__________________________________________________________

CECOS University of I.T. and EmergingSciences

Peshawar Pakistan

PROJECT NO. CE-2008-12-17

MEASUREMENT OF SUBGRADE PROPERTIES OF G.T ROAD ,

PIR PYAI AREA

MonibUllah Khan Bangash1

Aamir MahmoodEjaz Ahmad

Muhammad YousafMuhammad Ali Safdar

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CERTIFICATE OF APPROVAL

This is to certify that the work contained in this thesisentitled

“MEASUREMENT OF SUBGRADE PROPERTIES OF G.T. ROAD

PIR PYAI AREA”

was carried out by

MonibUllah Khan BangashAamir MahmoodEjaz Ahmad

Muhammad YousafMuhammad Ali Safdar

under my supervision and in my opinion, it is fully adequate,in scope and quality, for the degree of B.Sc. CivilEngineering from CECOS University of I.T. and EmergingSciences Peshawar, Pakistan.

Supervised By: Signature: ______________________

Prof. Dr. Noor-ul-Amin.

Department of Civil Engineering

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Approved By: Signature: ______________________

Engr. Iftikhar Mahmood

Chairman,

Department of Civil Engineering.

Abstract

Design of the various pavement layers is very much dependenton the strength of the subgrade soil over which they are goingto be laid. Subgrade strength is mostly expressed in terms ofCBR (California Bearing Ratio). Weaker subgrade essentiallyrequires thicker layers whereas stronger subgrade goes wellwith thinner pavement layers. The pavement and the subgrademutually must sustain the traffic volume.

The subgrade is always subjected to change in its moisturecontent due to rainfall, capillary action, overflow or rise ofwater table. For an engineer, it is important to understandthe change of subgrade strength due to variation of moisturecontent.

The laboratory tests were performed for the determination ofengineering properties of soil, of Pir pyai area, Nowshera.For this purpose the soil sample was collected form “Pir pyaiarea , Nowshera” & brought to CECOS soil mechanics laboratory.The sample was protected from sun light & air so that itsmoisture content did not disturbed. The liquid limit, plastic

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limit & plasticity index were found to be 26%, 15% and 11respectively. The soil was classified as CL according toUnified Soil Classification System. Standard Proctor test wasconducted on soil sample and maximum dry density was found tobe 114.3 pcf for 16.4 % OMC (optimum moisture content). CoreCutter test was conducted in the field and the field densitywas found to be 98.41 pcf. The California Bearing Ratio (CBR)value for max dry density of 114.3 lb/ft3 gave 7.65 %.

ACKNOWLEDGEMENTS

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We express our sincere gratitude to Prof. Noor-ul-Amin for his

constant inspiration and guidance without which it would have

been difficult for us to complete the project. It is only for

their constant suggestions that we have been able to finish

our project work. We are also thankful to staff members of

Highway Engineering Laboratory for their assistance and

cooperation during course of experimentation.

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Dedication

This project is dedicated to our loving parents and hard working teachers.

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chapter

1 Introduction 9

1.1 General 9

1.2 Aim and Objectives 9

1.3 Scope 9

1.4 Time schedule 9

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2 Literature review 10

2.1 The Subgrade 10

2.1.1 Definition 10

2.1.2 Subgrade Soil 10

2.1.3 Desirable Property Of Subgrade Soil 10

2.2 Methods for determining Subgrade strength for designing new roads

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2.2.1 Quick estimation of CBR 11

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2.3 Highway Subgrade 12

2.3.1 Definition 12

2.3.2 Types Of Highway Subgrade 12

2.4 Factors determining the strength and stability of subgrade

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2.5 Compaction devices 13

2.6 Preparing Subgrade Surface 14

2.7 Subgrade Design 14

2.7.1 General information 14

2.7.2 Site preparation 15

2.7.3 Design considerations 15

2.8 Subgrade construction 16

2.8.1 General 16

2.8.2 Compaction 16

2.8.3 Density/moisture 16

2.8.4 Strength/stiffness 17

2.8.5 Equipment 17

2.9 Introduction To Pavement 17

2.9.1 Basic Concepts 18

2.9.2 A Historical Perspective Of Pavement Design

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2.9.3 The Pavement System And Typical Pavement Types

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2.9.4 Components of a Pavement System 21

2.9.5 Alternate Types of Pavement 23

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2.9.6 Flexible Pavements (Adapted from AASHTO1993)

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2.9.7 Rigid Pavements 25

2.9.8 Composite Pavements 27

2.9.9 Unpaved Roads (Naturally Surfaced) 28

3 Methodology 29

3.1 Atterberg limits 29

3.1.1 Determination Of Liquid Limit 32

3.1.2 Determination Of Plastic Limit & Plasticity Index

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3.2 Determination of grain sizeanalysis

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3.3 Standard Proctor Test 35

3.4 Determination Of Field Density By Core Cutter Method

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3.5 Determination of California BearingRatio

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4 Analysis and Results 42

4.1 Atterberg Limits 42

4.2 Determination Of Grain Size Analysis 44

4.3 Standard Proctor Compaction Test 46

4.4 Determination Of filed Density by Core Cutter Method

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4.5 Determination Of California Bearing Ratio ( CBR )

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5 Conclusions 50

5.1 Summary 50

5.2 Results 50

Chapter: 01

Introduction 1.1 General: Although a pavement's wearing course is mostprominent, the success or failure of a pavement is more often

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than not dependent upon the underlying subgrade i.e., thematerial upon which the pavement structure is built. Subgradebe composed of a wide range of materials although some aremuch better than others with respect to type of soil..

1.2 Aim And Objectives:

To understand the importance of soil tests onsubgrade soil for the construction of flexiblepavements.Subgrade properties are essential pavement designparameters. Materials typically encountered in subgrades arecharacterized by their strength and their resistance todeformation under load (stiffness). To investigate about thesubgrade properties, we have performed the required tests.

The following tests are used to characterize subgrade materials.

1. Soil Density2. Atterberg’s Limits

3. Soil gradation

4. Proctor compaction tests

5. California Bearing Ratio (CBR)

1.3 Scope: The work is desired to its application in the constructionof flexible pavements as they are cheaper and expedient in itsconstruction for areas where soil of the subgrade is more thanrequired.

1.4 Time Schedule:

1) Literature Study 2 weeks

2) Accumulation or Collection of samples and testing

4 weeks

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3) Research Analysis 2 weeks

4) Thesis Write-up 3 weeks

Chapter: 02

LITERATURE REVIEW

2.1 The Subgrade 2.1.1 Definition

Subgrade can be defined as a compacted layer, generally ofnaturally occurring local soil, assumed to be 300 mm inthickness, just beneath the pavement crust, providing asuitable foundation for the pavement. The subgrade inembankment is compacted in two layers, usually to a higherstandard than the lower part of the embankment The subgrade,whether in cutting or in embankment, should be well compactedto utilize its full strength and to economize on the overallpavement thickness. The current MORTH Specifications requirethat the subgrade should be compacted to 100% Max Dry Density(MDD) achieved by the Modified Proctor Test (IS 2720-Part 7).For both major roads and rural roads the material used forsubgrade construction should have a dry unit weight of notless than 16.5kN/m3.

2.1.2 Subgrade Soil

Soil is a gathering or deposit of earth material, derivednaturally from the breakdown of rocks or decay of undergrowth

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that can be excavated readily with power equipment in thefield or disintegrated by gentle reflex means in thelaboratory. The supporting soil below pavement and its specialunder course is called sub grade. Without interruption soilbeneath the pavement is called natural sub grade. Compactedsub grade is the soil compacted by inhibited movement of heavycompactors.

2.1.3 Desirable Property of Subgrade Soil

The advantageous properties of sub grade soil as a highway material are

• Stability

• Incompressibility

• Permanency of strength

• Minimum changes in volume and stability under adverse conditions of weather and ground

water

• superior drainage

• Ease of compaction

2.2 Methods for determining Subgrade strength for designing new roads

For the pavement design of new roads the subgradestrength needs to be evaluated in terms of CBR value which canbe estimated by any of the following methods:

a) Based on soil classification tests and the table given in IRC: SP: 72-2007 which gives typical presumptive design CBR values for soil samples compacted to proctor density at optimum moisture content and soaked under water for 4 days.

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Typical presumptive CBR values

CBR VALUE SUBGRADE STRENGTH

3% or less Poor

3% - 5% normal

5% - 15% good

b) Using a Nomo graph based on wet sieve analysis data, for estimating 4 day soaked CBR values on samples compacted to proctor density.

c) Using two sets of equations, based on classification testdata, one for plastic soils and the other for non-plasticsoils, for estimating soaked CBR values on samples compacted to proctor density.

d) By conducting actual CBR tests in the laboratory.

2.2.1 Quick estimation of CBR

PLASTIC SOIL

CBR= 75/ (1+0.728 WPI),

Where WPI= weighted plasticity index= P0.075× PI

PI= Plasticity index of soil in %

P0.075= % Passing 0.075 mm sieve

NON- PLASTIC SOIL

CBR= 28.091(D60)0.3581

Where D60= Diameter in mm of the grain size corresponding to 60% finer.

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2.3 Highway Subgrade

2.3.1 Definition

Highway sub grade or basement soil may be defined as the supporting structure on which pavement and its courses rest.

