V Compaction - Universitas Brawijaya...Standard and Modified Proctor Compaction Test (Cont.) Summary of Modified Proctor Compaction Test Specifications (ASTM D-698, AASHTO) 16 Das,

VCompaction

1

Courtesy of U.S. WICK DRAIN, INC.

Outline

1. Soil Improvement2. Compaction3. Theory of Compaction4. Properties and Structure of Compacted Fine-

Grained Soils

2

4. Properties and Structure of Compacted Fine-Grained Soils

5. Field Compaction Equipment and Procedures6. Field Compaction Control and Specifications7. Estimating Performance of Compacted Soils8. Suggested Homework9. References

1. Soil Improvement

3

1.1 Methods for Soil Improvement

GroundReinforcement

GroundImprovement

GroundTreatment

• Stone Columns• Soil Nails• Deep Soil Nailing• Micropiles (Mini-piles)

• Deep Dynamic Compaction

• Drainage/Surcharge• Electro-osmosis

• Soil Cement• Lime Admixtures• Flyash• Dewatering

4

• Micropiles (Mini-piles)• Jet Grouting• Ground Anchors• Geosynthetics• Fiber Reinforcement• Lime Columns• Vibro-Concrete Column• Mechanically Stabilized

Earth• Biotechnical

• Electro-osmosis• Compaction grouting• Blasting• Surface Compaction

• Dewatering• Heating/Freezing• Vitrification

Compaction

Shaefer, 1997

1.1 Methods for Soil Improvement-Jet Grouting

5Courtesy of Menard-soltraitement

1.1 Methods for Soil Improvement-Soil Nailing

6

Courtesy of Atlas Copco Rock Drilling Equipment

1.2 Elephant and Compaction

Question?

The compaction result is not good. Why?

He He! I’m smart.

7

Heavy Weight

2. Compaction

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2.1 Compaction and Objectives

Compaction•Many types of earth construction, such as dams, retaining walls,highways, and airport, require man-placed soil, or fill. Tocompact a soil,that is, to place it in a dense state.

•The dense state is achieved through the reduction of the airvoids in thesoil, with little or no reductionin the water content. This processmust

9

soil, with little or no reductionin the water content. This processmustnot be confused with consolidation, in which water is squeezed out underthe action of a continuous static load.

Objectives:(1) Decrease future settlements

(2) Increase shear strength

(3) Decrease permeability (From Lambe, 1991; Head, 1992)

2.2 General Compaction Methods

Coarse-grained soils Fine-grained soils

•Falling weight and hammers

•Kneading compactors

•Static loading and pressLabo

rato

ry

•Vibrating hammer (BS)

dough

10

•Hand-operated vibration plates

•Motorized vibratory rollers

•Rubber-tired equipment

•Free-falling weight; dynamiccompaction (low frequencyvibration, 4~10 Hz)

•Hand-operated tampers

•Sheepsfoot rollers

•Rubber-tired rollers

Fie

ld

Vibration(Holtz and Kovacs, 1981; Head, 1992)

Kneading

3. Theory of Compaction(Laboratory Test)

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3.1 Laboratory Compaction

OriginThe fundamentals of compaction offine-grained soilsare relatively new.R.R. Proctor in the early 1930’swas building dams for the old Bureau ofWaterworks and Supply in Los Angeles, and he developed the principlesof compaction in a series of articles in Engineering News-Record. In hishonor, the standard laboratory compaction test which he developed iscommonly called theproctor test.Purpose

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PurposeThe purpose of a laboratory compaction test is to determinethe properamount of mixing water to use when compacting the soil in the field andtheresulting degree of denseness which can be expected from compactionat this optimum waterImpact compactionThe proctor test is animpact compaction. A hammer is dropped severaltimes on a soil sample in a mold.The mass of the hammer, height of drop,number of drops, number of layers of soil, and the volume of the mold arespecified.

