Flexible Pavement Failure

(1)

(2)

Table of content

1.

1. Flexible Pavement

Flexible Pavement

2.

2. Layer

Layer of

of Flexible Pavement

Flexible Pavement

3.

3. Failure In Flexible Pavement

Failure In Flexible Pavement

4.

4. Typical Failure Pattern

Typical Failure Pattern

5.

5. Conclusio

Conclusion And

n And Discussion

Discussion

6.

(3)

Table of content

1.

1. Flexible Pavement

Flexible Pavement

2.

2. Layer

Layer of

of Flexible Pavement

Flexible Pavement

3.

3. Failure In Flexible Pavement

Failure In Flexible Pavement

4.

4. Typical Failure Pattern

Typical Failure Pattern

5.

5. Conclusio

Conclusion And

n And Discussion

Discussion

6.

(4)

Flexible Pavement

•

Low

Low or

or negligible

negligible fflexural

lexural strength

strength

•

Flexible in their in structural action under

load

•

T

Transm

ransmits

its stre

stress

ss to

to lower

lower layer

layer by

by grain to

grain to

grain transfer

•

Generally

Generally Las

Last

t for

for 5- 20

5- 20 yrs

yrs

•

Low

Low initial c

initial cost

ost Easy

Easy to

to upgrade

upgrade

•

Bituminous roads

_–

DBSD, Asphalt

Concrete , Otta seal , DBM etc

11..

SSo

oiil

l ssu

ub

b ggrraad

dee

22.. SSu

ub

b-

- B

Baasse

e C

Co

ou

urrssee

33.. B

Baasse

e C

Co

ou

urrssee

4 4.. SSu

urrffaacce

e C

Co

ou

urrssee

T

ypical

Flexibl

e Pav

ement L

ay

er

2

(5)

(6)

Typical Flexible Pavement

Typical Flexible Pavement according to material quality

(7)

F exi e Pavement Fai ure



According to Highway Research Board, 1970 cited by Pavement

Interactive, 2010, pavement distress is "any indication of poor

or unfavorable pavement performance or signs of impending

failure; any unsatisfactory performance of a pavement short of

failure" To maintain the stability of the pavement structure as a

whole each layer should be stable within itself.

Pavement

Failure

External Failure Over loading Petroleum spillage Sink holes

Flooding, seepage, climate Other unforeseen –Earthquake

etc..

Internal Failure

Lack of Pavement Mixtures Poor materials

(8)

One of major cause of pavement failure

Water is enemy of pavement and can worsen cracked pavement problems .Freezing and thawing action makes pavement weak.

(9)

Failure in sub grade

Excessive deformation in sub-grade soil due to insufficient

bearing capacity or a shear failure in sub-grade soil.



Inadequate Stability

 inherent weakness of soil

itself,

 excessive moisture

 improper compaction



Excessive application of

Stress

_–

consolidation

deformation



Plastic deformation

(10)



Inadequate Stability

 Poor mix proportion , in adequate stability, poor ingradient



Loss of Binding action

 Repeated stress Application

 Internal movement of aggregate in base or sub base



Loss of Bearing Course Materials

 When Wearing course materials worn out



Inadequate Wearing Course



Use of inferior materials



Lack of lateral confinement of granular base course

(11)

Failure of wearing course



Improper mix design



Poor quality control



Volatilization and oxidation of binder



Improper gradation of aggregates



Inadequate binder content



Inferior type of binder etc.