2.3.2 Types of Highway Sub grade

1) In cut sections, the sub grade (defined as cut or excavation) is the original soil lying below the special layers designated as base and sub base materials.

Fig: 2.1

2) In fill sections, the sub grade (defined as embankment or embankment fill) is constructed over the native ground and consists of imported material from nearby roadway cuts or fromborrow pit.

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Fig: 2.2

2.4 Factors determining the strength and stability of subgrade

Strength and stability are the most importanttwo indexes of highway subgrade. Stability includes both temperature stability and moisture content stability of the soils for subgrade. The following factors most significantly influence the stability and strength of subgrade.

a. Types of soils b. Moisture Content (Water aids as a lubricant up to the

optimum moisture content)

c. Compaction methods and devices(kneading or rolling, vibrating, and heavy weight dropping)

2.5 Compaction devices

1) tamping or sheep’s foot roller

2) pneumatic-tire rollers

3) smooth-steel wheeled rollers

4) segmented plate compactors

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5) grid rollers

6) vibratory compactors in the form of vibrating pads, steel wheels or pneumatic tire

7) combinations of the above (e.g. smooth steelwheels and pneumatic tires)

8) hauling and spreading equipment

Fig: 2.3

2.6 Preparing Subgrade Surface

The subgrade shall be scarified to a depth of 150 mm, unlessotherwise specified. The loosened material shall be windrowedto the side, and the exposed surface shall be thoroughlycompacted. The windrowed material shall then be uniformlymixed, shaped to conform to the dimensions, lines, grades andcross-section as established by the Consultant, and compactedto obtain an average of one hundred percent, and with no testresults being less than ninety-seven percent of the maximumdry density at optimum moisture content established by theMoisture-Density Relation tests using Standard Compaction.Approved material shall be added or removed to restore truegrade and cross-section as directed by the Consultant. When

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material varies from optimum moisture content, it shall betreated in the following manner. When a deficiency in moisturecontent exists, the material shall be watered and thoroughlymixed until optimum moisture content is attained. When anexcess in moisture content exists, the material shall beworked and aerated until optimum moisture content is attained.Any large rocks encountered during the subgrade preparationprocess which constitute a hazard to traffic, due to size orprotrusion from the finished subgrade, shall be removed anddisposed off.

The finished subgrade surface shall be firm and uniform, trueto grade and cross-section, and shall be approved by theConsultant before placing subsequent material thereon.Subgrade that does not conform to the requirements as tograde, cross-section, moisture content or density shall bereworked until such requirements are met. Where required, thesubgrade shall be prepared to a depth exceeding 150 mm onsections of the roadway as designated by the Consultant. Whensuch work has been ordered, it shall be carried out in layers,each of which do not exceed 150 mm in depth, and requirementsfor density and optimum moisture as specified above shallapply for each layer. Subgrade ramps of whatever nature atapproaches to railway crossings, bridge structures, oradjacent to fixed obstructions, shall be removed to the linesand grades as directed by the Consultant. When the surplusmaterial has been removed, the subgrade shall then be preparedin accordance with these specifications. The Contractor shall,at his own expense, repair any damages to a prepared subgradesurface as well as repair damages done to culverts by hisequipment, and shall remove any obstructions he may haveplaced which will interfere with the normal function of adrainage system.

2.7 Subgrade Design

2.7.1 General information

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The subgrade is that portion of the pavement system that isthe layer of natural soil upon which the pavement or subbaseis built. Subgrade soil provides support to the remainder ofthe pavement system. The quality of the subgrade will greatlyinfluence the pavement design and the actual useful life ofthe pavement that is constructed. The importance of a goodquality subgrade to the long term life of the pavement cannotbe understated. As the pavement reaches design life, thesubgrade will not have to be reconstructed in order to supportthe rehabilitated subgrade or the reconstructed pavement. Inurban areas, subgrade basic engineering properties arerequired for design. This section summarizes the design andconstruction elements for subgrades.

2.7.2 Site preparation Site preparation is the first major activity in constructingpavements. This activity includes removing or stripping offthe upper soil layer(s) from the natural ground. All organicmaterials, topsoil, and stones greater than 3 inches in sizeshould be removed. Removal of surface soils containing organicmatter is important not only for settlement, but also becausethese soils are often moisture-sensitive, they losesignificant strength when wet and are easily disturbed underconstruction activities. Most construction projects will alsorequire excavation or removal of in-situ soil to reach adesign elevation or grade line.

2.7.3 Design considerations

Subgrade soil is part of the pavement support system. Subgradeperformance generally depends on three basic characteristics:

a. Strength. The subgrade must be able to support loadstransmitted from the pavement structure. This load-bearing capacity is often affected by degree ofcompaction, moisture content, and soil type. A subgradehaving a California Bearing Ratio (CBR) of 10 or greater

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is considered essential and can support heavy loads andrepetitious loading without excessive deformation.

b. Moisture content. Moisture tends to affect a number ofsubgrade properties, including load-bearing capacity,shrinkage, and swelling. Moisture content can beinfluenced by a number of factors, such as drainage,groundwater table elevation, infiltration, or pavementporosity (which can be affected by cracks in thepavement). Generally, excessively wet subgrades willdeform under load.

c. Shrinkage and/or swelling:

Some soils shrink or swell, depending upon their moisturecontent. Additionally, soils with excessive fines contentmay be susceptible to frost heave in northern climates.Shrinkage, swelling, and frost heave will tend to deformand crack any pavement type constructed over them.Pavement performance also depends on subgrade uniformity.However, a perfect subgrade is difficult to achieve dueto the inherent variability of the soil and influence ofwater, temperature, and construction activities. Emphasisshould be placed on developing a subgrade CBR of at least10. Research has shown that with a subgrade strength ofless than a CBR of 10, the subbase material will deflectunder traffic loadings in the same manner as thesubgrade. That deflection then impacts the pavement,initially for flexible pavements, but ultimately rigidpavements as well.

2.8 Subgrade construction

2.8.1 General:

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The most critical element for subgrade construction is todevelop a CBR of at least 10 in the prepared sub grade usingon-site, borrow, or modified soil (see Section 6H-1,Foundation Improvement and Stabilization). Uniformity isimportant, especially for rigid pavements, but the high levelof subgrade support will allow the pavement to reach thedesign life. In most instances, once heavy earthwork and finegrading are completed, the uppermost zone of sub grade soil(roadbed) is improved. The typical improvement technique isachieved by means of mechanical stabilization (i.e.,compaction). Perhaps the most common problem arising fromdeficient construction is related to mechanical stabilization.Without proper quality control and quality assurance (QC/QA)measures, some deficient work may go unnoticed. This is mostcommon in utility trenches and bridge abutments, where it isdifficult to compact because of vertical constraints. Thistype of problem can be avoided, or at least minimized, with athorough plan and execution of the plan as it relates to QC/QAduring construction. This plan should pay particular attentionto proper moisture content, proper lift thickness forcompaction, and sufficient configuration of the compactionequipment utilized (weight and width are the most critical).Failure to adequately construct and backfill trench lines willmost likely result in localized settlement and cracking at thepavement surface.

2.8.2 Compaction

Compaction of sub grade soils is a basic sub grade detail andis one of the most fundamental geotechnical operations for anypavement project. The purpose of compaction is generally toenhance the strength or load-carrying capacity of the soil,while minimizing long-term settlement potential. Compactionalso increases stiffness and strength, and reduces swellingpotential for expansive soils.

2.8.3 Density/moisture:

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The most common measure of compaction is density. Soil densityand optimum moisture content should be determined according toASTM D 698 (Standard Proctor Density) or ASTM D 4253 and D4254 (Maximum and Minimum Index Density for Cohesion lessSoils). At least one analysis for each material type to beused as backfill should be conducted unless the analysis isprovided by the Engineer. Field density is correlated tomoisture-density relationships measured in the lab. Moisture-density relationships for various soils are discussed in Part6A, General Information. Optimal engineering properties for agiven soil type occur near its compaction optimum moisturecontent, as determined by the laboratory tests. At this state,a soils-void ratio and potential to shrink (if dried) or swell(if inundated with water) is minimized.

For pavement construction, cohesive sub grade soil densityshould satisfy 95% of Standard Proctor tests, with themoisture content not less than optimum and not greater than 4%above optimum. For cohesion less soils (sands and gravel), aminimum relative density of 65% should be achieved with themoisture content greater than the bulking moisture content.

2.8.4 Strength/stiffness:

Inherent to the construction of roadway embankments is theability to measure soil properties to enforce quality controlmeasures. In the past, density and moisture content have beenthe most widely measured soil parameters in conjunction withacceptance criteria. However, it has been shown recently thatdensity and moisture content may not be an adequate analysis.Therefore, alternate methods of in-situ testing have beenreviewed. The dual mass Dynamic Cone Penetrometer (DCP) is amethod for estimating in-place stability from CBRcorrelations.

1.8.5 Equipment:

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Several compaction devices are available in modern earthwork,and selection of the proper equipment is dependent on thematerial intended to be densified. Generally, compaction canbe accomplished using pressure, vibration, and/or kneadingaction. Different types of field compaction equipment areappropriate for different types of soils. Steel-wheel rollers,the earliest type of compaction equipment, are suitable forcohesion less soils. Vibratory steel rollers have largelyreplaced static steel-wheel rollers because of their higherefficiency. Sheep foot rollers, which impart more of akneading compaction effort than smooth steel wheels, are mostappropriate for plastic cohesive soils. Vibratory versions ofsheep foot rollers are also available. Pneumatic rubber-tiredrollers work well for both cohesion less and cohesive soils.A variety of small equipment for hand compaction in confinedareas is also available.

