4_Compaction.pdf

8/21/2019 4_Compaction.pdf

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SOIL

COMPACTION

TOPIC 4



SOIL COMPACTION – History and Evolution



SOIL COMPACTION – History and Evolution



SOIL COMPACTION

Why and when is needed



SOIL COMPACTION

Why and when is needed

Changes in soil as it moves from its natural location to acompacted fill



Highway construction – cut and fill work

Site proposal



Oroville Dam – California (Earth dam)



Sanitary Landfill



Sanitary Landfill



Cut Slope – using compacted soil(Faculty of Economy UM – new wing



Cut slope – using key stone at the toe(Fakulty of Economy UM – New wing



Natural

soil

Backfillmaterial

Retaining Wall(Lembah Bertam, Pahang)



What is COMPACTION

Definition

Process of increasing the density of soil by packing the

particles closer together causing reduction in the volume ofair via mechanical techniques such as rolling, kneading,applying static weight and impact; without significant changein the volume of water.

air

water

solid

BEFORE AFTER

Dry density ↑

V

M s

d = ρ



Objective

To improve engineering properties of soil through

Increasing the shear strength; shear strength isat maximum when void ratio is minimum

Reducing the compressibility of soil – settlement

Reducing permeability

Reducing the potential of swelling (expansion)

and shrinkage (contraction) due to frost action.



Degree of Compaction

How compact the soil is; in other words the

condition of soil after compaction is termed asDEGREE OF COMPACTION

Measured in terms of DRY DENSITY

The dry density depends on water content,compactive effort, soil type and compaction

method.

V

M s

d = ρ

wd

+

=

1

ρ ρ



Compaction Test

(a) Cylindrical Mould ; volume = 1000 cm3

(b) Hammer 2.5 / 4.5 kgStandard Proctor

Test– BS 1377



Test Procedure

(a) Take 3 kg of soil (passed 20 mm sieve) and break up any lumps

(b)Assemble and weigh the mould (base + mould body)

(c) Add 3% water (% by weight) and mix

(d) Fix the extension and put soil in three layers; each layers receiving27 blows of rammer.

(e) Remove the extension and level off the excess

(f) Weigh the compacted soil and the mould

(g) Take out the soil from the mould, break them up and take smallamount for water content test.

(h) Repeat steps (c) – (g) with each repetition, increasing the volumeof water at 3% each time.

(i) Stop the process when the weight of the compacted soil start todecrease

(j) Draw compaction curve – dry density vs water content



Types of compaction tests

Test Refs. Rammer Volume ofmould

Layer No. ofblows

Mass Height of

drop

2.5 kgrammer

BS 1377 :1975 Test

12

2.5 kg 300 mm 1000 cm3 3 27

4.5 kgrammer BS 1377 :1975 Test13

4.5 kg 450 mm 1000 cm3

5 27

Std ProctorAASHTO

ASTM D-698-78

AASHTO T-99

2.49 kg 305 mm 944 cm3 3 25

ModifiedAASHTO

ASTM D-1557-78

AASHTO T-180

4.54 kg 457 mm 944 cm3 5 25



Compaction Test Results

Principles of compaction



Compaction Test Results

Relationshipbetween drydensity and water

content-Typicalcompaction curve

-Each compactioncurve is unique(one curve for aparticular

compactive effortor compactivemethod)

For each curve there is an optimum water content (wopt) thatcontribute to the maximum dry density (ρdmax)



Properties of Compaction Curve

Soil ratherstiff andlumpy.

Difficult tocompact.Mostcompactiveeffort isused tobreak uplumps

Water is adequate to produce workable soil, facilitating compactionhence resulting in higher dry density. For clayey soil, the water content

is adequate for adsorbed water to develop; therefore, forces betweenparticles are reduced allowing dispersed orientation to formed.

Compactive effort istaken up by water inthe pore which is

already full asexcess pore waterpressure. Thisexcess pressureresults in soilparticles expels andpushes each other;increasing spaces(voids); hence

decreasing the drydensity.



If all air in soil could beexpelled by compaction(A=0) (impossible inreality), then the soil

will be in fullsaturation. The max.dry density at thiscondition is called

Saturation dry density/ ‘zero air voids’ drydensity

s

ws

d

wG

G

+=1

ρ ρ

s

ws

d

wG

AG

+

−=

1

)1( ρ ρ

Saturation Line



Problem 1.5 – Craig pg 33

Soil has been compacted in an embankmentat a bulk density of 2.15 Mg/m3 and water

content of 12%. The value of Gs is 2.65.Calculate the dry density, void ratio, degreeof saturation and air content. Would it bepossible to compact the above soil at watercontent of 13.5% to a dry density of 2.00Mg/m3

Example



Example

Problem 6.22 – Coduto page 205

A well graded silty sand with a maximum dry unit

weight of 19.7 kN/m3 and optimum moisture contentof 11% is being used to build a compacted fill. Twofield density tests have been taken in the recentlycompleted field, but one of these tests has produced

results that are definitely incorrect. Test A indicateda relative compaction of 85% and a moisture contentof 8.9%, while Test B indicated a relative compactionof 98% and a moisture content of 14.9%. Which test

is definitely incorrect? Why? Assume G s as 2.70.



