pavement design kiran biradar

8/11/2019 Pavement Design Kiran Biradar

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BYKIRAN BIRADAR

PAVEMENT DESIGN


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Introduction

Pavement design is the major component in the

road construction.

Nearly one-third or one-half of the total cost ofconstruction , so careful consideration should be

taken in design of pavement.

Type of pavements:

Flexible pavement

Rigid pavement

Semi-rigid pavement


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Factors which affect the selection of these

pavements

Initial cost

Availability of good materials

Cost of maintenance

Environmental conditions

Availability of industrial wastes

Traffic intensity


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Design parameters

General:

Criteria for determining the pavement (flexible)

Thickness is vertical compressive strain comes to the

subgrade due to the standard axle laden of magnitude8.17 kN (8170 kg) , if more than this causes permanentdeformation in form of rutting. The maximum ruttingcan be accepted in village road as 50 mm before

maintenance and the analytical evaluation can be doneaccording to IRC:37.

For rigid and semi-rigid pavement tensile stress is takenas the design criteria.


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Traffic:

As per the IRC:37 design traffic should be 0.1 msa to2 msa (million standard axles).

Weight of commercial vehicle (laden) is consideredas 3 tonnes or more.

For design traffic we consider the existing traffic and

rate of growth.Traffic study should be done as per the IRC:9.


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Design life:

The no. of years to be taken until the majorreconstruction.

Design life depend upon the environmentalconditions, materials used ,maintenance etc.

For rural roads design life of 10 years is considered.

In low volume roads for the thin bituminoussurfacing design life of 5 years is considered.


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Computation of design traffic:

a=p(1+r)^(n+x)

Where,a=no. of commercial vehicles/day for design

p=no. of commercial vehicles/day at last count

r=annual growth rate of commercial traffic

n=no. of years between last count and year ofcompletion of construction

x=design life in years


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Pavement components

Subgrade Sub-base course

Base course Surface course


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Subgrade:

To provide support to the pavement as itsfoundation.

Top 30 cm of the cutting or embankment atformation level in rural roads consider as subgrade.

A minimum of 100% of standard proctorcompaction should be attain in subgrade.

For clayey soil 95% and moisture content of 2% inexcess of optimum value.

Soil below subgrade should be compacted to 97% ofstandard proctor compaction.


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CBR:

Conduct on sample which remoulded at OMC anddry density.

Test should be done per km depend on soil type.

If CBR less than 2% for 100 mm thickness thenminimum CBR of 10% is to be provided to the sub-base for CBR of 2%.

If CBR more than 15% , no need to provide sub-base.


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Sub-base course:

Selected materials placed on subgrade which iscompacted to 98% of IS heavy compaction.

Function of sub-base is to distribute the stressesover a wide area of the subgrade imposed by thetraffic.

Materials: CBR of 15%

Passing through 425 micron IS sieve

L.L


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Waste material such as

Fly ash

Iron and steel slag Recycled concrete

Municipal waste

When subgrade is silty or clayey soil and annual

rainfall of area is more than 1000 mm, a drainagelayer of 100 mm then formation width should beprovided.


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Base course:

to with stand high stress concentrations whichdevelop due to traffic under the wearing surface.

Different types of base course used are:

WBM

Crusher-run macadam

Dry lean concrete Soft aggregate base course

Lime-fly ash concrete


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Surface course:Thickness of surface course depend upon the traffic volumeand type of material used for it.

For gravel roads extra thickness should be provided because

of lost in thickness due to the traffic action.

Bituminous wearing courses must be made up of good quality

aggreagate with aggreagate impact value not exceeding 30 %

in order to reduce degradation of aggregates by crushing.


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pavement design kiran biradar

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