Objectives v Be able to use basic volume weight equations v Understand principal of soil compaction. v Explain how the compaction test is used in design.

ObjectivesObjectives Be able to use basic Be able to use basic

volume weight volume weight equationsequations

Understand principal Understand principal of soil compaction. of soil compaction.

Explain how the Explain how the compaction test is compaction test is used in design and used in design and quality controlquality control

Be able to perform Be able to perform basic compaction testbasic compaction test(LAB EXERCISE)(LAB EXERCISE)

plot compaction data plot compaction data and evaluate for and evaluate for accuracyaccuracy

Understand procedure Understand procedure for Atterberg Limit for Atterberg Limit Tests (LAB Tests (LAB EXERCISE)EXERCISE)

Review of Compaction PrinciplesReview of Compaction Principles

Compaction Tests are not suitable for Compaction Tests are not suitable for soils with more than 30 % by weight of soils with more than 30 % by weight of the sample being larger than a ¾” sieve.the sample being larger than a ¾” sieve.

Compaction tests are not usually Compaction tests are not usually performed on soils with 12 % or fewer performed on soils with 12 % or fewer finesfines

Review of Compaction PrinciplesReview of Compaction Principles

Relative Density testing is used for Relative Density testing is used for clean sands and gravels – covered later clean sands and gravels – covered later in classin class

Standard Procedures for testing are Standard Procedures for testing are available for soils with some gravel available for soils with some gravel (less than the maximum allowable (less than the maximum allowable content)content)

Principle of compactionPrinciple of compactionPrinciple of compactionPrinciple of compaction

Theory developed by R.R. Proctor in 1930’s Theory developed by R.R. Proctor in 1930’s

in Californiain California

Three Factors determine the density that Three Factors determine the density that

results from soil compactionresults from soil compaction

Proctor Developed PrincipleProctor Developed PrincipleProctor Developed PrincipleProctor Developed Principle

Three variables determine the Three variables determine the density of a compacted soildensity of a compacted soil– The energy used in compactionThe energy used in compaction

– The water content of the soilThe water content of the soil

– The properties of the soilThe properties of the soil

State DiagramState Diagram

Water content, %

Dry

Den

sity

, pcf

100 % saturation

curve

State DiagramState Diagram

Water content, %

Dry

Den

sity

, pcf

Energy Used in CompactionEnergy Used in Compaction

Assume you have some clay soil that is Assume you have some clay soil that is at a water content of 16 percent.at a water content of 16 percent.

Look at the effect different compaction Look at the effect different compaction energy has on the density of the soil.energy has on the density of the soil.

Energy expressed as number of passes Energy expressed as number of passes of a sheepsfoot roller on a lift of soilof a sheepsfoot roller on a lift of soil

Water content, %

Dry

Den

sity

, pcf

1 pass of equipment

2 passes of equipment




At this water content, energy has a large effect on compacted density

Water content, %

Dry

Den

sity

, pcf


At this point, the sample has had most of its air driven out by the compaction

100 % saturation

line

Water content, %

Dry

Den

sity

, pcf

1 pass of equipment





At a lower water content, energy has little effect on the compacted density of a clay soil

Compacting at low water contentsCompacting at low water contents

At low water contents, insufficient At low water contents, insufficient

water is available to lubricate the water is available to lubricate the

particles and allow them to be particles and allow them to be

rearranged into a dense structure. rearranged into a dense structure.

The frictional resistance of dry The frictional resistance of dry

particles is highparticles is high

Water content, %

Dry

Den

sity

, pcf

1 pass of equipment


3 passes of equipment4 passes of equipment


At a very high water content, energy has little effect on the compacted density of a clay soil because the water is incompressible and takes the applied force without densifying the soil

This results in a term called pumping

Compacting Very Wet SoilCompacting Very Wet Soil

At this point, few air pockets remain

– compaction forces are carried by water in soil

which is incompressible

Water has Zero Shear StrengthWater has Zero Shear Strength

Water has Zero Shear StrengthWater has Zero Shear Strength

Effect of Water ContentEffect of Water Content

Now examine the effect of just changing the Now examine the effect of just changing the water content on a clay soil, using the same water content on a clay soil, using the same energy each time the soil is compacted. energy each time the soil is compacted.

