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Guide to Pavement Technology Part 2: Pavement Structural Design

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Publication no: AGPT02-17 Pages: 295
Published: 22 December 2017


Guide to Pavement Technology Part 2: Pavement Structural Design provides advice for the structural design of sealed road pavements. The advice has been generally developed from the approaches followed by the Austroads member agencies. However, as it encompasses the wide range of materials and conditions found in Australia and New Zealand, some parts are broadly based.

This Part covers the assessment of input parameters needed for design, design methods for flexible and rigid pavements and gives guidance on the economic comparisons of alternative pavement designs.

Changes to this fourth edition of the Guide include:

  • Editorial changes and minor technical changes throughout
  • Major technical changes to Sections 5.3.8, 5.8, 6.4, 6.5, 6.6, 7, 8, 9.2.1, 9.4.6, 9.7, Appendix B, Appendix C, Appendix D, Appendix E, Appendix F, Appendix G, Appendix H, Appendix I, Appendix J, Appendix L, Appendix M and Appendix O.

AustPADS

In association with the revised 2017 edition of the Austroads Guide to Pavement Technology Part 2, pavement design software incorporating a finite element method based pavement response to load model has been developed.

This web-based software tool, AustPADS, is currently being finalised and it is expected to be made available early in 2018 for use by member road agencies and industry organisations working with road agencies.

A user name and password is required to access the software. Advice on establishing access to the AustPADS software tool will be provided when the software is available.

A 12 month member agency focussed trial of the AustPADS software has been agreed by the Austroads Pavements Task Force to commence in early 2018.

The primary target users for AustPADS are Austroads member road agencies in Australia and New Zealand and industry organisations working with member road agencies. During the trial period, access credentials will be prioritised for this target user group. Access may not be granted to other potential users until a later date.


Webinar: Pavement Design - Guide to Pavement Technology Parts 2 and 4C (2017 Editions)

This webinar, presented on 9 March 2018, provides an overview of the major changes to the design of heavy-duty flexible pavements, including the new: axle-strain approach central to the mechanistic-empirical design method, definitions of design traffic, and characterisation of cemented material and asphalt. The webinar was presented by Dr Michael Moffatt. Download the presentation slides