3.1.1 Various Types

Various types of compaction test

1

13

2

3

1: your test 2: Standard Proctor test 3: Modified Proctor test

3.1.2 Test Equipment

Standard Proctor test equipment

14Das, 1998

3.1.3 Comparison-Standard and Modified Proctor Compaction Test

Summary of Standard Proctor Compaction Test Specifications (ASTM D-698, AASHTO)

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Das, 1998

3.1.3 Comparison-Standard and Modified Proctor Compaction Test (Cont.)

Summary of Modified Proctor Compaction Test Specifications (ASTM D-698, AASHTO)

16

Das, 1998

3.1.3 Comparison-Summary

Standard Proctor Test

12 in height of drop

5.5 lb hammer

25 blows/layer

Modified Proctor Test

18 in height of drop

10 lb hammer

25 blows/layer

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25 blows/layer

3 layers

Mold size: 1/30 ft3

Energy 12,375 ft· lb/ft3

25 blows/layer

5 layers

Mold size: 1/30 ft3

Energy 56,250 ft· lb/ft3

Higher compacting energy

3.1.4 Comparison-Why?

• In the early days of compaction, because construction equipment wassmall and gave relatively low compaction densities, a laboratorymethod that used a small amount of compacting energy was required.As construction equipment and procedures were developed which gavehigher densities, it became necessary to increase the amount ofcompactingenergyin thelaboratorytest.

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compactingenergyin thelaboratorytest.

• The modified test was developed during World War II by the U.S.Army Corps of Engineering to better represent the compaction requiredfor airfield to support heavy aircraft. The point is thatincreasing thecompactive effort tends to increase the maximum dry density, asexpected, but also decrease the optimum water content.

(Holtz and Kovacs, 1981; Lambe, 1991)

3.2 Variables of CompactionProctor established that compaction is a function of four variables:

(1)Dry density (ρd) or dry unit weight γd.

(2)Water content w

(3)Compactive effort (energy E)

(4)Soil type (gradation, presence of clay minerals, etc.)

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(4)Soil type (gradation, presence of clay minerals, etc.)

)ft/lbft375,12(m/kJ7.592

m10944.0

)layer/blows25)(layers3)(m3048.0)(s/m81.9(kg495.2E

33

33

2

⋅

−

=

×=

Volume of mold

Number of blows per layer

Number of layers

Weight of hammer

Height of drop of hammer

× × ×E =

For standard Proctor test

3.3 Procedures and ResultsProcedures(1) Several samples of the same soil, but at different water contents, are

compacted according to the compaction test specifications.

The first four blowsThe successive blows

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(2) The total or wet density and the actual water content of eachcompacted sample are measured.

(3) Plot the dry densitiesρd versus water contents w for each compactedsample. The curve is called as acompaction curve.

w1,

VM

dt

t

+ρ=ρ=ρ Derive ρd from the known ρ

and w

3.3 Procedures and Results (Cont.)

Results

Zero air void

(Mg/

m3 )

(lb/ft

3 )

Line of optimums

Peak point

Line of optimum

Zero air voidρd max

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Water content w (%)

Dry

de

nsity

ρ d(M

g/m

Dry

de

nsity

ρ d

Modified Proctor

Standard Proctor

Zero air void

Holtz and Kovacs, 1981

ρd max

wopt


The peak point of the compaction curveThe peak point of the compaction curve is the point withthe maximumdry densityρd max. Corresponding to the maximum dry densityρd max is awater content known as theoptimum water content wopt (also known asthe optimum moisture content,OMC). Note that the maximum dry densityis only a maximum for a specific compactive effort and methodofcompaction. This doesnot necessarilyreflect the maximumdry density

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compaction. This doesnot necessarilyreflect the maximumdry densitythat can be obtained in the field.

