Index Properties of Soil.pdf

These Slides describe about the basics of Index properties of soil, definition and relations among different index properties of soil. These will be helpful for the students of civil engineering both Diploma and Degree Level. This chapter of Index properties of soil has been depicted in very easy and lucid manner.

1. GEOTECHNICAL
ENGINEERING
PHYSICAL & INDEX
PROPERTIES OF SOIL
PREPARED BY
GOURHARI BISWAS

2. INDEX PROPERTIES OF SOILS
•Indexpropertiesarethesimplephysical
propertiesofthesoils,whichareusedfor
identificationandclassificationofsoilsfor
variousengineeringapplications.
•Theyindicateaqualitativebehaviourofsoil
whensubjectedtovarioustypesofload.
•Todetermineindexpropertiessimpletestsare
required.Thesetestsarecalledclassification
tests.Thesoilsareclassifiedandidentified
basedonindexproperties.
•Engineeringpropertiesofsoilsarethose
propertieswhichcanbeusedforquantifyingthe
Engineeringbehaviourofsoils.

3. Different Index Properties
They can be listed as given below:
1.Water content
2.Specific gravity
3.Grain size distribution
4.PlasticitypropertiespopularlyknownasAtterberglimits
(Liquidlimit,PlasticlimitandShrinkagelimit)andtheir
indiceslikeplasticityIndex,LiquidityIndex,Consistency
Index,ShrinkageIndex.
5.In-situ density
6.Relative density
•Voidratio,porosity,degreeofsaturation,arenot
propertiesofsoils,butstateparametersindicatingthein-
situstateofsoil.

4. Different Engineering Properties of Soil
1.Shear strength (Cohesion intercept and
angle of internal friction)
2.Compressibility characteristics
(compression index and coefficient of
compressibility)
3.Permeability (Coefficient of Hydraulic
conductivity)
4.Compaction characteristics (Optimum
moisture content and Maximum Dry Unit
weight)
5.Swell/Collapse potential

5. PHASE DIAGRAM OF SOIL
•Soilisnotacoherentsolidmateriallikesteeland
concrete,butisaparticulate/granularmaterial.
Soils,astheyexistinnature,consistofsolid
particles(mineralgrains,rockfragments)with
waterandairinthevoidsbetweentheparticles.
Thewaterandaircontentsarereadilychanged
bychangesinambientconditionsandlocation.
•Astherelativeproportionsofthethreephases
varyinanysoildeposit,itisusefultoconsidera
soilmodelwhichwillrepresentthesephases
distinctlyandproperlyquantifytheamountof
eachphase.

6. Phase Diagrams
Aschematicdiagramofthe
three-phasesystemis
shownintermsofweight
andvolume symbols
respectivelyforsoilsolids,
water,andair.Theweight
ofaircanbeneglected.
Thesoilmodelisgiven
dimensionalvaluesforthe
solid,waterandair
components.
Totalvolume,V=Vs+Vw
+Vv

7. Phase Diagram for Fully Saturated
and Dry Soil
A phase diagram of soil indicating the masses
and volumes of air, solid, water, and voids.

8. Inter Relationship
Forthepurposeofengineeringanalysisand
design,itisnecessarytoexpressrelations
betweentheweightsandthevolumesofthe
threephases.
The various relations can be grouped into:
•Volume relations
•Weight relations
•Inter-relations

9. VOLUME RELATIONS
Astheamountsofbothwaterandairarevariable,the
volumeofsolidsistakenasthereferencequantity.Thus,
severalrelationalvolumetricquantitiesmaybedefined.The
followingarethebasicvolumerelations:
1.Voidratio(e)istheratioofthevolumeofvoids(Vv)to
thevolumeofsoilsolids(Vs),andisexpressedasa
decimal.
2.Porosity(n)istheratioofthevolumeofvoidstothetotal
volumeofsoil(V),andisexpressedasapercentage.

