Technical Note 126
Pavement Design Supplement
August 2014
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© State of Queensland (Department of Transport and Main Roads) 2014
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Technical Note, Transport and Main Roads, August 2014
TN126 Pavement Design Supplement
Introduction
The Queensland Department of Transport and Main Roads (TMR) adopts the fundamental pavement
design principles in Part 2: Pavement Structural Design of the Austroads Guide to Pavement
Technology (Austroads, 2012), hereafter referred to as AGPT02. TMR has published a Pavement
Design Supplement to complement the design guidance provided by Austroads, such as for
Queensland’s local materials, environment, loadings and pavement performance. The supplement
replaces the Pavement Design Manual (Main Roads, 2009).
It is intended that both documents be read together as the supplement generally does not repeat the
guidance already provided in AGPT02. For ease of reference, section numbers in the supplement
align with the applicable section numbers in AGPT02. Where additional sections, tables, figures,
equations and appendices are included in the supplement, these are numbered with a prefix of Q.
The Pavement Design Supplement
The supplement is not a prescriptive standard, rather it is intended to be a guide for professional,
trained, experienced and knowledgeable pavement designers. Exceptions (departures) to AGPT02
and the supplement’s typical design assumptions and standards may be necessary for the designer’s
project-specific engineering design. In such cases, the designer should adopt risk management
techniques in consultation with the TMR Project Manager.
Reference to the supplement in contract documents will typically require project-specific requirements
appropriate for the contract to be included in a pavement design brief. A pavement design brief is
essential for projects where the designer is external to TMR, particularly where the contract is a type
where the designer is employed or engaged by a third party, such as a construction contractor or
developer. A more detailed brief is likely required for these types of contracts, as compared to an
RCC-style (AS2124) contract.
The main driver for updating the Pavement Design Manual (Main Roads, 2009) was the Queensland
Government’s direction to review procedures with a view to mitigating State debt. The new Pavement
Design Supplement aims to:
•
increase the focus on value-for-money solutions, and reduce the initial cost of infrastructure
•
align with and supplement the content of the latest Austroads Guide
•
strengthen linkages to other relevant TMR technical documents
•
better enable the adoption of project-specific engineering solutions, and
•
adopt standards that are consistent with national guidelines.
The Pavement Design Supplement was drafted by TMR’s Engineering and Technology Branch, in
consultation with TMR’s Regions and State Program Office. Industry peak bodies were also consulted
(i.e. Consult Australia, Australian Asphalt Pavement Association, Australian Society for Concrete
Pavements, AustStab, Queensland Major Contractors Association, Civil Contractors Federation,
Cement Concrete Aggregates Australia and the Ash Development Association of Australia). An
independent review by the Australian Road Research Board (ARRB) was also undertaken.
Key changes that are adopted in the Pavement Design Supplement include:
•
restructuring of information, and updating of terminology, to align with AGPT02
Technical Note, Transport and Main Roads, August 2014
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TN126 Pavement Design Supplement
•
provisions for consideration of project-specific engineering designs, including guidance on
assessment of design alternatives and exceptions (Section 1.2.1)
•
improved guidance and greater flexibility in selection of pavement types (Section 2.2.1 and
Table Q2.1)
•
more detailed guidance on typical pavement structures (Tables Q2.2 to Q2.12)
•
amended project reliability levels (Table Q2.12)
•
provisions to omit the waterproofing seal in asphalt pavements where adequate compaction is
achieved (Section Q3.7)
•
greater range of options for improved layers (working platforms) under bound pavements
(Section 3.14.2)
•
guidance on moisture environment linked to median rainfall rather than average rainfall
(Figure Q4.3)
•
cover over expansive subgrades related to risk, with increased risk accepted for lower traffic
pavements (Figure Q5.1)
•
subgrade CBR test conditions more closely aligned to service conditions (Section 5.6.1 and
Table Q5.1)
•
improved guidance on selection of unbound granular materials (Table Q6.1)
•
increased design modulus for improved layers incorporating cement treated granular material
(Table Q6.3)
•
improved guidance on cement modified base (CMB) pavements as a value-for-money option
(Section 6.3)
•
improved guidance on relative performance of various cemented materials (Section 6.4.1)
•
presumptive design modulus for Category 2 cemented materials increased (Table Q6.4)
•
presumptive asphalt design moduli and binder volumes updated to align with currently
registered mixes (Table Q6.5)
•
presumptive heavy vehicle speed at intersections increased (Table Q6.6)
•
included guidance on binder selection for dense graded asphalt (Section 6.5.4 and
Table Q6.7)
•
provision for up to 15% reclaimed asphalt in asphalt mixes (Section 6.5.8)
•
inclusion of plant-mixed foamed bitumen stabilisation (Section Q6.7)
•
amended design periods (Table Q7.1)
•
improved site-specific design traffic estimation with no minimum heavy vehicle growth rate
(Section 7.4.5)
•
post-cracking life included in design of deep strength asphalt pavements at all traffic levels
•
better account for strength of lime stabilised subgrades (Section 8.2.2)
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