2.9 Introduction To PavementSatisfactory pavement performance depends upon the properdesign and functioning of all of the key components of thepavement system. These include:

1. A wearing surface that provides sufficient smoothness,friction resistance, and sealing or drainage of surface water(i.e., to minimize hydroplaning).

2. Bound structural layers (i.e., asphalt or Portland cementconcrete) that provide sufficient load-carrying capacity, aswell as barriers to water intrusion into the underlyingunbound materials.

3. Unbound base and subbase layers that provide additionalstrength - especially for flexible pavement systems - andthat are resistant to moisture-induced deterioration(including swelling and freeze/thaw) and other degradation(e.g., erodibility, intrusion of fines).

4. A subgrade that provides a uniform and sufficiently stiff,strong, and stable foundation for the overlying layers.

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5. Drainage systems that quickly remove water from the pavementsystem before the water degrades the properties of theunbound layers and subgrade.

6. Remedial measures, in some cases, such as soilimprovement/stabilization or geosynthetics to increasestrength, stiffness, and/or drainage characteristics ofvarious layers or to provide separation between layers (e.g.,to prevent fines contamination).

Traditionally, these design issues are divided among manygroups within an agency. The geotechnical group is typicallyresponsible for characterizing the foundationcharacteristics of the subgrade. The materials group may beresponsible for designing a suitable asphalt or Portlandcement concrete mix and unbound aggregate blend for use asbase course. The pavement group may be responsible for thestructural ("thickness") design. The construction group maybe responsible for ensuring that the pavement structure isconstructed as designed. Nonetheless, the overall success ofthe design - i.e., the satisfactory performance of thepavement over its design life - is the holistic consequenceof the proper design of all of these key components.

2.9.1 Basic ConceptsPavements are layered systems designed to meet the followingobjectives:

to provide a strong structure to support the applied traffic loads (structural capacity).

to provide a smooth wearing surface (ride quality). to provide a skid-resistant wearing surface (safety).

Additionally, the system must have sufficient durability so that it does not deteriorate prematurely due to environmental influences (water, oxidation, temperature effects).

The unbound soil layers in a pavement provide a substantialpart of the overall structural capacity of the system,especially for flexible pavements (often more than 50percent). As shown in Figure 2.4 , the stresses induced in a

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pavement system by traffic loads are highest in the upperlayers and diminish with depth. Consequently, higher quality- and generally more expensive - materials are used in themore highly stressed upper layers of all pavement systems,and lower quality and less expensive materials are used forthe deeper layers of the pavement (Figure 2.5).

Figure 2.4 Attenuation of load-induced stresses with depth.

Figure 2.5 Variation of material quality with depth ina pavement system with ideal drainage characteristics.

As is the case for all geotechnical structures, pavementswill be strongly influenced by moisture and otherenvironmental factors. Water migrates into the pavementstructure through combinations of surface infiltration (e.g.,through cracks in the surface layer), edge inflows (e.g.,from inadequately drained side ditches or inadequateshoulders), and from the underlying groundwater table (e.g.,via capillary potential in fine-grained foundation soils).In cold environments, the moisture may undergo seasonal

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freeze/thaw cycles. Moisture within the pavement systemnearly always has detrimental effects on pavementperformance. It reduces the strength and stiffness of theunbound pavement materials, promotes contamination of coarsegranular material due to fines migration, and can causeswelling (e.g., frost heave and/or soil expansion) andsubsequent consolidation. Moisture can also introducesubstantial spatial variability in the pavement propertiesand performance, which can be manifested either as localdistresses, like potholes, or more globally as excessiveroughness. The design of the geotechnical aspects ofpavements must consequently focus on the selection ofmoisture-insensitive free-draining base and subbasematerials, stabilization of moisture-sensitive subgradesoils, and adequate drainage of any water that doesinfiltrate into the pavement system.

2.9.2 A Historical Perspective Of Pavement Design

Pavements with asphalt or concrete surface layers have beenused in the United States since the late 1880s. Althoughpavement materials and construction methods have advancedsignificantly over the past century, until the last decade,pavement design has been largely empirical, based onregional experience. Even the empirically based designs ofthe 1980s and 1990s, as expressed in the AASHTO 1986, 1993,and 1998, guidelines have been, for most cases, modified bystate agencies, based on regional experience. For example,several agencies still use their own modifications of the1972 AASHTO design guidelines. Currently, approximatelyone-half of the state agencies are using the 1993 guide,albeit usually with some modification. This close relianceon empirical evidence makes it difficult to adopt newdesign concepts. Empirical designs are significantlychallenged by constantly changing design considerations(e.g., traffic loads and number of applications, types ofpavements, road base aggregate supply, etc.). An additionalchange is the type of pavement construction, which hasshifted over the past several decades from new constructionto rehabilitation. Recycled materials now often replace newconstruction materials. During the past ten years, a major

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thrust has been to develop a more scientific explanation ofthe interaction between the pavement structure, thematerials, the environment and the wheel loading. The needfor a more sophisticated design method becomes even moreapparent when considering the number of variables, withmore than twenty just for the geotechnical features (e.g.,unit weight, moisture content, gradation, strength,stiffness, and hydraulic conductivity that influence thedesign in a modern pavement system.

Fortunately, the tools available for design have alsosignificantly advanced over the past several decades.Specifically, computerized numerical modeling techniques(i.e.,

mechanistic models) are now available that can accommodatethe analysis of these complex interaction issues and, atthe same time, allow the models to be modified based onempirical evidence. The new national Pavement Design Guidedevelopment under NCHRP Project 1-37A (NCHRP 1-37A DesignGuide) provides the basis for the information in thesechapters. Several agencies have already adoptedmechanistic-empirical analysis, at least as a secondarymethod for flexible pavement design (Newcomb and Birgisson,1999). The newer, more sophisticated design models forflexible and rigid pavements rely heavily on accuratecharacterization of the pavement materials and supportingconditions for design input. As a result, there is agreater reliance on geotechnical inputs in the designmodels. Geotechnical exploration and testing programs areessential components in the reliability of pavement designand have also advanced significantly in the past severaldecades.

Better methods for subsurface exploration and evaluationhave been developed over time. Standard penetration tests(SPT), where a specified weight is dropped from a specificheight on a thick-walled tube sampler to obtain an indexstrength value and disturbed sample of the subgrade, wasdeveloped in the 1920s. A typical practice is to locate thesampling intervals at a standard spacing along the roadwayalignment. However, subgrade conditions can varyconsiderably both longitudinally and transversely to the

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alignment. This approach evaluates and samples less than abillionth of the soil along the roadway alignment, oftenmissing critical subsurface features and/or variations. Inaddition, the SPT value itself has a coefficient ofvariation of up to 100% (Orchant et al., 1988). Based on theseconsiderations, one must question the use of this approachas the sole method for subsurface evaluation.

Empirical design methods of the past often relied on indextests such as CBR or R-value for characterizing thesupporting aggregate and subgrade materials. Just as thedesign methods were modified for local conditions, agencieshave modified the test methods to the extent that there arecurrently over ten index methods used across the UnitedStates to characterize these materials. Tests include theIBR (Illinois), the LBR (Florida), the Washington R-value,the California R-value, the Minnesota R-value, and theTexas triaxial, to name a few. Rough correlations betweenmany of these methods are reviewed in Chapter 5.Considering that both the design and the input values mayrely upon local knowledge, it is not surprising thatcomparison of test sections constructed by differentagencies is often difficult. A method that allows fordirect modeling of the dynamic response of subsurface soilsand base course aggregate materials is the resilientmodulus test.

Throughout the history of pavement design, special problemshave been encountered in relation to pavement support.These include expansive soils, frost susceptible materials,caliche, karst topography, pumping soils and highlyfluctuating groundwater conditions. The solution to theseproblems is often to remove and replace these materials,often at great expense to the project.

2.9.3 The Pavement System And Typical Pavement Types

The purpose of the pavement system is to provide a smoothsurface over which vehicles may safely pass under allclimatic conditions for the specific performance period ofthe pavement. In order to perform this function, a variety

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of pavement systems have been developed, the components ofwhich are basically the same.

2.9.4 Components of a Pavement System

The pavement structure is a combination of subbase, basecourse, and surface course placed on a subgrade to supportthe traffic load and distribute it to the roadbed.

The subgrade is the top surface of a roadbed upon which thepavement structure and shoulders are constructed. Thepurpose of the subgrade is to provide a platform forconstruction of the pavement and to support the pavementwithout undue deflection that would impact the pavement'sperformance. For pavements constructed on-grade or in cuts,the subgrade is the natural in-situ soil at the site. Theupper layer of this natural soil may be compacted orstabilized to increase its strength, stiffness, and/orstability.

For pavements constructed on embankment fills, the subgradeis a compacted borrow material. Other geotechnical aspectsof the subgrade of interest in pavement design include thedepth to rock and the depth to the groundwater table,especially if either of these is close to the surface.

