APT needs & options

Michael Moffatt

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uncertainty

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time

certainty

today20 yearspast

20 yearsto come

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MINIMUM THICKNESS OF BASE MATERIAL

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105 106 107 108

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1520≥30

CBR

ThicknessofGranularMaterial(mm)

Design Traffic (ESAs)

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certainty = f ( time, research )

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Accelerated Pavement Testing

• increase load magnitude• increase load frequency• decrease pavement

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Accelerated Loading Facility

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NSW17%

VIC25%

QLD17%

SA5%

shed36%

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1985

Construction of Victorian section of Hume Hwy

• design traffic required very heavy duty pavement• needed a low risk solution• four main pavement options being considered:

rigid – jointed unreinforced concrete US$48/m2

asphalt on cement treated subbase US$46/m2

asphalt on unbound granular US$41/m2

two coat spray seal on unbound granular

US$26/m2

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ALF test of actual construction in-situ undertaken:– test of new spray sealed granular pavement design– new high standards for construction– aimed to prove pavement could carry heavy traffic and

reduce risk

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Results:

• structural adequacy of the pavement was confirmed

• higher construction standards adopted elsewhere

• extensive lengths of this pavement type were constructed at a significant cost advantage compared to other designs

• BCR of 5.4 resulted from the research

• long term pavement performance monitoring commenced

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uncertainty

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2007

Need means of predicting performance of unbound materials

• marginal materials• recycled materials• modified & proprietary materials

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Pavement plan

Rhyolite

150 mm Cemented

350 mm Unbound Granular

SandTuff

~50 m

Hornfels

Limestone

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uncertainty

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2009

Need to better estimate pavement performance under new load types

• currently presume performance = deflection • don’t understand new configurations

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crushedrock

clay

300 mm

400 mm

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uncertainty

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Three different examples

Uncertainty reduced by

• ALF proof loading specific pavement• laboratory processes to predict material performance

– ALF demonstrated ‘true’ performance• Modeling to understand ink between axle type and

performance – ALF will provide performance

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APT rocks! – I want one

What type?

• Dion: I’m a Wanderer• Pink Floyd: Wish You Were Here• Van Halen: Best of Both Worlds

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uncertainty

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certainty

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Accelerated Loading Facility (ALF)

• linear track– no turning forces– 12 metre test strip

• half axle / dual tyres• sideways wander

– Normal distribution– 1 m wide

• 20 km/h• 60 kN load for this trial

– i.e. 50% overloaded– 1 cycle = 5 ESA

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Monitoring

• NDM• Density• Moisture content

– Subbase– Bases

- Centreline- 1 m spacing

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Next….trafficking

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The shed

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The shed

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Outline

• four unbound granular base materials have been selected for full scale testing

• ALF test pavements have been constructed and sealed

• proposed test program

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certainty = f ( time, research )

time < research + time

research < time + research