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Design of Rigid and Flexible Pavements for Airport Runway

A SEMINAR

REPORT SUBMITTED IN PARTIAL

FULFILLMENT OF REQUIREMENTS FOR THE

AWARD OF THE DEGREE OF

MASTER OF ENGINEERING -CIVIL

(MAJOR: HIGHWAY ENGINEERING)

By

MOHAN M

I Semester M.E., (Civil)

Under The Guidance Of

Dr.L.Manjesh.

Asst Professor

Faculty of Civil Engineering

Bangalore University

Bangalore-560056

FACULTY OF CIVIL ENGINEERING

UNIVERSITY VISVESVARAYA COLLEGE OF ENGINEERING

BANGALORE UNIVERSITY, BANGALORE-560 056



ACKNOWLEDGEMENTS

I take the privilege to thank Dr. L.MANJESH, Assistant Professor, Department of Ci

Engineering, Bangalore University for suggesting this topic and for his untiring guidance a

constant inspiration throughout this work.

I like to thank Dr M.S.AMARNATH, Professor of Civil Engineering Department for h

suggestions to complete this work.

I am extremely thankful to Dr.G.SURESH, Senior Lecturer of Civil Engineering Department, f

his suggestions and guidance to complete this work.

I wish to express my gratitude to all my friends, classmates, seniors and technical assistants for th

kind co-operation during the experimental investigations and analysis of my seminar wo

successfully.

MOHAN M

I SEMESTER M.E

HIGHWAY ENGINEERING



SYNOPSIS

Airport pavements are constructed to provide adequate support for the loads imposed

airplanes and to produce a firm, stable, smooth, all-year, all-weather surface free of debris or oth

particles that may be blown or picked up by propeller wash or jet blast. In order to satisfactorily fulf

these requirements, the pavement must be of such quality and thickness that it will not fail under t

load imposed. In addition, it must possess sufficient inherent stability to withstand, without damage, t

abrasive action of traffic, adverse weather conditions, and other deteriorating influences.

BIAL is the main gateway to Silicon City. The airport is facing unexpected traffic growth sin

the globalization. The current parallel runway at th airport is already reaching its capacity limit. Wh

the operation reaches the capacity limit it will interrupt the airport operation, especially delay in t

arrivals and departure operations. This paper present the current runway operation and runway desi

capacity based on departure and arrival data. Based on the data and calculations, BIAL need ne

additional runway to cater for the future air traffic operation. Hence it is required to design an additio

runway. The calculation is presented based on the data collected.



CHAPTER - 1

INTRODUCTION

1.1. General

Airport pavements are constructed to provide adequate support for the loads imposed

airplanes and to produce a firm, stable, smooth, all-year, all-weather surface free of debris or oth

particles that may be blown or picked up by propeller wash or jet blast. In order to satisfactorily fulf

these requirements, the pavement must be of such quality and thickness that it will not fail under t

load imposed. In addition, it must possess sufficient inherent stability to withstand, without damage, t

abrasive action of traffic, adverse weather conditions, and other deteriorating influences. To produ

such pavements requires a coordination of many factors of design, construction, and inspection to assu

the best possible combination of available materials and a high standard of workmanship.

1.2. Types of Pavement.

Pavements discussed in this document are flexible and rigid. Various combinations of paveme

types and stabilized layers result in complex pavements classified between flexible and rigid. The desi

and evaluation guidance in this circular can be adapted to any pavement type.

1.3. Airfield Pavement Classification

Compatability of aircraft and pavement is necessary so that there is no excessive damage to t

pavement and air craft operations are unrestricted. So long as the aircraft is having single wheel, t

comparision of strength could be made by simple load tests. With the advancement of technology

aircraft design having complex wheel configurations and assemblies came in use and therefore

methodology to define the compatability between the aircraft and pavement with a common datum w

felt necessary. Different methods are available in use, however, it is required that a uniform meth

needs to be applicable to all types of aircrafts and the most widely accepted ones are stated here.

1. Aircraft classification number (ACN)

2. Pavement classification number (PCN)



1.4. Objectives

1. To evaluate the engineering properties of sub grade soil.

2. To design the overall thickness for the flexible pavement based on FAA method.

3.

To design the crust thickness and composition of proposed rigid pavement as per FAA methand IRC:58:2002.

1.5. Scope

To fulfill the above objectives, laboratory experiments are performed on the subgrade s

sample. Laboratory experiments are performed to evaluate the strength aspect.

To design the crust thickness, material, and density requirements for airfield pavements. It

includes criteria of the California Bearing Ratio (CBR) procedure for flexible pavements and theWestergaard Analysis for rigid pavements.



CHAPTER -2

LITERATURE REVIEW

A runway pavement is a surfaced area designed to carry aircraft traffic and includes the enti

pavement system structure above the subgrade. All slabs on grade required to support aircraft loading

whether interior (hangar floors) or exterior, are to be considered airfield pavements.

2.1.1 Flexible Pavement

Unified Facilities Criteria (UFC) in their advisory circular flexible pavements are so designat

due to their flexibility under load and their ability to withstand small degrees of deformation. The desi

of a flexible pavement structure is based on the requirement to limit the deflections under load and

reduce the stresses transmitted to the natural subsoil. The principal components of the pavement inclu

a bituminous concrete surface, graded crushed aggregate base course, stabilized material, drainage lay

separation layer, and sub base courses. A bituminous concrete surface course is hot mixed bitumino

concrete designed as a structural member with weather and abrasion resisting properties. It may cons

of wearing and binder or intermediate course. Figure 1-1 illustrates the components and the terminolo

used in flexiblepavements. Examples of All Bituminous Concrete pavements (ABC) and flexib

pavements utilizing stabilized layers are shown in Figures 1-2.

