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Pavement Design: Full Depth vs CompositePavement Design: Full Depth vs Composite
Stacie Steel, PE
Full‐Depth vs Composite – What we mean…Full‐Depth vs Composite – What we mean…
How Thick Does the Pavement Need to Be?How Thick Does the Pavement Need to Be?
STRUCTURAL NUMBER
SN = aiDi+ aiiDiimii+ aiiiDiiimiii+ …..
– ai – strength coefficient of layer
• 0.40 to 0.44 for asphalt concrete
• 0.10 to 0.14 for base course
– Di – layer thickness
– mi – drainage coefficient
• 1.0 for asphalt concrete
• 0.8 for base course
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AASHTO Guide for Design of Pavement Structures 1993AASHTO Guide for Design of Pavement Structures 1993
Just follow the nomograph…Reliability
Standard Deviation
ESALs
Soil Strength
Serviceability
AASHTO ‘93 in 2019AASHTO ‘93 in 2019
W18 – TrafficZR – ReliabilityS0 ‐ Standard DeviationPSI – Change in ServiceabilityMR – Resilient Modulus
SN – Structural Number
Pavement Design Inputs ‐ ReliabilityPavement Design Inputs ‐ Reliability
/reliability/ nounBeing able to be trusted to do what is expected or has been promised.
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Pavement Design Inputs – Standard DeviationPavement Design Inputs – Standard Deviation
Construction
MaterialsEnvironment
Pavement Design Inputs – Traffic / ESALsPavement Design Inputs – Traffic / ESALs
Pavement Design Inputs ‐ PSIPavement Design Inputs ‐ PSI
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Pavement Design Inputs – Resilient ModulusPavement Design Inputs – Resilient Modulus
Pavement SubgradePavement Subgrade
Subgrade performance generally depends on two interrelated characteristics:
– Load bearing capacity which is affected by degree of
• Moisture
• Compaction
• Soil type
– Volume changes (expansive soils, freeze/thaw cycles)
Subgrade InvestigationSubgrade Investigation
Field Investigation – borings, test pits, etc.– N‐Value
– Kessler DCP
Classification Testing
– Atterberg Limits
– % Passing No. 200
– Gradation (sands and gravels)
Support Testing
– CBR or R‐Value
– Swell
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Engineering Criteria Manual ‐ Strength CoefficientsEngineering Criteria Manual ‐ Strength Coefficients
PAVExpress Example – Scenario InformationPAVExpress Example – Scenario Information
PAVExpress Example – Design ParametersPAVExpress Example – Design Parameters
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PAVExpress Design Example – Traffic & LoadingPAVExpress Design Example – Traffic & Loading
PAVExpress Design Example – Pavement StructurePAVExpress Design Example – Pavement Structure
PAVExpress Design Example – Pavement Sub‐StructurePAVExpress Design Example – Pavement Sub‐Structure
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