Fundamentals of Asphalt Pavements and materials 4th July 2013
Pavement Assessment David O’Farrell PTS
Uses of assessment data •
Identifying locations from network survey for maintenance work
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Supporting evidence for funding bids
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Calculation of Performance Indicators
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Detailed investigation of a defined scheme to assist with design Investigation of claims against the Highway Authority
Measurement Techniques Visual
Machine based •
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CVI
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DVI
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VCS Footway surveys
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Deflectograph Falling Weight Deflectometer (FWD)
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SCRIM
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Griptester
High Speed Sensor Systems See HD29 and PCIS website •
http://www.pcis.org.uk for further information
Visual Techniques
CVI & DVI •
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Part of UKPMS CVI done from slow moving vehicle (10 – 15 kph) or on foot DVI done on foot. Similar defects recorded but in more detail Both identify defects which are ranked by a scoring system during data processing Used to produce Performance Indicators for Highway Authorities Procedures described in UKPMS Visual data collection manuals available from:http://www.pcis.org.uk/index.php?p=6/8/0/list,0,49
CVI Survey •
Defects grouped as:–
Length (edge defects, kerb defects, longitudinal joint defects, off carriageway defects)
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Lane length (major cracking, rutting)
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Count (transverse cracks, transverse joint defects)
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Area (all others)
Collected on data capture device and transferred to Pavement Management
CVI Survey
CVI Survey
CVI Survey
Visual surveys •
Cheap and relatively quick
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Reproducibility not always good
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Will only identify surface defects
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Cannot quantify pavement strength or life
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Difficult to do at night
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Increasing safety issues and delays to road users
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Structural assessment- Deflection measurement The structural condition of a flexible or flexible
composite pavement can be assessed by measuring its deflection under a standardised load.
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•
Deflection depends on pavement temperature, pavement thickness and how much traffic has been carried since construction Several methods of measuring deflection •
Deflection beam (Benkelman beam)
•
Deflectograph
Structural assessment- Benkelman beam
Structural assessment- Benkelman beam
Structural assessment - Deflectograph
Structural assessment - Deflectograph
Structural assessment - Deflectograph • •
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Described in LR 833 and HD 29 Travels at 3 – 4 kph so requires traffic management Measures deflection under load of a 6.35 tonne axle with twin wheels Analysis by comparison with charts showing deflection behaviour of documented sites Requires knowledge of pavement thickness and traffic volumes Analysed by PANDEF software or equivalent Methodology for overlay design based on deflection Seasonal use only
Structural assessment - Deflectograph Seasonal restrictions (based on HD29) Restrictions also based on pavement temperature
Structural assessment - FWD
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50kN load applied to plate Knowledge of pavement temperature and thickness required Measures the shape of the deflection bowl
Structural assessment - FWD
Structural assessment – FWD load transfer between concrete slabs
FWD results Deflection plots 200 180 160 140 120 100 80 60 40 20 0 184.100
184.200
184.300
184.400
184.500
184.600
184.700
184.800
184.900
Chainage
d1 is overall condition
d1
d1 - d4
d1-d4 is surface layer condition
FWD results Layer Stiffnesses 100000
10000
foundation Bound layer @ 20c
1000
3 GPa 7 GPa
100
10 184.100
184.200
184.300
184.400
184.500 Chainage
184.600
184.700
184.800
184.900
Safety assessment - SCRIM
Sideway Force Coefficient Routine Investigation Machine
Safety assessment - Griptester
Safety assessment - Griptesterr
High Speed Sensor Systems (contactless sensor systems) Surveys undertaken by vehicles travelling at or near normal traffic speeds covering large sections of a network
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HRM
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MRM
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HARRIS
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TRACS
High Speed Sensor Systems (contactless sensor systems) measures:•
Crossfall
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Gradient
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Rut depth
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Longitudinal Profile “ “ “
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Texture Depth
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The amount of surface cracking present
(10m & 100m average) “ “ “
Can also capture continuous image of network
Longitudinal Profile •
(riding quality)
Three profiles measured at different wavelengths •
3 metres
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10 metres
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30 metres
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3m identifies surface irregularities (potholes etc.)
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10m identifies structural problems in pavement layers
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30m identifies larger scale movement (embankment settlement) Important to compare profile on consecutive surveys rather than absolute value from one survey
High Speed Road Monitor (HRM)
Multifunction Road Monitor (MRM)
HA Routine Road Inspection System (HARRIS)
Traffic Speed Condition Survey (TRACS) Surface Condition Assessment for the National Network of Roads (SCANNER)
Suitability of surveys Visual surveys can be carried out on all types of road construction but there may be differences in the information that needs to be collected. Machine based surveys have some limitations due to pavement type, season and weather
Suitability of machine based surveys surveys Flexible
Flexible composite
Rigid
seasonal
Deflectograph
yes
yes
no
yes
FWD
yes
yes
yes
Temperature restrictions
SCRIM & Griptester
yes
yes
yes
yes
yes
No, but weather dependant
Pavement type
High Speed Sensor methods
yes
yes
Thank You for Listening
[email protected] www.ptsinternational.co.uk