Figure 2.1. Typical flexible pavement structure



2.1.2 Use of Flexible Pavements.

The use of flexible pavements on airfields must be limited to those pavement areas not subject

to detrimental effects of fuel spillage, severe jet blast, or parked aircraft. Jet blast damages bitumino

pavements when the intense heat is allowed to impinge in one area long enough to burn or soften tbitumen so that the blast erodes the pavement. Hot-mix asphaltic concretes generally will resist erosi

at temperatures up to 150 degrees Celsius (300 degrees Fahrenheit). Temperatures of this magnitude a

produced only when aircraft are standing and are operated for an extended time or with afterburne

operating. Fuel spillage leaches out the asphalt cement in asphaltic pavements. In an area subject

casual minor spillage, the leaching is not serious, but where spillage is repeated in the same spot

frequent intervals, the leaching will expose loose aggregate. Flexible pavements are genera

satisfactory for runway interiors, secondary taxiways, shoulders, paved portions of overruns, or oth

areas not specifically required to have a rigid pavement surfacing.

2.2.1 Rigid Pavement

A rigid pavement is considered to be any pavement system that contains portland ceme

concrete as one element. Rigid pavements transfer the load to the subgrade by bending or slab acti

through tensile forces as opposed to shear forces. The principal components of a rigid pavement are t

concrete slab, base course, drainage layer, and separation layer. However, a stabilized layer may

required based on site conditions. Figure 1-3 illustrates the components of a rigid pavement. T

drainage and separation layer will normally serve as the base course. The following pavements a

considered to be rigid pavements.

(1)Plain concrete pavement is a nonreinforced jointed rigid pavement.

(2) Reinforced concrete pavement is a jointed rigid pavement that has been strengthened with

deformed bars or welded wire fabric.

(3) Continuously reinforced concrete pavement is a rigid pavement that is constructed without

joints and uses reinforcing steel to maintain structural integrity across contraction cracks that form in t

pavement.

(4) Fibrous concrete pavement is a rigid pavement that has been strengthened by the

introduction of randomly mixed, short, small-diameter steel fibers. Nonsteel fibers have been used

portland cement concrete (PCC) to control shrinkage cracking, but their use is not covered in this TI.

(5) Prestressed concrete pavement is a rigid pavement that has been strengthened by the



application of a significant horizontally applied compressive stress during construction.

(6) Rigid overlay pavement is a rigid pavement used to strengthen an existing flexible or rigid

pavement.

(7) Nonrigid overlay pavement is either all-bituminous or bituminous with base course used

strengthen an existing rigid pavement.

Figure 2.2. Typical rigid pavement structure

2.2.2 Use of Rigid Pavements.

The following pavements will be rigid pavement: all paved areas on which aircraft or helicopt

are regularly parked, maintained, serviced, or preflight checked, on hangar floors and access aprons;

runway ends (305 meters (1,000 feet)) of a Class B runway; areas that may be used from the runway e

to 90 meters (300 feet) past the barrier to control hook skip; primary taxiways for Class B runwayhazardous cargo, power check, compass calibration, warmup, alert, arm/disarm, holding, and washra

pads; and any other area where it can be documented that flexible pavement will be damaged by jet bl

or by spillage of fuel or hydraulic fluid. Rigid pavements shall also be used at pavement intersectio

where aircraft/vehicles have a history of distorting flexible pavements and where sustained operations

aircraft/vehicles with tire pressures in excess of 2.06 MPa (300 psi) occur. Continuously reinforc

concrete pavement will be used in liquid oxygen (LOX) storage and handling areas to eliminate the u

of any organic materials (joint sealers, asphalt pavement, etc.) In those areas. The type of pavement

be used on all other paved areas will be selected on the basis of life cycle costs.

2.3 Subgrade

2.3.1 Suitability of Subgrade.



The information obtained from the explorations and tests previously described should

adequate to enable full consideration of all factors affecting the suitability of the subgrade and subso

The primary factors are as follows:

a. The general characteristics of the subgrade soils.

b. Depth to bedrock.

c. Depth to water table (including perched water table).

d. The compaction that can be attained in the subgrade and the adequacy of the existing density in t

layers below the zone of compaction requirements.

e. The strength that the compacted subgrade, uncompacted subgrade, and subsoil will have und

local environmental conditions.

f. The presence of weak or soft layers in the subsoil.

g. Susceptibility to detrimental frost action.

h. Settlement potential.

I. Expansion potential.

j. Drainage characteristics.

2.3.2 Grade Line.

The soil type together with information on the drainage requirements, balancing cut and fi

flooding potential, depth to water table, depth to bedrock, and the compaction and streng

characteristics should be considered in locating the grade line of the top of the subgrade. Generally, t

grade line should be established to obtain the best possible subgrade material consistent with the prop

utilization of available materials; however, economics of plans for construction must be given prim

consideration.

