Post on 30-Dec-2015
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Field Compaction Field Compaction EquipmentEquipment
and Procedures and Procedures
Dr. Talat BaderDr. Talat Bader
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Objective of field Objective of field CompactionCompaction
&&
Control ParametersControl ParametersThe objective of compaction is to The objective of compaction is to stabilize soils and improve their stabilize soils and improve their engineering behaviorengineering behavior
It is important to keep in mind the It is important to keep in mind the desired engineering properties of the desired engineering properties of the fill, dam, road, etc…fill, dam, road, etc…
The density of the fill in addition to The density of the fill in addition to the water content should be observed.the water content should be observed.From Holtz and Kovacs, 1981
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Design Procedure for Design Procedure for field Compactionfield Compaction
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Design and Selection of Design and Selection of Fill MaterialsFill Materials
1)1) Survey the local soil sources that could Survey the local soil sources that could possibly be used.possibly be used.
2)2) Obtain soil samples from each source Obtain soil samples from each source (borrow), and perform the necessary (borrow), and perform the necessary laboratory tests to classify the soil via either laboratory tests to classify the soil via either AASHTO or the UCS systems to define the propertiAASHTO or the UCS systems to define the properties required for design.es required for design.
The classification itself will often tell whether or not a given soil is suitable for an intended application.
Soils with large shrinkage ratios (SR) should be avoided.
Soils with high plasticity indices (PI) should be avoided, since they indicate a tendency to shrink/expand.
Organic matter which can decay should generally be avoided as fill material unless special precautions are taken.
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Design and Selection of Design and Selection of Fill MaterialsFill Materials
3)3) Once a soil is found to be suitable, for an Once a soil is found to be suitable, for an intended application, perform the necessary intended application, perform the necessary moisture-density study.moisture-density study.
4) If local codes/guidelines are not provided, a 4) If local codes/guidelines are not provided, a study would be needed to determine the study would be needed to determine the minimum relative field compaction of the soil. minimum relative field compaction of the soil. Factors would be:Factors would be: required shear strength of the soilrequired shear strength of the soil maximum allowable settlements under design maximum allowable settlements under design
loadsloads..
5)5) After the earth structure is designed,After the earth structure is designed,– The compaction specifications are written.The compaction specifications are written.– Field compaction Field compaction control testscontrol tests are specified, are specified,– And the results of these become the standard for And the results of these become the standard for
controlling the project.controlling the project.
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SpecificationsSpecifications1)1) End-product specificationsEnd-product specifications
This specification is used for most highways This specification is used for most highways and building foundation, as long as the and building foundation, as long as the contractor is able to obtain the specified contractor is able to obtain the specified relative compactionrelative compaction , how he obtains it doesn’t , how he obtains it doesn’t matter, nor does the equipment he uses.matter, nor does the equipment he uses.
Care the results only !Care the results only !
2)2) Method specificationsMethod specificationsThe type and weight of roller, the number of The type and weight of roller, the number of passes of that roller, as well as the lift passes of that roller, as well as the lift thickness are specified. A maximum allowable thickness are specified. A maximum allowable size of material may also be specified.size of material may also be specified.
It is typically used for large compaction It is typically used for large compaction project.project.
From Holtz and Kovacs, 1981
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Standard & ModifiedStandard & ModifiedProctor TestProctor Test
Dry
Den
sit
y (
d)
Water Content (w)
Modified
Standard
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Field & Laboratory Field & Laboratory CompactionCompaction
•It is difficult to choose a It is difficult to choose a laboratory test that laboratory test that reproduces a given field reproduces a given field compaction procedure.compaction procedure.
•The laboratory curves The laboratory curves generally yield a generally yield a somewhat lower somewhat lower optimum water content optimum water content than the actual field than the actual field optimum.optimum.
•The majority of field The majority of field compaction is compaction is controlled by the controlled by the dynamic laboratory dynamic laboratory teststests..
Curve 1, 2,3,4: laboratory compaction
Curve 5, 6: Field compaction
(From Lambe and Whitman, 1979)
S = 100%
S = 100%
4
Dry
Den
sit
y (
lb/f
t3)
120120
110110
100100
9090
Dry
Den
sit
y (
Mg
/m3)
1.91.9
1.81.8
1.71.7
1.61.6
1.51.5
Water Content (w)
1010 1515 2020 2525
1
65
2
3
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Smooth-wheel roller Smooth-wheel roller (drum)(drum)
100% coverage under 100% coverage under the wheelthe wheel
Contact pressure up to Contact pressure up to 380 kPa380 kPa
Can be used on all soil Can be used on all soil types except for rocky types except for rocky soils.soils.
