Soil Mechanics Lab Manual including some International Standards

Laboratory
Testing
in SoilEngineering
AN INSTRUCTIONAL GUIDE
FOR
UNDERGRADUATE
STUDENTS
CIVITENGINEERING
(FOR PRTVATE CTRCULATTON ONLYI
Edited bg :
DTVISION OF SOIL MECHANICS AND FOUNDATION ENGINEERING
ANNA UNIVERSITY
Prtbltshed bg
THE EITGINEERING
COIIEGE CO-OPERATMSOCIETY
LTD., (c.10431
CHENNAI
. 600 025
IN

PREFACE
The gtudy bf laboratary methods is a logical extension of all analytical
subjects. The use of accurate and even elaborate methods of testing
requires no justification in'a research laboratory. The extent to which these
methods should be adopted in routine testing depends largely on whether
or not they reduce the margin o1'uncertainly in design sufficiently to justi&
their cost. The answer in many cases, particularly in soils and foundation
engineering, is self evident.
The instruction volume is intended to serve as a helpful guide to civil
engineering students performing experiments in a soils laboratory. A
standard format of presentation, reference to IS codes, brief coverage of
theory etc. are features rvhich hopefully, would be welcomed. While the
equipments may be made in a variety of forms tle procedures outlined
should stitrl be broadly applicabft: in most cases. Short review questions to
be answered by the student rilong with his report have been added to
stimulate thinking and the instructor may add his own fund of knowledge.
The format is deliberately kept simple to keep down the cost. Suggestions
on improvement are most rvelcome.
Dhislon o.,fSoil Mechanics dnd. Foundation Englneerlng
College of Engtneerlng
Anna Untuersltg, Chennal - 600 O25,

CONTENTS
Specific Gravity of a Soil
ParticleSize Determination
(Mechanical
Method:Dry Siwing
ParticleSize Determination
(sedimentation
Method - Hdrometer Analysis)
Liquid and PlasticLimits of a Soil
StuinkageLimit of a Soil
Field Density Test
Moishre - Density Relationshipusing koctor Compaction
Direct Shear Test
Trkxial CompressionTest on Cohesionless
Soil
UnconfinedCompression
Test
Cqrsolidation Test
PerrneabilityTest
Revieu,Questions
1
5
9
15
19
23
27
32
37
4t
45
50
57

Experiment No.
SPECIFIC GRAVITY OF A SOIL
References
1) IS ZT20 (part III) - 1980 : Methodsof test for soils- Determinationof Specificgravity,
SectionI, Fine grainedSoil.
Z Lambe, T.W., (1951), Soil Testingfor Engineers,John Wiley & Sons, NewYork.
Objective
To determine the specific gravity of sqil.
Equipment
Specific gravity bottle/PycnometerNoltrmetric flask, Vacuum Source.
Desiccator
Balance(0.019 sensitivitY)
Thermometer, Distilled water
Introduction
The terms
'densi$l' and
'specific gravity' are sometimestrcedsome what loosely, the specific
gravity of a soil particle being describedas the density or absolute density and density being
sometimestermed the "apparnnt" o, bulk specificgravity. It is better to restrict the use of density
to mean the bulk density and refer the specific gravity to soil particles only'
The specific gravity of any substanceis defined as the unit weight of the material divided by
the unit weight of distilledwater at the standardtemperatureof 27'C. The specificgravity (usually
given the notation Gr) of the soil is often usedin relatingthe weight of soil to its volume. A value
lf specificgravity is
"necessary
to compute the void ratio of a soil. It is also used in Stoke's law
in particle-size
analysisand in the computationsof most laboratorytestsand unit weight of the soil.
Oclasionally, specific gravity may be useftdin soil mineral identification e.g., iron minerals have
a larger rnlue of speciiicgrauitythan silicas. The specificgravity of most soils,however lieswithin
a naffow range oI Z.6S-2"80. The specificgravity of a soil is by itself not an important factor
in influencingsoil action. As an indication of the presenceof mineral or organic content it may
be important For example,when clay soilsshow low specificgravitysuchas 2.3 o1.2.4this:may
be due to the presenceof organic content. Thesesoilsare generallyhighly undesirablefoundation
materials.
RecommendedProcedure
a) Cohesionless soil
If the Specific gravity bottle is used in the teststhe method is the most accurate. Volumehic
flask ard the pycnom eter are used for cohesionlesssoils and the pycnorneter being particularly
suitablefor gravelsand coarsesands. The test cannot be rushedthrough. An atttempt to speed
if up *1 pr"b"bb result in the sample frothing badly when placed under too high a vacuuln or
else all thci air will not be removed at all'
I

The soilusedin the specificgravitytestmaybe in its naturalmoistureor ovendried.The weight
of the test specimenon an ovendry basisshallbe at least25g with volumetricflaskand 10g with
stopperedbottleand around100g when the 500 ml flaskis used.
Weighthe empty pycnometeror specificgravip bottle (WJ
Tiansferthe specimen(ovendry or containingnafuralmoisfure)into the pycnometer/specific
gravip bottle. Weigh the pycnometerwith the soil (WJ
Add distilledwaterto fill the pycnometer/specific
gravitybottleaboutthree/fourthsfull or about
half full respectively.
Removethe entrappedair by subjecting
the contentsto a partialvacuum(air pressurenot
exceeding
100 mm of mercury)
Fill the pycnometer/specific
gravitybottlecompletelv
with distilledwater (uptothe mqrk)and
note the weightWo,,)
Removeall the soilparticlesandwashthe pycnometer/specific
gravitybottleand rinseit with
distilledwater.
Then fill the pycnomet
er/specificgravitybottlewith distilledwatercompletely(uptothe maik)
andcleananddry the outsidewith cleandry cloth andweighit (WJ. Note the temperahrefC
at which the test wasconducted.
b) Cohesive soil
Mix the appropriateamountof soilwith (distilled)
waterin an evaporating
dishto form a creamy
paste.
Weighthe dry volumetricflask(Wr)and collectand stabilizethe tgmperatureof a sufficient
quantityof waterfor the testto asneai 20"Caspossible.
If possible,
put the waterin a container
to which a vacuutncan be appliedto deairthe wateras muchas practicable.
Next kansfer the soil water mixtureto the volumefuic
flask. Be sureto washall the soil from
the dishinto the flask. Now addadditionalwaterto the flaskuntil it is two-thirdsto three-quarters
full. Do not fill water up to the neck of the flaskas this will reducettie efficiencyof vacuum.
Connectthe flaskto high vacuumfor atleast10 minutes. Duringthis time, gentlyagitatethe
mixtureby carefullyshakingand turningthe bottle.
Whende-airingprocessis completedcarefullyaddwater(fromthe containerof waterprepared
earlier)until the bottom of the meniscttsis exactlyat the volumemark.
Weighthe flaskand its contentsto the nearest0.019 (WJ
Pour the entire mixfure of soil and water into a deep anaporatirgdish. Rinsethe volumekic
flaskcarefullyto ensurethe collectionof all the soil, ovendry and weighthe driedsoil (W.).
Fitl the votumetricflaskpartly full of the temperaturestabilised
water and placeundervacuuln
for aboutS-lQminutes(Optional). Add waterto the volumehicmark and weigh. Callthis weight
(WJ

Computation
Cgmpute.G,
usingthe equation
G r =
( a t t " Q W ' + W o ' - W J
ard G.at standard
temperature
as crG,trt fc
Wherea is the temperature
correctioncoefficient
and is compgtedas
f at toC
A =
y at 27"C
'and
is the ratio of the unit weights of water at the temperature t"C of test and at 27"C. The
temperafurecorrection is however,more academicthan piactical, and I is the unit weight of water
in g,/cm3.
Two sources of important errors are non-uniform temperature and incomplete removal of
entrappedair in the soil. In the caseof fine grainedqoil,the smallsoil particlesare likelyto contain
a small film of adsorbedwater and therefore the specific gravity obtained is dependent on the
method of drying employed. The approximate ranges of specific gravity of water at different
temperafuresare given below
Temperature
oQ
*Specificgravity of
wateq G*
Temperature
oQ
*Specific gravity of
Water, G*
0-4
10-14
20-24
30-34
40-44
0.9999-7.0000
0.9997-0.9993
0.9982-0.9973
0.9957
-0.9944
0.9922-0.9907
5-9
15-19
25-29
35-39
45-50
1.0000-0.9998
0.9991-0.9984
0.997
7-0.9960
0.994L-0.9926
0.9902-0.9885
*Also unit weight of water in g/cm3
W
3
2

Soil Engineering Laboratory
Department of Civil Engineering
Anna UniversitY,Chennai
SPECIFIC GRAVITY
Descriptionof Soil SamPle
Data Sheet :
Date :
Tested bY i
OF SOIL SOLIDS
Test No.
Volumeof flask at 20'C
Method of air removal
Wt. of bottle (wo)S
Wt. of bottle+soils
(Wo.)s
Wt. of bottle+soil+water
(WoJg
volume of water
(W*= W,+W'*-W'JS
gravity of soil at toc
G.at toC= Wr/Ut
Specific gravity of soil at standard
temperature 27"C, G.
Mean value of G. =
Remarks
4

Experiment No.
PARTICLE SIZE DETERMINATION (Mechanical
Method: Dry Sieving)
Relerence;
lS : 2720 (PartIV) - 1974 GrainSizeAnalysis
Objective
of grainsizelargerthan 75 microns(lmicron :10-3mm)of a soil
grain soil
To Obtainthe distribLrtion
and to classifythe givencoarse
Equipment
Set of IS sieves,
SieveShaker
Balance,0.1g
Brush
Introduction
Soils,beingproductsof mcchanical
and chemical
weathering,
are foundin a wide rangeof
particlesizesand shapes. Coarseqrainedsoilsare adaptable
to differential
selection
by meansof
a simple sievean.ilysis,where the squareholesbetweenthe wires of the sievemesh provide a
limiting sizeof the particlesretainedon a lrarticularsieve. Howevernot all particlesare spherical,
squareor even of any regularshapewhich wouldconveniently
determinervhctheror not they slip
through a sieve. What valuecan we place upon a test that may fail to distinguish,as far as we
are concerned,betweena particle 5mm in diameter,and another particles5 mm square? The
answerobviouslydependson the use that we are going to make of the resultsof such a test, if
in the field, the behaviourof the materialwhich we are testingdependsupon the shape of the
particlesthen the test is not a validone and shouldnot be carriedout. To what extentis this true?
If it maybe postulated
(andthis is approximately
true)that the mechanical
behaviourof cohesionless
soil doesnot dependpredominantlyon the shapeof the grain, we may acceptthe resultsof such
a test as being quite adequate, especiallysince most cohesionlesssoils consist of roughly
equidimensional
blocky particles.
Thus the grain size distribution of soils smallerthan the 75 micron (sieveopening
=0.075mm)is of littleimpoftancein the soiutionof engineering
problems(shapeand surfaceelfects
assume
prominence).On the otherhand,the informationon grainsizedistribution
of largersizes
has severalimportant usesand well definedstatisticalrelationsbetweengrain and significantsoil
propertieshavebeenestablished
eventhough admittedlywithin smallregions. In suchregionsthe
grain sizecan be usedas a basisfor judgingthe significantpropertiesof soils. This is commonly
andsuccessfully
done. For example.part of the suitability
criteriafor road,airfieldand embankment
constructions
is usuallythe grain-size
analysis,
informationobtainedfrom grain-size
analysiscan be
usedto predict soil water movement.The susceptibility
to frost action, an extremelyimportant
consideration
in cold climate.can be predictedfrom this analysis. The proper gradationof filter
materialsis usuallyestablished
from gradationtests. The grain sizeanalysisis alsouniversally
used
in the engineeringclassification
of soils.