For example, assume soil is spread and For example, assume soil is spread and compacted with 4 passes of a sheepsfoot compacted with 4 passes of a sheepsfoot roller each time.roller each time.

Examine using State DiagramExamine using State Diagram

Effect of Water ContentEffect of Water Content

Dry

den

sity

, p

cf

Water content, %

Sample 1 compacted at 12 % water – Dry Density is 99.0

pcf

12 %

99.0 pcf

Effect of Water ContentEffect of Water ContentD

ry d

en

sity

, p

cf

Water content, %

Sample 2 compacted at 14 % water – Dry Density is 104.5 pcf

14 %

104.5pcf


ry d

en

sity

, p

cf

Water content, %

Sample 3 compacted

at 16 % water – Dry Density is 105.5 pcf

16 %

105.5pcf


ry d

en

sity

, p

cf

Water content, %

Sample 4 compacted

at 18 % water – Dry Density is 98.5 pcf

18 %

98.5 pcf

Effect of Water Content @ constant Effect of Water Content @ constant energyenergy

Dry

den

sity

, p

cf

Water content, %

Maximum dry

density, pcf

Optimum water content, %

Now, perform the same test at a Now, perform the same test at a different (Higher energy) on the soildifferent (Higher energy) on the soil

Dry

den

sity

, p

cf

Water content, %

4 passes of sheepsfoot

roller

10 passes of sheepsfoot

roller

Effect of Soil Type on CurvesEffect of Soil Type on CurvesD

ry d

en

sity

, p

cf

Water content, %

Plastic Clay Soils have Low Values of Maximum Dry Density

80-95 pcf


ry d

en

sity

, p

cf

Water content, %

20-40 %

Plastic Clay Soils have high values for optimum water content (20-40 %)


ry d

en

sity

, p

cf

Water content, %

Plastic Clay Soils have a Flat Curve for Lower Energies Density


ry d

en

sity

, p

cf

Water content, %

Sandy Soils with Lower PI’s have High Values of Maximum Dry Density

115-135 pcf

8-15 %


ry d

en

sity

, p

cf

Water content, %

Sandy Soils with Lower PI’s have Low Values of Optimum Water Content


ry d

en

sity

, p

cf

Water content, %

Sandy Soils have a Steep Curve – Short distance from plastic to liquid states of consistency

SummarySummaryD

ry d

en

sity

, p

cf

Water content, %

Lower PI – Sandier Soils

in this Region

110-135

Intermediate PI Soils in

this Region95-120 Higher PI –

Clayey Soils in this Region

75-95

SummarySummaryD

ry d

en

sity

, p

cf

Water content, %

Lower PI – Sandier Soils

in this Region

8-14

Intermediate PI Soils in

this Region

12-20

Higher PI – Clayey Soils

in this Region

20-40

Family Family of of Curves Curves (Covered (Covered Later)Later)

Family of CurvesFamily of Curves

water content, %

d, d

ry d

ensi

ty,

pcf

Line of Optimums

Zero air voids curve not parallel

to line of optimums at upper end

Using a standard energy, if a series of Using a standard energy, if a series of specimens of a soil are compacted at specimens of a soil are compacted at increasing water contents, the resultant increasing water contents, the resultant dry density of the specimens will vary. dry density of the specimens will vary. The density will increase to a peak value, The density will increase to a peak value, then decrease.then decrease.

Proctor’s principle of Proctor’s principle of compactioncompaction

Principle of CompactionPrinciple of Compaction

A plot of the dry density versus the A plot of the dry density versus the water content from a compaction test water content from a compaction test will be parabolic in shape. will be parabolic in shape.

The peak of the curve is termed the The peak of the curve is termed the maximum dry density, and the water maximum dry density, and the water content at which the peak occurs is the content at which the peak occurs is the optimum water content.optimum water content.