The subbase is a layer or layers of specified or selectedmaterials of designed thickness placed on a subgrade tosupport a base course. The subbase layer is usually ofsomewhat lower quality than the base layer. In some cases,the subbase may be treated with Portland cement, asphalt,lime, flyash, or combinations of these admixtures toincrease its strength and stiffness. A subbase layer is notalways included, especially with rigid pavements. A subbaselayer is typically included when the subgrade soils are ofvery poor quality and/or suitable material for the baselayer is not available locally, and is, therefore,expensive. Inclusion of a subbase layer is primarily aneconomic issue, and alternative pavement sections with andwithout a subbase layer should be evaluated during thedesign process.

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In addition to contributing to the structural capacity offlexible pavement systems, subbase layers have additionalsecondary functions:

Preventing the intrusion of fine-grained subgrade soils intothe base layer. Gradation characteristics of the subbaserelative to those of the subgrade and base materials arecritical here.

Minimizing the damaging effects of frost action. A subbaselayer provides insulation to frost-susceptible subgrades and,in some instances, can be used to increase the height of thepavement surface above the groundwater table.

Providing drainage for free water that may enter the pavementsystem. The subbase material must be free draining for thisapplication, and suitable features must be included in thepavement design for collecting and removing any accumulatedwater from the subbase.

Providing a working platform for construction operations incases where the subgrade soil is very weak and cannot providethe necessary support.

The base is a layer or layers of specified or selectmaterial of designed thickness placed on a subbase orsubgrade (if a subbase is not used) to provide a uniformand stable support for binder and surface courses. The baselayer typically provides a significant portion of thestructural capacity in a flexible pavement system andimproves the foundation stiffness for rigid pavements, asdefined later in this section. The base layer also servesthe same secondary functions as the subbase layer,including a gradation requirement that prevents subgrademigration into the base layer in the absence of a subbaselayer. It usually consists of high quality aggregates, suchas crushed stone, crushed slag, gravel and sand, orcombinations of these materials. The specifications forbase materials are usually more stringent than those forthe lower-quality subbase materials.

High quality aggregates are typically compacted unbound -i.e., without any stabilizing treatments - to form the baselayer. Materials unsuitable for unbound base courses canprovide satisfactory performance when treated withstabilizing admixtures, such as Portland cement, asphalt,

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lime, flyash, or a combination of these treatments, toincrease their strength and stiffness. These stabilizingadmixtures are particularly attractive when suitableuntreated materials are in short supply local to theproject site. Base layer stabilization may also reduce thetotal thickness of the pavement structure, resulting in amore economical overall design.

Finally, the surface course is one or more layers of apavement structure designed to accommodate the trafficload, the top layer of which resists skidding, trafficabrasion, and the disintegrating effects of climate. Thesurface layer may consist of asphalt (also calledbituminous) concrete, resulting in "flexible" pavement, orPortland cement concrete (PCC), resulting in "rigid"pavement. The top layer of flexible pavements is sometimescalled the "wearing" course. The surface course is usuallyconstructed on top of a base layer of unbound coarseaggregate, but often is placed directly on the preparedsubgrade for low-volume roads. In addition to providing asignificant fraction of the overall structural capacity ofthe pavement, the surface layer must minimize theinfiltration of surface water, provide a smooth, uniform,and skid-resistant riding surface, and offer durabilityagainst traffic abrasion and the climate.

Figure 2.6 expands the basic components, showing otherimportant features (e.g., drainage systems) that are oftenincluded in a pavement design. The permeable base drainagelayer in Figure 2.6 is provided to remove infiltrated waterquickly from the pavement structure. Suitable features,including edgedrains and drain outlets, must be included inthe pavement design for collecting and removing anyaccumulated water from the drainage layer. In order tofunction properly, the layer below the drainage layer mustbe constructed to grades necessary to promote positivesubsurface drainage (i.e., no undulations and reasonablecrown or cross slope). Filter materials (e.g., geotextiles)may also be required to prevent clogging of the drainagelayer and collector system.

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Figure 2.6 Pavement system with representative alternativefeatures.

The geotechnical components of a pavement system as coveredin this manual include surfacing aggregate, unboundgranular base, unbound granular subbase, the subgrade orroadbed (either mechanically or chemically stabilized, orboth), aggregate and geosynthetics used in drainagesystems, graded granular aggregate and geosynthetic used asseparation and filtration layers, and the roadwayembankment foundation.

2.9.5 Alternate Types of Pavement

The most common way of categorizing pavements is bystructural type: rigid, flexible, composite and unpaved.

Rigid pavements in simplest terms are those with a surfacecourse of Portland cement concrete (PCC). The Portland cementconcrete slabs constitute the dominant load-carryingcomponent in a rigid pavement system.

Flexible pavements, in contrast, have an asphaltic surface layer,with no underlying Portland cement slabs. The asphalticsurface layer may consist of high quality, hot mix asphaltconcrete, or it may be some type of lower strength andstiffness asphaltic surface treatment. In either case,flexible pavements rely heavily on the strength and stiffnessof the underlying unbound layers to supplement the loadcarrying capacity of the asphaltic surface layer.

Composite pavements combine elements of both flexible and rigidpavement systems, usually consisting of an asphaltic concretesurface placed over PCC or bound base.

Unpaved roads or naturally surfaced roads simply are not paved,relying on granular layers and the subgrade to carry the

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load. Seal coats are sometimes applied to improve theirresistance to environmental factors.

Pavements can also be categorized based on type ofconstruction:

New construction: The design and construction of a pavement on apreviously unpaved alignment. All pavements start as newconstruction.

Rehabilitation: The restoration or addition of structuralcapacity to a pavement. Overlays (either asphalt or Portlandcement concrete), crack and seat and full or partial depthreclamation are examples of rehabilitation construction.

Reconstruction: The complete removal of an existing pavement andconstruction of a new pavement on the same alignment. Exceptfor the demolition of the existing pavement (usually done instages, i.e., one lane at a time) and traffic control duringconstruction, reconstruction is very similar to newconstruction in terms of design.

2.9.6 Flexible Pavements (Adapted from AASHTO 1993)

As was described in Figure 2.4, flexible pavements ingeneral consist of an asphalt-bound surface course or layeron top of unbound base and subbase granular layers over thesubgrade soil. In some cases, the subbase and/or baselayers may be absent (e.g., full-depth asphalt pavements),while in others the base and/or subbase layers may bestabilized using cementitious or bituminous admixtures.Drainage layers may also be provided to remove waterquickly from the pavement structure. Some common variationsof flexible pavement systems are shown in Figure 2.7.

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Figure 2.7 Some common variations of flexible pavementsections (NCHRP 1-37A, 2002).

Hot mix asphalt concrete produced by an asphalt plant isthe most common surface layer material for flexiblepavements, especially for moderately to heavily traffickedhighways. Dense-graded (i.e., well-graded with a low voidratio) aggregates with a maximum aggregate size of about 25mm (1 in.) are most commonly used in hot mix asphaltconcrete, but a wide variety of other types of gradations(e.g., gap-graded) have also been used successfully forspecialized conditions. The Superpave procedure has becomethe standard for asphalt mixture design, although countyand local government agencies may still use the olderMarshall and Hveem mix design procedures (Asphalt InstituteMS-2, 1984).

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The asphalt surface layer in a flexible pavement may bedivided into sub-layers. Typical sub-layers, proceedingfrom the top downward, are as follows:

Seal coat: A thin asphaltic surface treatment used to increase(or restore) the water and skid resistance of the roadsurface. Seal coats may be covered with aggregate when usedto increase skid resistance.

Surface course (also called the wearing course): The topmost sublayer (inthe absence of a seal coat) of the pavement. This istypically constructed of dense graded asphalt concrete. Theprimary design objectives for the surface course arewaterproofing, skid resistance, rutting resistance, andsmoothness.

Binder course (also called the asphalt base course): The hot mix asphaltlayer immediately below the surface course. The base coursegenerally has a coarser aggregate gradation and often a lowerasphalt content than the surface course. A binder course maybe used as part of a thick asphalt layer either for economy(the lower quality asphalt concrete in the binder course hasa lower material cost than the higher-asphalt contentconcrete in the surface course) or if the overall thicknessof the surface layer is too great to be paved in one lift.

Additionally, thin liquid bituminous coatings may be usedin the pavement, as follows:

Tack coat: Applied on top of stabilized base layers and betweenlifts in thick asphalt concrete surface layers to promotebonding of the layers.

Prime coat: Applied on the untreated aggregate base layer tominimize flow of asphalt cement from the asphalt concrete tothe aggregate base and to promote a good interface bond.Prime coats are often used to stabilize the surface of thebase to support the paving construction activities above.Cutback asphalt (asphalt cement blended with a petroleumsolvent) is typically used because of its greater depthpenetration.

Proper compaction of the asphalt concrete duringconstruction is critical for satisfactory pavement

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performance. Improper compaction can lead to excessiverutting (permanent deformations) in the asphalt concretelayer due to densification under traffic; cracking orraveling of the asphalt concrete due to embrittlement ofthe bituminous binder from exposure to air and water; andfailure of the underlying unbound layers due to excessiveinfiltration of surface water. Typical constructionspecifications require field compaction levels of 92% ormore of the theoretical maximum density for the mixture.Layers of unbound material below the asphalt concretelayers must be constructed properly in order to achieve theoverall objectives of pavement performance.

