0.150 13.3 9.6 6.72 4.86

0.075 7.3 2.3 3.69 1.17

Retained 2.3 0.0 - -

Activity 2 :Activity 2 :

The results of a sieving analysis of a soil sampel are shown in Table A2. Plot the particles-size distribution curve of the soil sample. Classify the soil by using the USCS, USDA and AASHTO.

Given: PL – 35% LL – 42%

Sieve size (mm)

Weight retained (g)

Percentage passing (%)

10 0.0 100

6 7.5 95

2 33 73

1 30.75 52.5

0.6 30.75 32

0.3 21.75 17.5

0.15 15 7.5

0.063 3.75 5

0.02 4.5 2

Pan 3 0

Table A2

USCS MethodUSCS Method• From PSDG, passed o.o75mm. • Refer to USCS Chart• More than 50% retained on 0.075mm• Coarse-grained Soils• Sands or Gravels• From PSDG, 88% passed 4.75mm• More than 50% of coarse fraction

passes 4.75mm

• Sands• Sands with Fines or Cleans

Sands• 5% to 12% pass 0.075mm

sieve• Border classification requiring

use of dual symbols• Refer to Plasticity Chart• Given in question 6, PI=7%

and LL=42%• From Plasticity Chart, the soil

is ML or OL

USDA MethodUSDA Method

Adjust Percentage of Soils

%93%10073

573

%7%10073

05

Sands =

Silts =

Clay = 0%

From USDA Triangular Chart, The

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