Zero air voids curveThe curve represents the fully saturated condition(S = 100 %). (It cannotbe reached by compaction)

Line of optimumsA line drawn through the peak points ofseveral compaction curves atdifferent compactive efforts for the same soilwill be almost parallel to a100 % S curve, it is called the line of optimums


w

w

wd S

SS

+

ρ=ρ+

ρ=ρ

The Equation for the curves with different degree of saturation is :

23

ss

wd

GS

wSw +ρρ+

s

sd

wGSee1

=+ρ=ρ

You can derive the equation by yourself

Hint:


(wopt, ρd max)

3.3 Procedures and Results-Explanation

Below wopt(dry side of optimum):

As the water content increases, the particlesdevelop larger and larger water films aroundthem, which tend to “lubricate” the particlesand make them easier to be moved about andreoriented into a denser configuration.

Lubrication or loss of suction??

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w

ρdAt wopt:

The density is at the maximum, and it doesnot increase any further.

Above wopt(wet side of optimum):

Water starts to replace soil particles in themold, and sinceρw << ρs the dry densitystarts to decrease.


3.3 Procedures and Results-Notes

• Each data point on the curve represents a singlecompaction test, and usually four or five individualcompaction tests are required to completely determine thecompaction curve.

• At least two specimens wet and two specimens dry ofoptimum,andwatercontentsvaryingby about2%.

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optimum,andwatercontentsvaryingby about2%.• Optimum water content is typically slightly less than the

plastic limit (ASTM suggestion).• Typical values of maximumdry density are around 1.6 to

2.0 Mg/m3 with the maximumrange fromabout 1.3 to 2.4Mg/m3. Typical optimumwater contents are between 10%and 20%, with an outside maximumrange of about 5% to40%.


3.4 Effects of Soil Types on CompactionThe soil type-that is, grain-size distribution, shape of the soil grains,specific gravity of soil solids, and amount and type of clay mineralspresent.

26Holtz and Kovacs, 1981; Das, 1998

3.5 Field and Laboratory Compaction

• It is difficult to choose alaboratory test thatreproduces a given fieldcompaction procedure.

•The laboratory curves

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•The laboratory curvesgenerally yield a somewhatlower optimum water contentthan the actual fieldoptimum.

•The majority of fieldcompaction is controlled bythedynamic laboratory tests. Curve 1, 2,3,4: laboratory compaction

Curve 5, 6: Field compaction

(From Lambe and Whitman, 1979)

4. Properties and Structure of Compacted Fine-grained Soils

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4.1 Structure of Compacted Clays

•For a given compactiveeffort and dry density, thesoil tends to be moreflocculated (random) forcompaction on the dry sideascomparedon thewetside.

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ascomparedon thewetside.

•For a given molding watercontent, increasing thecompactive effort tends todisperse (parallel, oriented)the soil, especially on thedry side.

Lambe and Whitman, 1979

4.2 Engineering Properties-Permeability

• Increasing the water contentresults in a decrease inpermeability on the dry side ofthe optimum moisture contentand a slight increase inpermeabilityon the wet side of

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permeabilityon the wet side ofoptimum.

• Increasing the compactive effortreduces the permeabilitysince itboth increases the dry density,thereby reducing the voidsavailable for flow, and increasesthe orientation of particles.

From Lambe and Whitman, 1979; Holtz and Kovacs, 1981

4.3 Engineering Properties-Compressibility

At low stresses the sample compacted onthe wet side ismore compressible than the one compacted on the dry side.

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4.3 Engineering Properties-Compressibility

At the high applied stresses the sample compacted on the dry sideis more compressible than the sample compacted on the wet side.

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4.4 Engineering Properties-Swelling

• Swelling of compacted clays is greater for those compacteddry of optimum. They have a relatively greater deficiencyof water and therefore have a greater tendency to adsorbwater and thus swell more.

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w

ρd

(wopt, ρd max)Higher swelling potential

From Holtz and Kovacs, 1981

Higher shrinkage potential

4.5 Engineering Properties-Strength

Samples (Kaolinite)compacted dry ofoptimum tend to bemore rigid andstronger thansamples compactedwetof optimum

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wetof optimum

From Lambe and Whitman, 1979

4.5 Engineering Properties-Strength (Cont.)

The CBR (California bearing ratio)

CBR= the ratio between resistance requiredto penetrate a 3-in2 piston into thecompacted specimen and resistance

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compacted specimen and resistancerequired to penetrate the same depth into astandard sample ofcrushed stone.