Standard Proctor EnergiesStandard Proctor Energies

Several standard energies are used Several standard energies are used for laboratory compaction testsfor laboratory compaction tests– Standard – 12,400 ft-lbs/ftStandard – 12,400 ft-lbs/ft33

– Modified – 56,000 ft-lbs/ftModified – 56,000 ft-lbs/ft33

– California – 20,300 ft-lbs/ftCalifornia – 20,300 ft-lbs/ft33

Standard Proctor Compaction Test Standard Proctor Compaction Test SummarySummary

Uses 5.5 pound Uses 5.5 pound hammerhammer

dropped 12 inchesdropped 12 inches mold filled in 3 liftsmold filled in 3 lifts 25 blows of hammer 25 blows of hammer

per liftper lift Total energy is Total energy is

12,400 ft-lbs/ft12,400 ft-lbs/ft33

12”drop

3 lifts

5.5 # hamme

r

Modified Proctor Compaction Test Modified Proctor Compaction Test SummarySummary

Uses 10 pound Uses 10 pound hammerhammer

dropped 12 inchesdropped 12 inches mold filled in 5 liftsmold filled in 5 lifts 25 blows of hammer 25 blows of hammer

per liftper lift Total energy is Total energy is

12,400 ft-lbs/ft12,400 ft-lbs/ft33

18”drop

10 # hamme

r

5 lifts

Proctor Compaction Test SummaryProctor Compaction Test Summary

Several Standard molds are used Several Standard molds are used depending on maximum particle size in depending on maximum particle size in samplesample– 4”diameter mold (1/30 ft4”diameter mold (1/30 ft33) used for soils ) used for soils

with low gravel contentswith low gravel contents– Method A for soils with < 20 % gravelMethod A for soils with < 20 % gravel– Method B for soils with > 20 % gravel and < Method B for soils with > 20 % gravel and <

20 % larger than 3/8”20 % larger than 3/8”


Several Standard molds are used Several Standard molds are used depending on maximum particle size in depending on maximum particle size in samplesample– 6”diameter mold (1/13.33 ft6”diameter mold (1/13.33 ft33) used for ) used for

soils with significant gravel contents soils with significant gravel contents

– More than 20 % gravel larger than 3/8”More than 20 % gravel larger than 3/8”

– Must have less than 30 % larger than 3/4”Must have less than 30 % larger than 3/4”


Standardized tests are not available for soils Standardized tests are not available for soils with more than 30 percent by weight of the with more than 30 percent by weight of the total sample being larger than 3/4”in total sample being larger than 3/4”in diameter gravelsdiameter gravels

ASTM Compaction Test Methods are ASTM Compaction Test Methods are – D698AD698A D1557AD1557A– D698BD698B D1557 D1557BB – D698CD698C D1557C D1557C


Prepare 4 to 5 Prepare 4 to 5 specimens at increasing specimens at increasing water contents about 2 water contents about 2 % apart. Example - % apart. Example - prepared samples at 14, prepared samples at 14, 16, 18, and 20 percent. 16, 18, and 20 percent. Use range of moistures Use range of moistures based on feel and based on feel and experience.experience.


Then, compact Then, compact each sample each sample into a steel into a steel mold with mold with standard standard proceduresprocedures

Compaction mold

Cured soil

Hammer


Then, strike Then, strike off excess off excess soil so the soil so the mold has a mold has a known known volume of volume of soil. soil.


For each sample, measure the weight and the For each sample, measure the weight and the water content of the soil in the mold water content of the soil in the mold

The mold volume and weight are The mold volume and weight are pre-measured. pre-measured. Don’t assume nominal volumeDon’t assume nominal volume of of 1/30 ft1/30 ft33 or 1/13.33 ft or 1/13.33 ft33

Calculate moist densityCalculate moist density Calculate dry densityCalculate dry density Plot dry density and water content for each pointPlot dry density and water content for each point

Class ProblemClass Problem

Calculate Moist density, dry densityCalculate Moist density, dry density

Mold_Volume

Weight Moistmoist

100%

1w

moistdry

Point Mold+Soil

MoistSoil

MoistDensity

pcf

WaterContent

%

DryDensity

pcf

1 8.04 3.78 17.5

2 8.30 4.04 19.6

3 8.38 4.12 21.7

4 8.29 4.03 24.4


Mold wt = 4.26 #, Mold Vol. = 0.03314 ft3


Calculate Moist density, dry densityCalculate Moist density, dry density Plot curve of dry density versus Plot curve of dry density versus

water contentwater content Determine Maximum dry density Determine Maximum dry density