2.3.3 Subgrade CBR.

The strength of the subgrade may be expressed in terms of the CBR for flexible paveme

design. The CBR test is described in CRD-C 654. It includes procedures for making tests on samp

compacted to the design density in test molds and is soaked 4 days for making in-place CBR tests a

for making tests on undisturbed samples. These tests are used to estimate the CBR that will develop

the pavement structure. However, a subgrade design CBR value above 20 is not permitted unless t

subgrade meets the requirements for subbases. The CBR selected for the subgrade will be based on t



predominant moisture conditions occurring during the life of the pavement. This moisture situation c

be obtained from pavement evaluation reports and from soil tests under existing pavements. Where lo

duration soil moisture conditions cannot be determined with confidence, the soaked laboratory CBR w

be selected for the subgrade soil.

a. Laboratory Tests. Tests results should include a full family of curves (Figure 6-1) as described

CRD-C 654. These curves show the three-way relationship of water content at the time ofcompactio

compacted density, and CBR after soaking. These curves should be studied in view of the actual wa

contents and densities that can be expected considering the natural scatter when specific control valu

are specified. The scatter that can be expected with normal control procedures will vary with the s

type. A spread of plus or minus 2 percent can be anticipated for soils with low optimum moistu

contents (in the range of 10 percent), whereas a spread of plus or minus 4 percent can be anticipated f

soils with high optimum moisture contents (in the range of 25 percent). Poor construction control m

result in even greater scatter. A comparable scatter in the density can also be expected.

After the range of moisture contents and densities that can be expected during actual construction

estimated, the range of CBR values that will result from these variations in moisture and density shou

be determined. The design CBR value for the specific soil tested should be selected near the lower p

of the range. The following steps along with Figure 6-1 illustrate the selection of a design CBR value.

1. Determine moisture/density relationship. Plot density to which soil can be compacted in the field. F

the clay of this example,use 95 percent of maximum density. Plot the desired moisture content rang

For the clay of this example, use ±1-1/2 percent of optimum moisture content for approximately 13 a

16 percent. Shaded area represents compactive effort greater than 95 percent and within ±1-1/2 perce

of optimum moisture content.

(3) Plot CBR versus dry density at constant moisture content. Plot attainable compaction limits of 1,7

and 1,840 kg/m3 (110.6 and 115 lb/ft3) for this example. The hatched area represents attainable CB

limits for desired compaction 1,770 and 1,840 kg/m3 (110.6 to 115 lb/ft3) and moisture content (13

16 percent). CBR varies from 11 (95 percent compaction and 13 percent moisture content) to 26 (

percent moisture content and maximum compaction). For design purposes, a CBR at the low end

range is used. In the example, a CBR of 12 with a moisture content specified between 13 and 16 perce

is selected.



b. In-place Tests and Tests on Undisturbed Samples. Where an existing pavement at the site ha

subgrade constructed to the same standards as the job being designed, in-place tests or tests

undisturbed samples may be used in selecting the design CBR value. Also, where no compaction

anticipated, as in the layers below the zone of compaction, tests should be conducted on the natu

material.

2.4 Classification of Air Field Pavement

The scientists of UK air ministry observed that the load carrying capacity of pavement vari

with the tyre pressure or contact radius using the relationship (a1/a2)α. The aircraft is thus defined by

curve having exponent of α passing through the point obtained by contact area and the all up weight.

load classification number is assigned to such a sets of load on single wheel and tyre pressures which a

expanded to give a curve. A family of curves for various sets of load and tyre pressure is developed an

such cureve is assigned a number. The load classification number (LCN) defines the load effect of

aircraft. The safe load tested for pavement with reference to the area of contact rate used in the test, re

on such curves gives the LCN of the pavement.

Aircraft classification number (ACN) is defined as ‘the load carried by a single wheel in terms

500kg , at a constant tyre pressure of 1.2MPa by a pavement required for the aircraft using standa

method of design using CBR method for flexible pavement and PCA for interior loading for rig

pavement

Pavement classification number (PCN) is the ACN of aircraft which the pavement is capable

carrying for unrestricted movement. It may be noteworthy that the ACN/PCN are the ‘constant ty

pressure’ where as LCN is for constant contact area. This makes computations of permissible load of

aircraft compatible to the pavement strength.

2.4.1 Determination of PCN

PCN is defined for constant pressure and no method is available for direct measurement this h

therefore can be determined by combined analysis with the measurement, it provides a choice to t

airport authorities to use the method of there preference. Methods available presently use the stiffness

the pavement obtained by non destructive test method to this stiffness permissible deflection is appli

to obtain the maximum permissible load. This load which is for the particular contact area and pressu

is modified for standard contact pressure of 1.25MPa. This cycle is repeated for the stable values.

Basic Design Factors



Willows-Glenn County Airport Master Plan (Adopted August 19, 2008)

The Federal Aviation Administration (FAA) provides guidance and standards for airport design throu

a series of Advisory Circulars (ACs). These guidelines promote airport improvements which enhan

airport safety and operational utility. Major considerations include:

• The total volume of aircraft operations;

• The types of aircraft seeking to operate at the airport; and

• Availability of instrument approach procedures.

Airport Role

The purpose of the proposed airfield improvements is to continue to facilitate the established airport ro

and enhance the airport’s ability to accommodate the forecast growth in business aircraft operations. T

operational role of Willows-Glenn County Airport – that of a general aviation airport – requires it

serve a wide variety of aircraft sizes and types. Currently, the airport primarily serves agricultural (aer

applicators) and personal/recreational aircraft operations. The aerial applicators principally use sing

engine turboprop aircraft. The

Personal/recreational use aircraft are mostly single-engine, piston powered aircraft. The airport also se

regular, but less frequent use by piston and turboprop twins, and small-to-mid-size business jets.

