chapter 1- soil classification

8/17/2019 Chapter 1- Soil Classification

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CHAPTER 1

Composition and soil

classification


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• Mainly due to physical and chemical

weathering of rock

• Physical weathering causes reduction of sizewithout changes of the composition

* agent- erosion, freezing, unloading • Chemical weathering causes reduction in size

and altered the composition of rock*agent- hydration, carbonation, oxidation


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Weathering process


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Soil type

Residual soil

Alluial soil

!lacial soil

Marine soil

Aeolian soil


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1.1 COMPONENTS OF SOILS


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• A soil mass" consists of solid soil particles" containing oid

spaces #etween them$ %hese oids may #e filled either withair or water" or #oth$

• %he soil will #ehae as a two phase system" when its oid

space is filled with either water or air alone$• &n other words" the soil mass will consists of only two phases"

i$e$ solid and water 'li(uid)" or solid and air 'gas)" respectiely$• Such a condition is possi#le when either the soil is fully

saturated 'the oids are totally filled with water" and there is no

air) or when the soil is fully dry 'the oids are totally filled with

air" and no water)$

• +ut" as and when the soil mass is partially saturated its oidspace will #e filled up #y water as well as air" and hence it will

#ehae as a three phase system$


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1.2 Weight-Volume Relationships


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VOLUME

V = Vs + Vv = Vs + (Vw + VaWhere Vs = olume of soil solids

Vv = olume of oids

Vw , olume of water in the oids

Va = olume of air in the oids

WE!"#$

W = Ws + Ww 'Assume Wa , -)

where Ws = weight of soil solids

Ww , weight of water

.oid ratio" e ,

Porosity" n ,

/egree of saturation" Sr , 0 1--2

S

V

V

V

T

V

V

V

V

W

V

V



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%he relationship #etween oid ratio 'e) and porosity 'n)

e

e

+1

n ,

Moisture content"

s

w

W

W w =

3nit weight

V

W=γ

/ry 3nit weight or

V

W S

d =γ

wd

+=

1

γ γ


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&n 4nglish units

3nit weight" γ in pounds per cu#ic foot 'l#5ft6)$

&n S& units

3nit weight" γ in kilo 7ewtons per cu#ic meter 'k75m6)$

V

M

= ρ /ensity /ry /ensity V

Ms

d =ρ

where ρ = density of soil 'kg5m3 )

ρ d - dry density of soil 'kg5m3 )

M , total mass of the soil sample 'kg)

Ms , mass of soil solids in the sample 'kg)

V = Total volue !3 )

%he unit weight in k75m6 can #e o#tained from densities in kg5m6 as

REMEMBER THIS

NOTE

!raity Acceleration ,

8$91 m5sec:$

3nit weight of water" γ w

is e(ual to

8$91 k75m6 or

;:$< l#5ft6 or

1--- kg5m6

$1g5cm6


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Relationships among Unit Weight% Voi& Ratio% Moistu'e

ontent% an& )pe*ii* "'avit,

Assume .s , 1

!s , Ws5'γ w 0 .s)

W s = "sγ w

W w , wW s = w"sγ w

where

"s = specific graity of soil

solids

w = moisture content

γ w

= unit weight of water


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( )

e

Gw

e

wGG

V

W W

V

W w sw sw sw s

+

+=

+

+=

+==

1

1

1

γ γ γ γ

e

G

V

W w s sd

+==

1

γ γ 1==

d

w sGe

γ

γ

s

w

w s

w

s

w wGwGW

V === γ

γ

γ

e

wG

V

V S

s

s

w== #r e = w"s


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&f the soil sample is satu'ate&



( )

e

eG

e

eG

V

W W

V

W w sww sw s

sat

+

+=

+

+=

+==

11

γ γ γ γ

e = w"s Sr , 1 when saturated


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$w , density of water , 1--- kg5m6$

For Satrat!d soils


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For "nSatrat!d soils

M w = wM s = w"s ρ w

=rom 4($ '6$16)" density


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R!lations#ips amon$ "nit %!i$#t& Porosit'& and Moistr! Cont!nt

V

Vn v= &f V is e(ual to 1" then Vv is e(ual to n, so Vs = 1 > n


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R!lations#ips amon$ "nit %!i$#t& Porosit'& and Moistr! Cont!nt


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Va'ious Unit-Weight Relationships


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A specimen of clay was tested in the la#oratory and the following data were

collected%

Mass of wet specimen M1 , 1


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Wo'e& eample 1


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Wo'e& Eample 2

!ien @

1$ %he weight of a chunk of moist soil sample is


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Wo'e& Eample 2

3nit weight of moist soil 'γ )