2.9.7 Rigid Pavements

Rigid pavements in general consist of Portland cementpavement slabs constructed on a granular base layer overthe subgrade soil. The base layer serves to increase theeffective stiffness of the slab foundation. Gradationcharacteristics of the base and/or subbase are criticalhere. The base may also be stabilized with asphalt orcement to improve its ability to perform this function. Asubbase layer is occasionally included between the baselayer and the subgrade. The effective foundation stiffnesswill be a weighted average of the subbase and subgradestiffnesses. For high quality coarse subgrades (e.g.,stiffness equal to that of the base) or low traffic volumes(less than 1 million 80-kN (18-kip) ESALs), the base andsubbase layer may be omitted.

Because of the low stresses induced by traffic andenvironmental effects (e.g., thermal expansion andcontraction) relative to the tensile strength of Portlandcement concrete, most rigid pavement slabs are unreinforcedor only slightly reinforced. When used, the function ofreinforcement is to eliminate or lengthen spacing ofjoints, which fault and infiltrate water. Reinforcement inthe concrete does not influence subgrade supportrequirements. The subbase layer may be omitted if there islow truck traffic volume or good subgrade conditions. Forhigh traffic volumes and/or poor subgrade conditions, the

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subbase may be stabilized using cementitious or bituminousadmixtures. Drainage layers can and should be included toremove water quickly from the pavement structure, similarto flexible pavements. A geotextile layer may be used tocontrol migration of fines into the open graded base layer.

Rigid pavement systems are customarily divided into fourmajor categories:

Jointed Plain Concrete Pavements (JPCP) These unreinforced slabsrequire a moderately close spacing of longitudinal andtransverse joints to maintain thermal stresses withinacceptable limits. Longitudinal joint spacing typicallyconforms to the lane width (around 3.7 m (12 ft)), andtransverse joint spacing typically ranges between 4.5 - 9 m(15 - 30 ft). Aggregate interlock, often supplemented bysteel dowels or other load transfer devices, provides loadtransfer across the joints.

Jointed Reinforced Concrete Pavements (JRCP). The light wire mesh orrebar reinforcement in these slabs is not designed toincrease the load capacity of the pavement, but rather toresist cracking under thermal stresses and, thereby, permitlonger spacings between the transverse joints between slabs.Transverse spacing typically ranges between 9 - 30 m (30 -100 ft) in JRCP pavements. Dowel bars or other similardevices are required to ensure adequate load transfer acrossthe joints.

Continuously Reinforced Concrete Pavements (CRCP). Transverse joints arenot required in CRCP pavements. Instead, the pavement isdesigned so that transverse thermal cracks develop at veryclose spacings, with typical spacings on the order of a meter(a few feet). The continuous conventional reinforcement barsare designed to hold these transverse thermal cracks tightlytogether and to supplement the aggregate interlock at thecracks to provide excellent load transfer across the cracks.In addition to the benefit of no transverse joints, CRCPpavement designs are typically 25 - 50 mm (1 - 2 in.) thinnerthan conventional JPCP or JRCP systems.

Prestressed Concrete Pavements (PCP). PCP designs are similar toCRCP, except that the longitudinal reinforcement now consistsof continuous steel strands that are prestressed prior toplacing the concrete (or post-tensioned after the concrete

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has hardened). The initial tensile stress in thereinforcement counteracts the load- and thermal-inducedtensile stresses in the concrete and, therefore, permitsthinner slabs. Prestressed concrete pavements are morecommonly used for airfield pavements than for highwaypavements because of the greater benefit from thereinforcement in the comparatively thicker airfield slabs.Precast, prestressed concrete sections are also being usedfor pavement rehabilitation.

As suggested above, the basic components in rigid pavementslabs are Portland cement concrete, reinforcing steel,joint load transfer devices, and joint sealing materials.The AASHTO Guide Specifications for Highway Construction and theStandard Specifications for Transportation Materials provide guidance onmix design and material specifications for rigid highwaypavements. These specifications can be modified based onlocal conditions and experience. Pavement concrete tends tohave a very low slump, particularly for use in slip-formedpaving. Air-entrainment is used to provide resistance todeterioration from freezing and thawing and to improve theworkability of the concrete mix. Joint sealing materialsmust be sufficiently pliable to seal the transverse andlongitudinal joints in JPCP and JRCP pavements againstwater intrusion under conditions of thermal expansion andcontraction of the slabs. Commonly used joint sealingmaterials include liquid sealants (asphalt, rubber,elastomeric compounds, and polymers), preformed elastomericseals, and cork expansion filler.

Load transfer devices in JPCP and JRCP pavements aredesigned to spread the traffic load across transversejoints to adjacent slabs and correspondingly reduce oreliminate joint faulting. The most commonly used loadtransfer device is a plain, round steel dowel; these aretypically 450 mm (18 in.) long, 25 mm (1 in.) in diameter,and spaced at approximately every 300 mm (12 in.) alongtransverse joints. Tie bars, typically deformed steelrebars, are often used to hold the faces of abutting slabsin firm contact, but tie bars are not designed to act asload transfer devices.

2.9.8 Composite Pavements

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Composite pavements consist of asphaltic concrete surfacecourse over PCC or treated bases as shown in Figure 2.10Composite pavements with PCC over asphalt are also beingused. The treated bases may be either asphalt-treated base(ATB) or cement-treated base (CTB). The base layers aretreated to improve stiffness and, in the case of permeablebase, stability for construction.

Figure 2.8Typical composite pavement sections.

2.9.9 Unpaved Roads (Naturally Surfaced)

Why use a paved surface? Over one-half of the roads in theUnited States are unpaved. In some cases, these roads aresimply constructed with compacted or modified subgrade. Inmost cases, a gravel (base) layer is used as the wearingsurface. Because of sparse population and low volumes oftraffic, these roads will remain unpaved long into thefuture. Consideration for the subgrade are, again, the sameas with flexible pavement, albeit the load levels aregenerally much higher. The subgrade should also be crownedto a greater extent than paved sections to promote drainageof greater quantities of infiltration surface water. Thefunction of the gravel surfaced is now to carry the loadand to provide adequate service. The problems with this

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approach include roughness, lateral displacement of surfacegravel, traction, and dust. Maintenance of ditch lines isalso problematic, due to continuous infilling, but openditches are critical to long-term performance.

Chapter: 03 METHODOLOGY

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3.1 ATTERBERG LIMITS

Purpose:

This test is performed to determine the plastic and liquidlimits of a fine grained soil. The liquid limit (LL) isarbitrarily defined as the water content, in percent, at whicha part of soil in a standard cup and cut by a groove ofstandard dimensions will flow together at the base of thegroove for a distance of 13 mm (1/2 in.) when subjected to 25shocks from the cup being dropped 10 mm in a standard liquidlimit apparatus operated at a rate of two shocks per second.The plastic limit (PL) is the water content, in percent, atwhich a soil can no longer be deformed by rolling into 3.2 mm(1/8 in.) diameter threads without crumbling.

Standard Reference:ASTM D 4318 - Standard Test Method for Liquid Limit, PlasticLimit, andPlasticity Index of Soils

Significance:The Swedish soil scientist Albert Atterberg originally definedseven “limits of consistency” to classify fine-grained soils,but in current engineering practice only two of the limits,the liquid and plastic limits, are commonly used. (A thirdlimit, called the shrinkage limit, is used occasionally.) TheAtterberg limits are based on the moisture content of thesoil. The plastic limit is the moisture content that defineswhere the soil changes from a semi-solid to a plastic(flexible) state. The liquid limit is the moisture contentthat defines where the soil changes from a plastic to aviscous fluid state. The shrinkage limit is the moisturecontent that defines where the soil volume will not reducefurther if the moisture content is reduced. A wide variety ofsoil engineering properties have been correlated to the liquidand plastic limits, and these Atterberg limits are also usedto classify a fine-grained soil according to the Unified SoilClassification system or AASHTO system.

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Equipment:Liquid limit device, Porcelain (evaporating) dish, Flatgrooving tool with gage,Eight moisture cans, Balance, Glass plate, Spatula, Washbottle filled with distilled water, Drying oven set at 105°C.

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Fig : 3.1

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Fig :3.2

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TestProcedure:3.1.1 Liquid Limit:

(1) Take roughly 3/4 of the soil and place it into theporcelain dish. Assume that the soil was previously passedthough a No. 40 sieve, air-dried, and then pulverized.Thoroughly mix the soil with a small amount of distilled wateruntil it appears as a smooth uniform paste. Cover the dishwith cellophane to prevent moisture from escaping.

(2) Weigh four of the empty moisture cans with their lids, andrecord the respective weights and can numbers on the datasheet.(3) Adjust the liquid limit apparatus by checking the heightof drop of the cup. The point on the cup that comes in contactwith the base should rise to a height of 10 mm. The block onthe end of the grooving tool is 10 mm high and should be usedas a gage. Practice using the cup and determine the correctrate to rotate the crank so that the cup drops approximatelytwo times per second.