Recommended procedure (for soils with grain size > 75 micron)
Weighto 0.1g, eachsievewhichis to be used,makesureeachsieveis cleanbeforeweighingit.
=Obtain 200-300E o'f 'oven dry soil as a representativesarnple from the bag of material
Gi*u*r with instructor quartering and other methods to obtain representativesamples)or as
providedto you. Weigh the sampleto 0.1g passthe samplethrough 4.75mm IS sieveto find
percent gravel, if any
Sieve the remaining soil through a set of sievesby hand shaking. The sievingshould be
accompaniedby lateraland verticalmovementstogetherwith slightjolting. Use mechanicalshakers,
if available,sievingshould continue for at least l0minutes and take care to ensurethat sievingis
complete.
Weigh to 0.1g each sieveand the pan with the soil retainedon them. Find by subtraction
the weight of soil retainedon each sieve. Computethe percent retainedon each sieveby dividing
the weight retained on each sieveby the original sample weight.
Compute the percent passing(or percent finer) by startingwith 100 percent and subtracting
the percent retained on each sieve as a cumulativeprocedure.
Calculations
i) Percentage retained on any sieve
=Wt. of soil retaineA/total soil wt. x 100o/o
iil Cumulative percentage retained on any sieve
=sum of percentagesretained on all coarser sieves
iii) Percentagefiner than any sieve size
=(100%o - cumulativepercentageretained on that sieve)
Data Representation
The grain sizedistribution of a soil is presentedas a curve on a semi-logarithmicplot, the
ordinate being the percentageby weight of particlessmallerthan the size given by the abscissa.
Particle size is representedon a logarithmic scale so that two soils having the same degreeof
uniformity are representedby curvesof the same shape regardlessof their positions on the plot.
The general slbpe and shape of the distribution curve can be describedby means of the
coefficient of uniformity (C,) and the coefficient of curvature (C.) defined as follows'
Cu = Dro/Dro
c. = D23fD6oDro)
The particle sizesuchthat 10o/o
of the particlesare smallerthan that sizeis denotedby Dro.
OthersizessuchasDro and D.o canbe definedin a similarw9y.-SizeD-ro
is definedasthe."efiectue
size." The higher the value ol tfre uniforrnity coefficient,the larger the range of particle sizesin
a soil. A well-gradedsoil has a coefficient of curvafurebelvteen 1 and 3 provided Cut 4 or 6 for
gravel or sand respectivelY.
Points to ponder
The sievingprocessdoes not provide information on the shapeof the soil grains regarding
whether they are angular or rounded.

If fnore thein 10 percent of
'the
sample passesthe 75 micron 'sia,re,a hydrometer analysts
'strtiun
abo be performed on the soil.
Sieve analysis employed as a sizing analysis can b.e reasonq$ accurate as long as its
limitations are recognised. ' '1' ' '''::'f..l
":"'-'
'
;
Sie,,res
should be well maintained and never over loaded since this may lead to clogging of
the mesh.
For silts, silty clays etc, which have a measurableportion of their grains both coarsesand
finer than 75 microns size, combined wet sieve and hydrometer analysig is required.
Indian Standard Classification (IS z t498 -1970)
Basic Soil Component Size Rangg in mm Syrnbol
Gravel
Sand
silt
Clay
4.75-80
0.075-4.75
0,002-.-0.075
<0.002
G
S
M
c
i.; . 1r,,r,r
:-!".
ii
'o,,:;F*
..'."rg*
i'r"""i:i
, . . . u .
7

Soil Enginering Laboratory
Department of Civil Engineering
AnnaUniversitY,
Chennai
SIEVE
Description of samPle
Weight of total soil sampletaken for analysis
Weight of particlespassingon 4.75 mm IS sieve
Weight of particlesretainedon 4.75mm IS sieve
Percentageof particle retainedon 4.75mm
IS Sieve (Gravel)
Weight of partial sample taken for analysis
Note:W.a Wu
DataSheet
Date
Testedby
ANALYSIS
w , g
Wu'g
wb, g
(WbAV)x 100
W.'g
passingas percentage
of total soil
N=N' (W./W)
Soil passingas
percentageof partial
soil sampletaken N'
percentageof
partial soil taken
N,:(wdAA/.)100
2.36mm
1.18mm
710 micron
425 micron
2I2 micron
125 micron
75 micron
Result :
Effectivesize,D,o (rnm)
Uniformity coefficient,Cu
Curvaturecoefficient,C.
Gravel = o/o
Coarse Sand= o/o
Comment:
Sand
Medium Sand
Silt and claY =
Fine Sand =
= o/o
= o/o
o/o
o/o
8

Experiment No.
PARTICLE SIZE DETERMINATION
(SedimentationMethod-l{ydrometer Analysis)
F'eference
lS:2720 (PartlV- 7975; N{ethods<tftest for Soils - Grain Size analysis
Objective
To determinethe grain sizedistriburion
of
sieveand its classification.
Equipment
BouyoucusHYdrometer
Hydrometerjar (bath:optional)
Thermometer
Balance0.019 sensitivitY
Stop watch
Stirrer
soilswith significantfraction passing75 micron
Introduction
The significance
of the grain-size
disrributionof fine-grained
soilshasdecreased
considerably
in recentyearsas there has beena more -r;eneral
recognitionthat propertiesother than grain size
(suchas ,-hup",arrangementof grains,geologicalhistory)could be more important in influencing
their behaviour.Nevertheless
there are occ;rsions
in which a knowledgeof grain-size
distributionof
fine grainedsoilsis eminentlydesirable.Typicalexamplesare,designof filtersfor drainagesystems
anddeterminationof the susceptibility
of a soilto detrimentalfrostaction. Further,the riseof water
in a capillaryopening is proportionalto the reciprocalof the diameterof the opening. If pore
sizecan be relatedto particlesize a relationshipbetweencapillaryrise and particle sizecan be
obtained.It is with this obiectivethat the followingdescriptionof the methodof hydrometeranalysis
is presented.
Theory
The hydrometermethod.basedon continuoussedimentation
principle,is widelyusedin all
soil mechaniislaboratories. Sedimentation
is the processwherebya steadyfall of particlesoccurs
through a liquid at rest. Particlesizesare determinedfrom Stoke'slaw which relatesvelocityof
a part"icle
faliingthrough a liquidto the diameterof the particle.the specificgravityof the particle
and the viscosityof the liquid.
From Stoke'sLaw
D
tr
(HRlt)
sec/cmz
9
Where
Viscosityof fluid in dt'ne

HR = height of fall in cm
t = time of fall in minutes
D = diameter of particle in mm
This equationis valid for particlesizesranging from 0.0002mm to 0.2mm.
To obtain the effectivedepth, H* for a particular hydrometer a calibration procedureis to
be gone through and a calibrationchart is to be prepared. Note further, that the density and the
viscosityvary with temperafure and a temperafure record during test is necessary.
Stoke's law assumg.9.,$at
soil particlescould be treated as spheresand that soil suspension
is of sufficiently low cortdrtr:ation to permit individual settling of grains without interference by
others. A dispersingagent is usedto Lnsrrrethis and u .orr"ition *itt have to be applied to the
hydrometer readings
.on,.?ccountof this. Further, soil suspensionsare opaque and-while taking
readingswith'the trydrqln{el o!€ may be able'to read only the top of the meniscusfor which i
meniscuscorrectionalso'i3neC*Sary. Details of the corrections will be furnished during
the class.
At the start of a wet tnechanicalanalysisby the hydrometer method the soil suspensionis
shaken thoroughly and it is assumed that the soil grains (spheres)are uniformly distributed
throughout the suspension. Considerfirst, only those grains, of a particulardiameter,say D, and
let their settlingvelocity
9g
V, After time, 't'
thesegrainswill move through a height H=Vr*i und
thereforeabovea depth H in suspensionthere can be no grains of diametel Dn. Since grainswith
diameter greater than D, settle faster than thesegrains, there can also be no'grains co]arser
than
Pt uFu" the depth H after time t. Similar reasoningcan be applied to grains of other diameters
D, D, etc.
At depth H after time t, there-areno grainstargerin diameterthan Dr. However,grains
smaller in diameter than D, settle with velocitieslessthan V, and therefore mirst still be present
at depth, H. Thusat depjh H after time t all grainshaving'diametersequalto or lessthan D'
must be presentin the gq&,Concentration as they were at the start of the test. Hence in a small
volume V at a depth H after time t, the weight of solid particlesis equalto the weight of particles
finerthan D,, in this samevolumeat the starfof the test,when the solidswereunifori-,tyair*ibuted.
Sincethe proportion of grains_
< D, can be obtainedby measuringthe weight of solidsper
unit volume of suspensionat depth H:anil time t, it follows that the same resultscould also be
obtainedby measuringthe'specificgravityof the suspensionat depth H and time t, for if the specific
qravity of a suspensionis known together with the specificgravitiesof the liquid and solid piiu.".,
the weight of solids contained in a unit vr>lumeof the suspensioncan be readity computed.
In making a wet mtchanicirl analysisby.the'hpdrometermethod, the hydrometeritselfis thus
usedfor two purposes.
1. To measurethe spucificgravity of the soil suspension
2. To measurethe depth of that layerof the suspension
to which the recordedspecific
gravity corresponds
It can be shown that the percentage.ofgrainsN by weight havinga diameterlessthan D,.
viz.. Wo is given by I
1()

100Gs
ws(Gs-1)
Where W. = Weightof dry soil takenfor hydrometer
analysis,
g
G, = DensitYof soil solid
R. = Hydrometerreadingcorrectedfor meniscus,
dispersing
agentand
temperafure
V = Volumeof suspension
in cm3
By observinghydrometerreadingat differenttimesduringa test, any desirednumberof
pointson the grain sizedistributioncurvecan be obtained.
Beforecommencing
test,practiceby placingthe hydrometer
in the suspension
andreading
it. Hold hSrometer stemin both handsand lowergentlyto the depth at which it floats.
Mix a moistspecimenof soil passingT5micronsieveand representing
approximately
40-
50S dry weightwith distilledwaterto firm a smoothpaste.
Add a deflocculating
agent(sodium
hexametaphosphate,
2 to 3 cc, 10 percentstrengthto
the pastewashthe mixfureinto the mixingcup.
Mix the suspension
with the help of the stirrerfor aboutl0minutes. Whilemixingis on,
fill a graduated
jar with distilledwater. Usethisjar to storethe hydrometerin betweenthe readings.
After the mixing,washthe specimen
into a graduated
cylinder,add enoughdistilledwater
to makeup the volumeto 1,000cc
Mix the soil and water in the jar, by placinga rubberbung or palm of the hand over the
open end and stirring the graduatedcylinderupsidedown and back. Make suresoil is not sfuck
to the baseof the graduatedcylinder.
After shaking for approximately30sec, replacethe jar on the table, gently insert the
hydrometerimmediatelyand start the timer.
Takehydrometerreadings
R at total elapsed
timesoI 0.25,0.5,1 utd 2 minuteswithout
removinghydrometer. If readingscould not be taken accuratelyat the first time, removethe
hydrometeq
remix and repeat.
After the 2 minutesreadingremovehydrometer,remix and restart the test but take no
readinguntil 2 minuteone. For this and subsequent
readings,removehydrometerand transferit
to the jar or distilledwater after eachreading.
Take temperatureobservationsand hSrometer readingsin the jar of distilled water at
desirableintenrals. Obtain also the height of meniscus.
rise of pure
-distillesd
water on the
hydrometerstem, record this meniscuscorrection. Continue taking readingsuntil hydrometer
recordsapproximatelyone or until readinghave been taken for near! 24-hours. After final
readings,pour suspension
into largedishestaking carenot to looseany soil, ovendry and record
dry weight
(2
Rc
l l

Appendix
Corrections to be applied to the hydrometer test.
1. The meniscus correction, C., Owing to the opaquenature of the soil suspensionand to
the meniscuswhich forms at the hydrometer stem, the reading of the hydrometer at the surface
of the suspensioncannot be observedand it is necessaryto take the readingsat the upper edge
of the meniscus. Sincethe readingsdecreasetowardsthe top of the hydrometerstem,the observed
reading is lower than the true reading. Hence it is necessaryto add the correction C- to each
observedreading. The value of C* rnay be determined by placing the hydrometer in a graduate
full of cleanwater and observingthe dillerencein the hydrometerreadingsat surfacelevel and at
the upper rim or the meniscus.
2. The dispersing agent correction, Cdr In order to ensureas far as possiblethat the soil
is broken down into individualgrainsand that grainsdo not adheretogether,a smallquantityof
a suitable dispersingagent is addedto the soil suspension.The additionof the dispersingagent
increases
the specificgravityof the soilsuspension
by an amountC,. This correctionmusttherefore
be subtractedfrom each readingsin order to obtain the actualsiecific gravity of the suspension
in pure water. The valueof Comay be determinedby noting the hydrometerreadings,first in the
graduateof distilledwater and then after the same amount of dispersingagent as used in the
mechanicalanalysishas been addedto the water. The differencein the two readingsgivesthe
necessary
correctionfor the dispersingagent. It shouldbe noted that while this correctionmust
be appliedto the hydrometerreadingin order to obtainthe specificgravityof the soil suspension
in water, it is not applied in using the hydrometerreadingto determine the depth H* in the
suspension
to which the hydrometerreadingcorresponds.
3. The temperature correction, C,: The hydrometeris usuallycalibratedto measurethe specific
gravityof a fluid at a particularcalibrationtemperature,
normally 20oc. For example,the marking
20"c/20"c indicatedthat the hydrometer is calibratedso that when it is freely floating in a fluid
at a temperature of 20oc the readingson the stem at the level of the fluid surface multiplied by
the specificgravity of water at 20oc givesthe specificgravity of the fluid. For other temperafures,
a correctionis requiredand this may be computedfrom
Cr = [(Gwc-Gwr)
x a,,T.l 103
whereG*. =
G =
WI
a =
Specific gravity of water at calibration temperafure.
Specific gravity at temperafure of test.
Volume coefficient of expansion of glass.
Alternatively,this correctionmay be taken from a chart (which will be supplied)
Discussions
There are number of assumptionsin Stoke'sequation which are not completely fulfilled in
the hydrometermethod. They are
1. No interference of the particlesby other particles or by the walls of the container
2. Sphericalshapeof particles
t2