.oid ratio 'e)

Porosity 'n)

/egree of saturation 's)


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Wo'e& Eample 0

!ien@

1$ %he moist mass of a soil specimen is :-$? kg$

:$ %he specimenBs olume measured #efore drying is -$-11 m6$

6$ %he specimenBs dried mass is 1;$6 kg$


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Wo'e& Eample 0

.oid ratio 'e)


Wet unit mass 'ρ)


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Wet unit weight 'γ )

Wo'e& Eample 0

/ry unit weight 'γ d)

/ry unit mass 'ρd)


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Wo'e& Eample

!ien@

An undistur#ed soil sample has the following data@

1$ .oid ratio , -$?9$

:$ Water content , 1:2$6$ Specific graity of solids , :$;9$

&e'uired

!a) Wet unit weight '#) /ry unit weight 'c) /egree of saturation$

'd) Porosity$

Soltion(

Assume


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oid ratio !e) =

Wo'e& Eample


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Wet unit weight 'γ )

Wo'e& Eample

/ry unit weight 'γ d)


Porosity 'n)


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Wo'e& Eample

!ien@

1$ A 1--2 saturated soil has a wet unit weight of 1:- l#5ft6$

:$ %he water content of this saturated soil was determined to #e 6;2$&e'uired

!a) .oid ratio '#) Specific graity of solids$

Soltion(


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Wo'e& Eample

.oid ratio 'e)

Specific graity of solids '!s)


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Wo'e& Eample 3

!ien@

A soil sample has the following data@

1$ .oid ratio , -$8


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=rom the gien oid ratio"

Wo'e& Eample 3

Su#stitute 4($ 'A) into 4($ '+)

=rom the gien degree of saturation"

S , V W (V V = -$6

Water content$

3nit weight


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SOIL P)RTICLES SI*E )N+ SH)PE

Shape of soil particle

!rael Sand Silt Clay

=ine soilCoarse soil

isi#le to the naked eye

determined #y meansof an electron microscope$

Rounded Angular &rregular

4longated=laky=laky

4longated Scanning 4lectronMicroscope 'S4M)


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Particl!s Si,! +istri-tion

• Most natural soil is composite soil a mi0ture of different particles size and the

distri#ution and these characteristic also hae a significant on itsengineering #ehaiour$

• %wo methods are generally used to find particles size distri#ution of soil@

Siee analysis D for particles sizes larger than -$-?mm in diameter

Eydrometer analysis D for particles sizes smaller than -$-?mm in diameter$

Siee analysisEydrometer analysis


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Mechanical or siee analysis 'for grain sizes FG:-- siee)

Size 'Hm)

AS%M


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Sedimentation or hydrometer tests 'for grain sizes IG:-- siee)

#ased on Stoke$s law@


Hy rometer No. 769333 Part c e ens ty, Gs 2.63

Test Temperatre 26 ! Viscosity o" #ater, $ %.&72'(eniscs correction %.) *nitial dry mass o" soil 91.979 g+ea n n spersant so t on, + %- 1.)%%

/ate 0lapsed Hydometer Tre 0""ectie (odi"ied Particle Percentae

T me t me rea n rea n ept rea n ameter ner t an /t + - + H+ + d 4

mintes mm 5m

9.12 %

%.) 9.)% 1%.%% 1)&.2) 11.%% )9.%%% 19.2969.13 1 9.%% 9.)% 16%.16 1%.)% )1.2%& 1&.'199.1' 2 &.%% &.)% 163.9& 9.)% 36.639 16.66)

9.16 ' 7.)% &.%% 16).&9 9.%% 26.%)& 1).7&&9.2% & 6.)% 7.%% 169.71 &.%% 1&.637 1'.%3'

9.27 1) ).)% 6.%% 173.)3 7.%% 13.763 12.279

9.'2 3% '.%% '.)% 179.26 ).)% 9.&91 9.6'&1%.12 6% 3.%% 3.)% 1&3.%9 '.)% 7.%6& 7.&9'

11.12 12% 2.%% 2.)% 1&6.91 3.)% ).%)% 6.1'%1.12 2'% 1.)% 2.%% 1&&.&2 3.%% 3.)&9 ).263

'.'2 ')% %.)% 1.%% 192.6' 2.%% 2.6'7 3.)%&

1'2% %.%% %.)% 19'.)) 1.)% 1.'9& 2.631


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Siee size for arious classification system



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Siee test

Siee analysis consists of shaking the soil sample through a set of siee that

hae progressiely smaller opening

After the soil is shaken" the mass of soil retained on each siee is determined$


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Jnce the percent finer for each siee is calculated as in step " the

calculation are plotted on semilogarithmic graph paper with percent finer asordinate 'arithmetic scale) and siee opening as a#sicca 'logarithmic scale)$