Table of Contents

1. Introduction
  • 1.1 Scope of the Guide and this Part
  • 1.2 Project Scope and Background Data Requirements for Design
  • 1.2.1 Investigation and Design Proposal
2. Pavement Design Systems
  • 2.1 General
  • 2.2 Common Pavement Types
  • 2.2.1 General
  • 2.2.2 Granular Pavements with Sprayed Seal Surfacings
  • 2.2.3 Cemented Granular Bases with Sprayed Seal Surfacings
  • 2.2.4 Granular Pavements with Thin Asphalt Surfacings
  • 2.2.5 Asphalt over Granular Pavements
  • 2.2.6 Flexible Composite, Deep Strength and Full Depth Asphalt Pavements
  • 2.2.7 Concrete Pavements
  • 2.3 Overview of Pavement Design Systems
  • 2.3.1 Input Variables
  • 2.3.2 Selecting a Trial Pavement Configuration
  • 2.3.3 Structural Analysis
  • 2.3.4 Distress Prediction
  • 2.3.5 Comparison of Alternative Designs
3. Construction and Maintenance Considerations
  • 3.1 General
  • 3.2 Extent and Type of Drainage
  • 3.2.1 Purpose and Details of Drainage Measures
  • 3.2.2 Drainage of Pavement Materials
  • 3.2.3 Use of a Drainage Blanket
  • 3.2.4 Permeable Pavements on Moisture-sensitive Subgrades
  • 3.2.5 Full Depth Asphalt Pavements on Moisture-sensitive Subgrades
  • 3.2.6 Treatment of Stormwater Run-off
  • 3.3 Use of Boxed Construction
  • 3.4 Availability of Equipment
  • 3.5 Use of Staged Construction
  • 3.6 Use of Stabilisation
  • 3.7 Pavement Layering Considerations
  • 3.8 Use of Strain Alleviating Membrane Interlayers
  • 3.9 Environmental and Safety Constraints
  • 3.10 Social Considerations
  • 3.11 Construction under Traffic
  • 3.12 Maintenance Strategy
  • 3.13 Acceptable Risk
  • 3.14 Improved Subgrades
  • 3.14.1 Soft Subgrades
  • 3.14.2 Improved Layers under Bound Layers
  • 3.15 Surfacing Type
  • 3.15.1 Sprayed Seals
  • 3.15.2 Asphalt or Concrete Surfaces
  • 3.15.3 Open-graded Asphalt
  • 3.15.4 Surfacings in Tunnels
  • 3.16 Pavement Widenings
4. Environment
  • 4.1 General
  • 4.2 Moisture Environment
  • 4.2.1 Equilibrium Moisture Content
  • 4.3 Temperature Environment
5. Subgrade Evaluation
  • 5.1 General
  • 5.2 Measures of Subgrade Support
  • 5.3 Factors to be Considered in Estimating Subgrade Support
  • 5.3.1 Subgrade Variability
  • 5.3.2 Performance Risk
  • 5.3.3 Sequence of Earthworks Construction
  • 5.3.4 Compaction Moisture Content Used and Field Density Achieved
  • 5.3.5 Moisture Changes during Service Life
  • 5.3.6 Pavement Cross-section and Subsurface Drainage
  • 5.3.7 Presence of Weak Layers below the Design Subgrade Level
  • 5.3.8 Lime-stabilised Subgrades
  • 5.4 Methods for Determining Subgrade Design CBR Value
  • 5.5 Field Determination of Subgrade CBR
  • 5.5.1 In situ CBR Test
  • 5.5.2 Cone Penetrometers
  • 5.5.3 Deflection Testing
  • 5.6 Laboratory Determination of Subgrade CBR and Elastic Parameters
  • 5.6.1 Determination of Density for Laboratory Testing
  • 5.6.2 Determination of Moisture Conditions for Laboratory Testing
  • 5.7 Adoption of Presumptive CBR Values
  • 5.8 Limiting Subgrade Strain Criterion
6. Pavement Materials
  • 6.1 General
  • 6.2 Unbound Granular Materials
  • 6.2.1 Introduction
  • 6.2.2 Factors Influencing Modulus and Poisson’s Ratio
  • 6.2.3 Determination of Modulus of Unbound Granular Materials
  • 6.2.4 Permanent Deformation
  • 6.3 Modified Granular Materials
  • 6.4 Cemented Materials
  • 6.4.1 Introduction
  • 6.4.2 Factors Affecting Modulus of Cemented Materials
  • 6.4.3 Determination of Design Modulus
  • 6.4.4 Determination of Design Flexural Strength
  • 6.4.5 Factors Affecting the Fatigue Life of Cemented Materials
  • 6.4.6 Determining the In-service Fatigue Characteristics from Laboratory Fatigue Measurements
  • 6.4.7 Determining the In-service Fatigue Characteristics from Laboratory Measured Flexural Strength and Modulus
  • 6.4.8 Determining the In-service Fatigue Characteristics from Presumptive Flexural Strength and Modulus
  • 6.5 Asphalt
  • 6.5.1 Introduction
  • 6.5.2 Factors Affecting Modulus of Asphalt
  • 6.5.3 Definition of Asphalt Design Modulus
