SUBMITTED BY :

GARVIT GOYAL

B.TECH 4TH YEAR

CIVIL BRANCH

CONTENT

INTRODUCTION

TYPES OF PAVEMENTS

(a) Flexible pavements

(b) Rigid pavements

© Semi rigid pavements

Design factors

Reqirement of good pavement

California bearing ratio (CBR)

IntroductionPavement design is the major component in the road

construction.

Nearly one-third or one-half of the total cost of

construction , so careful consideration should be taken in

design of pavement.

For the better road condition ,good pavement is used

can eaisly bear the load as well eaisly transmit the load.

Flexible pavement has shorter life span as compared

to rigid pavements.

Type of pavements

FLEXIBLE PAVEMENT

RIGID PAVEMENT

SEMI-RIGID PAVEMENT

Flexible PavementsFlexible pavemants are those pavements which are

flexible under the action of load.

Bituminous is one of the best flexible pavement material.

Flexible pavement transmit the vertical stress to the lower layers.

Flexible pavement is form in layers , so first layer is form strong as compared to other.

It consist of 4 parts soil subgrade, subbase ,base course ,surface course.

Flexible Pavement Structure

Surface course

Base course

Subbase course

Subgrade

Design parameters for Flexible Pavements

1.VDF(Visual display factor)

It is a multiplier which converts the number ofcommericial vechiles of different axle loads and axleconfiguration to the number of standard loadrepetitions.

2. SUB GRADE:

IT Should be well compacted in cutting as well as filling .

Strength is assesed in terms of CBR value.

3. Traffic

As per the IRC:37 design traffic should be 0.1 msa to

2 msa (million standard axles).

Weight of commercial vehicle (laden) is

considered as 3 tonnes or more.

For design traffic we consider the existing traffic and

rate of growth.

4. Design life

The no. of years to be taken until the major

reconstruction.

Design life depend upon the environmental conditions,

materials used ,maintenance etc.

For rural roads design life of 10 years is considered.

In low volume roads for the thin bituminous surfacing

design life of 5 years is considered.

Flexible Pavement – Construction

Rigid PavementsRigid pavements are those pavements whose surface is

hard

This pavement is not transferd the load from ground surface to lower suface.

Rigid Pavement has the capacity to transfer the wheel load from wider area of roads.

Rigid pavement is formed either of opc slabs or cement conrete .

Rigid Pavement Structure

Surface course

Base course

Subbase course

Subgrade

Design Parameters for rigid pavement

1. Wheel load stresses :Westergaard developed relationships for the stress at interior, edge and

corner regions, denoted as i; e; c in kg/cm2.

2. Temperature Stress :

Temperature stresses are developed in cement concrete pavement due to variation in slab temperature.

This is caused by

(A) daily variation resulting in a temperature gradient across the thickness of the slab and

(B) seasonal variation resulting in overall change in the slab temperature.

The former results in warping stresses and the later in Frictional stresses.

Design of joints1. EXPANSION JOINTS :

The purpose of the expansion joint is to allow the expansion of the pavement due to rise in temperature with respect to construction temperature.

The design consideration are:

Provided along the longitudinal direction,

design involves nding the joint spacing for a given expansion joint thickness (say 2.5 cm specied by IRC) subjected to some maximum spacing.

2. Contraction joints

The purpose of the contaction joint is to allow the contraction of the slab due to fall in slab temperature below the construction temperature.

The design considerations are:

The movement is restricted by the sub-grade friction Design involves the length of the slab given by:

Lc =2* 10^4 Sc/W:fWhere, where, Sc is the allowable stress in tension in cement

concrete and is taken as 0.8 kg/cm2, W is the unit weight of the concrete which can be taken as 2400 kg/cm3 and

f is the coecient of sub-grade friction which can be taken as 1.5.

Computation of design traffic

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

Where,

a= no. of commercial vechiles per day for design

p= no. of commercial vechiles per day last count

r=annual growth rate of commercial traffic

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

completion of construction

Selection Factors Of Pavements Initial cost

Availability of good materials

Cost of maintenance

Environmental conditions

Availability of industrial wastes

Traffic intensity

Ease of labour

Favourable working conditions

Requirement Of Good PavementIt should be Economical.

It should be cheap and durable.

Ease to construct.

Good surface finish.

Eaisly visible marks on the pavements.

It should have low maintenance cost.

It should provide good visibility in night.

CALIFORNIA BEARING RATIO Conduct on sample which remoulded at OMC and

dry density.

Test should be done per km depend on soil

type.

If CBR less than 2% for 100 mm thickness then

minimum 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.