(4) Place a portion of the previously mixed soil into the cupof the liquid limit apparatus at the point where the cup restson the base. Squeeze the soil down to eliminate air pocketsand spread it into the cup to a depth of about 10 mm at itsdeepest point. The soil pat should form an approximatelyhorizontal surface (See Photo B). (5) Use the grooving tool carefully cut a clean straightgroove down the center of the cup. The tool should remainperpendicular to the surface of the cup as groove is beingmade. Use extreme care to prevent sliding the soil relative tothe surface of the cup (See Photo C).

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(6) Make sure that the base of the apparatus below the cup andthe underside of the cup is clean of soil. Turn the crank ofthe apparatus at a rate of approximately two drops per secondand count the number of drops, N, it takes to make the twohalves of the soil pat come into contact at the bottom of thegroove along a distance of 13 mm (1/2 in.) (See Photo D). Ifthe number of drops exceeds 50, then go directly to step eightand do not record the number of drops, otherwise, record thenumber of drops on the data sheet.

(7) Take a sample, using the spatula, from edge to edge of thesoil pat. The sample should include the soil on both sides ofwhere the groove came into contact. Place the soil into amoisture can cover it. Immediately weigh the moisture cancontaining the soil, record its mass, remove the lid, andplace the can into the oven. Leave the moisture can in theoven for at least 16 hours. Place the soil remaining in thecup into the porcelain dish. Clean and dry the cup on theapparatus and the grooving tool.

(8) Remix the entire soil specimen in the porcelain dish. Adda small amount of distilled water to increase the watercontent so that the number of drops required to close thegroove decrease.

(9) Repeat steps six, seven, and eight for at least twoadditional trials producing successively lower numbers ofdrops to close the groove. One of the trials shall be for aclosure requiring 25 to 35 drops, one for closure between 20and 30 drops, and one trial for a closure requiring 15 to 25drops. Determine the water content from each trial by usingthe same method used in the first laboratory. Remember to usethe same balance for all weighing.

3.1.2 Plastic Limit:

(1) Weigh the remaining empty moisture cans with their lids,and record the respective weights and can numbers on the datasheet.

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(2) Take the remaining 1/4 of the original soil sample and adddistilled water until the soil is at a consistency where itcan be rolled without sticking to the hands.

(3) Form the soil into an ellipsoidal mass (See Photo F). Rollthe mass between the palm or the fingers and the glass plate(See Photo G). Use sufficient pressure to roll the mass into athread of uniform diameter by using about 90 strokes perminute. (A stroke is one complete motion of the hand forwardand back to the starting position.)The thread shall bedeformed so that its diameter reaches 3.2 mm (1/8 in.), takingno more than two minutes.

(4) When the diameter of the thread reaches the correctdiameter, break the thread into several pieces. Knead andreform the pieces into ellipsoidal masses and re-roll them.Continue this alternate rolling, gathering together, kneadingand re-rolling until the thread crumbles under the pressurerequired for rolling and can no longer be rolled into a 3.2 mmdiameter thread (See Photo H).

(5) Gather the portions of the crumbled thread together andplace the soil into a moisture can, then cover it. If the candoes not contain at least 6 grams of soil, add soil to the canfrom the next trial (See Step 6). Immediately weigh themoisture can containing the soil, record its mass, remove thelid, and place the can into the oven. Leave the moisture canin the oven for at least 16 hours.

(6) Repeat steps three, four, and five at least two moretimes. Determine the water content from each trial by usingthe same method used in the first laboratory. Remember to usethe same balance for all weighing.

Analysis:Liquid Limit:

(1) Calculate the water content of each of the liquid limitmoisture cans after they have been in the oven for at least 16hours.

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(2) Plot the number of drops, N, (on the log scale) versus thewater content (w). Draw the best-fit straight line through theplotted points and determine the liquid limit (LL) as thewater content at 25 drops.

Plastic Limit:

(1) Calculate the water content of each of the plastic limitmoisture cans after they have been in the oven for at least 16hours.

(2) Compute the average of the water contents to determine theplastic limit, PL. Check to see if the difference between thewater contents is greater than the acceptable range of tworesults (2.6 %).(3) Calculate the plasticity index, PI=LL-PL.3.2 DETERMINATION OF GRAIN SIZE ANALYSIS

Purpose: This test is performed to determine thepercentage of different grain sizes contained within a soil.

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Fig:3.3

APPARATUS:Balance of capacity 15 Kg and sensitivity 1 gram.Sieves 100mm, 75mm, 19mm, 4.75mm, 2mm, 425microns and75microns conforming toIS: 460 (Part 1) 1978.Non-corrodible trays.Bucket 1no.

Sieving procedure

(1) Write down the weight of each sieve as well as the bottompan to be used in the analysis.(2) Record the weight of the given dry soil sample.(3) Make sure that all the sieves are clean, and assemble themin the ascending order of sieve numbers (#4 sieve at top and

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#200 sieve at bottom). Place the pan below #200 sieve.Carefully pour the soil sample into the top sieve and placethe cap over it.(4) Place the sieve stack in the mechanical shaker and shakefor 10 minutes.(5) Remove the stack from the shaker and carefully weigh andrecord the weight of each sieve with its retained soil. Inaddition, remember to weigh and record the weight of thebottom pan with its retained fine soil.

Significance:The distribution of different grain sizes affects theengineering properties of soil.

Grain size analysis provides the grain size distribution, andit is required in classifying the soil.

Data Analysis:

(1) Obtain the mass of soil retained on each sieve bysubtracting the weight of the empty sieve from the mass of thesieve + retained soil, and record this mass as the weightretained on the data sheet. The sum of these retained massesshould be approximately equals the initial mass of the soilsample. A loss of more than two percent is unsatisfactory.(2) Calculate the percent retained on each sieve by dividingthe weight retained on each sieve by the original sample mass.(3) Calculate the percent passing (or percent finer) bystarting with 100 percent and subtracting the percent retainedon each sieve as a cumulative procedure.

3.3 STANDARD PROCTOR COMPACTION TESTIntroduction

For construction of highways, airports, and other structures,it is often necessary to compact soil to improve its strength.Proctor (1933) developed a laboratory compaction testprocedure to determine the maximum dry unit weight ofcompaction of soils, which can be used for specification offield compaction. This test is referred to as the Standard

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Proctor Compaction Test. It is based on compaction of soilfraction passing No. 4 U.S. sieve.

Equipment

1. Compaction mold 2. No. 4 U.S. sieve3. Standard Proctor hammer (5.5 lb)4. Balance sensitive up to 0.01g5. Balance sensitive up to 0.1g6. Large flat pan7. Jack8. Steel straight edge9. Moisture cans10. Drying oven11. Plastic squeeze bottle with water

Proctor Compaction Mold and Hammer:

The Proctor compaction mold and hammer is 4” in diameter and4.584” in height. The inner volume is 1/30 ft3. The height offall of the hammer is 12".Weight of hammer is 5.5 lb.

Procedure

1. Obtain about 10 lb of air dry soil and break the soil lumps.2. Sieve the soil on a No. 4 U.S. sieve. Collect all the minus

4 sieve materials (about 6 lb) in a large pan.3. Add water to the minus 4 sieve materials and mix thoroughly

to bring the moisture content to about 5%.4. Determine the weight of the Proctor Mold + base plate (not

extension).5. Attach the extension to the top of the mold.6. Pour the moist soil in three equal layers. Compact each

layer uniformly with the Standard Proctor hammer 25 timesbefore each additional layer of loose soil is poured. Atthe end of the three-layer compaction, the soil shouldextend slightly above the top of the rim of the compactionmold.

7. Remove the extension carefully.8. Trim excess soil with a straight edge.

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9. Determine the weight of the Proctor Mold + base plate +compacted moist soil

10. Remove the base plate from the mold. Extrude thecompacted moist soil cylinder using a jack.

11. Take a moisture can and determine its mass.12. From the moist soil extruded in step 10, collect a moist

sample in a moisture can (step 11) and determine the mass ofmoist soil + can.

13. Place the moisture can with soil in the oven to dry to aconstant weight.

14. Break the rest of the soil cylinder by hand and mix withleftover moist soil. Add more water and mix to raisemoisture content by 2%.

15. Repeat steps 6-12. In this process, the weight of themold + base plate + moist soil will first increase with theincrease in moisture content and then decrease. Continuethe test until at least two successive decreased readingsare obtained.

16. The next day, determine the mass of the moisture cans +soil samples, (from step 13).

Calculation

1. Determine weight of the mold W1(step 4).2. Determine weight of the mold + compacted moist soil , W2

(step 9).3. Determine weight of the compacted moist soil = W2-W1.4. Moist unit weight γ = weight of the compacted moist soil /

volume of mold = (W2 - W1) / (1/30 ft3).5. Determine mass of moisture can, W3 (step 11).6. Determine mass of moisture can + moist soil, W4 (step 12).7. Determine mass of moisture can + dry soil, W5 (step 16).8. Compaction moisture content , w (%) = (W4 - W5) x 100 / (W5

- W3).9. Dry unit weight γd = γ / (1 + w (%) / 100).10. Volume of mold = 1/30 ft3

3.4 DENSITY OF SOIL BY CORE CUTTER METHOD

Aim of the Experiment:

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To determine the field or in-situ density or unit weight ofsoil by core cutter method

Apparatus Required:

a) Special:i. Cylindrical core cutterii. Steel rammeriii. Steel dollyb) General:i. Balance of capacity5 Kg and sensitivity 1 gm.ii. Balance of capacity 200gms and sensitivity 0.01 gms.iii. Scaleiv. Spade or pickaxe or crowbarv. Trimming Knifevi. Ovenvii. Water content containersviii. Desiccators.

