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DESIGN
OF
FLEXIBLE PAVEMENTS
V. VENKATA NARAYANA
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COMPONENTS OF ROAD
G.L
SUBGRADE
EMBANKMENT
PAVEMENT
SHOULDERCARRIAGEWAY
ROAD WAY
FORMATION
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PAVEMENTS
Pavement : Pavement is a structure.1. It consists of superimposed layers of
selected and processed materials.
2. It is placed on a Sub grade
3. It supports the applied traffic loads and
distributes them to the soil foundation.
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ESSENTIL REQUIEMENT OF PAVEMENTS
1) STRUCTURAL PERFORMANCE
A PAVEMENT SHOULD BE (i) STRONG enough to resist the stresses
imposed on it and
(ii) THICKenough to distribute the external loads
on the earthen subgrade. 2) FUNCTIONAL PERFORMANCE
A PAVEMENT SHOULD HAVE
(i) Riding quality, (ii) Surface friction for skid resistance,
(iii) Low noise and
(iv) Good geometrics.
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TYPES OF PAVEMENTS
1) FLEXIBLE PAVEMENTS,
2) RIGID PAVEMENTS,
3) SEMI-RIGID PAVEMENTS,
4) COMPOSITE PAVEMENTS.
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1) FLEXIBLE PAVEMENTS1. Consists THREE Layers.
2. It has low FLEXURAL strength.
3. Transfers the traffic loads by DISPERSION.
Wearing Course
SUB-BASE COURSE
BASE COURSE
Binding CourseSURFACE COURSE
SUB GRADE
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1) FLEXIBLE PAVEMENTS
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2) RIGID PAVEMENTS1. These consist of only TWO Layers.2. Transfers the traffic loads by FLEXURE.
CC WEARING COURSE
SUB-BASE COURSE
SUB GRADE
Sub-base may be DLC/ PCC/ WMM/WBM
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2) RIGID PAVEMENTS
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3) SEMI-RIGID PAVEMENTS Surface course is FLEXIBLE.
Base/ Sub-base is RIGID.
BITUMINOUS WEARING COURSE
RIGID BASE COURSE
SUB GRADE
Rigid Base may be DLC/ Lime-fly ash/ soil-cement concretes
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4) COMPOSITE PAVEMENTS
These Pavements comprises ofmultiple, structural layers of different,heterogeneous, composition.
Ex:: Brick sandwiched pavement,which consists CC pavement layers at
bottom and top duly sandwiching bricklayer.
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DESIGN OF FLEXIBLE PAVEMENTS
Design of FLEXIBLE PAVEMENTSinvolves the interplay of severablevariables
Wheel Loads.Traffic.
Climate.Terrain.Subgrade condition.
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DESIGN OF FLEXIBLE PAVEMENTS
TWO CODES for DESIGNVillage Roads and Rural Roads ::Traffic Less than 450 CVPD
IRC:SP:20-2002 (Rural Road Manual)
Expressways, NH, SH, MDR
Traffic Greater than 450 CVPD (1 msa to 150msa)
IRC:37-2001 (Guide lines for the design offlexible pavements)
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IRC:37-2001
GUIDELENES FOR THE DESIGN OF
FLEXIBLE PAVEMENTS
This code uses mathematical modeling
of the pavement structure usingMULTIPLE LAYER ELASTIC theory
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COMPONENTS OF FLEXIBLE PAVEMENTS
FLEXIBLE PAVEMENTS Essentially consists of
THREE Layers.1) Surface Course::
i) Wearing Course ::PC, SDBC, BC.
ii) Binding course::BM, DBM,
2) Granular Base ::
WBM, WMM,
3) Granular Sub-Base ::
SUBGRADE
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FLEXIBLE PAVEMENTS
STRAINS/DEFORMATIONS and their REMEDIES
1. Pavement deformation withinBITUMINOUS layers.
1. Controlled by meeting the MIX DESIGNrequirements as per MORT&H Specifications.
SUB-BASE COURSE
BASE COURSE
BITUMINOUS COURSE
SUB GRADE
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STRAINS/DEFORMATIONS ------ REMEDIES
2. Horizontal Tensile strain at the bottom ofBITUMINOUS layer.
2. Controlled by selecting the THICKNESSES ofGranular and Bituminous layers as perDesign.
SUB-BASE COURSE
BASE COURSE
BITUMINOUS COURSE
SUB GRADE
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STRAINS/DEFORMATIONS ------ REMEDIES
3. Vertical compressive strain the top ofthe SUBGRADE.
3. Controlled by selecting the THICKNESSESof Granular and Bituminous layers as perDesign.
SUB-BASE COURSE
BASE COURSE
BITUMINOUS COURSE
SUB GRADE
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PARAMETERS FOR DESIGN
1 DESIGN TRAFFIC . Cumulative number of Standard Axles.
2 CBR value of Subgrade.
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TRAFFIC
IRC:37 Considers traffic in terms of
STANDARD AXLES to be carried by the pavementduring the
DESIGN LIFE.