Airport Classification

For airfield design purposes, the FAA has established a set of airport classifications known as Airpo

Reference Codes (ARC). An ARC is applicable to each airport and its individual runway and taxiway

components. The primary determinants of these classifications are the critical aircraft (design aircraft

runway or taxiway is intended to serve and the instrument approach minimums applicable to a

particular runway end. Each ARC consists of two components relating to an airport’s design aircraft:

Aircraft Approach Category — depicted by a letter (A-E), this component relates to aircraft approa

speed, an operational characteristic that provides an indication of runway length requirements. With

this category, aircraft that have gross weights of 12,500 pounds or less are classified as small and ha

distinct airfield design criteria.

Airplane Design Group — depicted by a Roman numeral (I-VI), the second component relates

airplane wingspan, a physical characteristic.



Generally, Aircraft Approach Category applies to runways and runway related facilities. Airpla

Design Group primarily relates to separation criteria involving taxiways and taxi lanes.



CHAPTER 3

MATERIALS AND METHODOLOGY

3.1 Introduction

The properties of soils used in the present study and the details of the test procedures adopted a

described in this chapter.

3.2 Collection of soil samples

The sub-grade soil samples were obtained from BANGLORE INTERNATIONAL AIRPOR

DEVANAHALLI, BANGLORE DISTRICT. For this purpose 19 trenches were cut open near t

proposed pavement edges. Then from each trench a minimum of 25 kgs of soil samples were obtain

and collected in neat water proof bags. The bags were numbered and labeled for easy identification. S

samples were collected in small sealed covers for determining of field moisture. Undisturbed sampl

were collected with the core cutter to determine the bulk density and dry density. Then the samples we

transported to the laboratory to carry out further laboratory investigations.

3.3 Laboratory Test Results on Subgrade Soil samples

The laboratory investigations have been carried out on Subgrade soil samples collect

BANGLORE INTERNATIONAL AIRPORT, DEVANAHALLI, BANGLORE DISTRICT

Karnataka state.

Wet sieve analysis, consistency limits, modified Proctor compaction test and CBR tests we

carried out on untreated subgrade soil sample and results have been recorded in tabulated as in Chap

4.

3.4 Methods of Testing

3.4.1 Wet sieve analysis

Grain size analysis is also known as mechanical analysis of soils is the determination of t

percent of individual grain sizes present in the sample. The results of the test are of great value in so

classification. In mechanical stabilization of soil and for designing soil-aggregate mixtures the results

gradation tests are used.



Sieving is performed by arranging the various sieves one over the other in the order of their me

openings. Wet sieve analysis was carried out by washing the oven dried and weighed soil sampl

through 75µ sieve. The samples were soaked in water for 24 hrs prior to washing to break the s

lumps. The dried residues were sieved through a set of IS sieves and weight of soil samples retained

each sieve was measured accurately the percentages of Gravel, Sand, Silt and Clay are shown in Tab

3.1.

Fig 3.1 Set Of Sieves

3.4.2 Liquid limit

The liquid limit for all the samples were conducted as procedure given in IS: 2720, (part-5

1985. The Liquid limit reported is an average of three determinations.

3.4.3 Plastic limitThe plastic limit of the various samples were determined as per the standard method (test f

determination of plastic limit of soil IS: 2720 (part-5)-1985. The plastic limit reported is an average

three determinations.



Fig 3.2 Casagrande’s Apparatus

3.4.4 Compaction

Compaction of soil is a mechanical process by which the soil particles are constructed to

packed more closely together by reducing the air voids. Soil compaction causes decrease in air voids a

consequently an increase in dry density. The possibility of future settlement or compressibility decreas

and also the tendency for subsequent changes in moisture content decreases. Degree of compaction

usually measured qualitatively by dry density.

Increase in dry density of soil due to compaction mainly depends on two factors:

1. Moisture content.

2. Amount of compaction.

Practically all soils it is found that with increase in moisture content, dry density first increas

and then decreases

3.4.5 California Bearing Ratio (CBR) Test

The CBR is a measure of resistance of material to penetration of standard plunger und

controlled density and moisture conditions. The CBR test was developed as a method of classifying aevaluating soil sub-grade and base course materials for flexible pavement. The CBR test may

conducted in re-molded or undisturbed specimen in the laboratory. Many methods exist today whi

utilize mainly CBR test values for designing pavement structure.

CBR tests were carried out in the laboratory for each soil sample, passing through 20 mm siev

The samples were compacted in the CBR mould at OMC and soaked for 4 days. The soaked sampl



were subjected to CBR test. Atleast 2 specimens were prepared for each soil sample and average of t

results was considered for analysis. A graph was plotted between penetration v/s load. The unit lo

values corresponding to 2.5 mm and 5.0 mm penetration values are found from the graph. The CB

value is calculated by

% CBR = (load × 100) / 1370 for 2.5 mm penetration

% CBR = (load × 100) / 2055 for 5.0 mm penetration

Fig 3.3 California bearing ratio test



CHAPTER 4

ANALYSIS OF RESULTS

4.1 Introduction

In this chapter details about the experiments performed and a brief discussion on the experime

results is presented. In the present investigation for the subgrade soil samples, the index properties,

strength properties are studied.

