Venkat FlexiblePavement Design

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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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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



Tandem Axle Load :: Equivalency Factor =(Axle Loan in kg/14968)4

Equivalency Factor of 8160 kg =(8160/14968)4 =0.07





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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


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


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 +

=


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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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).



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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 .



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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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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



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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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635



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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

[email protected]


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THANK YOU

V. VENKATA NARAYANA

Venkat FlexiblePavement Design

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