STANDARD AXLE = 8160 Kg
DESIGN LIFE = Period in which the cumulative
number of standard axles carried by the pavement.
CVPD :: Commercial Vehicles Per Day
Vehicle having LADEN weight more than 3.00 mt.
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TRAFFIC
For estimating the DESIGN TRAFFIC information
required ::
i. INTIAL TRAFFIC :: After construction (before theroad is opened to traffic) in terms of CVPD.
ii. TRAFFIC GROWRT RATE ::iii. DESIGN LIFE :: in number of years,
iv. VEHICLE DAMAGE FACTOR ::
v. DISTRIBUTION of commercial traffic over thecarriageway.
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i) INITIAL TRAFFIC
Only the number of commercials (W>3.0t) and The Axle- Loading of Commercial Vehicles are
considered.
The initial daily average traffic flow based 7 days
X 24 hours classified counts.
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ii) TRAFFIC GROWTH RATE
Traffic growth rate is estimated :: By studying the past trends of traffic growth and By establishing economic models as per
procedure out lined in IRC:108.
The code recommends averageannual growth rate as 7.50 % .
In case adequate data is not available.
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iii) DESIGN LIFE
Definition ::
Design life of a pavement is the CUMULATIVENUMBER of standard axles that can be carriedbefore strengthening of pavement is necessary.
DESIG LIFE for ::
Express ways & Urban Roads. -- -- -- 20 yrs.
National Highways & State Highways 15 yrs. Other category of roads -- -- 10 to 15 yrs.
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iv) VEHICLE DAMAGE FACTOR
Definition ::
It is an equivalent number of STANDARD AXLEper COMMERCIAL VEHICLES.
STANDARD AXLE = 8160 kg
It is a multiplier to convert COMMERCIAL VEHICLESof different axle loads and configuration to
STANDAD AXLE ::
COMMERCILA VEHICLE * VDF = STANDARD AXLE.
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iv) VEHICLE DAMAGE FACTOR
Single Axle Load ::
Equivalency Factor =(Axle Loan in kg/8160)4 Equivalency Factor of 4540 kg =(4540/8160)4=0.08
Equivalency Factor of 8160 kg =(8160/8160)4=1.00
Equivalency Factor of 16320 kg =(16320/8160)4=15.5
Equivalency Factor of 22680 kg =(22680/8160)4=55.0
Tandem Axle Load :: Equivalency Factor =(Axle Loan in kg/14968)4
Equivalency Factor of 8160 kg =(8160/14968)4 =0.07
Equivalency Factor of 14968 kg =(14968/14968)4=1.00
Equivalency Factor of 22680 kg =(22680/14968)4=5.28
Equivalency Factor of 36288 kg =(36288/14968)4=31.7
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iv) VEHICLE DAMAGE FACTOR
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iv) VEHICLE DAMAGE FACTOR
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Where sufficient information is not available & project
size does not warrant axle load survey
INDICATIVE VDF VALUES
Initial traffic volume interms number of CVPD
Terrain
Rolling/plain Hilly
0 150 1.50 0.50
iv) VEHICLE DAMAGE FACTOR
150 1500 3.50 1.50
More than 1500 4.50 2.50
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v) LANE DISTRIBUTION FACTOR
Distribution of commercial traffic by LANE
DIRECTION
Necessary in arriving realistic total equivalent standard axleload used in design.
Types of Carriageways Single Lane carriageway ( No median of divider),
Dual lane carriageway ( With Median or Divider).