Wet sieve analysis, density determination by core cutter method, Liquid limit, Plastic li

Modified Proctor’s Compaction and CBR tests were conducted for the subgrade soil samples.

4.2 Results

4.2.1 Atterberg Characteristics

i) Liquid limit

The Liquid limit is a measure of water content of soil when it approaches a particul

shearing resistance and it is amount of water which must be added to soil in order that layer mu

distant from soil particle acquires the property of free water. The shearing resistance at t

particle level and the thickness of diffused double layer primarily controls the liquid limit

clays.

ii) Plastic limit

Plastic limit is the water content corresponding to an arbitrary limit between plastic a

semi soild state of consistency of soil.

Plastic limit is affected by the following factors:

Surface area: Generally, it is known that decrease in specific surface of soil particles increa

the plastic limit though not in direct proportion.Thus the plastic limit increases with increase

coarser fraction.



iii) Plasticity Index

The range of consistency within which a soil exhibits plastic properties is called plas

range and is indicated by plasticity index.

4.2.1.2 Test Results

As per experimental programme liquid limit and plastic limit tests are conducted

explained in section 3.4.2 and 3.4.3. Table 4.3 presents the plasticity characteristics of subgra

soils.

Table 4.1 Plasticity Characteristics Of Soil Subgrde



Soil

Sample

Liquid

Limit

Plastic

Limit

Plasticity

Index

C1 34.30 21.30 13.00

C2 33.10 20.60 12.50

C3 36.00 24.00 12.00

C4 33.10 20.80 12.30

C5 34.50 21.00 13.50

C6 35.20 22.10 13.10

C7 36.00 24.00 12.00

C8 32.10 19.50 12.60

C9 31.50 18.00 13.50

C10 34.10 21.50 12.60

C11 33.90 20.10 13.80C12 34.60 20.20 14.40

C13 31.40 16.00 15.40

C14 30.40 17.20 13.20

C15 30.90 17.10 13.80

C16 33.90 21.40 12.50

C17 34.80 20.10 14.70

C19 29.25 17.00 12.25

C20 32.00 19.00 13.00



4.2.2 Wet Sieve Analysis

The test results of the wet sieve analysis of the the subgrade soil samples are given tabulate

below in table 4.1

Table 4.2 Grain size distribution Of Subgrde soil sample

C1 59.80 37.16 3.04

C2 56.44 40.48 3.08

C3 65.20 29.68 5.18

C4 55.24 40.28 4.48

C5 59.24 36.74 4.02C6 60.26 36.96 2.78

C7 65.18 31.78 3.04

C8 55.58 37.38 7.04

C9 52.52 40.76 6.72

C10 58.06 37.58 4.36

C11 56.30 38.38 5.32

C12 57.84 39.10 3.06

C13 45.18 48.94 5.88

C14 51.04 39.02 9.94C15 50.52 45.52 6.96

C16 57.62 33.80 8.58

C17 61.00 38.56 0.40

C19 44.24 41.06 14.70

C20 52.16 32.02 15.82

% Silt

and Clay% Sand % GravelSample



4.2.3 Density Determination

The bulk density and dry density were determined by driving in the core cutters in site. Table 4

shows the density characteristics.

Table 4.3 Density Characteristics Of Soil Subgrde

C1 1.99 9.09 1.83

C2 2.00 5.73 1.89

C3 1.97 8.37 1.82C4 2.08 16.36 1.79

C5 2.07 11.11 1.86

C6 2.15 9.09 1.97

C7 2.12 9.45 1.93

C8 1.97 20.88 1.63

C9 1.98 11.11 1.79

C10 1.79 8.30 1.65

C11 2.01 14.29 1.76C12 2.27 25.71 1.81

C13 2.00 7.05 1.87

C14 2.11 8.82 1.94

C15 2.10 14.29 1.84

C16 2.01 13.60 1.77

C17 1.92 6.92 1.79

C19 2.32 19.15 1.95

C20 1.87 10.70 1.69

Sample noBulk density

γbulk(g/cc)

Moisture

content (%)

Dry density

γdry (g/cc)



4.2.4 Compaction Characteristics

Compaction is a process by which the soil particles are artificially rearranged and pack

together in to a closer state of contact by mechanical means in order to decrease porosity of the soil a

thus increase its dry density. In the present investigation, Modified proctor compaction test a

performed on the subgrade soil and the results are presented below.


As per experimental programme compaction test is conducted as explained in section 3.4

Table 4.4 presents the compaction characteristics of subgrade soil.



Table 4.4 Compaction Characteristics Of Soil Subgrde

OMC

(ω)%

Maximum Dry

Density(γdry)

Degree Of

Compaction(%)

C1 7.70 2.01 90.90

C2 7.80 2.03 93.03

C3 10.80 2.21 82.40

C4 11.00 1.88 95.14

C5 7.70 1.99 93.62

C6 10.90 2.21 89.02

C7 7.60 1.94 99.71

C8 11.00 1.96 83.01

C9 8.30 1.98 90.20

C10 9.30 2.23 74.10

C11 7.90 1.91 91.98

C12 8.00 2.01 89.85

C13 7.45 1.99 93.74

C14 7.60 2.05 94.68

C15 7.90 1.92 95.84

C16 7.40 2.02 87.68

C17 8.00 2.02 88.78

C19 7.90 1.98 98.24

C20 7.90 1.91 88.29

Sample

Theoritical Compaction

4.2.5 California Bearing Ratio

CBR test is an arbitrary strength test and it cannot be used to evaluate the soil properties li

cohesion or angle of friction or shearing resistance. This is a penetration test developed by Californ

Division of Highway, a method for evaluating the stability of soil subgrade and other flexible pavem

materials.