Compactive effort: Compactive effort: static weight static weight
The most common use The most common use of large smooth wheel of large smooth wheel rollers is for proof-rollers is for proof-rolling subgrades and rolling subgrades and compacting asphalt compacting asphalt pavement.pavement.
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Smooth-wheel roller Smooth-wheel roller (drum)(drum)
Suitable for:Suitable for:– well-graded sands well-graded sands
and gravelsand gravels– silts and clays of low silts and clays of low
plasticityplasticity
Unsuitable for:Unsuitable for:– uniform sands;uniform sands;– silty sands;silty sands;
– soft clayssoft clays
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Pneumatic (or rubber-tired) Pneumatic (or rubber-tired) rollerroller
80% coverage under the wheel
Contact pressure up to 700 kPa
7 to 13 wheels are arranged in two rows.
Compactive effort: static weight and kneading.
Direction of Motion
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Pneumatic (or rubber-tired) Pneumatic (or rubber-tired) rollerroller
Small Tired RollerStraight rollingWobble Action
Heavy Tire Roller50 to 100 tonsTire pressure 90-150 psiAdditional weight
– Water, Sand or Steel
Can be used for both granular and fine-grained soils.
Can be used for highway fills or earth dam construction.
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Pneumatic (or rubber-tired) Pneumatic (or rubber-tired) rollerroller
Suitable for: most – Coarse– fine soils.
Unsuitable for:– very soft clay– highly variable
soils
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Sheepsfoot rollersSheepsfoot rollersHas many round or Has many round or rectangular shaped rectangular shaped protrusions or “feet” protrusions or “feet” attached to a steel drumattached to a steel drum
8% ~ 12 % coverage8% ~ 12 % coverage
Contact pressure is from Contact pressure is from 1400 to 7000 kPa1400 to 7000 kPa
It is best suited for It is best suited for clayed soils.clayed soils.
Compactive effort: static Compactive effort: static weight and kneading.weight and kneading.
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loose liftof soil
compacted lift
(a)
loose liftof soil
compacted lift
(b)
Heavy footed compactors Heavy footed compactors with large feet that fully with large feet that fully penetrate a loose lift of penetrate a loose lift of soil are ideal.soil are ideal.
Minimum Minimum specifications:specifications:
• weight : 18000 kgweight : 18000 kg
• foot length: 18 cm to 20 foot length: 18 cm to 20 cmcm
• number of passes: 5number of passes: 5
footfoot
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Drum may be loaded Drum may be loaded withwith
WaterWater
SoilSoil
Loaded weight Vary Loaded weight Vary fromfrom
6,000 #6,000 #
80,000 #80,000 #
DrumDrum
Drum Length from 48” to 72”
Drum Diameter from 40” to 72”
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Sheepsfoot rollersSheepsfoot rollers
Suitable for:Suitable for:– fine grained soilsfine grained soils– sands and sands and
gravels, with gravels, with >20% fines>20% fines
Unsuitable for:Unsuitable for:– very coarse soilsvery coarse soils– uniform gravelsuniform gravels
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Tamping foot rollerTamping foot roller
About 40% coverage About 40% coverage
Contact pressure is Contact pressure is from 1400 to 8400 from 1400 to 8400 kPakPa
It is best for It is best for compacting fine-compacting fine-grained soils (silt grained soils (silt and clay).and clay).
Compactive effort: Compactive effort: static weight and static weight and kneading.kneading.
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Mesh (or grid pattern) Mesh (or grid pattern) rollerroller
50% coverage50% coverage
Masses range from 5-12 Masses range from 5-12 TonesTones
Contact pressure is from Contact pressure is from 1400 to 6200 kPa1400 to 6200 kPa
Compactive effort: static Compactive effort: static weight and vibration.weight and vibration.
High towing speed, the High towing speed, the material is vibrated, material is vibrated, crushed, and impacted.crushed, and impacted.
Suitable for:Suitable for:– well-graded sandswell-graded sands– soft rockssoft rocks– stony soils with fine fractionsstony soils with fine fractions
Unsuitable for:Unsuitable for:– uniform sandsuniform sands– Silty sandsSilty sands– Very soft clays Very soft clays
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Vibrating drum on smooth-Vibrating drum on smooth-wheel rollerwheel roller
Vertical vibrator attached Vertical vibrator attached to smooth wheel rollers.to smooth wheel rollers.