3. Specificgravity of all particlesare same.
The first of the above assumptionscan be practically satisfiedby limiting the maximum
concentrationof soil in suspension
around50g in 1000m1of suspension.
The shapeof the most
of the particleslargerthan 0.005mm can be considered
as that of a sphere. Particlessmallerthan
0.005mm are plate shapedand they fall in water like the downward drift of a leaf from the tree.
These platesare surroundedby a water film of unknown thicknessthe specificgravity of suchsoil
particlesis likely to be around 1.8 to 1.9 rather than a normal anticipatedvaluearound 2.7 to
2.8. The phenomena mentioned above combined their effectswhile the first two tend to make
the diameter computed by the hydrometer proceduretoo small, the third too large. Net effect is
that the hydrometer proceduretends to result in particle diameterswhich are lessthan the length
and the width of the plate sizedparticles, Montmorillonite and some illite mineral particlesin clay
soilsmay breakdown into smalleroneswhen stirredinto suspension
in water in addtitionto changes.
in the thickness of absorbedwater film. This phenomena, makes it difficult to obtain by the
hydrometer method the particle sizesof some soils that exist in nafure. Calcariousand lateritic
soils may also present problems in the determination of particle size distribution by hydrometer
method, which however can be overcomeby appropriate pretreatment.
1 3

Departrnent of CMI Engineering
Anna universip, chennai
Data Sheet :
Date :
TestedBy :
HYDROMETERANALYSIS
Description of Sample =
Weight of dry soil taken for analysis,W. =
Specific gravity of soil solid, G, =
Dspersing agent correction, Co =
Meniscuscorrection, Cn, =
Hydrometer No =
Silt i
Clay :
Elapsd
timet,
min
Temperature
Obse,nred
J,.l-^-r^"
nW.Keadna
C6necd
foi
meniscus
only
R.=
R+C*
Temp. Combind
conection
C=Cr+C.+C,
Conatd
Hyd.
Reding
R,=R+c
Effectv(
depth
HR
Particle
Danre{er
D,mm
Percent
finer
Remarls
T0c
a)uvlrErga
reading,
R q
r/^
,/,
1
2
4
8
15
30
60
L20
240
480
t440
Result :
t4

Experiment No.
LIQUID AND PLASTIC LIMITS Of: A SOIL
Reference
lS: 2720 (PartV)- I97A, Determinationof liquidandplasticlimits
Objective
To classifythe givenfine-grainedsoil basedon its plasticitycharacteristics
fuuipment
Liquid limit devicewith groovingtool
Moisturecups,Oven
Plasticlimit plate
Soil mixing equipment(porcelaindish,spafula,plastic queeze bottle etc.)
Balance,sensitivity
0.019.
Introduction
A fine grainedsoilcanexistin anyof s.everal
states;which statedependson the amountof water
in the soilsystem.Usingwatercontentasa measureof wetness,Atterberg(1911) proposedfour states
of soil and the €orrespondingthree boundariesbetweenthesestates.
Relative locations of Atterberg limits
Soil in the liquid statebehaveslike a liquid, i.e., it exhibitsnegligibleshearstrength. As the
watercontentis reducedto its liquidlimit soilbeginsto exhibitsomeshearstrength. Soil in the plastic
statehasa watercontentwhichenables
the soilto behavelikea plasticmaterialthatis,the soilcanbe
mouldedor shapedwithout being ruptured. At plasticlimit the soiljust beginsto rupture or crumble.
The water content of the soil is saidto havereachedthe shrinkagelimit when particleshave
come as.nearto eachother asis physicallyfeasibleundera set of arbitrarilyspecifiedambientcondi-
tions.
In order to obtain definite reproduciblevaluesof theselimits, the liquid limit is definedas that
watercontentat which a pat of soil placedin a brasscup, cutwith a standardgrooveandthendropped
from a height of 1cm will undergoa groove closureof about 1cm (7/2 inchl when droppped 25
times.The liquidlimit isa measureof strengthanalogous
to a sheartestandit hasbeenfoundthat each
blowto closethe standardgroovecorrespoftlsto about I g/cm2 of shearstrength.The liquidlimit thus
representsfor all soilsa constantshearstrengthvalueof 20-25 g/cmz
The plasticlimit representsthe lower boundaryrangeof plasticbehaviourof a soil, that is the
moisturecontent at which soil beginsto cnrmblewhen rolled into threadsof 3mm size.This test is
somewhatmore subjectivethan the liquid lirnit test sincejust what constitutescrumblingand what is
3mm diameterare subjectto someinterpretation.
WL
WP
WS
Brittle
(Solidstate)
Non Plastic
(semisolidstate)
Plasticrange
Soil behavesasa
viscousfluid
l 5

The Atterberg limit testsare usuallycarriedout on soilsamplespassing425 micronsieve. The
limits have beenwidely usedall over th.eworld primarily for soil identificationand classification,
It is
now recognisedthat they rnaypossess
even greatersignificance.
a) Liquid Limit Test ( Arthur Casagrande)
Checkthe heightof fallof theliquidlimit device,usingthe 1 cm calibration
blockon the endof
the groovingtool for makingthe adjustment.
Takeabout I20g of the givensoiland mix thoroughly with distilledwaterto form a uniform
paste.The amountof waterto be addedshallbe such,so asto require30 to 35 drops.ofthe cup to
causethe requiredclosureof the groove.
Placea smallamount of soil to the correctdepth of the groovingtool, well centredin the cup
with respectto the hinge. Smooththe surfaceof the soilpat carefully,andusingthe groovingtool, cut
a cleanstraightgroovethat completelyseparates
the soil pat into two parts.
Thedepthof thesoilin thedeepest
partof thepatshouldbejustevenwith thetop of theASTM
tool.
Turn the crank at a rate of abouttwd revolutionsper secondand count the blowsnecessary
to
closethe groovein the soilfor a distanceof about12mm.
Takea moisturesamplein the pre-weighedmoisturecups,beingsureto take the watercontent
samplefrom the closedpart of the groove. Weighthe sample. Removethe reminder of soil from
brasscup and returnit to the porcelindish. Washanddry the cup.
Add a smalldmountof waterto the soilin the dishandcarefullymix to a consistency
to yielda
blowcountof between25 and 30 + blows.
Repeatthesequencelor
two additionaltests
for blowcountsof between20 and25 andbetween
15 and 20, for a total of four testdeterminations.
Be sureto cleanthebrasscupaftereachtest. After weighingthe moisturecontainers
from the :
testtransferto oven(105 to 110o C)anddry overnight.
b) Plastic Limit Test
Breakabout 20g of soil into four peanut-sized
samples,usinglittle water.
Rollthe peanutof soil on a glassplateuntill it just crumblesat 3mm (usea glassor weldingrod
for comparisonif you areunsureof what 3mm is). Placethe crumbledsoilin the pre-weighedmoisfure
cup,coverwith the lid.
Repeatthissequence
threemoretim,zs.
Weighthe coveredmoisturecup,renlovethe lid and placethe moisfurecup in the oven.
Computations
Returnto the laboratory the followingdayandweighallthe dry moisfuresamplescomputethe
water contents.
Plot the liquid limit data on the semi-loggraph sheet (watercontent versusblow count)and l
obtainthe liquidlimit. Computethe flow inrlex,if asthe slopeof the flow curveor from i
16

(w1-w2)
=
loglnN2Ar)
, Where
Wl = moisfure
contentcorresponding
to N' dropsand
':
W2 moisture
contentcorresponding
to N, drops
Alsocomputetheplasticlimitandtheplasticity
indexIp as
Plasticity
index ( Io)=Liquidlimit(wul- Plastic
limit(Wo) (21
Nowtheshearing
strength
of a soilat itsplastic
limitisa measure
of tlretoughness
of theclay;
the shearing
strengthoi all soilsat the liquidlimit is constant(verynear$. This leadsto another
Atterbergindex,cdlledthetoughness
index.I,givenbg
Toughness
inden<
{J = {IrZlJ
(1)
(3)
l7

Soil EngineeringLaboratory
Department
of CivilEngineering
-<r. Annauniversity
Chennai
- 25
Description
of sample
LiquidLimit
ATTERBERG
LIMITS
Data Sheet i
Date :
Testedby :
TrialNo 1 2 3 4
No of blows
TareNo
Wt. of tare,g
Wt. of wetsample+tare,g
Wt. of drysoil+tare,g
'Wt. of water,g
Wt. of drysoil,g
Watercontent,percent
PlasticLimit
TrialNo 1 2 3 4
TareNo
Wt. of tare,g
Wt. of wetsample+tare,
wt g
Wt. of drysample+ tare,g
Wt. of water,g
Wt. of drysoil,g
Watercontent,percent
Result
Remarks
It

ExperimentNo.
SHRINKAGELIMIT OF A SOIL
Reference
lS:2720 Methods
of testfor soilspartVII - (1972. Determination
of shrinkage
factors
Objective
Toobtainthemoisture
contentbelowwhichno furthervolumechangeof soilmassoccurs
F4uipment
Petridish
Glass
platewithprongs,flatglass
plate
Largeevaporating
dish
Mercurysupply,
Balance,
0.019sensitivitY
Desiccator,
Oven
Distilled
water
Introduction
The liquidandplasticlimitsmaybe usedto predictpotentialtroublein soilsdueto volurne
changes.Howeverto obtainan indicationof how muchchangein moisturecanoccurbeforeany
appreciable
volumechange
occurs,
a shrinkage{imit
testshould
beperformed.
Thistestbegins
withagivenvolume
offullysaturated
soil,atwatercontentabouttheliquidlimit,
thesoilisdried. Itls assumed
duringdrytngthatdownto acertainlirritingvalueofwatercontent,any
lossof waterisaccompanied
bya corresponding
change
jn bulkvolume.Belowthislimitingvalueof
watercontent,no furtherchange
involumeoccurs
withlossof porewater.Thislimitingwatercontent
istermedthe shrinkage
limit. Physically
thismeans
that anymoisture
changes
belowthe shrinkage
limitdo not cause
soilvolumechanges.
Recommended
Procedure
Takeabout40g of theminus42lmicron sievematerialusedfor liquidandplasticlimitsandmix
withdistilled
waterto makea creamypaste.Useawatercontentslightly
aboveliquidlimitsothatthe
pastecanbeplacedin theshrinkage
dishwithoutairvoids.
Coattheinsideof theshrini<age
dishwithaverythinlayerof grease,
weighthedishandrecord
theweight.
Fitlthe dishwith wet soilin approximately
threelayers,tappingthe dishgentlyeachtimeto
exclude
airbubbles.Fillthelastlayerto slightlyoverflowthedish,tap andstrikethedishoff smooth
witha strainght
edge.Weighthedishwiththewetsoil'
Allowthewet soilpat to slightlyairdry untilthe surface
of the pat changes
to a lightcolour.
Ovendrythe patat 1050-110oc
to constant
weight(12to 18 hrs.),coolin desiccator
andweighthe
dishwithpatimmediately
thereafter.
Findthevolumeof theshrinkage
dishbyfirstfillingit withmercurysothatit slighflyoverflows
in
therlargeevaporating
dish. Press
aflatglass
platedownonthemercury
surface
to remove
theexcess.
Weigh th" dirh *ith -"rcury and computethe volume of dish as weight of mercury/
19
4