Siee test

PARTICLE SIZE DISTRIBUTION

BRINCHANG BH13 (6.0-7.0 m)

%

1%

2%

3%

'%

)%

6%

7%

&%

9%

1%%

%.%%1 %.%1 %.1 1 1% 1%%

SIEVE SIZES (mm)

P E R C E

N T A G E P A S S I N G (


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Siee analysis e0ample


Si!! m!s#si,! /mm0 Mass

r!tain!d /$0

P!rc!nta$!

r!tain!d

P!rc!nta$!fin!r

/passin$0

1


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Particl!s Si,! +istri-tion Siee analysis e0ample

%he soil comprises@192 grael"

graded !raelly

Sand


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)nal'sis of Particl!si,! +istri-tion

A > a poorly>graded medium SA7/ 'pro#a#ly estuarine or flood>plain alluium)

+ > a well>graded !RA.4K>SA7/ 'i$e$ e(ual amounts of grael and sand)

C > a gap>graded CJ++K4S>SA7// > a sandy S&K% 'perhaps a deltaic or estuarine silt)

4 > a typical silty CKAL 'e$g$ Kondon clay" J0ford clay)


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)nal'sis of Particl!si,! +istri-tion

Eff!cti! si,!

d1-"niformit' co!ffici!nt

Cu , d;- 5 d1-

Co!ffici!nt of $radation

Ck , d6- 5 d;- d1-

Cu F indicates a well>graded soilCu I 6 indicates a uniform soil

Ck #etween -$ and :$- indicates a well>graded soil

Ck I -$1 indicates a possi#le gap>graded soil


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Consist!nc' of Soil

• Consistency is the characteristic of fine>grained material 'silt and clay) which

related with moisture content$

• %he fine grained soil can #ehae as solid" semi solid" plastic and li(uid

depending on the amount of water

P

KKPKSK


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)tt!r-!r$2s Limit and Consist!nc'

Plastic limit" PK

•%he a#ility of soil to change their shape without #reak or crack$

•%he alue of plastic limit is determine #y rolling the soil #y hand and #reak or

crack at 6mm in diameter$

Ki(uid limit" KK• &s the amount of water content when the soil change from plastic phase to

li(uid phase$

•%he moisture content corresponding to : drops '#lows) as read from the

represents li(uid limit or

•%he moisture content corresponding to :- mm penetration for second

Plasticity inde0" P&

•%he range of water content for soil in plastic state

• 4!= LL - 4L


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'-$--?mm)


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Li3id Limit +!t!rmination /Casa$rand! m!t#od0

Ki(uid limit test results #y using Casagrande method


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Ki(uid limit test results #y using Casagrande method


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Li3id Limit +!t!rmination /Con! p!n!trom!t!r0

Ki(uid limit and Plastic limit test results #y using


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Ki(uid limit and Plastic limit test results #y using

Cone Penetrometer method


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Plastic Kimit

6mm

A i i


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Actiity

• %he proportion of clay mineral 'I : µm size) in a fine soil

affects its current state" particularly its tendency to swell

and shrink with changes in water content$

• %he degree of plasticity related to the clay content is

called the actiit' of the soil$

Actiity , P& 5 '2 clay particles)


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Soil Classification

• Classification systems proide a common language to e0press

concisely the general characteristic of soil$

• %he grain size distri#ution and plasticity of soils are commonly

used to classify the soil

• %here are some system in soil classification of soil such as/i0 T#! "nifi!d Soil Classification /"SC0 S'st!m

/ii0 ))SHTO Classification S'st!m

/iii0Britis# Soil Classification S'st!m


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Soil Classification /"SCS0

'-$-? mm)


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3SCS


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=or !raelly and sandy soil


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=or !raelly and sandy soil

=or &norganic silty and clayey soil


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=or &norganic silty and clayey soil

=or organic


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=or organic

silty and

clayey soil


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AASE%J System


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y

AASE%J flow chart 'Coduto et al :-11)


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AASE%J flow chart 'Coduto et al$ " :-11)

!roup &nde0 '!&)


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!roup &nde0 '!&)

• %o ealuate the (uality of a soil as a highway su#grade

material$• %he smaller the alue of the !&" the #etter the soil as a

highway material

• !&,'=>6)O-$:-$--'KK>


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40ample 1


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40ample :

+SCS 'Coarse soil)


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' )


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+SCS '=ine soils)

Pro#lems


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Pro#lems

chapter 1- soil classification

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