A greater compactive effort produces agreater CBR for the dry of optimum.However, the CBR is actually less forthe wet of optimum for the highercompaction energies (overcompaction).

4.6 Engineering Properties-Summary

Dry side Wet side

Permeability

Structure More random More oriented (parallel)

More permeable

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Compressibility

Swelling

Strength

More compressible in high pressure range

More compressible in low pressure range

Swell more, higher water deficiency

Higher

Please see Table 5-1

*Shrink more

4.6 Engineering Properties-Summary (Cont.)

Please find this table in the handout

37Holtz and Kovacs, 1981

4.6 Engineering Properties-Notes

• Engineers must consider not only the behavior of the soil as compactedbut the behavior of the soil in the completed structure, especially at thetime when the stability or deformation of the structure is most critical.

• For example, consider an element of compacted soil in a dam core. As theheightof thedamincreases,thetotal stresseson thesoil elementincrease.

38

heightof thedamincreases,thetotal stresseson thesoil elementincrease.When the dam is performing its intended function of retaining water, thepercent saturation of the compacted soil element is increased by thepermeating water.Thus the engineer designing the earth dam mustconsider not only the strength and compressibility of the soil element ascompacted, but also its properties after is has been subjected to increasedtotal stresses and saturated by permeating water.

Lambe and Whitman, 1979

5. Field Compaction Equipmentand Procedures

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5.1 Equipment

Smooth-wheel roller (drum) • 100% coverage under the wheel

• Contact pressure up to 380 kPa

• Can be used on all soil typesexcept for rocky soils.

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• Compactive effort: static weight

• The most common use of largesmooth wheel rollers is for proof-rolling subgrades and compactingasphalt pavement.


5.1 Equipment (Cont.)

Pneumatic (or rubber-tired) roller• 80% coverage under the wheel

• Contact pressure up to 700 kPa

• Can be used for both granular andfine-grained soils.

41

• Compactive effort: static weightand kneading.

• Can be used for highway fills orearth dam construction.



Sheepsfoot rollers • Has many round or rectangularshaped protrusions or “feet”attached to a steel drum

• 8% ~ 12 % coverage

• Contact pressureis from 1400 to

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• Contact pressureis from 1400 to7000 kPa

• It is best suited forclayed soils.




Tamping foot roller • About 40% coverage

• Contact pressure is from 1400 to8400 kPa

• It is best for compacting fine-grainedsoils(silt andclay).

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grainedsoils(silt andclay).




Mesh (or grid pattern) roller • 50% coverage

• Contact pressure is from 1400 to6200 kPa

• It is ideally suited for compactingrocky soils, gravels, and sands.

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rocky soils, gravels, and sands.With high towing speed, thematerial is vibrated, crushed, andimpacted.

• Compactive effort: static weightand vibration.



Vibrating drum on smooth-wheel roller

• Vertical vibrator attached tosmooth wheel rollers.

• The best explanation of why rollervibration causes densification ofgranular soils is that particle

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granular soils is that particlerearrangement occurs due to cyclicdeformation of the soil producedby the oscillations of the roller.

• Compactive effort: static weightand vibration.

• Suitable for granular soils


5.1 Equipment-Summary


5.2 Variables-Vibratory Compaction

There are many variables which control the vibratory compaction or densification of soils.Characteristics of the compactor:(1) Mass, size(2) Operating frequency and frequency range

Characteristics of the soil:

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Characteristics of the soil:(1) Initial density(2) Grain size and shape(3) Water content

Construction procedures:(1) Number of passes of the roller(2) Lift thickness(3) Frequency of operation vibrator(4) Towing speed


5.2.1 Frequency

The frequency at whicha maximum density isachieved is called theoptimum frequency.


5.2.2 Roller Travel Speed

For a given number ofpasses, a higher density isobtained if the vibrator istowed more slowly.