As per experimental programme CBR test is conducted as explained in section 3.4.5. Table 4

presents the CBR values of subgrade soil after soaking for 4 days.

Table 4.5 CBR values Of Soil Subgrde after 4 days soaking

C1

C2

C3

C4C5

C6

C7

C8

C9

C10

C11

C12

C13

C14

C15

C16

C17

C19

C20

4.67

3.25

10.73

5.62

3.87

8.91

5.26

5.77

4.42

2.12

4.38

4.72

4.86

5.01

8.90

5.30

3.21

4.20

2.85

4.233.28

4.04

2.91

4.11

3.45

6.81

4.48

2.53

3.993.11

3.16

2.04

3.50

SAMPLE

NO.

CBR RESULTS FOR SAMPLES

CBR @2.5 mm CBR @5.0 mm

3.11

3.50

3.18

2.12

4.53



4.3.1 Procedure For Design of Flexible Pavement By FAA Method

1. Series of design curves based on the CBRdesign method

2. Design curves depend on gear configuration

3. Curves provide total pavement thickness

4. Curves based on 20 year design life

5. Load: Pavement design based on maximum anticipated takeoff weight

6. Assumes 95% of the load on main gear

7. Design Inputs

Subgrade CBRvalue

Subbase CBRvalue

Design aircraft gross weight

Number of annual departures of the design aircraft

Subgrade CBR Design Value

8. Determine Design Aircraft

9. Forecast annual departures by aircraft type

10. Determine required pavement thickness for each aircraft type

11. Annual Departures of Design Aircraft

12. Group all aircraft traffic into gear configuration of design aircraft

13. Convert all departures into equivalent annual departures of the design aircraft

Hence from the charts the thickness obtained for computations in Table 4.6 is 40 in = 101.6 cm

upon the prepared subgrade

But as per the required PCN value of 80 the required thickness is 108.14 cm provide 110 cm

overall thickness.

Provide 25 cm thick SDBC (Semi Dense Bituminous Concrete) as the wearing course or surfac

courseProviding graded bituminous macadam Base Course, the thickness of Base course required 35

cm

Similarly using 20% CBR for sub base course the required thickness is 45 cms.



4.3.2 Procedure For Design of Rigid Pavement By FAA Method:

1. Note the gear type, Dual or Dual Tandem or Double dual tandem

2. Convert all the gears into Equivalent Dual tandem Gear departures.

Equivalent dual tandem gear departures =conversion factor X Annual Departure

3. Calculate Aircrafts wheel loads.

Aircraft wheel load =Gross weight X 0.95X .5

2

4. Compute Equivalent design departure

Equivalent Design departure => log(R1)= log (R2)x 1

2

Where R1= equivalent annual departures by the design aircraft

R2= annual departures expressed in design aircraft landing gear

W1= wheel load of the design aircraft

W2= wheel load of the aircraft in question

5. Sum the total Number of departures, this will be the design departure and the design load will b

that of the design air craft

6. Using FAA charts find the thickness corresponding to 6978 departures of 172.60 T

We get for k= 95 pci. Flexural strength of concrete = 653 psi

Thickness of runway t= 13.5 in = 34.29 cm

Provide 40 cm thick pavement.

7. Calculate the temperature stresses and the edge load stresses.

8. Design the dowel bars.

Also as per requirement provide Dry lean concrete of thickness 10 cm



29

Table 4.6: COMPUTATION AND CONVERSION OF GEAR, WHEEL LOADS AND EQUIVALENT DESIGN DEPARTURES FOR

DUAL GEAR

AircraftAnnual

Departure

Gross

Weight

(T)

Gear

type

Equivalent dual gear

departure

Aircraft wheel

loads (T)

Equivalent design

departures

Airbus A320-200 568 73.900 DT 966 17.550 26

Boeing 737-100 406 50.349 D 406 11.957 10

Boeing 737-200 408 58.332 D 408 13.850 11

Airbus A320-200 14 44.400 D 14 10.545 4

Airbus A300-600 521 172.600 DT 521 40.990 74

Airbus A310-300 104 142.900 D 104 33.938 104

Boeing 757-200 1562 116.900 DT 2656 27.570 94

Airbus A330-200 346 230.900 DDT 589 54.830 122

Boeing 747-400 183 414.130 DT 311 98.355 303

MD11 ER 212 287.124 DT 360 68.192 159

Boeing 747-800 34 443.613 DDT 58 105.358 58

Airbus A380-800 34 591.995 DDT 58 140.589 41

1006



30

Table 4.7: COMPUTATION AND CONVERSION OF GEAR, WHEEL LOADS AND EQUIVALENT DESIGN DEPARTURES FOR

DUAL TANDEM GEAR

Airbus A320-200 568 73.900 DT 568 17.550 64

Boeing 737-100 406 50.349 D 244 11.957 20Boeing 737-200 408 58.332 D 245 13.850 24