10. Inter relation between Void ratio and
Porosity
Void ratio and porosity are inter-related to each other as
follows:
1/n=V/Vv= (Vv+vs)/Vv
1/n= 1+ (1/e) = (1+e)/e
n=e/ (1+e) …….(a)
1/e= (1/n)-1= (1-n)/n
e=n/ (1-n)………. (b)
•Inequations(a)and(b),theporosityshouldbe
expressedasaratioandnotpercentage.
•Theporositycannotbesmallerthan0,andcannotbe
greaterthan1.Thevoidratiocanbegreaterthan1.

11. Degree of saturation
•Theporesofasoilmaycontainwaterandair.To
describetheratioofthesetwothedegreeof
saturationSisintroduced.Thedegreeof
saturationistheratioofthevolumeofwaterto
thevolumeofvoids.Itisdenotedby‘S’.
•S=Vw/Vv
•Thedegreeofsaturationisgenerallyexpressed
asapercentage.Itisequaltozerowhenthesoil
isabsolutelydryand100%whenthesoilisfully
saturated.
•Foradrysoil,S=0%,andforafullysaturated
soil,S=100%.

12. Air Content and Percent Air Voids
Air content (ac) is the
ratio of the volume of air
(Va) to the volume of
voids.
Also, n
a=n a
c

13. WEIGHT RELATIONS
Densityisameasureofthe
quantityofmassinaunit
volumeofmaterial.Unit
weightisameasureofthe
weightofaunitvolumeof
material.Bothcanbeused
interchangeably.Theunits
ofdensityareton/m3,kg/m3
org/cm3.Thefollowingare
thebasicweightrelations:
1.Watercontent,whichis
alsocalledmoisturecontent,
isthequantityofwater
containedinamaterial,
suchassoil.
Watercontentis
denotedbysmall
letterw.Hereweight
ofwaterisWwand
weightofsolidsis
Ws.Itsvalueis0%
fordrysoilandits
magnitude can
exceed100%.

14. contd...

15. INTER RELATIONS
•Itisimportanttoquantifythestateofasoil
immediatelyafterreceivinginthe
laboratoryandpriortocommencingother
tests.Thewatercontentandunitweight
areparticularlyimportant,sincetheymay
changeduringtransportationandstorage.
•Somephysicalstatepropertiesare
calculatedfollowingthepractical
measurementofothers.Forexample,dry
unitweightcanbedeterminedfrombulk
unitweightandwatercontent.The
followingaresomeinter-relations:

16. Inter Relations

17. VOLUME-MASS RELATIONSHIPS
1. BULK MASS DENSITY: The bulk mass density
(ρ) is defined as the total mass (M) per unit volume
(V), ρ=M/V
2. DRY MASS DENSITY: The dry mass density
(ρd) is defined as the mass of solids per unit total
volume, ρd= Ms/V
3. SATURATED MASS DENSITY : The saturated
mass density (ρsat) is the bulk density of the soil
when it is fully saturated. ρsat= Msat/V

18. contd...
4. SUBMERGED MASS DENSITY : When
the soil exists below water, it is in a
submerged condition. The submerged mass
density (ρ’) of the soil is defined as the
submerged mass per unit total volume.
ρ’= Msub/V
5.MASS DENSITY OF SOLIDS :The mass
density of solids (ρs) is equal to the ratio of
the mass of solids to the volume of solids
ρs=Ms/Vs

19. VOLUME-WEIGHT RELATIONSHIPS
1.BULK UNIT WEIGHT (γ)= W/V
2.DRY UNIT WEIGHT (γd) = Ws/V
3.SATURATED UNIT WEIGHT (γsat) =
Wsat/V
4.SUBMERGED UNIT WEIGHT (γsub or γ’)
= Wsub/V
5.UNIT WEIGHT OF SOIL SOLIDS (γs) =
Ws/Vs

20. SPECIFIC GRAVITY OF SOLIDS
•The specific gravity of soil particles (G) is
defined as the ratio of the mass of a given
volume of solids to the mass of an equal
volume of water at 4°C.
•G = ρs/ρw
•The mass density of water ρw at 4°C is
1gm/ml, 1000 kg/m3 or 1 Mg/m3

21. BASIC RELATIONSHIPS

22. Relative Density/Density Index
Itisaratioofdifferencebetweenmaximumvoidratioand
naturalvoidratiotothedifferencebetweenmaximumvoid
ratioandminimumvoidratioexpressedinpercentage.