and optimum water contentand optimum water content

{

Set Up Plot – Form SCS-352Set Up Plot – Form SCS-352

5 pound

s

90

110

Set Up Plot – Form SCS-352Set Up Plot – Form SCS-352

Make each vertical division equal to 1 percent water

content


Calculate Moist density, dry densityCalculate Moist density, dry density Plot curve of dry density versus water Plot curve of dry density versus water

contentcontent Determine Maximum dry density and Determine Maximum dry density and

optimum water contentoptimum water content Plot zero air voids ( 100 % saturation Plot zero air voids ( 100 % saturation

curve assuming specific gravity = 2.68curve assuming specific gravity = 2.68

Zero Air Voids CurveZero Air Voids Curve

After you plot a compaction test, plotting After you plot a compaction test, plotting a zero air voids curve is very important. a zero air voids curve is very important. This curve is also called the 100 % This curve is also called the 100 % saturation curvesaturation curve

This curve shows for a range of dry This curve shows for a range of dry density values what the saturated water density values what the saturated water content is for any given valuecontent is for any given value

Compaction Problem Compaction Problem

1001

(%) xG

wsdry

watersat

Zero air void equation

Assume 3 values of d and calculate wsat%

85

95

105

115

125

135

10 12 14 16 18 20 22 24 26 28 30 32 34

Water Content, %

Dry

Den

sity

, pcf

100G

1(%)w

sd

wsat

100 % Saturation Curve



assumed Gs = 2.70Unit wt. water = 62.4

Assumed dry density = 105 pcf

wsat(%) = 22.1(%)


Dry Unit Weightpcf

SaturatedWater %

95

100

105

Plotted Class ProblemPlotted Class Problem

95

96

97

98

99

100

101

102

103

104

105

15 17 19 21 23 25 27 29

w %

Dry

De

ns

ity

, p

cf

Maximum drydensity = 102.5 pcf

optimum w % = 21.0 %

zero air voids curve


The 100 % saturation curve is used to The 100 % saturation curve is used to judge the reliability of the compaction judge the reliability of the compaction curve and of field measurements of curve and of field measurements of compacted soil density and water contentcompacted soil density and water content

Compacted soils for NRCS Compacted soils for NRCS specifications are usually at a degree of specifications are usually at a degree of saturation of about 75 to 95 percentsaturation of about 75 to 95 percent




EvaluatingEvaluating Compaction TestsCompaction Tests– Standard requirements - spread in Standard requirements - spread in

water content about 2 % and at least water content about 2 % and at least two points above and below optimumtwo points above and below optimum

– Typical shape - soil type ?Typical shape - soil type ?

Review of CompactionReview of Compaction

Compaction Problem Compaction Problem

Other given information:

LL = 47, PI = 30, classified as CL soil

Gs = 2.68

Evaluating compaction testEvaluating compaction test

95

96

97

98

99

100

101

102

103

104

105

15 17 19 21 23 25 27 29

w %

Dry

De

ns

ity

, p

cf


2.1 %

Are points about two percent apart ?

2.1 % 2.7 %

2.7 %

Evaluating compaction testEvaluating compaction test

95

96

97

98

99

100

101

102

103

104

105

15 17 19 21 23 25 27 29

w %

Dry

De

ns

ity

, p

cf


2.1 %

2.1 %

2.1 %

2.7 %

Are two points below and 2 above optimum ?

Optimum water content about Optimum water content about 80 % saturated water 80 % saturated water content ? - Acceptable range content ? - Acceptable range is 75-95is 75-95


1001

xG

wsdry

watersat

(%)

Optimum w% = 21.0

(%)6.2310068.2

1

5.102

4.62(%)

xwsat

% sat = 21.0÷23.6=89%

102.5 pcf


95

96

97

98

99

100

101

102

103

104

105

15 17 19 21 23 25 27 29

w %

Dry

De

ns

ity

, p

cf




wsat @ 102.5 pcf =(62.4/102.5 - 1/2.68) * 100 = 23.6

%

wopt/wsat = 21.0/23.6 = 89 %

Wet side parallel to Wet side parallel to saturation curve at saturation curve at 90 % saturation ?90 % saturation ?