If A is replaced by 5%and 10% curves for aircontent of 5% and 10

% can be drawn hencecan be used to indicateat what percentage ofair content max. drydensity occur for aparticular soils

Test curve must be at

the left of saturationline

Air Content Line

s

ws

d

wG

AG

+−=

1)1( ρ

ρ



Factors affecting compaction

The higher the

compactive effort – thehigher the degree ofcompaction

Compaction curve shiftto the left and upwardwhen there is anincrease

Compaction energy perunit volume (E) = (no ofblows per layer x no oflayers x weight of

rammer x drop height)/ vol. of mould

Compactive Effort



For the samecompactive effort

Coarse-grained soilcan be compacted toa higher degree ofcompaction.

Well graded soil?

Soil Type




Granular material with some fines will exhibits higher degree of

compaction compared to granular material without fines or fine-grained soil alone.

Soil Type




Compaction method


Rolling – granular soil?

Impact – granular / fine?

Kneading – fine-grained?Vibration – granular?

Static load – fine/ coarse-grained?



Compaction Curves

Common shape ; 30 wL 70

Single peak type

1½ peak type

For soil where wL < 70100% or high % of sand andremaining is either illite /montmorillonite

Typical for non-cohesive soil

(a) Type A

(b) Type B



Lengkung Pemadatan

For soil wL < 30Portion of soil is sand andsome kaolinite

2 peaks type

No peak

Fines where wL > 70

Main portion is montmorillonite

Some linear part of the curvepresence

(c) Type C

(d) Type D

Dry and Wet side of Optimum



Dry and Wet side of Optimum

DRY WET

AT OPTIMUM

At any particular ρd value, apart from ρdmax; there exits 2corresponding values of w (one at the dry and another at

the wet side). Which value is to be used in engineeringwork?

w1 w

2

ρd

Effect of compaction on the dry and



Effect of compaction on the dry and

wet side

Part of water

content

Engineering propertiesdry wet

strength high lowCompressibility(at low consolidation pressure)(at high consolidation pressurei)

lowHigh

highlow

Swelling High lowShrinkage low high

Structure of Compacted Clay Soil



Structure of Compacted Clay Soil

Increase in water content (B-C)increases repulsion bet. Clayptcl. results in dispersed

structure. Increase dispersionas compactive effort increases

On the dry side, thestructure is flocculated

irrespective of compactiveeffort (Seed and Chan,1959). Due to less water fordiffused double layers of

ions to developed aroundptcls. hence reducingrepulsion.

At B, when water contentincrease, diffuse doublelayer expand and thisincrease repulsion bet. Clay

particle and hence reducingdegree of flocculation

Field Compaction



Field Compaction

Fill material that has been excavated from a borrow siteneed to be compacted.

Fill materials that has been excavated will be brought tothe construction area and levelled in several layers of(150 mm – 500 mm thickness) depending on the types of

soil and equipment used. If the soil to be compacted is naturally dry, the soil need

to be wet prior to compaction according to the watercontent required for certain degree of compaction. On

the other hand, if the soil is wet, they need to be driedup to the required water content.

Field Compaction Equipment



Field Compaction - Equipment

Excavators / Rippers – Excavate soil

Backhoe + loader

Excavator (large hoe)

Wheel-mounted loader




End Dump Truck





Spreader






Equipment –plates, power rammersand many different

types of rollers

Vibrating

Methods – combination

of static pressure,kneading action,vibration or impact.

Compactive effort – no. ofpasses or coverages

Type of equipment – type of soiland site condition / fill




Vibrating Plates / Power Rammers

Usage – small areas with limited access e.g. bridgeabutment, narrow trenches, pavement, road subbase

Compaction method – vibration and static weight

CAUTION ! – normally hand operated and self-propelled





Smooth-wheeled Rollers

Usage – subgrade or basecourse compaction of well-graded sand/gravel mixtures orasphalt pavements. May beused for fine material provided

not too wet and not to be usedfor compaction of impermeablecore section of eater retainingstructure due to smooth

interface being introducedCompaction method – staticweight ~ 400 kN/m2

Can be self-propelled or towed





Sheepsfoot rollers

Usage – for fine-grained

soil ( >20% fines),particularly applicable inearth dam constructionwhere bonding between

lifts of impermeablecore are ensured.