Types of Lanes
Single - Lane (only in single carriageway)
Two Lane,
Three Lane (only in dual carriageway)
Four Lane
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v) LANE DISTRIBUTION FACTOR
SINGLE CARRIAGEWAY ROAD
SNo Number of Lanes Width L.D.F. (%)
1 Single Lane 3.75 m 100
2 Two Lane 7.00 m 75
3 Four Lane 14.0 /15.0 40
DUAL CARRIAGEWAY ROAD
1 Two Lane 7.0 + 7.0 75
2 Three Lane 10.5 + 10.5 60
3 Four Lane 14.0 + 14.0 40
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2
)1()1)(1( rPrrP +=++
)1( rP +
3)1()1)(1)(1( rPrrrP +=+++
rPxrrrPx=+=+++ )1()1)(1)(1(
P
Estimation of TRAFFIC
Suppose TRAFFIC in the year of CENSUS is (CVPD) - - - - - - - -
TRAFFIC after ONE year (CVPD) - - - - - - - - - - - - - - - - -
TRAFFIC after TWO years (CVPD) --
TRAFFIC after THREE years (CVPD) - - -
TRAFFIC after x years (CVPD) - - -- - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - -
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)1(**365 rA +
[ ]r
rAn
1)1(**365 +
A
Estimation of TRAFFIC
Suppose TRAFFIC in the year of COMPLETION is (CVPD) - - - - - -
TOTAL number of vehicles in SECOND year (CVPD)
CUMULATIVE TRAFFIC for n years (CVPD)(By adding the TRAFFIC from FIRST to n th year)
A*365TOTAL number of vehicles in FIRST year (CVPD) -- - -
2)1(**365 rA +
=== === === === === === === === === ===
)1(
)1(**365
+
n
rATOTAL number of vehicles in n th year (CVPD)
TOTAL number of vehicles in THIRD year (CVPD)
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TRAFFIC
For estimating the DESIGN TRAFFIC information
required ::
i. INTIAL TRAFFIC :: -------------------- A CVPD
ii. TRAFFIC GROWRT RATE :: --------- r %
iii. DESIGN LIFE :: ----------------------- n years
iv. VEHICLE DAMAGE FACTOR ::------- F
v. LANE DISTRIBUTION FACTOR ::--- D
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[ ]FDAN
r
rn
***1000000*1)1(*365 +
=
Estimation of TRAFFIC
CUMULATIVE NUMBER OF STANDARD AXLES TO
BE CATERED IN THE DESIGN ARE IN TERMS OFmsa (Millian Standard Axles)
A = Initial Traffic,
r = Growth Rate,
D = Lane distribution factor,
n = Design life in years
F = Vehicle Damage Factor.
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CBR of SUBGRADE (foundation) Definition ::
It is the top 500 mm of FORMATION and is FOUNDATION
to the pavement.
It should be well copacted.
Density ::
The DRY DENSITY not less than 1.75 gm/cc.
Strength ::
The STRENGTH of subgrade is assesed in terms ofCBR(California Bearing Ratioo).
Maximum = 10 % and Minimum = 2 %
The CBR should be found on remoulded samples in the labat the weakest condition under the road afterconstruction.
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PAVEMENT THICKNSS AND COMPOSITION
Pavement Thickness Design CHARTS ::
These charts are used to obtain
TOTAL thickness of Pavement.
From CBR and Traffic in msa.
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Pavement Thickness Design CHARTS
These CHARTS are used to obtain the total thickness ofpavement from the TRAFFIC and CBR.
TRAFFIC :: Traffic is assessed in terms of cumulative number ofstandard axles to be carried over the design life.
Unit = msa (million standard axles)
Range ::
1 to 10 msa Fig.1, 10 to 150 msa Fig.2.
CBR :: The CBR of SUBGRADE ,
Minimum = 2 %,
Maximum = 10 % For CBR less than 2 %, Capping layer 150 mm thickness of
material with 10% CBR should be provided, and considerCBR as 2% for design.
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Chart 1 : Traffic 1-10 msa: CBR 2-10 %
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Chart 2 : Traffic 10-150 msa: CBR 2-10 %
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PAVEMENT THICKNSS AND COMPOSITION
Pavement Thickness Design CHARTS ::
These charts are used to obtain TOTAL thickness ofPavement.
Pavement Composition ::
Sub-base course,
Base course, Bituminous Surfacing
Binder Course,
Wearing course.
Pavement Design CATALOGUE :: These charts are used to obtain the MINIMUM
THICKNESS and COMPOSITION of pavementlayers.
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GRANULAR SUB-BASE COURSE (GSB)
GRADATION ::
The Sub-base materials should conform to theGrading (Grain size distribution)of Clause 401 ofMORT&H.
The material passing 425 micron sieve
should have LIQUIE LIMIT not more than 25 %,
PLASTICITY INDEX not more than 6 %.
The CBR Values Traffic up to 2 msa min CBR = 20 %,
Traffic exceeding 2 msa CBR = 30 %.