(12)

Typical Flexible Pavement Failures

1. Surface Deformation 2. Surface Defects 3. Cracking's 4. Patching and Potholes 1. Shoving 2. Corrugation 3. Rutting 4. Depression 1. Bleeding Flushing 2. Ravelling 3. Polishing 4. Surface lifting / Seal Break /Upheaval 5. Water bleeding and pumping 1. Fatigue /alligator crack 2. Block Cracking 3. Longitudnal Cracking 4. Transverse(ther mal ) Cracking 5. Edge Cracking /Edge Break /Edge drop offs 6. Crescent shape /slippage cracks 1. Patch detoritio n 2. Potholes

(13)

Surface Deformation

Possible Causes

 Excess asphalt

 too much fine aggregate;

rounded aggregate;

 Low modulus of base course

, thin wearing course

 High stress due to braking

and acceleration Probable Treatment

 Partial or full depth patch  Reconstruction of base  Bituminous overlay

1.1 Shoving :

•Formation of waves across a pavement,

(14)

Possible Causes

 Inadequate stability of bituminous

surface

 Heavy traffic on steep downgrade or

upgrade

 Inadequate stability of base course  Compaction of base in wave form

Probable Treatment

 Base reconstruction

 Mill off the corrugated surface and

replace with the stiffer mix or use hot mix asphalt

1.2Corrugations :

•Transverse ridges and valleys (or ripples) occurring at regular Intervals, • Usually occurs at points where traffic starts and stops

(15)

Possible Causes

 Inadequate pavement thickness  Unsuitable bituminous mixes  consolidation or lateral

movement of any layer due to traffic loading

 Insufficient compaction

Probable Treatment

 Strengthening overlay or

reconstruction

 Base or sub base strengthening

1.3Rutting :

•

Surface/channelized depressions in the wheel-tracks

, •

evident after a rain when they are filled with water

(16)

Possible Causes

 Differential settlement of sub

grade or base materials

 Volume change of subgrade due

to environmental inf luences

 settlement due to instability of

embankment

Probable Treatment

 Applying a thin surface patch  Base or subgrade reconstruction  Embankment stabalization and

drainage improvement

1.4 Depression (birds baths):

•

Surface areas with slightly lower elevations than the surrounding

pavement

(17)

Possible Causes

 Excessive asphalt in the surface

layer

 Lack of proper rolling during

placement

Probable Treatment

 Applying coarse sand

 cutting off excess asphalt with a

motor grader or removing it with a heater planer

 Resurfacing the asphalt

2.1 Bleeding/ Flushing:

•

shiny, glass-like reflecting surface , thin sticky bitumen layer

•

Loss of skid resistance when wet

(18)

Possible Causes

 Insufficient bitumen content  Inadequate compaction or

construction during wet weather

 Poor adhesion of bitumen

binder

Probable Treatment

 Thin bituminous overlay

2.2Ravelling(very porous asphalt):

•

Separation of aggregate particles in a pavement from the surface

downward or from the edges inward

(19)

Possible Causes

 Inadequate resistance to

polishing of surface aggregates

 Use of naturally smooth

uncrushed aggregates

 Repeated traffic on an aging

pavement system. Probable Treatment

 The bituminous overlay of use

of stiffer mix

2.3Polishing:

(20)

Possible Causes

 Inadequate cleaning or

inadequate tack cot before placement of upper layers

 Adhesion of surface binder to

vehicle tyres

 Seepage of water through

asphalt swelling of the subgrade

inadequate tack coat before placement of upper layers Probable Treatment

 Reconstruction of weak layer  Thin bituminous overlay

2.4 Surface lifting /Seal Break/Upheaveal

:

(21)

Possible Causes High water table

 Poor drainage

 Poor mix design and

compaction

Probable Treatment

 slurry seal to limit water

infiltration

 Lower water table and good

drainage

2.5 Water Bleeding and pumping

:

• Water seeps out of joints or cracks or through an excessively porous • Water and fine material is ejected from underlying layers through

cracks

•Decreased skid resistance , decreased structural support •

(22)

3. Cracking Cracks

Possible Causes

 Inadequate pavement

thickness

 Increase in loading

 Brittle base and wearing course  Poor base drainage and

inadequate structural design

Probable Treatment

 Strengthen the pavement or

reconstruction

 Base recycling or reconstruction

3.1 Fatigue /Alligator /Crocodile crack:

•

load associated structural failure cracks allow moisture

infiltration, roughness, may further deteriorate to a pothole

•

Repeated loading, the longitudinal cracks connect forming

(23)