5.2.3 Roller Passes

When compactingpast five or socoverages, there isnot a great increasein density


•240 cm think layerof northern Indianadune sand

•5670 kg rolleroperating at afrequency of 27.5Hz.

5.2.4 Determine the Lift Height


5.3 Dynamic Compaction

Dynamic compaction was first used in Germany in the mid-1930’s.

The depth of influence D, in meters, of soil undergoing compaction is conservatively given by

52

D ≈ ½ (Wh)1/2

W = mass of falling weight in metric tons.

h = drop height in meters


5.4 Vibroflotation

Vibroflotation is a technique forin situ densification of thicklayers of loose granular soildeposits. It was developed inGermany in the 1930s.

53From Das, 1998

5.4 Vibroflotation-Procedures

54

Stage1: The jet at the bottom of the Vibroflot is turned on and lowered into the ground

Stage2: The water jet creates a quick condition in the soil. It allows the vibrating unit to sink into the ground

Stage 3: Granular material is poured from the top of the hole. The water from the lower jet is transferred to he jet at the top of the vibrating unit. This water carries the granular material down the hole

Stage 4: The vibrating unit is gradually raised in about 0.3-m lifts and held vibrating for about 30 seconds at each lift. This process compacts the soil to the desired unit weight.

From Das, 1998

6. Field CompactionControl and Specifications

55

6.1 Control Parameters

• Dry density and water content correlate well with theengineering properties, and thus they are convenientconstruction control parameters.

• Sincethe objectiveof compactionis to stabilizesoils and

56

• Sincethe objectiveof compactionis to stabilizesoils andimprove their engineering behavior, it is important to keepin mind the desired engineering properties of the fill, notjust its dry density and water content. This point is oftenlost in the earthwork construction control.


6.2 Design-Construct Procedures

• Laboratory testsare conducted on samples of the proposedborrow materials to define the properties required fordesign.

• After the earth structure is designed,the compactionspecificationsare written. Field compactioncontrol tests

57

specificationsare written. Field compactioncontrol testsare specified, and the results of these become the standardfor controlling the project.


6.3 Specifications

(1) End-product specifications

This specification is used for most highways and buildingfoundation, as long as the contractor is able to obtain thespecified relative compaction , how he obtains it doesn’tmatter,nor doestheequipmentheuses.

58

matter,nor doestheequipmentheuses.

Care the results only !

(2) Method specifications

The type and weight of roller, the number of passes of thatroller, as well as the lift thickness are specified. A maximumallowable size of material may also be specified.

It is typically used for large compaction project.


6.4 Relative Compaction (R.C.)

%100.C.Rlaboratorymaxd

filedd ×ρ

ρ=−

−

Relative compaction or percent compaction

59

rD2.080.C.R +=

Correlation between relative compaction (R.C.) and the relative density Dr

It is a statistical resultbased on 47 soilsamples.

As Dr = 0, R.C. is 80

Typical required R.C. = 90% ~ 95%

6.5 Determine the Water Content (in Field)

Control

(1) Relative compaction

(2) Water content (dry side or wet side)

100% saturation

ρ d

ρd max

Line of optimums

90% R.C.


Note: the engineeringproperties may be differentbetween the compactedsample at the dry side and atthe wet side.

Water content w %

wopt

Dry

den

sity

, ρ

12

3

a c

Increase compaction energy

b

6.6 Determine the Relative Compaction in the Field

Where and When• First, the test site is selected. It should be representative or typical of the

compacted lift and borrow material. Typical specifications call for a newfield test for every 1000 to 3000 m2 or so, or when the borrow materialchanges significantly. It is also advisable to make the field test at leastoneor maybetwo compactedlifts below the alreadycompactedground

61

oneor maybetwo compactedlifts below the alreadycompactedgroundsurface, especially when sheepsfoot rollers are used or in granular soils.

Method• Field control tests, measuring the dry density and water content in the

field can either bedestructive or nondestructive.