13.58,13.58glcm3 beingthe unit weighto[ mercury. This is alsothe initialvolumeof the soil pat.
Determinethevolumeof thedry soilpatbythe samemercurydisplacement
rnethod. Fillthe glasscup
with mercury.Removeexcess
mercuryby pressing
firmlytheglassplatewith threeprongsoverthetop
6 thecup,iollect andremovetheexcess.Placethe ovendry pat on the surfaceof mercuryin thecup
andgentlyforcethe patinto themercurywith thethreeprongedglassplate. Volumeof mercuryequal
to thevolumeof soilpatwillsurplusintotheervaporating
dishwhichiscollected
andweighed.Calculate
volumeof soilby dividingthis mercuryweiglrtby 13.58.
Calculations
Calculate
the shrinkagelimit (remoulcled
soil)usingthe followingformula
(v-vo)T*
w s = w -
Where ws =
w =
v =
V o =
,
I w
W o =
x 100
wo
Shrinkagelimit in percent
Moisturecontentof thewet soilpat in percent
Volumeof wet soil pat in cm3
Volumeof dry soil pat in cm3
Unit weight of water g/cms
Weight of ovendry soil pat in g
(1)
Calculate
the shrinkageindex(lJ usingthe followingformula
J = w.-w^
s L 5
wherew, = Liquidlimit of the soil
Calculate
Shrinkageratio (SR)from
SR =W.Aoy,
Where
W. = Weightof ovendry pat in g ancl
%= Volumeof ovendry Patin cm:t
The shrinkage
ratiogivesan indicationof how muchvolumechangemayoccurwith changes
in
watercontent.Fromthedefinitionaboveit rnaybe seenthat the shrinkage
ratioactuallythe apparent
specificgravityof the dry soilpat.
Data presentation and discussion
Presentdatain standardformatand,:alculate
the shrinkageindex.shrinkageratio etc.
ldentifytheswellPotential
of thesoil (ina qualitative
sense)
based
on criterialsetin tabledbelow.
TableI
(AfterHoltz and Gibbs,1956)
ColloidalContent,7o Plasticitylndex, )/o Shrinkage
limit.()ir SwellClassification
0-15 0-15 >12 low
ro-25 10-35 8-18 medium
20-35 20-45 6-12 high
>35 >30 <10 veryhigh
20

Table II
(After Ranganathanand Sathyanarayana,1965)
Shrinkage Index, 96 Swell classification
0-20
20-30
30-60
>60
low
medium
high
very high
2 l

Departmentof civil Enginerring
Anna University,Chennai
Descriptionof samPle :
Result
Remarks
SHIIINKAGELIMIT
DataSheet
Date
Testedby
TrialNo 1 2 3
ContainerNo
Wt. of tare container,g
Wt. of wet samPle+tare,g
Wt.of drysample+tare,g
Wt. of water,g
Wt. of dn7soilpat,Wo,g
Watercontent,o/o
Vol.of Container,
V cm'
Vol.of drysoilpat,Vo,cm3
Shrinkagelimit , w,
Shrinkage
ratio (Wo//oY*)
22

Experiment
No
FIELDDENSITYTEST
Reference
lS z 2720(partXXVIil)- 1970, methodsof testfor soils:Determination
of dry densityof
soils,in placeby the sandreplacement
rnethod'
lS: 2720(PartI0 - 1970,Determination
of moisturecontent
Obiective
To determine,in place,the dry densityof compactfine and rnediumgrainedsoilsby sand
replacement
method.
Equipment
Sandpouring cYlinder
Cylindricalcalibratingcontainer
Toolsfor a<ca'uating
holes
MetalhaYwith hold, glassPlate
Balance
Introduction
Ifuowledgeof the rn placedensrtyof soilsis necessary
for calcuracing
borrow or cut-and-fill
quantitiesin adiition to its usefor compaction^control.For example,if the naturalfielddensityis
]OOOkglmt a'd the compacted
densityis 1920 kil^'approximately 20 percentreductionin
volumewiil occut when the soil is compacted'
Fielddensitytestsmay either be direct,by excavating
a hole and measuringthe volumeof
hole and the weig-htof the materialor they may be indirect,by geophysical
method'
In the fielddensitytesta holeabout10cmin diameterandasdeepasthe thickness
of the
compacted
ruv"t L Jugin the soil.All the materialremovedis carefullyrecovered
andis immediately
weighed.Itsmoisture-content
is alsofoundby usinga representative
sample.Thenthe volumeof
the hole,whichis the volumeof the soilsamplebeTore
iis removal,is measured
by fillingthe hole
with some,uurtu"." *hose specificgravityis known,The weight of this substance
requiredto fill
the hole is converted
into volume. in. *nigtt of the soil removedfrom the holedividedby the
volumeof the hole is the wet densityof the soil
Therearethreesubstances
in usefor measuring
thevolumeof the hole: motoroil, cleandry
cohesionless
sandandwater. If wateris rced it muit be confinedin a thin rubbermembrane
or
balloonwhichis expanded
by wateror air pressure
into the hole. The volumeof the holeis read
directlyfrom the loweringof the waterlevelin a calibrated
reservoir
termed
'volumer'' Motor oil
doesnot requireanymembrane.*ornu"r, if the soilis unusually
dry, it is saferto useeitherthe
sandmethodor the watermethod.
The sandmethod,described
herein,involves
standard
sandanda standardised
procedure
for
pouring.The latter is done by utilizinga standard"sandcone". The amount of sand usedis
determined
uv ,r"ignirg. A *"isni is sirbtracted
for sandin the cone,andthe resultis converted
into volume. Note that construction
traffic mustbe haltedduringthe test sincevibrationsaffect
packingof sand(a point to be ,e-e-bered whileconstructing
earthdams,embankment
etc')'
29

Recommended procedure
A. Calibration of Apparatus
Take about 5kg of standard(Ennore)sandif availableor usecleansandpassing600 microns
sieveand retained on 300 microns sieve.
Obtain the internal volume M in ml of the calibratingcontainer by filling it with water upto
the brim or by measurement.
The sandpouring cylindershallbe filled so that the levelof the sandin the cylinderis within
about 10mm of the top. Its initial weight shallbe found and recordedas W, (g). Placethe sand
pouring cylinder on a plane surfacesuchas a glassplate. Open the shutter'and allow the sandto
run out and fill the bottom lying cone. When no further movement of sand takes place in the
cylinderclosethe shutterand removethe cylindercarefullyand the weight of sandpouring cylinder
with remaining sand. Repeatthese measurementat leastthree times and record the mean weight
W,(s).
Next placethe sandpouring cylinder filled with sandto weigh W' concentricallyon the top
of the calibrating cylinder, open the shutter and allow the sand to i-un out. When no further
movementof sandtakesplace,closethe shutter. The pouring cylinder is removedand weighedto
the nearestgram. Repeat these measurementsat least three times and record the mean weight
as Wr(s).
B. Measurement of soil Density
A flat area,approximately45cm square..of
the soil to be testedshallbe exposedand trimmed
to a level surfacewith a scraper.
A round hole approximately 10 cm in diameter and 15 cm deep (maximum) shall be
excavated. No loose material shallbe left in the hole. The metal tray with a central hole shallbe
laid on the prgparedsurfacewith the hole r>verthe portion of the soil to be tested; the hole in the
soil shall then be excavatedusing the hole in the tray as a pattern. The excavatedsoil shall be
carefullycollectedand weighedto the nearestgram. Recordthis as W. (g)
A representativesample of the excavatedsoil shall be weighed and ovendried to find the
percentageof moisture content, w, of the in-situ soil.
The sandpouring cylinderfilledto constantweight W' is placedconcentricallyover the hole.
The shutteris opened an{ sandallow€dto run out. The sani pouring cylinder and the surrounding
areashallnot be subjectei'to any vibrationduring this period.
-
When-no furthe, movementof sand
takes place, closethe shutter,remove the cylinder and weigh it to the nearestgram. Recordthis
weight as Wn.
Computations
1. Compute weight of sand (W")requiredto fill the calibratingcontainer from
wu = (w1_w3)
_1wr_wr),
(s)
2. The calibratedbulk density of sand is y, calculatedfrom
T. = W^fr1k,/cm31
(1)
2)

3. The weightof sand,Worequiredto fill the excavated
hole is calculated
from
Wb = (Wr-Wo)
-(W,-Wr),9
4. The bulkdensity,y'of the wet soilis calculated
T6 = (W*AlJo)Y,,
9/cm3
5. The dry densityY6of the soilis calculated
from
(vJ
T 6 = , 9/cm3
(1+w/100)
Reporting of results
The resultsof the testshallbe recordedsuitably. The methodusedfor obtainingthe test
results
shallbe stated..Thedry densityof thesoilshallbe reportedin unitsof kg,/m3
to the nearest
wholenumberor in g/cm3correctto the second
placeof decimal.The moisturecontentof the soil
shallbe repeated
in percent,correctto the first decimalplace.
Discussions
Duringthetestanyjarringor vibrationhasto beprevented
sinceit maysettlethesandin the
testholeduringmeasurement
or in the container
duringcalibration.Largediametertestholesand
largecalibrating
containers
haveto be usedin materials
with largeaggregates.This methodmay
nol be suitable
in opengradedaggregates
in whichsandmayflow into voids. If the soilat the site
is fine grainedthen corecuttermethodis bestsuited.
(3)
(4)
25

Deparhrentof civil Engineering
Anna University,Chennai
Data Sheet
Date
Testedby
FIELDDENSITYTEST
(a)
1.
2.'
Calibration of apparatus
Weight of sandpouring cylinder+ sand W' g
Mean weight of sandpouring cylinderwith remaining
sandafter filhngthe cone W2,g
3. Volumeof calibratingcan V cmt
4. Mean weight of sandpouring cylinerwith remaining
sandafter filling the cone and calibratingcan
5. Weight of sandfilling calibratingcan
6. Calibratedbulk densityof sand
(b) Measurementof insitu soil densily
7. Weight of excavatedsoil
8. Weight of sandpouring cylinderand sandafter filling
the hole and cone
9" Weight of sandin hole
10. Bulk densityof insitu soil
11. Watercontentof insitusoil
12. Dry densityof insitusoil
Results
W",9
W . q
f ,, 9/cm:l
W.rg
Wo,9
wt,'9
!r, 9/cm:'
w, o/rt
T6, 9/cm'a
1. Bulkdensityof insitusoil
2. Dry densityof insitusoil
3. Watercontentof insitusoil
T6,9/cm3
Ta,9/cm3
w , 0 / o
25

ExperimentNo.
MOISTURE- DENSITY RELATIONSHIPUSING PROCTOR COMPACTION
Reference
lS: 2720(partVII)- 1980 : Determination
of moisture
content-dry
densityrelationusinglight
compaction
lS: 2720(PartII)- 1979,Methodsof testfor soils; part 2. Determination
of watercontent
Obiective
To determine
therelationbetween
nroisture
contentandthedrydensityof soilsusingproctor
compaction
Equipment
Compaction
mouldwith baseplateandcollar
Compactionhammer
Sampleejector
Largemixingpan, scales,
moisturecans
Measuring
jar
Introduction
Manytypesof earthconstruction,
suchasdams,embankments,
highways
andqirportsrequire
soilfill whichis placedin layersandcompacted.A wellcompacted
soilis mechanically
morestable
than a loose soil, it has a high compressive
strengthald high resistanceto deformation.
Compaction
maybedefinedusu-pto."ssof increasing
the soil.unit.weight
by forcingthe soilsolids
in to'tighter staieandreducingthe air voidsandis aicomplished
by staticor dynamicloads.
The purposeof a laboratory
compaction
teqtis.todetermine
the properamountof moulding
water.tobe'used
whencompacting
tne ioil in the fieldandresulting
degreeof denseness
whichcan
Un
"*pl.t.a.
To accompfirntnir a laboratory.
test which will give the degreeof compaction
compirableto that obtainedby the methodusedin the fieldis necessary.
The standardmethodfor light compaction
wasdeveloped
by Proctorin 1933 takinginto
considerationwith the field complactionequipmentthen available,which gave a relativelylow
;;;;tty. As fieldcompacting
equipment
becimeheavierandmoreefficient,it became
necessary
to
increase
the amountbf .o,ipu.ting energyin the laboratorytest. Hencea distinctionhasto be
madebetweenlight compaction(Standard
Proctor)andhearnT
compaction
(Modified
Proctor)test,
whichis shownin Tablebelow
Proctor Compaction Tests
Test Hammer Mass,Kg HammerDrop,m 3ompactive Energy kI / t,-
StandardProctor 2.5
(25blowsperlayer,3 laYers)
0.3 590
ModifiedProctor 4.5
(25 blowsper layer,5 laYersl
0.46 2740
Note : Mouldvolume,945 X 10-5m3
tfrai"" St*aard Sficification for light compactionis similarto standardproctorandthat for hearn/
compactionis similarto modifiedproctor.)
. 2T