Airbus A320-200 14 44.400 D 14 10.545 4

Airbus A300-600 521 172.600 DT 313 40.990 313

Airbus A310-300 104 142.900 D 63 33.938 104

Boeing 757-200 1562 116.900 DT 1562 27.570 416

Airbus A330-200 346 230.900 DDT 346 54.830 865

Boeing 747-400 183 414.130 DT 183 98.355 3196

MD11 ER 212 287.124 DT 212 68.192 1002

Boeing 747-800 34 443.613 DDT 34 105.358 285

Airbus A380-800 34 591.995 DDT 34 140.589 685

6978

Aircraft

wheel loads

Equivalent design

departuresAircraft

Annual

Departure

Gross

Weight

Gear

type

Equivalent dual

tandem gear



31

4.3.3 DESIGN ASPECTS FOR CC PAVEMENT (M40) SLAB (As per IRC 58 – 1988)

Flexural strength of cement concrete = 45 kg/cm²

Elastic modulus of concrete (E) = 3 x 105kg/cm

2

Poisson’ ratio (μ) = 0.15

Coefficient of thermal coefficient of concrete (α) = 10x 10-6 /ºC

Length of the Pavement Slab, L = 500 cm

Width of the Pavement Slab, B = 500 cm

Maximum temperature differential during day between top and

Bottom of the slab for the Banglore Region = 26º C

Design Load on the dual wheel assembly = 172600 kg

Tyre Pressure = 14.15 kg/cm2

Design life = 30 years

Thickness of slab = 40 cm

Temperature Stresses

The temperature stress at the critical edge region is obtained as per Westergaard analysis using

Bradbury’s coefficient as follows:

Edge warping stress, Ste = CEαt

2

Radius of relative stiffness (l), l = ℎ 3

12 (1− 2)

4= 133.15 cm

Bradbury’s Coefficient, C = 0.37375 (As per IRC 58- 1988 for L/l =3.755)

Edge warping stress, Ste = 14.576 kg/cm²

Residual available strength of concrete for supporting traffic loads



32

= Flexural Strength of cement concrete – Edge Warping Stress

= 45.00 kg/cm² - 14.576 kg/cm² = 33.133 kg/cm²

Edge Load Stress, Se:

Using Westergaard Equation as under:

Se = 0.572

ℎ20.359 + 4 log10

b = radius of equivalent distribution of pressure

= a (Radius of load contact) for a/h > 1.724

= ((1.6 a2

+ h2)0.5

) - 0.675h for a/h < 1.724

Radius of load contact, cm, (assumed circular), a = 115.81 cm

b = 115.81 cm

Edge Load Stress, Se = 30.424 kg/cm² < 45 kg/cm² (Flexural Strength of cement concrete)

Corner Load Stress, Sc:

Corner load stress, Sc =3ℎ2

1 − 2 0.6

Sc = 38.43 kg/cm² < 45 kg/cm² (Flexural Strength of cement concrete)

Factor of Safety (FOS) = Residual Strength of concrete

Edge Load Stress

FOS = ℎ

=33.133

30.424= 1.089 > 1

Designed concrete pavement thickness of 40 cm is ok



33

4.3.4 DESIGN OF DOWEL BARS (AS PER IRC 58 – 2002)

Design Wheel Load = 140.589 T(Dual Wheel Load)

Percentage of Load Transfer =95%

Slab Thickness, h = 40 cm

Joint width, z = 3.0 cm

Radius of Relative Stiffness, l = 133.15 cm

Permissible bearing stress in concrete is calculated as under:

Fb = (10.16 – b) fck/9.525

fck = Characteristic compressive strength of concrete cube (15 cm) after

28 days of curing concrete = 400 kg/cm2

for M – 40 Grade.

b= diameter of the dowel bar = 3.0 cm (FAA specification)

Fb = (10.16 – 3.0)x400/9.525 = 272.79 kg/ cm2

Spacing between the dowel bars = 38 cm (FAA specified)

First dowel bar is placed at a distance = 15 cm from the Pavement Edge

Length of the dowel bar = 51 cm (FAA Specified)

No. of Dowel bars participating in Load transfer = 1 + l /Spacing = 1+133.15/38 = 4 dowels

Assuming that the load transferred by the first dowel is Pt and assuming that the load on dowel

bar at a distance of ‘l ’ from the first dowel to be zero, the total load transferred by the dowel bar

system

= 1 +133.15−38

133.15+

133.15−76

133.15+

133.15−114

133.15 = 2.287

Load carried by the outer dowel bar, Pt = (140.589 x 1000 x 0.95 /2.287) = 58267 kg.



34

4.4 Joints And Spacing

Variations in temperature and moisture content can cause volume change and slab warping

resulting in significant stresses. In order to reduce the detrimental effects of these stresses and to

minimize random cracking, it is necessary to divide the pavement into a series of slabs of

predetermined dimension by means of joints. Pavement joints are categorized according to the

function that the joint is intended to perform. The following joints are envisaged in this project.

4.4.1 Thickened Edge Isolation Joint

The function of the isolation joints is to isolate intersecting pavements and to isolate the

structures from the pavement this is used when conditions preclude the use of load transfer

devices that span across the joint, such as where the pavement abuts the structure or where

horizontal differences in movement of the pavement occur(e.g. at catch pits, longitudinal drain,

fuel hydrant pits etc) these joints are formed by increasing the thickness of the pavement along

the edge slab. No dowel bars are provided.