d, p

cf

w, %


1001

(%) xG

wsdry

watersat

% Sat = 24.3 ÷ 26.4 = 92.0 %

Check a point on wet side at 98 pcf, w % on curve is

24.3%

(%)4.2610068.2

1

0.98

4.62(%)

xwsat


95

96

97

98

99

100

101

102

103

104

105

15 17 19 21 23 25 27 29

w %

Dry

De

ns

ity

, p

cf




wopt/wsat = 24.3/26.6 = 91 %

wsat @ 98.0 pcf =(62.4/98.0 - 1/2.70) * 100 =

26.6 %

Evaluating Compaction TestsEvaluating Compaction Tests Typical value for fine-grained soils Typical value for fine-grained soils

compared to Navdocks equationscompared to Navdocks equations

dmax = 130.3 - 0.82 *LL + 0.3*PI

wopt = 6.77 + 0.43 * LL - 0.21 * PI


Evaluating Compaction TestsEvaluating Compaction Tests Typical value for fine-grained soils Typical value for fine-grained soils

compared to Navdocks equationscompared to Navdocks equations

dmax = 130.3 - 0.82 *47 + 0.3*30 = 100.8 pcfOK - test value was 102.5 pcf

wopt = 6.77 + 0.43 * 47 - 0.21 * 30 = 19.6 % OK Test value was 21.0 %


Soils are compacted to improve the Soils are compacted to improve the engineering properties over those of loosely engineering properties over those of loosely placed soils.placed soils.

The engineering properties are affected both The engineering properties are affected both by the density to which the soil is compacted by the density to which the soil is compacted and the water content at which it is compactedand the water content at which it is compacted

Purposes of compactionPurposes of compaction

Role of compaction tests Role of compaction tests in earth fill projectsin earth fill projects

Samples are obtained in site investigation and sent to Samples are obtained in site investigation and sent to laboratory for testinglaboratory for testing

Soils are tested to determine reference density - as well Soils are tested to determine reference density - as well as other index propertiesas other index properties

Engineering properties are measured by testing at a Engineering properties are measured by testing at a percentage of the reference test density. For example, a percentage of the reference test density. For example, a shear test might be performed at 95 percent of the shear test might be performed at 95 percent of the Standard Proctor maximum dry density of the soil. Standard Proctor maximum dry density of the soil.

The engineering properties are used in analyses to The engineering properties are used in analyses to determine a suitable designdetermine a suitable design

For example, the shear strength is used in a slope For example, the shear strength is used in a slope stability analysesstability analyses

If the engineering properties allow a satisfactory If the engineering properties allow a satisfactory design, then the degree of compaction is used in a design, then the degree of compaction is used in a contract specification.contract specification.


If an unsatisfactory design results, the soil is re-tested If an unsatisfactory design results, the soil is re-tested at a different degree of compaction to obtain better at a different degree of compaction to obtain better engineering propertiesengineering properties

The design is re-analyzed and the process repeated until The design is re-analyzed and the process repeated until a final satisfactory degree of compaction is decideda final satisfactory degree of compaction is decided

Then the degree of compaction is used in a contract Then the degree of compaction is used in a contract specification.specification.


Quality control processes are used to ensure that Quality control processes are used to ensure that the earth fill is compacted to the degree of the earth fill is compacted to the degree of compaction specified, within a range of specified compaction specified, within a range of specified water contentswater contents

Field compaction tests are performed to assure Field compaction tests are performed to assure that the proper reference density is being usedthat the proper reference density is being used


Compaction Compaction Tests as Tests as Used in Used in Design of an Design of an Earth FillEarth Fill

E n g in e erin g P rop e rtie s a re u sedin a n a na lyses - e .g .,

s lo p e sta b ility a n a lys is

E n g ine e ring P rop e rtyT e s ts a re p e rfo rm e d a t

th e p re lim in a ry d e s ig n de n s itye .g ., sh ea r te s ts

A P re lim in ary d e gre e o fco m pa c tio n is a ssu m ed

e .g ., 9 5 % S T a nd a rd P roc to r

S a m p les a re ob ta in e d a nd sub m ittedto a la b ora to ry fo rco m p a ctio n te s ts

in d ex te s ts

Q u a lity C o n tro l T e s tsa re pe rfo rm ed du ring

co n stru ctio n to e n su re th a tth e re q u ire d d e ns ity a n d w ate r co n te n t a re m et