The StandardProctor is adequatefor most applications(retainingwall back fill, highwayfill
and earth dams )while the modified proctor finds favour in heavier load applications(airport base
coursesfor instance).
The testprocedureoutlinedhereinis however,confinedto StandardProctorCompactiontest
only.
Theory
Proctor discovered an important relationship between soil density, water content and
compactiveeflort and found that by mouldinga seriesof specimenswith different moisturecontents,
usingthe samecompactiveeffortfor eachspecimen,the densi$ on a dry densitybasiswouldshow
a peak.
It was once believedthat water added upto the optimum moisture improved "lubrication"
betweenthe soilgrainsand hencecompaction(lubrication
theory). Instead,it wouldbe more correct
to say that moisture contents below optimum cause increasedcapillarity or negative pore water
pressurewhich pullsgrainstogetherand preventssliding.
The maximum density obtained is called standardproctor density (sincethe American
Associationof State Highway Officialshave adoptedthis test procedure,it is alsoknow as standard
AASHO density).The rnoisturecontent correspondingto this maximum density is called the
optimum moisture content. The amount of compactiveenergy usedin the test was established
by
Proctor as the amount which would give a maximum densityin the laboratoryapproximatelyequal
to that which is feasibleto obtain in field compactionoperation
Zero air void curve - the right hand limb of moisture- densitycurve roughly parallelsa line
designated
as "zero air voids"This line represents
the dry densityif the entirevolumeis water and
solids. Sincecompactionis a processfor expellingair,the moisturedensitycurvescannotcrossthis
line. Sincethe line represents
a theoreticallimit on densityat anywatercontent,its positionis often
shown on moisturedensity plots. The zero air-voidsdensity for any moisture content may be
calculatedfrom
Tz,,u
= GX/O+ (w G./100))
where Tr(uu)
= dry densityat saturation,Gr= the specificgravity of soil particles,T* = the unit weight
of water and w, the moisfurecontent in percent.
Recommended procedure
Take about 3kg (nominalweight) of air dry - material passingthrough 4.75 mm sieve.
Measurethe diameter and height of the mould without collar and find the volume of the
mould (V).
Cleanthe emptymouldandweighit to the nearestgram(W,).Greasethe insideof the mould
lightly. Fit the mould with the collar on to the base plate and place it on the solid base.
Add enoughwater to the soil to bring its moisturecontent to about 6 percent (or asspecified
by the instructor in charge). Mix thoroughly to ensureuniform distribution of moisture.
Placethe moist soil in the proctor mould in three layersof aboutequalthicknessand compact
eachlayer by 25 blowswith the hammer. Takecareto uniformly distributethe blowsand to scarify
the surfaceof each layer before the next layer is added.
2a

If the mould is not filled abovethe collar joint for the last compactedlayer, do not add the
soil to make up the deficiency. Redo the test. You can avoid this difficulg by carefullywatching
and, after about 10 blows on the last layer if the soil is below the collar joint add enough material
and then continue with the reminder of the blows. You shouldtry to have not more than about
0.5 cm of compactedsoil abovethe collarjoint.
Removethe collar and carefullystrikeboth the top and baseof the compactedcalinderof soil
with a steelstraightedge(afterremovingthe baseplate).Fill in any holesin the compactedspecimen
with soil if the smootheningprocessremovesany small pebbles.
If the collar is hard to remove,do not risk twisting off the lastlayer of soil, take a spafulaand
trim along the sidesof the collar until it comesoff easily. Weigh the mould and cylinder of soil to
the nearestgram (Wr)
Eject the cylinder of soil from the mould, split it and take two water content samples,one
near the top and the other near the bottom. Weigh these samplesand ovendry
Break up the sampleand mix it with the unusedportion. Add sufficientwater to raisethe
water content by about 2-3 percent,careftillyremix and repeat the experiment until the peak wet
density is followed by two slightly lessercompactedweights.
Return the followingday to determinethe water contents
Computbtions
Compute the dry density and make a plot of dry density versuswater content. Note the
maximum dry density and optimum water content for the type of soil tested and the compactive
energy used.
On the curveof dry densityversuswater content, plot the zero-air-voids
curve (Askinstructor
for G, value). Be sure to use a good scalefor the compaction plot.
Discussion
Laboratory compaction tests are not directly applicable to field compaction since the
compactive effort in the laboratory test are usually different from those produced by the field
compaction equipment. Further, the laboratory tests are usually carried out on material with
particlessizessmallerthan those likely to be encounteredin the field. Laboratorytestsprovide only
a rough guideto the water content at which the maximum dry densitywill be obtainedin the field.
The main value of the laboratorytestsis usedin the classificationand selectionof soils for use in
fills and embankments.
The dry densityachievedafter field compaction expressedas a percentageof the maximum
dry densityin a particular laboratorytest is defined as the relativecompaction. The requiredfield
standardrnay be specifiedin terms of relativecompaction. For example,a specificationmay state
that the dry densityshouldnot be lessthan 95 percentof the maximumdry densityobtainedin the
laboratory,In addition,watercontentlimitsmustbe specified,
compactionbeingallowedto proceed
only if the naturalwater content of the soil is within theselimits.
Because the physical properties of granular soils are improved by compaction to the
maximum dry unit weight, there is a tendencyto assurnethat this appliesto all soils. However,in
Erraticresultscan be avoidedby allowingthe moist soilto standovernight
29

the caseof finegrained soils the shear strength, compressibility, swelling-potential and permeability
are not pn."r*rily improved by compaction to a maximum unit weight (becauseof strucfure effects).
Fstablishingthe optimum compaction conditions for a given soil usuallyinvolves extensivetesting.
In generalcompactionis likely to increasethe shearstrength,swellpotential, and dry density
and decreasethe shrinkage, permeability, and compressibility. Compaction on the wet side of
optimum permits a low pnrrnulblu soil to undergolargedeformationwithout cracking. Compaction
oi .tuv roil on the dry side of optimum, may make it less susceptibleto shrinkage but more
,*.uptibl" to swelling,and brittlenessand crackingevenunder low deformations. This leadsto ttie
concllsion that compaction criteria should be based on considerationof soil strucfure and other
desired properties apart from increaseddensity. Availabledata also indicatesthat soil'structure,
density and-optimum moisturecontent depend on method of providing compaction energy versus
kneading, vibration and impact and its magnifude.
3()

Department
of CMI Engineering
Anna UniversitY,
Chennai
Dia of mould,cm
Ht of mould,cm
Wt. of mould,Wr(S)
Vol. of mouldV(cm3)
Description
of SamPle
DataSheet i
Date :
TestedbY :
COMPACTION TEST
Sp.Grof soil :
Ht. of fall i
Wt. of hammer,kg :
Description
Trials
1 2 3 4 5
Wt. of mould + compactedsoil, W2, g
Wt. of compacted
soilW, - W'g
Wet density,Tb= (W2-W1)// 9/cm3
Dry density,Yd= T,o
/$+w/100),g,/cm3
Voidratio, e = (G.y*/yJ _ 1
Zeroair void densityY4uu1=G,
T*/Q+w G/100), g/cm3
ContainerNo.
Wt. of container,g
Wt. of container+ wet soil, g
Wt. of container+ dry soil,g
Wt. of water, g
Wt. of dry soil,g
Watercontent,w,0/o
3 1
Result :

ExperimentNo.
DIRECT SHEAR TEST
Reference
lS 2720(PartXIID- 1972:Methods
of testfor soils- Directshear
test.
Objective
To determinethe shearstrengthof soilswith a maximum particle sizeof 4.75 mm, by direct
shear test.
Equipment
Direct shear machine, with all accessories
Balance, Moisture cans.
Introduction
Shear strength evaluation is necessaryin most soil stabil'rtyproblems. Soil tests commonly
employed to obtain the strength parametersinclude (in order of increasingcost)
Unconfined compressiontest
Direct shear test
Confined compressionor triaxial test.
The direct sheartest is a simple,straightforward testto perform. The test is madeby placing
a soil sample into the shear box. The box is split, with the bottom half fixed and the top half
Iree to translate The box is availablein severalsizesbut commonly is 6.4 cm in diameter or
5 to 6 cln square. The sample is carefullyplaced in the box; a loading block, which includesa
serratedporous stone* for rapid drainage, is placed on the sample. Next a normal load, Pu,is
applied by dead weightsacting through a lever arm. A horizontal force, Pn,is then applied to'the
upper part of box through a proving ring and the sample is shearedthrdirgh the plane between
the parts of the shearbox. Volumechangesof the sampleduring the test can be observedby means
of a dial gauge. Two or more additionaltestsat larger valuesof P" are performed to make scalled
plots of
r = (Ph,/A)versusGn = (P/AI (1)
where A = afea of sample, so that a graphical solution of the equation r = c+ontancpcan be
obtained.
Depending upon the applicaton of shear load the direct shear test is of two types, namely
controlledstresstest (shearingforcesincreasedat a constantrate)and controlledstraintest (shearing
strainincreasedat a constantrate)the advantages
of controlledstraintestsare that it providesbetter
control at the point of maximum shear stressand it provides an opportunity to sfudy the soil
behaviourafter maximum has been reached.A controlled strain machine is also easierto operate
and hence are most commonly used.
Recommended Procedure (for dry, granular soils)
1. ' Weigh a large dish with dry sand (enoughsand so that three tests can be performed on
samplesof approximately the same weight for density. Size of box; 6cm x 6cm)
* Sandsamples
areoftentestedin thedry state,sothattheresults
correspond
to thoseof a drainedtestfor
dry sands,
toothednon-coffosive
metalgridplatesmaybeused,in the placeof porousstones.
g2

2. Using rne two pins (separation
setscrews)
lock the two parts of the box together' Measure
the dimensionsof the box and computesamplearea.
3. Carefullyplacethe sandin the shearbox to about5mm from the top and placethe loading
block (with its serratedunderside)
on top of the soil sample. Ensurethat the block is set
level.
4. Weigh the container of sand and determine the weight of material used to form the
specirnen.
Note: It may be necessary
to mark the loadingblock or use some other convenientmethod to
control the placementdensity. Talk to the courseinstructor.
5. Placethe hanger frame and apply the requirednormai load (leveragefactor = 5)
6. Set the proving ripg and selectthe desiredrate of strain (0.2 mm per min for sand)and
record the initial proving ring reading,and in most instancesit is preferableto keep it to
zero.
7. Removethe separationscrewsand startthe motor to apply the horizontal(shear)
load. For
one of the trials,preferrablythe last,take readingsof the shearload, shearingdisplacement
and verticaldispiacement
at every15 seconds
for the first 2 minutes,then every30 seconds
thereafter. Continueall trialsto a horizontaldisplacement
of approximately13 percentof
the samplelength unlessa constantshearingforce was obtainedfirst.
8. Stop the motor, remove the normal load and the shearbox.
g. Repeatthe testwith a freshsamplefor other normalloads. A minimumof three (preferably
four) testsshouldbe conductedon separatesamplesplacedat the same density.
COMPUTANONS
Computethe shearingdisplacement
(AH) and the verticaldisplacement
(AV) for each load
increment
Compute the shearstressas
r = (PhlA) (2)
for squareboxes,preferablyuse a correctedarea basedon sheardisplacement,as follows
Corrected
area,A = Ao (1-AH/3) (3)
WhereAo =
A H =
initial area of the samplein cm2
shearingdisplacement
in cm
Compute the normal stressas
on = PvlA)
(4)
Draw a graph of shearingstressx versusshearingdisplacementAH and obtain the maximum
value of t. Diu* a graph oi shearingsiressversusnormal stressand determinethe angle of
shearingresistance
and cohesionintercept(if any). In your report, make appropriatecomments
on the information obtainedfrom thesegraphs. Also draw a graph AH versesAV and obtain the
relationshipbetweenshearingdisplacement
r.rersus
normal displacement.
33