The best explanation of The best explanation of why roller vibration why roller vibration causes densification of causes densification of granular soils is that granular soils is that particle rearrangement particle rearrangement occurs due to cyclic occurs due to cyclic deformation of the soil deformation of the soil produced by the produced by the oscillations of the roller.oscillations of the roller.
Compactive effort: static Compactive effort: static weight and vibration.weight and vibration.
Suitable for granular Suitable for granular soilssoils
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Vibrating Plate & Power Vibrating Plate & Power RammerRammer
Range from hand-guided Range from hand-guided machines to larger roller machines to larger roller combinations combinations
Suitable for:Suitable for:– most soils with low to most soils with low to
moderate fines moderate fines content content
Unsuitable for:Unsuitable for:– large volume worklarge volume work– wet clayey soilswet clayey soils
Also called a 'trench Also called a 'trench tamper' tamper'
Hand-guided pneumatic Hand-guided pneumatic tamper tamper
Suitable for:Suitable for:– trench back-filltrench back-fill– work in confined areas work in confined areas
Unsuitable for:Unsuitable for:– large volume worklarge volume work
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Compactor Zones of Compactor Zones of ApplicationApplication
SheepsfootSheepsfoot
High speed tamping footHigh speed tamping foot
Towed tamping footTowed tamping foot
Multitired pneumaticMultitired pneumatic
Smooth steel drumsSmooth steel drums
VibratoryVibratory
GridGrid
Heavy pneumaticHeavy pneumatic
Static wt, KneadingStatic wt, Kneading
Static wt, KneadingStatic wt, Kneading
Static wt, VibrationStatic wt, Vibration
Static wtStatic wt
Static wt, KneadingStatic wt, Kneading
Static wt, KneadingStatic wt, Kneading
Static wt, KneadingStatic wt, Kneading
100 %100 %ClayClay
100 %100 %SandSand RockRock Compactive EffortCompactive Effort
Static wt, Kneading, impact, VibrationStatic wt, Kneading, impact, Vibration
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Equipments & Soil TypeEquipments & Soil Type
Special compaction equipment is Special compaction equipment is then used to compact this lift of soil:then used to compact this lift of soil:
Equipment TypeEquipment Type • Smooth-Wheeled Rollers• Pneumatic Rubber-Tired
Rollers• Sheepsfoot Rollers• Vibratory Rollers• Vibratory Tampers
Soil TypeSoil Type • sands & gravels • silts & clays • silts & clays• sands & gravels • sands & gravels
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Variables-Vibratory Variables-Vibratory CompactionCompaction
There are many variables which control the There are many variables which control the vibratory compaction or densification of vibratory compaction or densification of soils.soils.
Characteristics of the compactor:Characteristics of the compactor:(1) Mass, size(1) Mass, size(2) Operating frequency and frequency range(2) Operating frequency and frequency range
Characteristics of the soil:Characteristics of the soil:(1) Initial density(1) Initial density(2) Grain size and shape(2) Grain size and shape(3) Water content(3) Water content
Construction procedures:Construction procedures:(1) Number of passes of the roller(1) Number of passes of the roller(2) Lift thickness(2) Lift thickness(3) Frequency of operation vibrator(3) Frequency of operation vibrator(4) Towing speed(4) Towing speed
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Roller PassesRoller Passes
When compacting When compacting past five or so past five or so coverage's, there coverage's, there is not a great is not a great increase in densityincrease in density
240 cm think layer of 240 cm think layer of northern Indiana dune northern Indiana dune sandsand
5670 kg roller 5670 kg roller operating at a operating at a frequency of 27.5 Hz.frequency of 27.5 Hz.
Holtz and Kovacs, 1981
02 roller passes 05 roller passes 15 roller passes
45 roller passes
40 50 60 70 80 90 100Relative Density (%)
95 100 105 110
Dry density (lb/ft3)
0
2
3
4
5
6
1
Depth
(f
t)
Init
ial fill
densi
ty
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Roller PassesRoller Passes
Low Low Compaction at Compaction at the surfacethe surface
Max. Dr. is Max. Dr. is approximately ½ approximately ½ meter bellow the meter bellow the surface.surface.
Most effective Most effective compaction is compaction is done during the done during the first 5-7 passes.first 5-7 passes.