Theory:Field density is defined as weight of unit volume of soilpresent in site. That is = W/V

Where, = Density of soil W = Total weight of soil V = Total volume of soil

The soil weight consists of three phase system that issolids, water and air. Thevoids may be filled up with both water and air, or only withair, or only with water. Consequently the soil may be dry,saturated or partially saturated.

In soils, mass of air is considered to be negligible, andtherefore the saturateddensity is maximum, dry density is minimum and wet density isin between the two.Dry density of the soil is calculated by using equation,

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γd=

γb1+w

Where, rd = dry density of soil rb= Wet density of soil w = moisture content of soil.

Density or unit weight of soils may be determined by using thefollowing method:

i. Core cutter methodii. Sand replacement testiii. Rubber balloon testiv. Water displacement methodv. Gamma ray method

Hear we use core cutter method, the equipment arrangement isshown as fall

Fig: 3.4

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Application:

Field density is used in calculating the stress in the soildue to its overburdenpressure it is needed in estimating the bearing capacity ofsoil foundation system,settlement of footing earth pressures behind the retainingwalls and embankments.Stability of natural slopes, dams, embankments and cuts ischecked with the help ofdensity of those soils. It is the density that controls thefield compaction of soils.Permeability of soils depends upon its density. Relativedensity of cohesion less soilsis determined by knowing the dry density of soil in natural,loosest and denseststates. Void ratio, porosity and degree of saturation need thehelp of density of soil.Core cutter method in particular, is suitable for soft tomedium cohesive soils, inwhich the cutter can be driven. It is not possible to drivethe cutter into hard, boulderor murrumy soils. In such case other methods are adopted.

Procedure:i. Measure the height and internal diameter of the corecutter.ii. Weight the clean core cutter.iii. Clean and level the ground where the density is to bedetermined.iv. Press the cylindrical cutter into the soil to its fulldepth with the help of steel rammer.v. Remove the soil around the cutter by spade.vi. Lift up the cutter.vii. Trim the top and bottom surfaces of the sample carefully.viii. Clean the outside surface of the cutter.ix. Weight the core cutter with the soil.x. Remove the soil core from the cutter and take therepresentative sample inthe water content containers to determine the moisturecontent.

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Precautions:i. Steel dolly should be placed on the top of the cutterbefore ramming it down into the ground.ii. Core cutter should not be used for gravels, boulders orany hard ground.iii. Before removing the cutter, soil should be removed aroundthe cutter to minimize the disturbances.

3.5 DETERMINATION OF CALIFORNIA BEARING RATIOSTANDARDDEFINITION· California bearing ratio is the ratio of force per unit arearequired to penetrate in to a soilmass with a circular plunger of 50mm diameter at the rate of1.25mm / min.APPARTUS· Moulds 2250cc capacity with base plate, stay rod and wingnut confirming to 4.1, 4.3 and4.4 ofIS: 9669-1980.· Collar confirming to 4.2 of IS: 9669-1980.· Spacer Disc confirming to 4.4 of IS: 9669-1980.· Metal rammer confirming to IS: 9189-1979.· Expansion measuring apparatus with the adjustable stem,perforated plates, tripodconfirming and to weights confirming to 4.4 of IS: 9669-1980.· Loading machine having a capacity of at least 5000kg andequipped with a movable head orbase that travels at a uniform rate of 1.25mm / min for use inforcing the penetration plungerin to the specimen.· Penetration plunger confirming to 4.4 of IS: 9669-1980.· Dial gauge two numbers reading to 0.01mm.· IS sieves 37.50 or 22.50 or 19mm and 4.75mm.· Miscellaneous apparatus such as mixing bowl, straight edge,scales, soaking tank, dryingoven, filter paper, dishes and calibrated measuring jar.

PROCEDURE

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· There are two types of methods in compacting soil specimenin the CBR mouldsi. Static Compaction method.ii. Dynamic Compaction method.· The material used in the above two methods shall pass 19mmsieve for fine grained soilsand 37.50mm sieve for coarse materials up to 37.50mm.· Replace the material retained on 19mm sieve by an equalamount of material passing 19mmsieve and retained on 4.75mm sieve· Replace the material retained on 37.50mm sieve by an equalamount of material passing37.50mm sieve and retained on 4.75mm sieve.

Static Compaction· In this method calculate the mass of wet soil at requiredmoisture content to give a desireddensity when compacted in a standard test mould as given belowVolume of mould = 2250cc.Weight of dry soil (W) = 2250 x MDD.mWeight of wet soil =1+ ---------- x W100Weight of water = Weight of wet soil - Weight of dry soil.m = Optimum moisture content obtained from the laboratorycompaction test.· Take oven dried soil sample of calculated weight andthoroughly mix with water (OMC) asobtained from the above equation.· Record the empty weight of the mould with base plate, withextension collar removed (m1).· Place the correct mass of the wet soil in to the mould infive layers.· Gently compact each layer with the spacer disc.· Place a filter paper on top of the soil followed by a 5cmsdisplacer disc.· Compact the mould by pressing it in between the platens ofthe compression testingmachine until the top of the spacer disc comes flush with thetop of the mould.· Held the load for about 30 seconds and then release.

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· In some soil types where a certain amount of rebound occurs,it may be necessary to reapplyload to force the displacer disc slightly below the top of themould so that on rebound theright volume is obtained.· Remove the mould from the compression testing machine.· Remove the spacer disc and weigh the mould with compactedsoil (m2).· Replace the extension collar of the mould.· Prepare two more specimens in the same procedure asdescribed above.

Dynamic Compaction· Take representative sample of soil weighing approximately6kg and mix thoroughly atOMC.· Record the empty weight of the mould with base plate, withextension collar removed (m1).· Replace the extension collar of the mould.· Insert a spacer disc over the base plate and place a coarsefilter paper on the top of thespacer disc.· Place the mould on a solid base such as a concrete floor orplinth and compact the wet soilin to the mould in five layers of approximately equal masseach layer being given 56 blows38with 4.90kg hammer equally distributed and dropped from aheight of 450 mm above thesoil.· The amount of soil used shall be sufficient to fill themould, leaving not more than about6mm to be struck off when the extension collar is removed.· Remove the extension collar and carefully level thecompacted soil to the top of the mouldby means of a straight edge.· Remove the spacer disc by inverting the mould and weigh themould with compacted soil(m2).· Place a filter paper between the base plate and the invertedmould.· Replace the extension collar of the mould.

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· Prepare two more specimens in the same procedure asdescribed above.· In both the cases of compaction, if the sample is to besoaked, take representative samplesof the material at the beginning of compaction and anothersample of remaining materialafter compaction for the determination of moisture content.· Each sample shall weigh not less than 100g for fine-grainedsoils and not less than 500 forgranular soils.· Place the adjustable stem and perforated plate on thecompacted soil specimen in the mould.· Place the weights to produce a surcharge equal to the weightof base material and pavementto the nearest 2.5kg on the perforated plate.· Immerse the whole mould and weights in a tank of waterallowing free access of water tothe top and bottom of specimen for 96 hours.Test for Swelling· This test is optional and may be omitted if not necessary.· Determine the initial height of specimen (h) in mm.· Mount the expansion-measuring device along with the tripodon the edge of the mould andrecord the initial dial gauge reading (ds).· Keep this set up as such undisturbed for 96 hours notingdown the readings every dayagainst the time of reading.· Maintain a constant water level throughout the period ofsoaking.· Note the final reading of the dial gauge at the end ofsoaking period (dh).Penetration Test· After 96 hours of soaking take out the specimen from thewater and remove the extensioncollar, perforated disc, surcharge weights and filter paper.· Drain off the excess water by placing the mould inclined forabout 15 minutes and weighthe mould.· Place the mould on the lower plate of the testing machinewith top face exposed· To prevent upheaval of soil in to the hole of surchargeweights, place 2.5kg annular weights

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on the soil surface prior to seating the penetration plungerafter which place the reminder ofthe surcharge weights.· Set the plunger under a load of 4kg so that full contact isestablished between the surface ofthe specimen and the plunger.· Set the stress and strain gauges to zero.· Consider the initial load applied to the plunger as the zeroload.· Apply the load at the rate of 1.25 mm / min as shown in Fig:2.9.1.· Take the readings of the load at penetration of 0, 0.5, 1.0,1.5, 2.0, 2.5, 3.0, 4, 5, 7.5, 10 and12.5.· Raise the plunger and detach the mould from the loadingequipment.· Collect the sample of about 20 to 50gms of soil from the top30mm layer of specimen anddetermine the water content in accordance with IS: 2720 (Part4) 1973.· Examine the specimen carefully after the test is completedfor the presence of any over sizesoil particles, which are likely to affect the results if theyhappen to be located directlybelow the penetration plunger.40CALCULATION OF CBR : Penetration 10 blows 30 bows 65

blowsStress 10

Stress 30

Stress65

252 27 40 183 5.27958

7.82161

35.788

CBR 10 30 650.1 in 7.510083 11.12605 50.90167

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Chapter : 04

ANALYSIS ANDRESULTS

4.1 Atterberg limits :

Liquid Limit Determination

Sample no. 1 2 3 4

MC = Mass of empty, clean can +lid (grams)

