sm 03 mechanical analysis of soil
DESCRIPTION
Soil MechanicsBasicsTRANSCRIPT
-
SoilMechanicsICE225CE 225
Originofsoilandgrainsize
1
-
2WhySoilproblemsareUNIQUE?
Soildoesnotpossessalinearoruniquestressstrainrelationshipp
Soilbehaviordependsonpressure,time,andenvironmentThesoilatessentiallyeverylocationisdifferentI l ll h f il i l d i d dInnearlyallcasesthemassofsoilinvolvedisundergroundandcannotbeseeninitsentiretybutmustbeevaluatedonthebasisofsmallsamplesobtainedfromisolatedlocations
Mostsoilsareverysensitivetodisturbancefromsampling,and thus the behavior measured by a laboratory test may beandthusthebehaviormeasuredbyalaboratorytestmaybeunlikethatoftheinsitusoil
-
Soilparticlesize 3
Soilsaregenerallycalledgravel,sand,siltorclay.
Gravelsarepiecesofrocks.
Sandparticlesaremadeofmostlyquartzandfeldspar.
Siltsaremicroscopicsoilfractionsthatcontainveryfinep yquartzgrainsandsomeflakeshapedparticles.
Claysaremostlyflakeshapedmicroscopic/submicroscopicparticlesofmica,claymineralsetc.
No.200 No.4 3in.
cobblessandfines gravel
.075mm 4.75mm 75mm
-
Clays 4
Whatmakesclayssuchinterestinganddangeroussoilsforfoundations?
Thissimpleexperimentshows the range ofshowstherangeofstrengthforasingleclaysample
-
Clays 5
Thetermclayreferstoanumberofearthymaterialsthatarecomposedofmineralsrichinalumina,silicaandwater.Clayisnotasinglemineral,butanumberofminerals.
Whenmostclaysarewet,theybecomeplastic meaningthatcanbeformedandmoldedintoshapes.
Whenclayisfired,thewaterisdrivenoffandtheybecomey , yashardasstone.
Clay is easily found all over the world. As a result, nearly allClayiseasilyfoundallovertheworld.Asaresult,nearlyallcivilizationshaveusedsomeformofclayforeverythingfrombrickstopotterytotabletsforrecordingbusinesstransactionstransactions.
-
Soilcomposition 6
Thecompositionofsoilandrockisquitedifferentfromthatofothercivilengineeringmaterials.g g
Engineeringpropertiesofsoilsvarysignificantlyfromplace to place and even across a single building siteplacetoplace,andevenacrossasinglebuildingsite.
Soilisaparticulatematerialthatconsistsofindividualparticles.
Soil can contain all three phases of matter (solidSoilcancontainallthreephasesofmatter(solid,liquid,andgas)simultaneously,andthesethreephasescanbepresentinvaryingproportions.p p y g p p
-
Soilasaparticulatematerial 7
Mostcivilengineeringmaterialsconsistofacontinuousmassheldtogetherwithmolecularbonds.
Incontrast,soilisaparticulatematerialthatconsistsofindividualparticlesassembledtogether.g
Itsengineeringpropertiesdependlargelyontheinteractionbetween these particles, only secondarily on their internalbetweentheseparticles,onlysecondarilyontheirinternalproperties.
-
Thethreephases 8
Soilisdifferentfrommostcivilengineeringmaterialsinthatitcansimultaneouslycontainsolid,liquid,andy , q ,gasphases.
The liquid and gas phases are contained in the voidsTheliquidandgasphasesarecontainedinthevoidsorporesbetweenthesolidparticles.
The three phases often interact and these Thethreephasesofteninteract,andtheseinteractionshaveimportanteffectsonsoilsbehavior.
-
Soilcomposition 9
Thesoiliseithercoarseorfinegrained.
Coarse grained are visible to the naked eye: G (gravels) + SCoarsegrainedarevisibletothenakedeye:G (gravels) S(sands)
Finegrainedareinvisibletothenakedeye:M (silts)+C (Clays)
Coarsegrainedsoilsarealsocalledgranularandfinegrainedsoilsarecommonlyreferredtoascohesive.
ThenamegravelcomesfromFrenchwordgreve.ItssymbolisG.
ThesymbolSforsandcomesfromFrenchwordsable.
ThesymbolMforSiltcomesfromSwedishwordmjala.
-
Mechanicalanalysis 10
Mechanicalanalysisisthedeterminationofthesizerangeofparticlespresentinasoil,expressedasapercentage of the total drypercentageofthetotaldryweight.