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GRANULAR SUB-BASE COURSE (GSB)
Construction ::
The GSB should be extended over entirewidth of formation.
When CBR Value of GSB is less than 2 %,
a capping layer of 150 mm thickness ofmaterial with 10 % CBR is provided.
MINIMUM THICKNESS :: Traffic less than 10 msa Minimum = 150 mm Traffic more than 10 msa Minimum = 200 mm
G B E E
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GRANULAR BASE COURSE
MATERIAL :: The unbound granular base
comprises of any one of the following. WBM Water Bound Macadam or
WMM Wet Mix Macadam.
THICKNESS :: WMM
Traffic up to 2 msa Min = 225 mm.
Traffic exceeding 2 msa Min = 250 mm.
WMM
Traffic up to 2 msa Min = 225 mm
Traffic exceeding 2 msa Min = 300 mm
BITUMINOU URFACING
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BITUMINOUS SURFACINGS
The Bituminous Surfacing consists of
Wearing Course ony or Binder Course + Weaing Courses
WEARING COURSE :: commonly usedWearing courses are Surface Dressing (SD),
Open-graded premix carpet (OGPC),
Mix seal surfacing (MS), Semidense Bituminous Concrete (SDBC),
Bituminous Concretd (BC).
BITUMINOUS SURFACINGS
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BITUMINOUS SURFACINGS
BINDER COURSE :: commonly usedBinder courses are Bituminous Macadam (BM) ,
Dense Bituminous Macadam (DBM).
BITUMINOUS MACADAM :: For traffic less than 5 msa .
DENSE BITUMINOUS MACADAM :: For traffic more than 5 msa .
BITUMINOUS SURFACINGS
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BITUMINOUS SURFACINGS
SELECTION :: The choice of appropriatetype of wearing courses depend on
Desine traffic, Type of Base course,
Type of Binder Course,
Rainfall of the area.
NOTE :: The thickness of Surface dressing,
Open graded premix carpet and
Mixseal surfacing
Will not be counted in designing the totalthickness of pavement.
PAVEMENT DESIGN CATALOGUE
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PAVEMENT DESIGN CATALOGUE
Based on the results of
Analysis of Pavement Structure
Specification requirement. Plate 1
Used to design for the traffic upto 10 msa
1, 2, 3, 5, 10.
Plate 2 Used to design for the traffic upto 150 msa
10, 20, 30, 50, 100, 150.
CBR 2, 3, 4, 5, 6, 7, 8, 9 and 10.
For intermediate traffic ranges, the pavement layerthickness will be interpolated linearly.
LINEAR INTERPOLATIONLINEAR INTERPOLATIONLINEAR INTERPOLATIONLINEAR INTERPOLATION
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LINEAR INTERPOLATIONLINEAR INTERPOLATIONLINEAR INTERPOLATIONLINEAR INTERPOLATION
First Ordinate = y1
Second Ordinate = y2
Distance between y1 & y2 = x1
y1
y2
x1
x
1*)12(1x
xyyyy +=
1*)12(1 x
x
yyyy=
1*)12(1x
xyyyy +=
x
x
PAVEMENT DESIGN CATALOGUE
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PAVEMENT DESIGN CATALOGUE
PLATE-1 ::
DRECOMMENDED DESIGN FOR TRAFFICRANGE 1-10 msa, for CBR of 2%, 3%,
4%, 5%, 6%, 7%, 8% and 9% &10%. PLATE-2 ::
DRECOMMENDED DESIGN FOR TRAFFIC
RANGE 10-150 msa, for CBR of 2%, 3%,4%, 5%, 6%, 7%, 8%, 9% and 10%.
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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Chart 2 : Traffic 10-150 msa: CBR 2-10 %
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635
DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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DSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLEDSIGN EXAMPLE
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References
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IRC : 37-2001 Guidelines for thedesing of Flexible Pavements.
MORT&H Specifications for Road andBridge works ( Fourth Revision).
Principles and practices of HighwayEngineering. L.R. Kadiyali.
Some sites in Internet.
acknowledgements
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1) NAC :: National Academy of Construction.
2) Sri F.C.S. Peter, D.G., NAC3) Sri S. Jaswant Kumar, C.E.(D&P), R&B Dept.
4) Sri A. B. V. Subba Reddy, NAC, Hyderabad.
5) Master V. Shraman,
-- V. VENKATA NARAYANA
Dy. Executive Engineer (R&B),
9440818440, 07799139399
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THANK YOU
V. VENKATA NARAYANA