6.6.1 DestructiveMethodsMethods(a) Sand cone

(b) Balloon

(c) Oil (or water) method

Calculations

(a)

(b)


Calculations•Know Ms and Vt

•Get ρd field and w (water content)

•Compare ρd field with ρd max-lab

and calculate relative compaction R.C.

(c)

6.6.1 Destructive Methods (Cont.)

Sometimes, the laboratory maximumdensity may not beknown exactly. It is not uncommon, especially in highwayconstruction, for a series of laboratory compaction tests to beconducted on “representative” samples of the borrowmaterialsfor the highway. If the soils at the site are highly

63

materialsfor the highway. If the soils at the site are highlyvaried, there will be no laboratory results to be comparedwith. It is time consuming and expensive to conduct a newcompaction curve. The alternative is to implement afieldcheck point, or 1 point Proctor test.



Check Point Method

Dry

den

sity

, ρd

100% saturationLine of optimums

A

•1 point Proctor test

•Known compaction curves A, B, C

64Water content w %

wopt

Dry

den

sity

,

ρd maxB

M

C

X

Y(no)curves A, B, C

•Field check point X (it should be on the dry side of optimum)



• The measuring error is mainly fromthe determination ofthe volume of the excavated material.

For example,• For the sand cone method, the vibration from nearby working

equipment will increase the density of the sand in the hole, which willgivesa largerholevolumeanda lower field density.

65

givesa largerholevolumeanda lower field density.

• If the compacted fill is gravel or contains large gravel particles. Anykind of unevenness in the walls of the hole causes a significant error inthe balloon method.

• If the soil is coarse sand or gravel, none of the liquid methods workswell, unless the hole is very large and a polyethylene sheet is used tocontain the water or oil.

tsfieldd V/M=ρ −


6.6.2 NondestructiveMethodsNuclear density meter(a) Direct transmission

(b) Backscatter

(c) Air gap

(a)

PrinciplesDensity

66


(b)

(c)

DensityThe Gamma radiation is scattered by the soilparticles and the amount of scatter isproportional to the total density of the material.The Gamma radiation is typically provided bythe radium or a radioactive isotope of cesium.

Water contentThe water content can be determined based onthe neutron scatter by hydrogen atoms. Typicalneutron sources are americium-berylliumisotopes.

6.6.2 Nondestructive Methods (Cont.)

CalibrationCalibration against compacted materials of known density isnecessary, and for instruments operating on the surface thepresence of an uncontrolled air gap can significantly affectthemeasurements.

67

themeasurements.

7. Estimating Performance of Compacted Soils

68

7.1 Definition of Pavement Systems


7.2 Characteristics Pertinent to Roads and Airfield

70

Please refer to the handoutHoltz and Kovacs, 1981

7.2 Characteristics Pertinent to Roads and Airfield (Cont.)


Please refer to the handout

7.3 Engineering Properties of Compacted Soils


Please refer to the handout

8. Suggested Homework

1. Read Chapter 5 (Holtz’s book)

2. Example 5.1 ~ Example 5.4

3. Problem 5.9, 5.12, 5.14

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9. References

Main References:Holtz, R.D. and Kovacs, W.D. (1981). An Introduction to Geotechnical

Engineering, Prentice Hall. (Chapter 5)

Others:Das, B.M. (1998). Principles of Geotechnical Engineering, 4th edition,

PWS Publishing Company.

74

PWS Publishing Company.

Lambe, T.W. and Whitman, R.V. (1979). Soil Mechanics, SI Version, John Wiley & Sons.

Schaefer, V. R. (1997). Ground Improvement, Ground Reinforcement, Ground Treatment, Proceedings of Soil Improvement and Geosynthetics of The Geo-Institute of the American Society of Civil Engineers in conjunction with Geo-Logan’97. Edited by V.R. Schaefer.

Documents

V Compaction - Universitas Brawijaya...Standard and Modified Proctor Compaction Test (Cont.) Summary of Modified Proctor Compaction Test Specifications (ASTM D-698, AASHTO) 16 Das,