22.23

23.31 21.87 22.58

MCMS = Mass of can, lid, andmoist soil (grams)

28.56

29.27 25.73 25.22

MCDS = Mass of can, lid, and drysoil (grams)

27.40

28.10 24.90 24.60

MS = Mass of soil solids (grams) 5.03 4.79 3.03 2.02

MW = Mass of pore water (grams) 1.16 1.17 0.83 0.62

w = Water content, w% 23.06

24.43 27.39 30.69

No. of drops (N) 31 29 20 14

Plastic Limit Determination :Sample no. 1 2 3

MC = Mass of empty, clean can +lid (grams)

7.78 7.83 15.16

MCMS = Mass of can, lid, andmoist soil (grams)

16.39 13.43 21.23

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MCDS = Mass of can, lid, and drysoil (grams)

15.28 12 .69 20.43

MS = Mass of soil solids (grams) 7.5 4.86 5.27

MW = Mass of pore water (grams) 1. 11 0.74 0.8

w = Water content, w% 14.8 15.2 15.1

Plastic Limit (PL)= Average w % = 14.8 + 15.2 + 15.1 = 15.0 3 LIQUID LIMIT CHART :

From the above graph, Liquid Limit = 26 %

Final Results: Liquid Limit = 26 % Plastic Limit = 15 % Plasticity Index =11 Aashto Classification:

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Group: A-6 Soil Type: ClayeyGeneral Rating as a Subgrade: Fair to poor

Unified Soil Classification :

Soil Type :

64

The soil was classified as CLaccording to Unified Soil Classification System.

4.2 DETERMINATION OF GRAIN SIZE ANALYSIS weight of sample=1000 gm

Sieve NoSieve size (mm)

Wt of Soil (gm) retained

% wt retained

Cumulative % wt retained

% passing

#4 4.76 280 28 28 72#10 2.00 150 15 43 57#40 0.425 200 20 63 37#50 0.300 80 8 71 29#60 0.251 30 3 74 26#100 0.150 50 5 79 21#120 0.125 110 11 90 10#200 0.075 15 1.5 91.5 8.5PAN 85 8.5 100 0

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Coefficients of Uniformity , Cu :

D60 = 2.6 mm D10 = 0.125 mm

Cu= 20.8

Coefficient of curvature , Cc :

D30 = 0.3 mm

Cc= 0.276

4.3 Standard Proctor Compaction Test :

Determination of water content : w % ( w = Ww/Wd x 100 )

1 2 3 4

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Wt of empty Container (gm)

23.3 24 27.3 25

Wt of empty Container + compacted soil (gm)

55.8 56.2 58.1 57

Wt of Container + Dry soil

52.3 51.7 53.8 51.7

Wt of water (gm) 3.5 4.5 4.3 5.3

Wt of Dry soil (gm) 30 33.1 26.5 26.7

Water content , W % 11.66 13.6 16.22 19.85

Determination of Dry density:

Wt of empty mould 3395 (g)

3395 (g)

3395 (g)

3395 (g)

Wt of empty mould + Compacted Soil

4970 (g)

5215 (g)

5385 (g)

5235 (g)

Volume of mould 945 c.c 945 c.c 945 c.c 945 c.c

Wt of Compacted Soil 1575 (g)

1820 (g)

1990 (g)

1840 (g)

Bulk Density , Ws/V 1.67 g/c.c

1.93 g/c.c

2.11 g/c.c

1.95 g/c.c

Dry density 93.43 pcf

105.88 pcf

112.74 pcf

101.53 pcf

67

9 12 15 18 21 24 27 30 3310

20

30

40

50

60

70

80

90

100

110

120Standard Proctor Test

water content , w %Dry

dens

ity

, pc

f

OMC = 16.4 %

MDD = 114.3 lb/ft3

4.4 Determination Of filed Density by Core Cutter Method :

Internal diameter of cutter : 10 cm

Height of the cutter : 11.5 cm

Cross sectional area of the cutter : 78.54 cm2

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Volume of the cutter, V :903.2 cm3

Sample 1 2 3

Wt of empty Cutter (W1)

735 gm 735 gm 735 gm

Wt of Cuter + Wet Soil (W2)

2200 gm 2350 gm 2500 gm

Volume of Cutter , V

903.2 cm3 903.2 cm2 903.2 cm2

Wt of Wet Soil ,W3 = W2-W1

1465gm 1615 gm 1765 gm

Bulk Density = W3/V

1.62 gm/c.c 1.79 gm/c.c

1.95 gm/c.c

Wt of empty Container

25 gm 24.8 gm 24.3 gm

Wt of Container + Wet Soil

100 gm 105 gm 110 gm

Wt of Container + Dry Soil

89 gm 96 gm 102 gm

Wt of Water , Ww 11 gm 9 gm 8 gm

Wt of Dry Soil ,Wd

64 gm 71.2 gm 77.7 gm

Water Content , W

17.2 % 12.6 % 10.3 %

Dry Density 1.38 g/c.c 1.59 g/c.c 1.77 g/c.c69

Average dry density = 1.58 gm/c.c or 98.41 pcf

4.5 DETERMINATION OF CALIFORNIA BEARING RATIO

Table1 of CBR test sample 1

no. of blows 10 30 65mould + sample

11205 g 11640 g 11870 g

wt of mould 6775 g 6750 g 6730 gvolume 2115 g/c.c 2110 c.c 2120 c.cwet density 2.095 g/c.c 2.318 g/c.c 2.425 g/c.cdry density 1.80 g/c.c 1.991 g/c.c 2.083 g/c.cwt of soil 4430 g 4890 g 5140 g

Area of plunger=11.66 cm2

Providing Ring Reading Ring Factor=2.28

Table 2 Sample 1Penetration (mm)

10 blows

30 blows

65 blows

load for10

loadfor 30

loadfor 65

stress 10

stress 30

stress65

0.64 5 10 21 11.4

22.8 47.88

0.97770

1.95540

4.106346

1.27 10 19 48 22.8

43.32

109.44

1.95540

3.71526

9.385935

1.91 18 30 119 41.04

68.4 271.32

3.51972

5.86620

23.2693

2.52 27 40 183 61.56

91.2 417.24

5.27958

7.82161

35.78388

3.81 45 60 313 102.6

136.8

713.64

8.79931

11.7324

61.20412

5.08 60 81 403 136.8

184.68

918.84

11.7324

15.8387

78.80274

7.62 95 125 520 216 285 1185 18.57 24.44 101.6870

.6 .6 63 25 1

50 75 100 125 150 1750

10

20

30

40

50

60

Dry density , Pcf

CBR

Chapter : 05

CONCLUSIONS

5.1 Summary:

71

CBR 10 30 650.1 in 7.510083 11.12605 50.90167

114.3pcf D.D

7.65 CBR

The laboratory tests were performed for the determination ofengineering properties of soil, of Pir pyai area,Nowshera.For this purpose the soil sample was collected form “Pir pyaiarea , Nowshera” & brought to CECOS soil mechanics laboratory.The sample was protected from sun light & air so that itsmoisture content did not disturbed. After collecting sample,laboratory work began in CECOS soil laboratory. The liquidlimit, plastic limit & plasticity index were found to be 26%,15% and 11 respectively. Standard Proctor test was conductedon soil sample and maximum dry density was found to be 114.3pcf for 16.4 % optimum moisture content. Core Cutter test wasconducted in the field and the field density was found to be98.41 pcf. The California Bearing Ratio ( CBR ) value for maxdry density of 114.3 lb/ft3 gave 7.65 %. After the completionof these tests, the data was plotted on graphs& tables inexcel sheets.

5.1 Results:The results of laboratory tests on soil of Pir Pyai area , Nowshera is summarized in the table 5.1.

Table 5.1

S. no Test description Result

1 Liquid limit 26%

2 Plastic limit 15%

3 Plasticity index 11

4 Type of soil, as per USCS and AASHTO Cl

5 Optimum moisture content 16.4 %

6 Maximum dry density 114.3lb/ft3

7 Field density 98.41

72

lb/ft3

8 Wet Density 110.9lb/ft3

9 CBR 7.65 %

References: Soil testing is a very common field. A lot of work is previously done in the field oflaboratory tests on soil. The literature available in the field of soil testing was fully utilized in this project. The available literature on internet websites,available standards books on soil mechanics and previously done projects were thoroughly studied. Some references of available literature are:

“Soil mechanics and foundation 13th edition” by DR. B.CPunmia, Ashok Kumar Jain, XIII, (1973). New DelhiLaxmi publishers.

“The mechanics of engineering soil, 6th edition” by P. LeonardCapper, W. Fisher Cassie, A Halsted press bookJohnWilev& Sons. New York.

“Basicand applied soil mechanics” by GopalRanjan and A.S. R. RAO, VII. (2000), New Delhi, KhannaPublishers.

Engineering Properties of Soils Based on Laboratory Testing, Prof. Krishna Reddy, UIC.

ASTM standards (2004)

Internet websites and search engines:

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www.google.com www.wikkipedea.com www.aboutcivil.com www.civil.eng.ox.ac www.astm.org www.googlebooks.com www.googleimages.com www.geotechlinks.com www.geotechnicalinfo.com

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