4.4.2 Sawn Contraction Joint

The function of contraction joint is to provide controlled cracking of the pavement when the

pavement contracts due to decrease in in moisture content or a temperature drop. Contraction

joint also decrease stresses caused by slab warping.

4.4.3 Doweled Construction Joints

Construction joints are required when two abutting slabs are placed at different times, such as at

the end of a day’s placement or between paving lanes.

4.4.3.1 Dimensions And Spacing Of Dowels

Dowels are used at joints to provide for transfer of load across the joint and to prevent relative

vertical displacement of adjacent slab ends. For the slab thickness of 400 mm, the FAA

recommends the following dowel dimension and spacing.

Diameter = 30 mm Length= 510 mm Spacing= 380 mm

The same are adopted in the present project.



35

4.4.4 Joint Spacing

According to FAA, the maximum spacing of 6.1m is recommended for is recommended for slabs

equal to or thicker than 400 mm since the slab thickness for the present project is 400mm, a

maximum joint spacing of 6.1m will be adopted. The ratio of the longest side of a slb to the

shortest side of a slab at two intersecting sides shall not exceed 1.25.

4.4.5 Runway Length

Design Condition Data

Airplane 747-400 (PW4056)

Mean daily maximum temperature of hottest month at airport1 80.6° Fahrenheit (27° C)

Airport Elevation 2935 feet above MSL

Maximum design landing weight 574,000 pounds

Maximum design takeoff weight 875,000 pounds

95% design takeoff weight 831,250 pounds

Takeoff Length Requirements 95% Useful Load

Takeoff Length with 20 degree flap setting @ 92°F3 10,171 feet

Adjusted Takeoff Length for Elevation (dry pavement)4 10,234 feet

Existing main runway length = 10,400 feet

Hence provide runway length of 10,400 feet



36

4.4.6 Cost abstract of Flexible Pavement

Sl no Description Unit Quantity Rate Amount

1Dressing of earth work including cutting

and filling up to 15 cm thick or depth. cum35662.50 19.20 684720.00

2

Construction of granular sub base byproviding coarse graded material

spreading in uniform layer, mixing atmix plant at OMC and compacting with

vibratory power roller to achieve desireddensity. cum

14265000.00 927.00 13223655000.00

3

Providing and applying primer coat withbitumen emulsion on prepared surface

of granular sub base of low porositysuch as WBM and WMM including

clearing of road surface and sprayingprimer at the rate of 0.75 kg/sqm using

mechanical means. sqm

142650.00 26.35 3758827.50

4

Providing and laying bituminous

macadam 50 mm thick as per MORTHspecification clauses 501.6 and 501.7 to

achive the desired compaction with80/100 grade bitumen. cum

7132.50 5136.00 36632520.00

5

Providing and laying semi densebituminous concrete 25 mm thick as per

MoRTH specification clause No. 508 inall respect over B.T.surface using

80/100 grade bitumen cum

3566.25 7465.00 26622056.25

Total Estimated amount in

Rupees 13291353124.00



37

4.4.7 Cost abstract of Rigid Pavement

Sl no Description Unit Quantity Rate Amount

1 Dressing of earth work including cuttingand filling up to 15 cm thick or depth.

cum

35662.50 19.20 684720.00

2

Construction of granular sub base by

providing coarse graded materialspreading in uniform layer, mixing at mix

plant at omc and compacting withvibratory power roller to achieve desired

density. cum

21397.50 927.00 19835482.50

3

Construction of base courseby providingDry lean concrete spreading in uniform

layer, mixing at mix plant and compactingwith vibratory compactor. cum

14265.00 2900.00 41368500.00

4

Construction of surface course by

providing Pavement quality concretespreading in uniform layer, mixing at mix

plant and compacting with vibratorycompactor.

cum

57060.00 3450.00 196857000.00

Total estimated amount in

Rs 258745702.50



CHAPTER 5

DISCUSSIONS AND CONCLUSIONS

5.1 Discussions

The subgrade soil when tested possessed the following details

1. The soil is mainly composed of around 50% of silt and clay.

2. The soil density varies between 1.7g/cm3

to 2.1g/cm3.

3. The optimum moisture content varies between 7.40% to11.00%.

4. The strength of the soil determined by 3rd

energy level CBR has the lowest value of

2.12%.

Since the strength of the soil is too low for an air field pavement (minimum 3% CBR) the

soil should be stabilized by suitable means so as to obtain a target strength of 6% CBR.

5.2. Conclusions

1. The runway length to be provided is 10,400 feet (3170 m).

2. Thickness for the flexible pavement shall be 110 cm above the prepared subgrade.

The components are

Provide 2.5 cm thick SDBC (Semi Dense Bituminous Concrete) as the wearingcourse

Provide graded bituminous macadam Base Course, the thickness is 7.5 cm.

Provide granular subbase course of thickness is 100 cms.

3. The thickness of the rigid pavement to be provided is 40 cm.

4. Number of dowel bars shall be 4.

5. The pavement composition and layer thickness are as follows

Pavement quality concrete (PQC) = 400 mm

Dry lean concrete (DLC) = 100 mm

Granular sub-base (GSB) = 150 mm

6. Observing the cost abstract it is feasible to provide the Rigid pavement for the present

project.

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