Two methods used:Twomethodsused: Sieveanalysis:forparticlesizeslargerthan0.075mmingdiameter.
Hydrometeranalysis:forparticlesizessmallerthan0.075mmindiameter.
-
Sieveanalysis 11
-
Sievedesignation larger 12
SieveslargerthantheNo.4sievearedesignatedbythesizeoftheopeningsinthesieve.
Commonlyusedlargersievesizes: 3in. 2in. 1.5 in.1.5in. 1in. 3/4in. 1/2in. 3/8in.
-
Sievedesignation smaller 13
Smallersievesarenumberedaccordingtoth b f i
10openingsthenumberofopeningsperinch.
Commonly used smaller
perinch
Commonlyusedsmallersizesieves: No.4
1 inch
No.10 No.20 No 40No.40 No.60 No.140
N 200No. 10 sieve
No.200
-
USstandardsievesizes 14
SieveNo. Opening(mm) SieveNo. Opening(mm)
3inch 76.200 20 0.8502inch 50.800 25 0.710c 50 800 5 0 01.5inch 38.100 30 0.6001inch 25.400 35 0.5003/4 inch 19.000 40 0.4253/4inch 19.000 40 0.4253/8inch 9.520 50 0.355
4 4.750 60 0.2505 4 000 70 0 2125 4.000 70 0.2126 3.350 80 0.1807 2.800 100 0.1508 2 360 120 0 1258 2.360 120 0.12510 2.000 140 0.10612 1.700 170 0.09014 1 400 200 0 07514 1.400 200 0.07516 1.180 270 0.05318 1.000
-
15
Book:GeotechnicalEngineering(CODUTO)Page115
-
16
Coarsegravel19 0 75 0
Finegravel4 75 19 0 mm 19.0 75.0mm4.75 19.0mm
Coarse SandM di S dFi S d CoarseSand2.00 4.75mm
MediumSand0.425 2.00mm
FineSand0.075 0.425mm
-
Sieveanalysis 17
Soilusedinsieveanalysisisovendriedandalllumpsarebroken.
Thesoilisthenshakenthroughastackofsieveswithopeningofdecreasingsizefromtoptobottom.p g g p
Apanisplacedbelowthestack. Breaking lumps in clayey soils may be difficult Breakinglumpsinclayeysoilsmaybedifficult.
Inthiscase,thesoilmaybemixedwithwatertomakeaslurry and then washed through sievesslurryandthenwashedthroughsieves.
Portionsretainedoneachsievearecollectedseparatelyandovendried.
Massretainedoneachsieveisdetermined.
-
Sieveanalysis calculations 18
Determinethemassofsoilretainedoneachsieve(i.e.M1,M2,...,Mn)andinthepan(i.e.Mp).
Determinethetotalmassofthesoil:M=M1 +M2 +...+Mn+Mp.
Determinethecumulativesoilmassretainedaboveeachsieve.Fortheith sieve,itis(Mi)retained =M1 +M2 +...+Mi.
Themassofsoilpassingtheith sieveis(Mi)passing=M (M1 +M2 +...+Mi).
Thepercentofsoilpassingith sieve(orpercentfiner)isF=(Mi)passing/M100.
-
D10,D30,andD6019
DeterminingD10,D30,andD60
p
a
s
s
i
n
g
60
P
e
r
c
e
n
t
30
10D60D30D10
Grain Diameter
-
Cu andCc20
C ffi i f if iD Coefficient of UniformityHigh Values Indicate Well-Graded Soil10
60
DDCu =
Coefficient of CurvatureValues Between 1-3 ( )
230
DDDCc = Indicate Well-Graded Soil( )1060 DD
Alsocalledcoefficientofgradation,Cz
-
Cu andCc21
D
10
60
DDCu =
2D( )1060
30
DDDCc =
-
Cu andCc22
-
Grainsizedistributioncurve 23
A fi i d ilA:finegrainedsoilsCu =5Cc =0.8
B i d ilB:coarsegrainedsoils
Cu =13Cc =0.83
-
Grainsizedistributioncurve 24
C l d d
Cu =1.63Cc =0.96
C:poorlygradedoruniformlygraded
-
Grainsizedistributioncurve 25
D ll d d il
Cu =190Cc =1.18
D:wellgradedsoils
E:gapgradedsoils
Cu =111C = 0 18Cc =0.18
-
Grainsizedistributioncurve 26
Wellgraded poorlygradedsoil (uniformlygraded)soil
-
27Grain-size distribution curve
3/4 in No 4 No 10 No 40 No 200 Hydrometer3 in
80
1003/4 in. No. 4 No. 10 No. 40 No. 200 Hydrometer 3 in.