Compaction method –static pressure andkneading

May be self-propelled ortowed


Tapered protrusion ‘feet’ exertingcontact pressure 1500 – 7500 kN/m2




Rubber-tyred rollers

Usage –for fine andcoarse-grained soilexcept uniformly graded

Compaction method –

static pressure up to700kN/m2 and kneading





Vibratory Rollers

Usage – For granular soilwithout fines

Vibrators are attached tosmooth rollers

Compaction methods –vibration ranges 20 – 80

Hz





F mp q pm

Application of Field Compaction Equipment



Specification and Control of Field Compaction



The extent to which field compaction iseffective depends on

Types of soil

Water content

Lift thickness

Type of compaction equipment The size of fill area

No. of passes / coverages

Why specification is required? –to ensure compaction iscarried out adequately on-site

Compaction Specification



p p

SPECIFICATION

Method of Compaction

Engineer prescribe weightand type of rollers, numberof coverages, liftsthickness

Combination of the threefactors can be determinefrom several trial exercises

on actual sites usingdifferent equipments, liftsthickness, compactiveeffort etc.

End Result To be Achieved

Prescribe a requiredRelative Compaction and w

RC =(ρdfield/ρdmax)x 100%

RC of normally between (90-100%), compaction may beachieved via two w (dry /wet side). Hence, specify was well (range).

Alternatively, specify finalair voids content with

associated max. watercontent

Compaction Specification



p p

SPECIFICATION

Method of CompactionEnd Result To be Achieved

Which one do youchoose?

CONSULTANT

CONTRACTOR

Why?

Control of Field Compaction



p

The need…




CONTROL TEST

Coarse-grained soilTest holeBS 1377:1975, Test 15(A) – (C)Determine mass and volume

Determine w

Fine-grained Soilcylindrical core-cutter BS1377:1975, Test 15(D)Determine mass and volumeDetermine w

Objective – to ensure work meets specification forcompaction

Technique – Need to find ρ (from M and V) put them back in

ρd (need also w)

Nuclear Method




Fine-grained Soil (Cylindrical core cutter)Push the core cutter until full,dug out and trimmed flush the

end.Cylinder having known volume V

Weigh the cutter before and

after soil extraction to get M

Moisture content test to getw - let some sample to dry for

24 hr in the oven

)1(

,

w

V

M

d +=

=

ρ ρ

ρ




Coarse-grained Soil – Test HoleExcavate a hole at the desired level in the soil

Place the excavated soil into a container and weight for MTake some sample for moisture content test ; w

Determine the volume V from either

Volume of Hole (V)

Rubber Balloon Method

ASTM D-2167-66

Sand Replacement Method

BS 1377 : 1975 Test 15(A)




Sand Replacement Method

Determine V by filling theexcavated hole with sand of known

bulk density.From the mass of sand being filledup, V can be calculated

Problem – vibration fromsurrounding operation mightintroduced errors.




Rubber Balloon MethodDetermine V by filling the rubber balloonwith water so that it stretches across the

holeProblem – error is introduced when thesides of the hole is too rough




Water Ring Test




Problems with traditional methods

M – OK ? Errors?

V- OK? Errors?

w – require 24 hours / use ‘speedy moisture tester’

The ease of repetitive of test over the wholeconstruction area

To overcome – consider using the Nuclear Method




Nuclear Method

Objective – to determine ρ and w

Basic Principle2 emission sources and 2 detectors

γ ray ρ (γ ray scattered as they collided with soil particles)

Neutron w (energy ↓ when neutron collided with hydrogen atom

Results can be achieved in minutes; hence allowing correctiveaction to be taken.

Many repetitive test can be carried out over the whole field –good control practice




Nuclear Test Equipment – ASTM D-2922-78Direct Transmission - Fine-grainedsoil

Insert probe into the soil and placethe detector onto the soil surface.

Back-scatter – Coarse-grained soil

A single unit is placed on the surfaceof the soil and the same work as both

emission source and detector




Nuclear density and water content determination transmission(after Troxler Electronic Laboratories,. Research Triangle Park, NorthCarolina)

(a) Direct transmission

(c) Air-gap

(a) backscatter

Example



Problem 6.19 – Coduto page 204

A fill soil with a natural a moisture content of 10% and

an optimum moisture content of 14% is being used toconstruct a compacted fill. The contractor is placingthis soil in 400mm lifts, spraying the top with a watertruck, and compacting it using a towed sheepfoot

roller. A soil technician has performed a series of fielddensity tests in this fill and has found relativecompaction values between 80% and 92%. Themeasured moisture contents ranged from 10 to 23%.

The specifications require a relative compaction of atleast 90%, so the fill is not acceptable. What is wrongwith the contractor’s methods, and what needs to bedone to remedy the problem

Compaction in engineering industry



Review on Menard Geosystem

CEEC Technical talk on Sept. 05

Presentation –

4_Compaction.pdf

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