If th e D e s ign is S a tis fac to ry,C o n tra c t sp e cs a re w ritten

re q u irin g the d eg ree o f co m p ac tionn e ed e d fo r th e p ro p erties

Q u a lity C o n tro l T e s tsa re pe rfo rm ed du ring

co n stru ctio n to e n su re th a tth e re q u ire d d e ns ity a n d w ate r co n te n t a re m et

W h en a sa tisfa c to ry de s ign is a ch ie vedfo r th e tes ted de gre e o f

co m pa c tio n , sp ec if ica tio n s a re w ritten

If th e D e sig n is n o t S a tis fa cto ry,a d iffe ren t d e gre e o f co m p a ction

is a ssu m e d, a nd m o re e n g in e eringp ro pe rty te s ts a re p e rfo rm ed

Example of ProcessExample of Process

Sample obtained to determine suitability as Sample obtained to determine suitability as clay linerclay liner

Sample Sent to LaboratorySample Sent to Laboratory Laboratory performs Standard Proctor TestLaboratory performs Standard Proctor Test A Permeability Test is performed at 95 % of A Permeability Test is performed at 95 % of

maximum Standard Proctor Dry Densitymaximum Standard Proctor Dry Density


The sample is remolded at 2 percent wet of The sample is remolded at 2 percent wet of optimum (for this sample, 85 % saturated)optimum (for this sample, 85 % saturated)

The permeability test measures an The permeability test measures an acceptably low permeabilityacceptably low permeability

A recommendation is given to the field A recommendation is given to the field office that compaction to this combination office that compaction to this combination of density and water content results in of density and water content results in acceptably low permeabilityacceptably low permeability


During construction, measurements of dry During construction, measurements of dry density and water content are made during density and water content are made during construction.construction.

If the degree of compaction and percent If the degree of compaction and percent saturation are equal to or better than saturation are equal to or better than specified, the liner is judged to have a low specified, the liner is judged to have a low permeability and is considered acceptable.permeability and is considered acceptable.

A compaction test measures a maximum A compaction test measures a maximum dry density of 104.0 pcf and an optimum dry density of 104.0 pcf and an optimum water content of 18.0 %. The soil has an water content of 18.0 %. The soil has an estimated Gestimated Gss value of 2.68 value of 2.68

A contract requires compaction to 95 % of A contract requires compaction to 95 % of maximum dry density at a water content maximum dry density at a water content of optimum or greaterof optimum or greater

Class Problem 2Class Problem 2

A field test measures a moist density of 126.3 A field test measures a moist density of 126.3 pcf and a water content of 23.4 %pcf and a water content of 23.4 %

Does the compacted fill meet the contract Does the compacted fill meet the contract requirement requirement ? ?

Use the values given for measured moist density Use the values given for measured moist density and water content, calculate the dry densityand water content, calculate the dry density

Assume a Gs value of 2.68 and compute a wsat Assume a Gs value of 2.68 and compute a wsat valuevalue

Class Problem 2Class Problem 2

Class ProblemClass Problem Compare the reported compaction water Compare the reported compaction water

content to theoretical saturated water contentcontent to theoretical saturated water content Compacted soils are commonly in the range of Compacted soils are commonly in the range of

75-95 percent saturated75-95 percent saturated What do the results tell you about the What do the results tell you about the

reliability of the field data?reliability of the field data? What would you look for to explain any What would you look for to explain any

problems?problems?

Conclusions of Class ProblemConclusions of Class Problem

The measured data appears to have The measured data appears to have problems.problems.

Possible errors are in the measurement of Possible errors are in the measurement of the dry density, the water content, or the the dry density, the water content, or the specific gravity value used in computationsspecific gravity value used in computations

Recommend investigating most probable Recommend investigating most probable causescauses

Objectives v Be able to use basic volume weight equations v Understand principal of soil compaction. v Explain how the compaction test is used in design.

Documents

soil compaction slide

passes of equipment

effect of water content

clay soil slide

high water content

compacted density slide

pcf slide

lower water content