60
s
s
i
n
g
D10 =0.10D30 =0.18
40
P
e
r
c
e
n
t
p
a
s
D60 =0.25
Cu = 2.50
0
20Cu 2.50Cc =1.30
0.0010.010.1110
Grain diameter (mm)
GRAVEL SANDSILT or CLAY
Coarse Fine Coarse Medium Fine
-
28
-
Hydrometeranalysis 29
Basedontheprincipalofsedimentationofsoilgrainsinwater.
Particlesinwatersettleatdifferentvelocities,dependingontheirshape,size,weight,andviscosity of waterviscosityofwater.
Particlesareassumedtobespheresandtheirvelocities can be expressed by Stokes law.velocitiescanbeexpressedbyStokeslaw.
2
18Dv ws
=where v = velocity(cm/s)
s = densityofsoilparticles(g/cm3) = density of water (g/cm3)w = densityofwater(g/cm3) = viscosityofwater(gsec/cm2)D = diameterofsoilparticles(cm)
-
Hydrometeranalysis 30
-
StokesLaw 31
2
18Dv ws
= where v = velocity s = densityofsoilparticlesw = densityofwater = viscosityofwaterD = diameterofsoilparticles
L1818 LDi
p
tLvD
wsws
==1818
tLv ==
TimeDistance where
wss G = ( ) tL
GD
ws 1
18=
-
StokesLaw 32
IfLisincm,tisinmin,w ing/cm3, ingsec/cm2,andDinmm,thenequationcanbewrittenas
( )( )
18mm = LD ( ) 60110 tG ws LL30
( ) tLK
tL
GD
ws
== 1
30
( )130 where, = sG
K Assumingw =1g/cm3
-
Stokeslaw 33
ValuesofKforseveralspecificgravityofsolidsandtemperaturecombinations
-
Hydrometeranalysis 34
Whenahydrometerisplacedinthesoilsuspensionatatimet,measuredfromthestartofsedimentation it measures the sp gravity in thesedimentation,itmeasuresthesp.gravityinthevicinityofitsbulbatadepthL.
Hydrometersaredesignedtogivetheamountofsoil,ingrams,thatisstillinsuspension.Theyarecalibratedforsoilsthathaveasp.gravityGsof2.65(forotherGsvalues,correctionisrequired).
Byknowingtheamountofsoilinsuspension,L,andt,wecancalculatethe%ageofsoilbyweightfinerthan a given diameterthanagivendiameter.
ForASTM152Hhydrometer(cm)16402916(cm) RL = (cm)164.029.16 (cm) RL =
whereR=hydrometerreadingcorrectedformeniscus
-
Particleshape 35
Theshapeofsilt,andgravelsvariesfromveryangulartowellrounded.
Angularparticlesarefoundneartherockfromwhichtheyaref d hil d d ti lformed,whileroundedparticlesarefoundfartherawayfromtheirorigin.
Angularparticleshaveagreaterstrengththansmoothones,because it is more difficult tobecauseitismoredifficulttoslidepastoneanother.
Thisiswhycrushedaggregateiss s y c us ed agg egate susedasthebasematerialinpavements.
-
Soil TexturesSoilTextures
To determine the texture of To determine the texture ofa soil sample, find itspercent for sand, silt, andclay.
The texture of the soil willbe where all three linesintersect.
-
Claysoils 37
Soilsthatconsistofsilt,sand,orgravelareprimarilytheresultofphysicalandmildchemicalprocessesandretainmuchofthechemicalstructureoftheirparentrocks.
Claysoilsexperienceextensivechemicalweatheringandareh d i i l i diff f hchangedintoanewmaterialquitedifferentfromtheparentrocks.
A lt th i i ti d b h i f l Asaresult,theengineeringpropertiesandbehaviorofclaysquitedifferentfromothersoils.
-
Clays 38
Physicalcharacteristicsofclaysare:
They can absorb water or lose water from simple humidity Theycanabsorbwaterorlosewaterfromsimplehumiditychanges.
When water is absorbed clays will often expand as the Whenwaterisabsorbed,clayswilloftenexpandasthewaterfillsthespacesbetweenthestackedsilicatelayers.
Due to the absorption of water the specific gravity of clays Duetotheabsorptionofwater,thespecificgravityofclaysishighlyvariableandisloweredwithincreasedwatercontent.
Claystendtoformfromweatheringandsedimentaryprocesseswithonlyafewexamplesofclaysformingin
hprimaryigneousormetamorphicenvironments.
-
Claysoils 39
Clayparticles