Discussion
The direct shear test suffersfrom severaldisadvantages.The test forces the direction and
locationof the failureplane,a conditionwhich may not be practicallyobtained. Drainageconditions
cannot be controlled. As pore water pressurecannot be measured,only the total normal stress
can be determined,although this is equalto the effectivenormal stress,if the pore water pressure
is iero. Only an approximation to the stateof pure shearis producedin the specimensinceshear
stresson the failureplane is not uniform and failureis occuringprogressively
from the edgestowards
ihe centre of the specirnen. A correction for area reduction can easily be made of squarebox
samples,but it is not very practicalto make this correctionfor round boxesdue to the considerable
mathematicsinvolved. ihe advantagesof the test are its simplicity and in the caseof sands,the
easeof specimenPreParation.
With a densesandthere will be a considerable
degreeof interlocking' betweenparticiesand
before complete shearfailure can take placethis interlockingmust be overcomein addition to the
frictional resistanceat the points of contact. After a peak stressis reachedat a low valueor shear
displacement,the degreeoi interlockingdecreased
and the shearstressnecessary
to continueshear
displacementis .orrurpondingly reduced. The decreasein the interlocking producesan increase
in ine volume of the ipecim-n. The term
'dilatancy' is used to describethe increasein volume
of the dense sand as rhnur failure is approached. The interlocking component of the shearing
strength, Td,can be derived from strain energy principles'
Shearingstrength(to)x shearingdisplacementat peak (AH) = Applied normal stressx normal
displacement(AV) and from this the dilatancy angle, 06' can be calculatedas
0a = tan-t fto/c^) - tan'l (AVIAH) (5)
34

Departmentof CivilEngineering
Anna_university
Chennai- 25
Rateof strain
Calibrationfactorfor
proving ring. 1 div
Loadhangerleverratio
Hangerweight
DIRECT
SHEARTEST
Data Sheet :
Date :
Testedtry :
Samplesize =
Area of sample,Au =
Volumeof sample,V =
Weightof sample,W =
Densityof sample =
Cohesionc =
Remarks :
Applied
load
kg
; Angle of internal friction, <p=
NormalforceP, =
(Hangerwt. + applied
loadx leveragefactor)
ks
6 ,
35

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Experiment
No.
TRIAXIAL COMPRTSSIONTEST ON COHESIONLESSSOL
References
lS 2720 (Part)Q- 7972 : Methodsof test for soils- Triaxialcompression
test.
T.N.Lambe(1951),Soil Testingfor Engineers,
John Wiley& Sons,New York.
Objective
To determinethe shearstrengthof cohesionless
soilin its dry state,by triaxialcompression
test.
Equipment
Triaxialloadframewith orovingring and deformationdial
Specimenmould
Tamper
VacuumsupPlY :
Balance
'O' Rings
Rubbermembrane
Introduction
In the preceding
instruction
sheets
the basictheoryof shearstrengthof soils,and.
the three
most well known ty$ of sheartestswere illustrated. Of thesethree types of teststhe triaxial
compression
test hasthe followingadvantages
overdirectsheartest.
i) Progressive
effects
dueto nonuniformshesses
andstrains
causing
a failuremechanism
similarto that of a tearingof paperare minimumin triaxialcompression
test.
ii) Measurement
of specimen
volumechangeis moreaccurate,
and-controlof drainage
and measurement
of pore waterpressure
are possible
in triaxialcompression
test.
iil) Complete
stateof stress'in
thespecimen
isknownthroughout
theprogress
of thetest.
iv) Triaxialcompression
test is adoptable
to any specialrequirement.
The hiaxialmachineasthat of directshearcanbe stressor straincontrolled. Because
of
manyadvantages
asalready
illustrated
in preceding
instruction
sheets,
straincontrolled
machines
are
normallyprefJned.FromMohr-Coulomb's
failuretheory,thebasicrelationship
between
majorand
minorprincipalstresses
in a triaxialteston a cylindrical
sample
at the vergeof failurecanbeshown
as
Gr = 6g tan2 (45+ Q/21 + 2c tan (45 + q/2)
and in the case of cohesionlesssoils as sandsand clean gravels,since c = 0
(21
or = os tan2(45 +<P/2
The Mohr strength envelope,for cohesionless
soils being tangentialto Mohr stresscircles,
passesthrough the origin in a graph showing the plot of shear slressversusnormal stress. The
inclination oiMohr .nullopu wiln tne horizontalso obtainedin sucha plot representsthe angle of
(1)

internalfriction of the cohesionless
soil. The resistance
to shearof cohesionless
soil is normally
derived from friction between grains and interlocking of grains. Becauseof the phenomenon of
interlo[king the-strengthof densecohesionless
soil tends to Uugreater at smalldisplacements
than
at large displacementswhere the effectsof interlocking has been overcome. The higher strength
is calledpeak strength,the lower strengthis ultimatestrength. In cohesionless
soils,volumechange
which occur during shear, play an important role in maxinium mobilisation of angle of internal
friction. This importance of volumechangeshaveled to the developmentof concept of criticalvoid
ratio with which when a soil is shearedthe resultantvolumechangeat failurdis almostzero. Hence
this leadsto the conclusionthat the measuredangle of internal friction is dependenton the initial
void ratio at which the sample is sheared,apart from other factors and extreme care has to be
exercisedin preparing a labotatorysampleasrepresentativeas possiblefor the stabilip problem on
hand. In all casesit is desirablethat the valueof angle of internal friction shouldbe reported along
with the relativedensitv at which the test was conducted.
Recommended Procedure
Placea porousstone37mm diameterat the baseof triaxialcelland roll up a membraneand
slideit on the base. Bind the membranewith an
'O'
ring or rubberstrip.
Place a split barrel type specimen mould around the rubber membrane and fold the top
portion of the rnembranedown over the rnould.
Weigh,dry sandupto 0.1g and plac<:
the sandwithin the membraneby tamping,takingcare
not to tear the membrane. Amount of tampingdependson the denseness
of the sampledesired.
After obtaininga length of sample2 to 2.25 times its diameteqagainweigh the remainingsand.
The difference in ihe weight is the weight of sand used in the preparation of the sample.
Put the top porousstoneand the loadingblockon the sample. Roll up the remaininglength
of membraneon to the top loadingblock and sealit with
'O'
rings.
Now removethe split barreltype specimenmould and apply a vacuum20 to 25cm mercury
to the sample,through the botton duct of the triaxial base- observethe membrane for holes and
ductsand if found, the samplemust be renrade. Take two to four measurementsof length Lo and
the diameterdo of the sampleand compute:
the average. Computethe initialarea of crosssection
Ao cm2usingthe averagediameter. Placethe lucitecylinderon the cell basewhich is free of dirt
and by tighteningthe screwsget an airtight seal. Placethe cell in the compressionmachineand
make the contact of the loading piston with the proving ring of the loading machine.
Apply a predeterminedlateral pressureo. to the cell using appropriate lateral pressure
device,chamberfluid being,water in most instances.During this period the proving ring dial is likety
to deflectdue to the upwardcell pressureon the pistonbase. Carefullyraisethe cellunit mounted
on the machine so that the recontact beb"r.reen
the top of the loadi4g block and loading ring is
established. Now note down the initial reirdingon the proving ring dial, and in most instancesit
is preferableto keep it to zero.
Attach a deformationdial to the top of the triaxialcell and set the dial to zero.
Set the compression
machineto the desiredstrainrate between0.05 to .lcm,/min. Switch
on the compressionmachineand takesimultaneously
loadversusdeformationdial readings. Take
readingsuntil load holdsconstantand then falls off or to slightlybeyond the estimated20o/o
strain
value. Throughout the duration of the test ensurethat the lateralpressuredo not vary appreciably.

,
li,
After the samplefails shut off the bottom valve connectingthe lateral pressurechamber,
reversethe compressionmachineand drain of the cell water.
Remove the lucite cover. Prepare a new specimento the same approximate density and
make atleasttwo additional test with different lateral pressures.
Computations
Compute the axial strain, e = LL/''
Calculatethe correctedarea, A = Ao/(1-e),cni2 (4)
Deviatoric.load.P = Provingring readingx calibrationfactor (5)
Obtain the deviatoric stress, od = P/A Kg/cmz (6)
Obtain a plot of deviatoricstressversusaxial strain and scaleoff the peak value of the oo
or od correspondingto 20o/oaxialstrain, if t occurs earlier. With this deviator stressobtain the
value of the major principal stress
01 = 03* oa Q)
:, Plot, Mohr's circlesfor three or more number of testsand fit a tangent to these circles
passingthrough the origin and obtain the slope of the tangent as the angle of internal friction of
the sand sample tested.
Compute the tangent modulusand the secantmodulususing the slope of the stress-strain
curveand report the observedvalues. Report the dry densityof the samplesat which it wastested.
l)iscussion
The shear strength of cohesionless
soil is likely to influenced,by its texture, relativedensity
and rate of strain at which it is sheared. Researchhasindicatedthat whilb the specimenshapehas
appreciablyno effect, higher strengthshave been reported to have been obtained on smallertest
specimens. There is evidence,that length to diameter,ratios of 2.25 to 2.5, lead to fairly
satisfactoryresults. Ratesof strain in the neighbourhoodof /4o/o to 2o/o
per minute are normally
satisfactoryfor many of the routine testing of sand samples. Membranethicknesshad also been
found to have appreciableinfluenceon the shapeof stressstrain curve obtainedin the triaxial test
but little influence on maximum deviatoric stress.
Typical values
Peak friction angle in a well graded coarse sand usuallyranges from 37o to 60o and in
uniform fine sand the variation is from 33o to 45". There is lessvariation in the ultimate friction
anglea typical valuebeing 30o. The volunrechangesthat occur during sheardependon the initial
void ratio. Normally, the loose sandstend to show net negativevolume change or contraction
at failure and dense sandsshow positive volume change or expansion at failure.
(3)
39

Soil EngineeringLaboratory DataSheet :
Deparbnentof Civil Engineering Date :
Anna University,Chennai TestedbY
TRIAXTAL COMPBESSIONTEST ON COHESIONLESSSOIL
Descriptionof soil
Average
diameterof the sampleDo,cm :: Dry weightof sandusedin the
Initiallength,Lo cm ;: samplepreparation,
g =
InitialArea Ao,cm = Specific
gravityG. =
Volumeof sarnple,
V cm3 : Volumeof solids.
V*, cm3 =
Calibration
factorfor provingring, 1 div.= Dry densityT,1,
g/cm3 =
Leastcountof deformation
dial 1 div. = Voidratio,e =
CellPressure,
03, kglcm2 :
Results
'
Angle of internal friction :
Initial tangent Modulus, kg/cm2 :
Secant modulus, kg/cm2 =
Deformation
dial reading
div.
Change in
length
AL. cm
Axial strain
e : LL/Lo
Corrected Area
A : Aoll-e
cm2
Proving
ring dial
readino
Deviatoric
load, P
kg
Deviatioricstress
6a: P/A
kq/cmz
40

Experiment No
UNCONFINEDCOMPRESSION
TEST
Reference
IS , 2720 (part X) - 1g7O : Methods of test for soils : Determination of unconfined
compressivestrength
Objective
To introduce the student to an approximate but quick procedure for evaluatingthe shear
strength of a cohesivesoil
F4uipment
Unconfined compressiontestingmachine(anyload frame fitted with a proving ring of a low
rangeto obtain accurateload readings,specimentrimmer, vernier caliper,balance,oven, desiccator
and moisturecontent cans'
Introduction
The shearing resistanceof fine grained cohesivematerial is a function of the applied normal
pr"rrur",'t6;;.solidation load oir the soil and drainage conditions and is best shrdiedby
conductingtriaxial compressiontests. Unconfined compressiontests may be describedas triaxial
compressiontest perfoimed al zerolateral pressure. They may be run with triaxial equipmentor
Jth'specially designedequipment,the later beingmore common. Since thereis no lateralpressure,
tf,i, tot -uy b" pJrfor-"d only on a soil and sufficientcohesionto maintainits shapeunderits own
weight and shess-shaincurvesfrom an unconfinedcompressiontest are similar in nature to those
obtained from hiaxial tests.
.From a Mohr's circle construction the relationship between major and minor principal
stresseso, and 03 can be shov.rnas
o, : 6.tanz 1450+ Q/21 + 2'c tan @50+ i/21
(1)
with the minor principal stressor being zero (atmospheric)in an unconfinedcompressiontest, it is
evidentthat the shearstrengthoi cohesion,Cuof a soil samplecan be approximatelycomputedas
(if d is assumedto be zeroas normally happJns in the caseof the safuratedsoils,when testedin
undrained condition)
(21
C . . = o r / 2 = g u / 2
u
Where euisthe generallyusedsymbol for the unconfinedcompressivestrength of the soil'
Thus shearingstrengthis assumedto be one-halfof the.failureload regardlessof the normal
stressand such an assumptionis valid for design of small structureson cohesivesoils' It is not
recommendedfor large structuressince it is o,ierly conservativeand of course, it is unusablefor
sandswhere eu = 0. The unconfined cornpressiontest may be either strain controlled or stress
controlled. The straincontrolledtestis almostuniversallyused.-since the testspecimensare usuah
exposedto the laboratoryair, the test shouldbe conduciedwithin about 10 minutes,otherwise,the
changein water conte#may affect the unconfinedcompressivestrength'
4l