  • 6.5.4 Determination of Design Modulus from Direct Measurement of Flexural Modulus
  • 6.5.5 Determination of Design Modulus from Measurement of ITT Modulus
  • 6.5.6 Design Modulus from Bitumen Properties and Mix Volumetric Properties
  • 6.5.7 Design Modulus from Published Data
  • 6.5.8 Poisson’s Ratio
  • 6.5.9 Factors Affecting Asphalt Fatigue Life
  • 6.5.10 Fatigue Criteria
  • 6.5.11 Means of Determining Asphalt Fatigue Characteristics
  • 6.5.12 Permanent Deformation of Asphalt
  • 6.6 Concrete
  • 6.6.1 Introduction
  • 6.6.2 Subbase Concrete
  • 6.6.3 Subbase Concrete for Flexible Pavements
  • 6.6.4 Base Concrete
7. Design Traffic
  • 7.1 General
  • 7.2 Role of Traffic in Pavement Design
  • 7.3 Overview of Procedure for Determining Design Traffic
  • 7.4 Procedure for Determining Total Heavy Vehicle Axle Groups
  • 7.4.1 Introduction
  • 7.4.2 Selection of Design Period
  • 7.4.3 Identification of Design Lane
  • 7.4.4 Initial Daily Heavy Vehicles in the Design Lane
  • 7.4.5 Cumulative Number of Heavy Vehicles when Below Capacity
  • 7.4.6 Cumulative Number of Heavy Vehicles Considering Capacity
  • 7.4.7 Cumulative Heavy Vehicle Axle Groups
  • 7.4.8 Increases in Load Magnitude
  • 7.5 Estimation of Traffic Load Distribution (TLD)
  • 7.6 Design Traffic for Flexible Pavements
  • 7.6.1 Damage to Flexible Pavements
  • 7.6.2 Pavement Damage in Terms of Equivalent Standard Axle Repetitions
  • 7.6.3 Design Traffic for Mechanistic-empirical Design Procedure
  • 7.7 Design Traffic for Rigid Pavements
  • 7.8 Example of Design Traffic Calculations
8. Design of Flexible Pavements
  • 8.1 General
  • 8.2 Mechanistic-empirical Procedure
  • 8.2.1 Selection of Trial Pavement
  • 8.2.2 Procedure for Elastic Characterisation of Selected Subgrade and Lime-stabilised Subgrade Materials
  • 8.2.3 Procedure for Elastic Characterisation of Granular Material
  • 8.2.4 Procedure for Determining Critical Strains for Asphalt, Cemented Material and Lean-mix Concrete
  • 8.2.5 Procedure for Determining Allowable Loading for Asphalt, Cemented Material and Lean-mix Concrete
  • 8.2.6 Consideration of Post-cracking Phase in Cemented Material and Lean-mix Concrete
  • 8.2.7 Design of Granular Pavements with Thin Bituminous Surfacings
  • 8.3 Empirical Design of Granular Pavements with Thin Bituminous Surfacing
  • 8.3.1 Determination of Basic Thickness
  • 8.3.2 Pavement Composition
9. Design of Rigid Pavements
  • 9.1 General
  • 9.2 Pavement Types
  • 9.2.1 Base Types
  • 9.2.2 Subbase Types
  • 9.2.3 Wearing Surface
  • 9.3 Factors used in Thickness Determination
  • 9.3.1 Strength of Subgrade
  • 9.3.2 Effective Subgrade Strength
  • 9.3.3 Base Concrete Strength
  • 9.3.4 Design Traffic
  • 9.3.5 Concrete Shoulders
  • 9.3.6 Project Reliability
  • 9.4 Base Thickness Design
  • 9.4.1 General
  • 9.4.2 Base Thickness Design Procedure
  • 9.4.3 Minimum Base Thickness
  • 9.4.4 Example of the Use of the Design Procedure
  • 9.4.5 Example Design Charts
  • 9.4.6 Provision of Dowels
  • 9.4.7 Provision of Tiebars
  • 9.5 Reinforcement Design Procedures
  • 9.5.1 General
  • 9.5.2 Reinforcement in Plain Concrete Pavements
  • 9.5.3 Reinforcement in Jointed Reinforced Pavements
  • 9.5.4 Reinforcement in Continuously Reinforced Concrete Pavements
  • 9.6 Base Anchors
  • 9.7 Joint Types and Design
  • 9.7.1 Introduction
  • 9.7.2 Transverse Contraction Joints
  • 9.7.3 Transverse Construction Joints
  • 9.7.4 Expansion and Isolation Joints
  • 9.7.5 Longitudinal Joints
  • 9.7.6 Joint Design
10. Economic Comparison of Designs
  • 10.1 General
  • 10.2 Method for Economic Comparison
  • 10.3 Construction Costs
  • 10.4 Maintenance Costs
  • 10.5 Salvage Value
  • 10.6 Real Discount Rate
  • 10.7 Analysis Period
  • 10.8 Road User Costs
  • 10.9 Surfacing Service Lives
11. Implementation of Design and Collection of Feedback
  • 11.1 Implementation of Design
  • 11.2 Collection of Feedback
  • 11.2.1 Need
  • 11.2.2 Benefits
  • 11.2.3 Current Australian LTPP Program