Holtz and Kovacs, 1981
02 roller passes 05 roller passes 15 roller passes
45 roller passes
40 50 60 70 80 90 100Relative Density (%)
95 100 105 110
Dry density (lb/ft3)
0
2
3
4
5
6
1
Depth
(f
t)
Init
ial fill
densi
ty
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Density-depth relationship for large liftlarge lift height
using 5 roller passes
Determine the Lift Determine the Lift HeightHeight
0.0
0.5
1.0
0.5
Minimum Minimum allowable allowable relative relative
density = density = 75%75%
60 70 80 90500
1
2
3
4
5
6
Relative density (%)Relative density (%)
Depth
(ft
) D
epth
(ft
) (m
)(m
)
For most For most compaction compaction equipment, equipment, lift lift thicknesses thicknesses should should typically be typically be on the on the order of six order of six inches (6") inches (6") or 15cm if or 15cm if no no experience experience or testingor testing
1818 inin
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Determine the Lift Determine the Lift HeightHeight
0.0
0.5
1.0
0.5 Density-depth relationship for large liftlarge lift height
using 5 roller passes
60 70 80 90500
1
2
3
4
5
6
Relative density (%)Relative density (%)
Depth
(ft
) D
epth
(ft
) (m
)(m
)
For most For most compaction compaction equipment, equipment, lift lift thicknesses thicknesses should should typically be typically be on the on the order of six order of six inches (6") inches (6") or 15cm if or 15cm if no no experience experience or testingor testing
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Lift ThicknessLift ThicknessIf lift thicknesses are too large:If lift thicknesses are too large:Soil at the top of the lift will be well-Soil at the top of the lift will be well-
compacted. compacted. Soil at the bottom of the lift will not Soil at the bottom of the lift will not
be compacted. be compacted. Why?Why?This is sometimes called the Oreo-This is sometimes called the Oreo-
Cookie effectCookie effect..
The Wheel of compaction equipmentThe Wheel of compaction equipment
High stress region is well-compactedHigh stress region is well-compactedLow stress region is not Well Low stress region is not Well compactedcompacted
FF
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FrequencyFrequency• Compacted Compacted Density Density increases with increases with increasing increasing operation operation frequency.frequency.
• The operating The operating frequency frequency should be at should be at least as large as least as large as the resonant the resonant frequency to frequency to obtain the most obtain the most efficient use of efficient use of thethe
95 100 105 110
Dry density (lb/ft3)
0
2
3
4
5
6
1
Depth
(f
t)
40 50 60 70 80 90 100Relative Density (%)
20 Hz 30 Hz
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FrequencyFrequency
The frequency at The frequency at which a which a
maximum maximum density is density is
achieved is achieved is called the called the optimum optimum
frequency.frequency.Roller wt. in lb
= 3600 = 5800 = 7500a = 7500b = 17000
1000 2000 3000
150
140
130
120
110
100
90
Dry
Densi
ty (
lb/f
t3)
Vibration frequency (cpm)
Heavy clay
Heavy clayHeavy clay
Clay soil
Gravelly sand
Gravel-sand-clay
Uniform sand
Well-graded sand
Gravelly sand
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StressesStresses
)()(@)( passiveprestoactivea KKK
Horizontal stress measurements indicated that Horizontal stress measurements indicated that lateral stresses are much grater than at rest lateral stresses are much grater than at rest condition.condition.
20
1.0
3.0
2.0
0 84 12 16
Dry
Densi
ty (
lb/f
t3)
Lateral stresses were found to increase with Lateral stresses were found to increase with
Number of passesNumber of passes
Operating frequenciesOperating frequencies
v
h
v
hoK
Parallel to roller pathPerpendicular to
roller path
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Roller Travel SpeedRoller Travel SpeedFor a given number For a given number of passes, a higher of passes, a higher density is obtained if density is obtained if the vibrator is towed the vibrator is towed more slowly.more slowly.
20
110
140
130
120
100
0 84 12 16
1.60
2.00
1.90
1.80
1.70
110
100
090
080 1.28
1.76
1.64
1.52
1.40
2.25 mph
1.50 mph
0.75 mph
Dry
Densi
ty (
lb/f
t3)
Roller Coverage
Mg/m
3 For the same speed, For the same speed, the higher the the higher the number of passes number of passes the higher the the higher the densitydensity
Well graded sand(moisture = 7.5 %)
Heavy clay(moisture = 21 %)