1. Removethe undisturbed
samplefrom the samplingtube.
2. Carefullytrim the sampleends. The trimming processshouldremoveall soilthat has
been disturbed. Checkto seethat the trimmed sampleis preferably2 to 2.5 times
high as its lateraldimension(preferable
Loratio is 2.25).
3. Weigh the sampleand determineits exactdimensions.
4. Placethe samplein the testingmachinewith its verticalaxisas nearthe centreof the
loadingplatesas possible. Adjustthe measuring
dialsto zero. Note the provingring
details.
5. Start the motor and apply the load at a strain rate of I to 2 percent. Record
simultaneously
load and straindial gaugereadingsat frequentintervalsto definethe
stress-strain,
ralationship.
6. Continuethe test till cracksand well defined failureplane havedevelopedor atleast
20-22 percentstrainhas been reached.
7. Removethe specimen,measrlrethe anglebetweenthe failureplane and horizontal.
Sketchthe shapeof failedspecimen(on the stress-strain
plot)
B. Weighthe sampleafter ovenr1rying
to constantweightat 1100Cand find its moisture
content.
Computations
Calculatethe axial strain,from
(3)
r LL/LQ
where
AL = changein specimenlengthas read by extensometer/strain
dial gauge
Lo = initial specimenlength
In calculatingunit stresson specimen,usea correctedcross-sectional
area,A givenby
A = Aol(l_e)
where
Ao = initial area of crossse<:tion
of the specimen
Plot the stress-strain
relationshipand determine the unconfined compressivestrength as the
maximumordinateof the stress-strain
curvebetween0 to 20 percentstrain. Wheremaximumwell
developedpeak strength is not reflectedin the stress-strain
relationship,the strength at some
arbitaritydefinedstrainas 15 or 20(%is usedfor peak.
Discussion
The unconfined-compression
testmay not providea veryreliablevalueof soilstrengthfor the
followingreasons:
1. The effect of lateral restraintprovidedby the surroundingsoil mass is lost when
sampleis removedfrom the ground.
2. The internalsoilconditions(degree
of saturation,pore water pressureetc.)can notbe
controlled.
3. Frictionon specimenendsfrom loadingplates,providesa lateralrestrainton the ends
which altersthe internalstresses
to an unknown extent.
(4)

Howeverthe unconfinedcompressiontestis widelyusedfor a quick, economicalmeansof obtaining
the approximate shear strength of cohesivesoils (saturated,soft, unfissuredclaysin particular)
Presentationof data
1. Plot the stress-strain
curve and indicatethe mode of failure on this plot.
2. Draw a Mohr's circle using the averag"d % from the two (or more) testsand show
the valueof undrainedcohesion.
3. Comment on the consistencyof the sampleand any other pertinent feafuresof the
test.
4. Measurethe slope of the initial portion of the stress-strain
curve and give the value
of rnodulusof deformation of soil as observedin the unconfinedcompressiontest.
5. Report the observedorientation of failure plane if any
Typical Values of Unconfined Compressive Strength
Consistencyof Clay Unconfined CompressiveStrength (kN/mr)
Verysoft
Soft
Medium
stiff
VeryStiff
Hard
<25
25 to 50
50 to 100
100 to 200
200 to 400
> 400
43

Departnent of Civil Engineering
,AnnaUniversity,Chennai
Descriptionof sample
Rate of strain
Initial diameter of sample,do cm
Initial length of sample, Lo .-
Initial area of cross section, Ao, cm
Least count of strain dial, 1 division
Calibrationfactor for proving ring, 1
Initial weight of sample,g
Oven dried weight of sample, g
Water content of sample,o/o
Bulk unit weight of sample,g/cm
Dry unit weight of sample,g/cm
DataSheet :
Date :
Tested'by :
UNCONFINED
COMPRESSION
TEST
division =
S.No
Strain dial
reading,
div.
Axial
deformation,
AL mm
Axial
strain, E
Correctedareao:
crosssection,A
cm2
Proving ring
dial reading
div.
Axial loac
P,ks
Axial shess
cfP/A,
kg/cmz
Remarks
on the observed
natureof failure'ofsample:
44

Experiment No-
CONSOLIDATIONTEST
Reference
lS : 2720 part (XV) 1970, Consolidationtest.
T.W. Larnbe(1951) soil testingfor Engineers,John Wiley & Sons , Newyork.
Objective
To obtain the time compressionrelalionship of given saturatedfine grained soil and the
coefficientof consolidationfor one load increment.
Equipment
One dimensionalconsolidationunit with fixed ring containerand deflection.
dial
Knife for trimming / wire saw.
Balancewith sensitivity
0.01 to 0.1 g.
Drying oven
Loading weights
Stop clock
Introduction
Application of stressto any material will causea coffesponding strain. Sand and gravelshave
relativelylarge pore sizesand do not exhibit considerable
time lag betweenthe applicationof stress
and resultingstrain. However, fine grained soilsusuallyexbihit a measurabletime lag betweenthe
application of stressand resulting strain. This phenomenon of time dependent compression of
saturatedfine grained soil is calledconsolidation,which may be one or three dimensional,In most
casesone dimensionalconsolidationhas Inany direct applications.For example the settlementof
clay layer occuring at some depth below llround level and sandwitchedbetween two sand layers
will be due to one dimensionalconsolidation.In proportioning the foundationsfor many strucfures,
computationof total and time rate of settlementsof fine grainedsoil is essential.This text is devoted
to considerationof the processof one dimensionalconsolidationof fully saturatedfine grainedsoil
and method of evaluation of relevant soil parameter for measuring time rate of settlement of
structuresfounded on them.
Theory
Theory of one dimensionalconsolidationas envisagedby K. Terzaghiwith a set of simplifying
assumptionsis given blow :
e)=',(#)
Cu = Coefficient of consoildationcm2/s.
u = excesshydrostatisticstressat any time t and at any depth z in kg/cmz
The theory predicts the rate at which the excesshydrostaticstresscausedby the foundation
contact stressesin the underlying saturatedfine grained soil dissipates,leading to time delayed
compression.
Obviouslythis processis infltrenced
by the permeabilityof the soils.Solutionsto the
46

onedimensional
consolidation
process
for tlifferent
boundary
conditior-rs
havebeehobtained
in the
form.
U = f (Tl
U = the degreeof consolidation
T = the dimensionsless
time factcrand
r=(+)
H ,
H = Distanceof one dimensionalflow in cm
t = time in s.
The relationshipis usefulin finding the trmerate of settlementsof structurefoundedon saturated
fine grained soils and is presentedin the table for uniformly stressedsoilsthroughout its depth in
appendix.Resultsof laboratoryconsolidationtestson saturaiedfine grainedsoilsf,ave indicatedthe
presenceof three distinctportions of time consolidationcurve,comprisingof initial compression.
primary compressionand secondarycompnassion.
Positiveinitial compressionin most instancesis
due to the presenceof entrappedair, primery compressionis due to cliainageof pore water caused
by excesshydrostatic stressand secondarycompiession being causeclby plastic flow or due to
qradualadjustmentof soil particlesunderimposedload. The timZ rate of compressionobtainedfrom
Terzaghitheory coversonly the primary ccmpressionor consolidation.
In runningconsolidation
test, undisturbe.d
soil samplesare required.The samplesare usually6
to 10cmdiameterand 1.25 to 4 cm.thick.The sampleis fed in a fixeclring or floatingring container
and provided with drainageaccessboth at top ani bottom. The ring container tolether with the
porous stonesand the outfit assemblyis calledas oedometer.The oeclometeroutfit is fitted in a
load frame and after saturation,the sameis loadedin smallloaclincrements.After applyingeach
load increment, compressiondial versustirne readingsare noted at chosen interval of time until
consolidation
under the load incrementis r:ompletea.
the load incrementis generallystartedwith
a tow valueof 0.S kg/cmt and at the end of 24 hrs it is increasect
to i in^;r. 6,i'lu."o.iu"
daysfoadintensities
are increased
to 2,4,8, and 16 kg/cm'and for eachloadi-ntensity,
compression
dial versustime readingsare noted in a rgutine consolidationtest.
Measurethe insidedaimeterD (cm)and height 2H (cm)of the fixed ring samplecontainerand
lubricatethe insidesurfacewith thin film tf oil and find the wcight nnurit to 0.f g, Wr(g).
Carefully feed the soil sampleinto the fixed ring samplecontainerwith the help of sample
eiector.Trim the ends of the samplewith leastdisturbanceto soil structure.
From the leftoverof the trimmedsoil srmple obtaintwo samplespecimensand after weighing
put them in the oven for water content determination.
Find the weight of the soil sampleanclthe fixed ring containerw,(g).
Wet two filter paperswith water and lit them at both end of the soil sample.
Place the bottom porous stone after soaking in water on the baseof the oedometer unit and
give connectionto water leveland graduallyraisethe water lerrelab6vethe porous stone.

Placethe samplecontainer on the porclusstone. Put the secondporous stone which has been
wefl soakedin water and a loeidingblock on the soil sample. Feed the rubber washer and place
the outsidering and tighten the whole systemwith a given set of screws. Mount the oedometer
assemblyin the consolidationload frame. Immerse the sample completely in water.
Adjust the loading platform till the loadingyoke touchesthe loading block. Check the deflection
dial whetherit hasfree run and note the initialdial readingdr. Allow the sampleto reachequilibrium
under a ring load of very small magnifude.
After a lapse oI 24 hours note the dial readingd, and apply the first load increment. Usually
0.5 kglcm2 and start a stop clock.
Notedownthe compression
dialreading
at elapsed
timesof 0, 0.25, 7,2'25, 4, 6.25,9; 2.25,
75, 20.25, 25, 36, 49 minutesetc., until about 90 to 950loconsolidationis reached.
At the end of 24 hourstake the final readingand increasethe loadintensitywith the next desired
load increment.
The test will be continued under load intensitiesof L,2,4,8 and 16 kg/cmz in all soil testing
laboratories,to get a completepicture of load intensityversuscompressionand compressionversus
time relationshipsat different load intensities.At the end of the test the sample container will be
dismantledand final weight of container and the sample will be noted. Then the sample will be
oven dried for final water content determination.
Computational Procedure
The resultsof the time compressionrelationshipcan be presentedeither in afor log plot and
the coefficient of consolidationcan be evaluatedfor the given load increment through apropriate
fitting methods.
Square root time fitting rnethod ( D.W. Taylor)
After plotting the dial readings,d (Y axis)u"trurvf(x axis)relationship,the initial straight line
portion of the curve is extendedback to intersectthe 0 time and corrected zero d, is obtained.
Through d" another straight line having an inverseslope of 1.15 times that of initiai straight line
is drawn. The straight line cuts the experimentaltime compressioncurve correspondingto 907o
compression.From this d and t are obtained and the coefficient of consolidationis evaluated
from
eo eo
Cu (cm2ls)= ( 0.848 tl'tt/
Log fitting method
In this method, compressiondial readings,d, versuslogrotplot from the observedreadings,is
first made. Two straight line portions, of the curve in the later stage of the consolidation are
extendedto intersectat 100o/o
primary cornpressionand henced,onis obtained.The correctedzero
point d. is locatedby laying off abovea point in the neighbourhoodof 0.1 minute a distanceequal
to vertical distancebetween this point an<tone at a time which is four times greater. The 507o
compressionpoint-duois midway betweend, and d* and the correspondingtime t"ois scaled.This
method assutnesthat the early portion of the compressioncurve is parabola. Then Cu can be
calculatedfrom
Cu(cmz,/s) : (0.797tl1 /n
47