  • 11.2.4 Data Collection
12. Design of Lightly-Trafficked Pavements
  • 12.1 General
  • 12.2 Pavement Design Systems
  • 12.2.1 Selecting a Trial Pavement Configuration
  • 12.3 Construction and Maintenance Considerations
  • 12.3.1 Extent and Type of Drainage
  • 12.3.2 Use of Boxed Construction
  • 12.3.3 Availability of Equipment
  • 12.3.4 Use of Staged Construction
  • 12.3.5 Environmental and Safety Constraints
  • 12.3.6 Social Considerations
  • 12.3.7 Maintenance Strategy
  • 12.4 Environment
  • 12.4.1 General
  • 12.4.2 Moisture
  • 12.4.3 Temperature
  • 12.5 Subgrade Evaluation
  • 12.5.1 Methods for Estimating Subgrade Support Value
  • 12.6 Pavement Materials
  • 12.6.1 Unbound Granular Materials
  • 12.6.2 Cemented Materials
  • 12.6.3 Asphalt
  • 12.6.4 Concrete
  • 12.7 Design Traffic
  • 12.7.1 Procedure for Determining Total Heavy Vehicle Axle Groups
  • 12.7.2 Design Traffic for Flexible Pavements
  • 12.8 Design of Flexible Pavements
  • 12.8.1 Mechanistic-empirical Procedure
  • 12.8.2 Empirical Design of Granular Pavements with Thin Bituminous Surfacing
  • 12.8.3 Mechanistic-empirical Procedure – Example Charts
  • 12.9 Design of Rigid Pavements
  • 12.9.1 General
  • 12.9.2 Pavement Types
  • 12.9.3 Factors Used in Thickness Determination
  • 12.9.4 Base Thickness Design
  • 12.9.5 Reinforcement Design Procedures
  • 12.9.6 Joints
  • 12.10 Implementation of Design and Collection of Feedback
References
Appendix A Australasian Road Agency Pavement Design Manuals or Supplements
Appendix B Weighted Mean Annual Pavement Temperature
Appendix C Calculating CGF For Non-Constant Annual Growth Rates
Appendix D Example Determination of Cumulative Number of Heavy Vehicles Considering Capacity
  • Design parameters
  • D.1 Calculation of Annual Number of Heavy Vehicles
  • D.2 Calculation of Maximum Annual Number of Heavy Vehicles
  • D.3 Adjusted Annual Number of Heavy Vehicles
  • D.4 Cumulative Number of Heavy Vehicles
Appendix E Characteristics of Traffic at Selected WIM Sites
Appendix F Adjustment of Design Traffic for Anticipated Increases in Load Magnitude
  • Estimation scenario #1
  • Estimation scenario #2
Appendix G Traffic Load Distribution
Appendix H Pavement Damage in Terms of Equivalent Standard Axles
  • H.1 Evaluation of Number of Equivalent Standard Axle (ESA) Repetitions per Axle Group
  • H.2 Specification of Design Traffic Loading and its Calculation
Appendix I Example of Design Traffic Calculations
  • Design parameters:
  • I.1 Total Number of Heavy Vehicle Axle Groups
  • I.2 Design Traffic for Flexible Pavements
  • I.2.1 Estimating Equivalent Standard Axles per Heavy Vehicle Axle Group
  • I.2.2 Design Traffic Loading Calculation in ESA
  • I.2.3 Design Traffic Loading Calculation for Bound Materials
  • I.3 Design Traffic for Rigid Pavements
Appendix J Procedures for Evaluation of Pavement Damage Due to Specialised Vehicles
  • J.1 Introduction
  • J.2 Granular Pavements with Thin Bituminous Surfacings
  • J.3 Flexible Pavements which include Bound Materials
  • J.4 Rigid Pavements
  • Attachment – Example of the Use of Evaluation Procedures for Specialised Vehicles
Appendix K Effect of Asphalt Thickness on Fatigue Life of Asphalt-Surfaced Pavements
Appendix L Examples of Use of the Mechanistic-Empirical Procedure for Flexible Pavements
  • L.1 Sprayed Seal Surfaced Unbound Granular Pavement
  • L.2 Full Depth Asphalt Pavement
  • L.3 Asphalt Pavement Containing Cemented Material Subbase
Appendix M Examples of Use of the Empirical Design Charts for Granular Pavements with Thin Bituminous Surfacings
  • M.1 Example 1: Utilising Unbound Granular Materials
  • M.2 Example 2: Utilising Crushed Rocks and Selected Subgrade Materials
  • M.3 Example 3: Utilising Crushed Rocks and Lime-stabilised Subgrade Materials
Appendix N Examples of Use of the Design Procedure for Rigid Pavements
Appendix O Traffic Load Distributions for Lightly-Trafficked Roads

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