lecture #6 pavement management (evaluation)

8/10/2019 Lecture #6 Pavement Management (Evaluation)

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H22 IS3 : Transport Infrastructure

Topic #6 :

Pavement Management (Evaluation)


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Pavement Management System (PMS) Deterioration of the Highway

Pavement Cracks Surface Deformation

Routine Assessment Visual Surveys Skid Resistance Surveys Profile Surveys Deflection Surveys


Contents


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Pavement Management System (PMS)

Pavement management is the task of monitoring & maintaininga road network in as economic a way as possible.



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Subgrade soil Pavement materials characteristics

Asphalt cement Aggregate Modifiers for asphalt cement (e.g., rubber and polymers) Additives or stabilizing agents for aggregates (e.g., lime and

cement) Traffic loading Environment

Moisture Temperature


Factors affecting pavement performance


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Cracking : Crocodile / alligator cracks, Block cracks, Longitudinalcracks, Transverse cracks, Edge cracks, Crescent shaped cracks

Deformation : Rutting, Corrugation, Depression, Shoving Deterioration : Delamination, potholes, patching, raveling,stripping, polished aggregate, pumping

Mat problems : Segregation, checking, bleeding Problems associated with seal coats: Rock loss, segregation,

bleeding/fat spots, Delamination


Common Flexible Pavement Distresses

Distress TypeCategory


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Pavement Cracks


Figure 6.1 : Type of Cracks


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Crocodile / Alligator Cracks


Crocodile cracks are interconnected / interlaced cracks whichform a network of multi-sided blocks resembling the skin of acrocodile.

Figure 6.2 : Crocodile Cracks


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Block Cracks


Block cracks are interconnected cracks forming a series ofblocks , approximately rectangular in shape .

Figure 6.3 : Block Cracks


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Longitudinal Cracks


Longitudinal cracks are cracks which are usually straight & parallelto the center line , situated at or near the middle of the lane.It can happen singly or as series of almost parallel cracks or withsome limited branching.

Figure 6.4 : Longitudinal Cracks


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Transverse Cracks


Transverse cracks are unconnected cracks running transversely(relatively perpendicular to pavement center line) across thepavement .

Figure 6.5 : Transverse Cracks


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Edge Cracks


Edge cracks are crescent shaped or fairly continuous cracks,parallel to pavement edge .

Figure 6.6 : Edge Cracks


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Surface Deformation


Deformation takes place when a road surface undergoes changesfrom its original constructed profile.

There are 4 major types of surface deformation ;1) Rutting2) Corrugation

3) Depression4) Shoving


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Surface Deformation


Figure 6.8 : Type of Surface Deformations


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Rutting


Figure 6.9 : Rutting

Rutting is longitudinal deformation or depression in thewheel paths which occur after repeated applications of axleloading .It may occur in 1 or both wheel paths of a lane .


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Corrugations


Figure 6.10 : Corrugations

Corrugations are regular transverse undulations , closely spacedalternative valleys & crests with wavelengths of less than 2 m.Generally, it will result in a rough ride & will become more worsewith time.


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Shoving


Figure 6.12 : Shoving

Shoving is the bulging of the road surface generally parallel tothe direction of traffic and/or horizontal displacement of surfacingmaterials , mainly in the direction of traffic where braking oracceleration movements occur, caused by traffic pushing againstthe pavement.


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Routine Assessment


To monitor the performance of a pavement, the HighwaysAgency requires the use of a number of assessment machines &methods.

These include: High Speed Road Monitor (HRM)

Deflectograph Sideways Force Coefficient Routine Investigation Machine

(SCRIM) Visual condition surveys , etc.

In this way, the appropriate timing can be chosen for the

various necessary maintenance processes which all pavementseventually require.


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Visual Surveys


These are the most basic & widely used means of evaluation. They are inevitably operator dependent. Every road is assessed

visually in some way. UK systems:

RMMS (Routine Maintenance Management System) CHART (Computerised Highway Assessment Ratings and

Treatments) MARCH (Maintenance Assessment Rating for Condition of

Highways)


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Skid Resistance Surveys


Skid resistance tests are conducted on wet surfaces & producea coefficient of friction measured by a portable skid resistancetester.

The device consists of a pendulum with a rubber pad fixed tothe lower end, & a graduated scale.

The device is operated by swinging the pendulum through astandard distance such that the rubber pad touches the surfaceto be tested, reducing the pendulum's inertia as it completesthe arc.

A light pointer indicates the peak of the first swing, which ismeasured against the graduated scale giving the coefficient of

friction of the surface tested. The result is expressed as a decimal fraction which when

multiplied by a hundred gives the skidding resistance of thesurface.


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The Sideway-Force Coefficient Routine Investigation Machine(SCRIM) tests by mounting the test wheel obliquely at 20 tothe direction of travel.

The sideway-force coefficient (SFC) is given by the ratio of theforce developed at right angles to the wheel to the load actingon the it.

A mean figure for SFC is obtained using results taken every 5,10, or 20 metres while the SCRIM travels at 50 km/hr.


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Results of SCRIM surveys have legal implications in the UK. Authorities must act to correct any deficiencies on motorway &

trunk roads. The requirement on local authority roads in morevague.


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The Griptester may bepushed by hand or towedbehind a vehicle at speedsof up to 120 km/hr.

The test wheel turns slowerthan the main wheels,acting similar to a brakingvehicle wheel.

A small electronic deviceon-board constantlymonitors the drag & load ,

while location referencesare entered manually forlater interpretation.


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Profile Surveys


The profile surveys are measured by the HRM (High SpeedRoad Monitor) on trunk roads & motorways.


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Profile Surveys


Longitudinal profile gives: A direct measure of ride quality An indication of structural condition Surface unevenness (profile) Average rut depth Crossfall Gradient Radius of curvature Surface texture (macro texture)


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Deflection Surveys


The standard tool used on trunk roads & motorways is theDeflectograph. Deflectograph is slowly being replaced by Traffic Speed Road

Assessment Condition Survey (Tracs), now called "SCANNER". Extensive trials have lead to the development of relationships

between deflection & remaining life & also overlay treatment. The Deflectograph is based on the same principles as the

Benkelman beam. The Benkelman beam is a device for measuring the deflection at

a point in the surface of a pavement caused by the passage of awheel load.


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Deflection Surveys


The deflection is measured whilst the road is subject to astandard load, this is provided by loading dual wheels on therear axle of a suitable vehicle to 3175 kg.

A sufficient space is left between the wheels for the measuringarm of the deflectograph to pass, hence recording the deflectionwhen the load is imposed, & obviously the weakest parts of theroad pavement will deflect the most.

The deflection is measured in the inside & outside wheel tracks.


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Deflection Surveys



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Deflection Surveys


- Benkelman Beam

The End of Topic #6

lecture #6 pavement management (evaluation)

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