H = One half of the averagethic'gressduring the load incrementin cm
t.ru,t.,n = Correspondingtime t obtaine
,d frorn Vf or log t plots in s.
Discussion
The test resultsur" likuly to be influemed by the size of the sample, sample disturbance,side
friction,preSsure
incrementratio and tempe'rature.
Thinner samplesare preferableforthe following
reasons(1 ) economyin collectingutr6islLrrlred
samplesfrom the field(2 ) rate of consolidation
will
be faster(3) thinner the specimenof a givt:ndiameterthe sidefriction is small.Howeverwith too
thin samplesand especiall-v
low pressureino'ementratiosthe effectof secondarycompression
will
be predominantand this is lil<ely
to leadtc misinterpretation
of field behaviorof thick clay layers.
In generala ratio of specirnencliameterto thicknessof aboutthree to four with a load increment
ratio of 1 is normallypreferred.If the sampleis highlysensitive
to rernouldingeffectsthen general
tendencywill be to retardthe procressof ,;onsolidation.
This effectwill becomevery predominant
if the sampleis too thin. By suitablylubric'ting the ring containerwith silicongreaseor teflon the
side friction can be minimisedwhich will lror,vever
have predominanteffect on effectivepressure
versusvoid ratio relationship.
Sincethe coefficientof consolidation
is a functionof permeability
which is dependanton ternperature.
this a fectsthe determination
of Cr,.In generalin betweena
changeof 200C to 400C a fluctuationu1,to3504can be expectedin the Cu values.The effect
of temperaturehas also bcen found to be more significanton secondarycompression.Hence
normally it is recommendedto report C,, valuesalong with test temperature.
Appendix :
Time factorversusdegreeof consolidatiorr
relationship
LJ ij'h T
0 0.000
l 0 0 008
20 0.031
30 0.017
40 0 . 7 2 ( t
D I J 0.197
uo,lt T
60 0.287
70 0.40:J
80 4.567
90 0 848
100 U.
il
.t
l *
Percentageof corrsolicltitiort
Time factor
4 a

Soil EngineeringLaboratory Data Sheet:
Deparbnent of Civil Engineering Date :
TestedBy :
Anna University, Chennai
CONS()LIDATIONTEST
Diameter of Sample, D (cm) = Least count of compressiohdial 1 div =
Height of the sample2H (cm) = Pressureincrement,From =
Weight of fixed ring
Sample Container, Wr(s) = To =
Weight of Sample + iixed ring 6 t*r" ,,
Sample Container, Wr(S) = Temperaturn* t'C =
CONSOLN)ATIO}.I TEST DATA
Time Minutes ,rr logrot
0.00
0.25
1.00
2.5
4.00
6.25
9.00
L2.25
16.00
20.25
25.00
49.00
64.00
81.00
144.00
480.00
900.00
sl.
No
ContainerNo. Wt. of empty
container
(q)
I
2
Compressiondial reading Compressionin mm
Wt. of container+
wetsamplek)
Wt. of container+
dry samde(g)
Water
content(%)
49
MOISTURE
CONTENTDETERMINATION

ExperimentNo.
ExperimentNo.
PERMEABILITYTEST {ONS'FANT AND FALLING HEAD METHODS
Reference
IS :2720 (Part XV0 1g7O : Methods of test for soils: Laboratory Determination of
permeability
Objective
To determinethe permeabilitycoefficientof soilsthrough (1) constanthead permeameterand
(2) Variablehead permeameterin the laboratory.
Equipment
Permeameter
Vacuum Pump
Timer, thermometer.graduatedcylirrder,meter scale.
Introduction
The facilityof fluidthroughany porousrnediumis an engineering
propertytermedpermeability.
For geotechnical
engineeringproblemsthe fluid is water and the porousmediumis the soil mass.
The permeabilityof a soil massis requiredin:
1. Evaluating
the quantityof seepage
throughor beneathdamsand leveesand into waterwells.
2. Evaluatingthe uplift or seepageforces beneath hydraulic strucfure for stability analysis.
3. Providingcontrol of seepage
velocities
so that fine grainedsoil particlesare not erodedfrom
the soil mass.
4. Rate of settlement(Consolidation)
studies.
Darcy in consideringthe flow of w;rter through sand filters in France,proposedthat flow
of water through a soil could be expressedas
,r : ki
Where i = (h/L), h, being the head lossin a length L of filter bed (Commonly refened,
to as hydrualicgradient)
k - Coefficient of permeability(with units of velocity)
Darcy's law is a statisticalrepresentation
of the averageflow conditionsin a porous medium.
This equationis considered
to be one of the importantequationsin soil mechanici.tsy comparing
the relationshipgoverning the flor,vof watr:r through round capillarytubes of small diameter,with
Darcy's law. D.W. Taylor (1948) has shov.,n
that
l v , : ' l .
v = D-2
l-ILlf 3-l c i
" u / t + eI '
5()

r n
wnere [-rs =
g =
c =
S
Y * =
Diameter of equivalentsphericalgrain.
Void ratio
Composite shape factor
Unit weight of fluid
1 to 10cm/s
10-3 to lcm,/s
10-5to 10-3cmls
Lessthan 10-6 cm,/s.
tl = Viscosity
'k'
thus depends on the unit weight and viscosity of the fluid which is dependent on
temperafure and the fube radius. The tubes through a soil mass are of irregular shape and are
dependenton the void ratio and, in particular,on the grain siie. For this reason,k in coarsesands
is larger by many orders of magnitudethan in silts and clays. The degree of saturation and the
amount of undissolvedgas within the porewater also affects the permeability.
Darcy's law is generally-valid
for laminar flow only, (in which all particlesmove in paths
parallelto the container walls and to each other). For many fine-grainedsoils the flow velocity is
so low ( under the field hydraulicgradient)that the flow is indeed laminar and the inertial forces
are insignificant.Laminar flow becomesfurbulentwith increasein velocity.For grainslargerthan
0.5 mm in a uniform soil, turbulencemay be expected.
Range of permeability values
Permeability of different soils may be expectedto fall with in the following approximate
ranges:
Gravel
Sand
Very fine sands,silts
Clay
A permeameteris a devicefor measuringpermeabilityin the laboratory.Permeameters
may
be set up in any number of ways,but actualtestsmust be conductedwith either a constant-head
of wateror varyingheadtest.The constant-head
testis prelenedfor soils.suchassandsand gravels
which havelargevoid ratiosand for which a largeflow quantityis requiredto improve computational
precision.In most instancesfield hydraulicgradientis likelyto be the order of 0.5 to 1.5 whereas
in the laboratoryit is generally5 or mor€r.
The constanthead permeameter'isnot suitablefor testingfine graihedsoilsbecauseof the
very small dischargeinvolved.For clays,it is more feasibleto measurepgrmeability by noting the
quantity of water going into the specinren rather than that coming out. The falling head
permeameteris basedon this principle. Both the proceduresare coverbdherein.
Recommended Procedure (for coarse grained soils)
A. Constant-head permeability test
Weigh ttre permeameter mould and base plate. Take mould measurementsto compute V,
the volume of the mould, the area A and the length L of the sample.
Place a filter paper on the bottom porous plate. Using the given sand sample, prepare a
test sample by loosely pouring or using severallayer with uurying d"grees of vibraiion ito obtain
density variation for the different runs)
5 t

Placea filter paper on top of the sand.Carefullycleanthe rim of the mould, placea rubber
gasketand then firmly seat the top cover (Followdirectionsof the instructor)
Placethe permearneterin a large sink in which the water is about Scm above thecover.
Be surethat the outlet pipe of the mould is open so that the water can backupthrough the sample.
This procedurewill saturatethe samplewith a minimum of entrappedair. When *ut", in the inlet
tube on top of the mould reacheseqtrilibriurnwith the water in the rink th" samplemay be assumed
to be saturated.
Alternately, extract the air inside by attaching a vacuum line to the top of the mould and
following (preferablyde-aired)water to move up from the bottom outlet. Follow directions of the
coarse instructor,depending on type of e<luipmentused.
After the sample is fully saturated.close the top and bottom outlets, remove vac'um.
Connect the inlet valve on top of the mould to the constant head water reservoir.
De-air the tines at the top of the soil sampleby opening the hose clamp on the inlet and
opening the bleeder valve on top of the mould cover. When no more air comes out, close the
bleedervalve, Measurethe hydraulichead acrossthe sample (differen
ce betweenoverflow level in
the reservoirand the outlet levelat bottom of mould).Open the bottom outlet, allow sometimefor
steadystate condition to set in.
When steadyflow is established
thrr>ughsoil samplecollecta .reasonable
quantityof water
(500-1000 cc) flowing out. Recordthe tirne requiredto collect this flow,. Repeat tr,voor three
additional readingsuntil two runs agree reasonabp well. Record the temperatuie of the test and
ensurethat the dischargeis atleast15 to 20 cm"/minuteduring the tests.
Computations
Compute the valve of k for the ternperatureof test from

= (QL/ Aht) cm,/s
a = Total dischargevolume in cnr3
f = Time in seconds
A = Area of crosssectionof samplein cm2
h = The constant head causingflow in cm, and
L = The length of the samplein cm.
. ^_r9o"-pute
also.krr,thn coefficientof permeabilitycorresponding
to the standardtemperature
of 27"C from
Krna ft
roa
F 27"c
(3)
K o =
27-C
(4)
tl = Viscosity of water, T"C = Test temperature
Note : The test has been standardisedfor a teryperafureof 27aC as a convenience(the viscosity
of water variesfrom 0.0157 dyne.s/cm" at 4oc to 0.00835 dyne. s/cm' at 27oC. Thus
180 percentdifferencein k can be obtainedfrom two testsat 4 and 27oc."
* 27oC according to IS. The referenceternperatureis 200C overseas.
52

B. Falling - head permeability (for fine grained soils)
The soil sampleto be usedmay be either an undisturbed
sampleor a sampleof cohesive
materialdisturbedand compactedto somerlesireddensity,dependingon the practicalrequirements.
For testingundisturbed
sample,the specimenshallbe trimmed in the form of a cylindernot
largerthan about85mm in diameterand havinga heightequalto that of the mould.The specimen
shallbe placedcentrallyover the bottom porousdisc and annularspacebetweenthe mould and
the sampleshallbe filledwith an imperviotrs
materiallike cementslurryor a mixture of 10 percent
bentoniteand 90 percentsandby weight to providea seal.The drainagecap shallthen be fixed
over the top of the mould.
For disturbedsoil sample,the test specimenshallbe preparedin the permeametermould
by compaction to the desired dry density at optimum moisture content (as determined.bv
compactiontests).The mould with the compactedspecinienshall then be weighed.
The mouldwith the specimeninsideshallbe assembled
to the drainagebaseand cap having
porous discs.The porous disc shallbe saruratedbefore assembling
the mould.
In the case of soils of low permeabilitythe specimenshall be subjectedto a gradually
increased
vacuurnwith bottom outlet close,d
to removeair from the soil voids.The vacuumshall
then be increased
to at least70 cm of mercurywhich shallbe maintainedfor 15 minutesor more.
The evacuation
shallbe followedby a very slow saturationof the specimenwith de-airedfrom the
bottomupwardsunderfullvacuum.Whenthe specimenis saturated
both the top and bottom outlets
shallbe closed.
The specimenshallthen be conne(tedthrough the top inlet to a selectedstandpipefilled
with water. The set up is now ready for ,r falling head permeabilitytest.
Open the bottom outlet atrd measurethe time intervalrequiredfor the water levelto fall
from a known initial head to known final head ui meusuredabovethe centre of the outlet.
Refillthe standpipewith water and ''epeatthe testtill three successive
observations
givethe
sametime interval;the time intervalsbeing recordedfor the drop in head from the sameinitial
to final values,as in the first determination.Alternatively,selectsuitableinitial and final headch,
and h, and note time intervalsfor the herd to fall from n., tqfn,-I. and similarlyfro- ,,fh_ 6,
to h".The two time intervalsso observed
s,hould
be the same.Oth6rwfsethe observations
shaf bj
repdatedafter refilling the standpipe.
Computations
For the fallingheadtestthe effectiveheadvariesduringthe testand hencethe computations
are slightlymore involved.
Compute k from
aL
k = 2 3 0 3 - l
t
At
'o''n
= Coefficient
of fiermeability
at toCin cmls.
= Inside
crosssectional
rreaof standpipe
in cm'.
= area of cross section ,:f the specimen in crn:
= Length of specimen hr cm
h
1
h
k
a
A
L
53
Where

Soil Mechanics Lab Manual including some International Standards

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