Possible Causes

 Joints in underlying layer  Shrinkage and fatigue of

underlying cemented materials

 Shrinkage cracks (due to

bitumen hardening) in bituminous surfacing Probable Treatment

 Crushed aggregate overlay  Replace underlying cemented

materials

 Cut and patch or crushed

aggregate overlay

3.2 Block Cracking :

•

Large interconnected rectangles (roughly) is not load-associated,

(24)

Possible Causes

 Reflection of shrinkage cracks  Displacement of joints at

pavement widening

 Differential settlement between

cut and fill

Probable Treatment



Cut and patch

 Replace bituminous surfacing  Crushed aggregate overlay or

reconstruction of joints.

3.3 Longitudnal Cracking :

(25)

Possible Causes

 Reflection of shrinkage cracks  Construction joint in

bituminous surfacing

 Shrinkage crack bituminous

surfacing

 Reflection of joints in the

underlying base Probable Treatment



Cut and patch



Crack sealant

3.4Transverse or thermal Cracking :

•

Perpendicular to the pavement's centerline or laydown direction

•

Induced by daily temperature cycles, and poor construction

(26)

Possible Causes

 Poor drainage conditions and lack of

support at the pavement edge

 Excessive traffic loading at the

pavement edge

 Inadequate pavement width  Insufficient bearing support  Edge drop-off

 Heavy vegetation along the pavement

Probable Treatment

 Widen the pavement or strengthen

the pavement edge

 Improve drainage and shoulder

3.5Edge Cracks /Edge Breaks /Edge Drop off :

•

Edge Cracks travel along the inside edge of a pavement surface

(27)

Possible Causes



Lack of bond between wearing

course and the underlying layer



Thin wearing course



High stress due to braking and

acceleration movements

 By dirt, oil, or other contaminants

preventing adhesion Probable Treatment



Partial or full depth patch



Reconstruction of base



Bituminous overlay

3.6Crescent /Parabolic /Slippage /Shear cracks :

•

Slippage cracks are crescent-shaped cracks or tears in the surface

layer(s) of asphalt where the new material has slipped over the

underlying course

(28)

.

atc ng an ot o es

Possible Causes

inadequate tack cot before placement of upper layers

 Weak, loose layer immediately

underlying seal

 Break the bond between surface

and lower layers

Probable Treatment

 Reconstruction of weak layers  Mill off and re-lay upper layers  Replace wearing course or thin

bituminous overlay

4.1Patch deterioration :

•

An area of pavement that has been replaced with new

material to repair the existing pavement.

A patch is considered a defect no matter how well it

performs.

(29)

Possible Causes

 Loss of surface course

 Moisture entry to base course

through a cracked pavement surface

 Load associated disintegration of

base

Probable Treatment



Patching



Cut and patch



Base reconstruction

4.2Pot Holes:

•

Small, bowl-shaped depressions in the pavement surface

that penetrate all the way through the asphalt layer down

to the base course

(30)

Conclusion and Discussion

 Flexible pavement failures are affected by various factors such as

sub grade soil , drainage , climate ,traffic and environmental condition etc.

 There is not just one type of road failure, and there is not just

one reason for each type of failure, this attempt is made to give guidance and supply some information

 Localized settlement of any component layer of flexible

pavement structure could be strong enough to cause pavement failure.

 Timely maintenance reduce operation cost and life of pavement  The aging and oxidization of bituminous films lead to the

deteriorations of bituminous pavement.

 A proper drainage system or good protection measure on

(31)

References

.

 Highway Engineering –Book by Dr S.K Khanna and Dr C E G Justo  Highway specification and maintenance pdf –

http://ww.pavementinteractive .org

 Proceeding of Malaysian Universities Transportation Research Forum

and Conferences 2010 (MUTRFC2010), University Tenaga Nasional ,21 December 2010

 Vehicles of today and motor ways in Myanmar (4). Retrieved on 16

August 2010 from http://www.mrtv3.net.mm/open6/230909for1.html

 http :// www.uotechnology.edu.iq

 Data Collection Strategies in Malaysia, Public Work Department