flexible pavement failure

Table of content

1. Flexible Pavement 2. Layer of Flexible Pavement 3. Failure In Flexible Pavement4. Typical Failure Pattern 5. Conclusion And Discussion 6. Reference

04/08/23 Flexible pavement Failure 2

Flexible Pavement • Low or negligible flexural strength• Flexible in their in structural action

under load• Transmits stress to lower layer by

grain to grain transfer• Generally Last for 5- 20 yrs• Low initial cost Easy to upgrade• Bituminous roads – DBSD, Asphalt

Concrete , Otta seal , DBM etc

1. Soil sub grade2. Sub- Base Course 3. Base Course4. Surface Course

Typical Flexible Pavement Layer

04/08/232

Flexible pavement Failure


Typical Flexible Pavement X section

Typical Flexible Pavement

04/08/23 5Flexible pavement Failure

Typical Flexible Pavement according to material quality

Loading pattern

Flexible Pavement FailureAccording 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.


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.

Failure in sub gradeExcessive 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

Pavement Failure



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 CourseUse of inferior materials Lack of lateral confinement of granular base

course

Failure in Sub Base –Base Course

Failure of wearing courseImproper mix designPoor quality control Volatilization and oxidation of

binder Improper gradation of aggregates Inadequate binder content Inferior type of binder etc.


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 patchReconstruction of base Bituminous overlay


1.1 Shoving : •Formation of waves across a pavement,• Occur at severe horizontal stresses like intersection

Possible CausesInadequate 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

Possible CausesInadequate pavement

thickness Unsuitable bituminous mixesconsolidation 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

Possible CausesDifferential settlement of sub

grade or base materials Volume change of subgrade

due to environmental influences

settlement due to instability of embankment

Probable Treatment Applying a thin surface patchBase or subgrade

reconstruction Embankment stabalization and

drainage improvement04/08/23 Flexible pavement Failure 15

1.4 Depression (birds baths): • Surface areas with slightly lower elevations than the surrounding pavement•Usually on left lane and shoulder

Possible CausesExcessive 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

2.Surface Defects

Possible CausesInsufficient bitumen

contentInadequate 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•more common in the northern regions(snow belt)

Possible CausesInadequate 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 04/08/23 Flexible pavement Failure 18

2.3Polishing: • surface consisting of rough exposed aggregates

Possible CausesInadequate 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 cleaning or inadequate tack coat before placement of upper layers

Probable Treatment Reconstruction of weak layerThin bituminous overlay


2.4 Surface lifting /Seal Break/Upheaveal: • Upward movement in a pavement

Possible CausesHigh water table

Poor drainage Poor mix design and

compaction Probable Treatment slurry seal to limit water

infiltration Lower water table and

good drainage04/08/23 Flexible pavement Failure 20

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 •

3.Cracking Cracks

Possible Causes Inadequate pavement

thicknessIncrease 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 many-sided sharp-angled piece like crocodile

Possible CausesJoints in underlying layer Shrinkage and fatigue of underlying

cemented materialsShrinkage 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, but generally caused by shrinkage of the asphalt pavement

Possible CausesReflection of shrinkage cracksDisplacement of joints at pavement

widening Differential settlement between cut

and fill

Probable Treatment Cut and patchReplace bituminous surfacing Crushed aggregate overlay or

reconstruction of joints.


3.3 Longitudnal Cracking : •Cracks that are parallel to the pavements centerline

Possible CausesReflection of shrinkage cracksConstruction 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

Possible CausesPoor 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 pavementProbable 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 within one or two feet

Possible CausesLack 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

4.Patching and Potholes

Possible Causes Inadequate cleaning or

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 layersMill off and re-lay upper

layersReplace wearing course or

thin bituminous overlay 04/08/23 Flexible pavement Failure 27

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.

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

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 moisture elongates pavement life.


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.iqData Collection Strategies in Malaysia, Public Work

Department Malaysia ,Zakaria, S. & Hasan, M. Z. (2005).

flexible pavement failure

Documents

inadequate tack cot

high stress due

typical flexible pavement

flexible pavement failure

inadequate cleaning

pavement failure

pavement surface

excess asphalt