sample pavement design report

Graham Foley & Associates Yarrab P/L T/A Graham Foley & Associates ABN: 36 005 180 665 ACN: 005 180 665 Phone 03 9578 0480 Fax: 03 9578 8970 23 Eumeralla Rd. S Caulfield Vic. 3162 E-mail: [email protected]

Ballarat Road: Pavement Design Report

Black Contractors (Vic) P/L

July 2003

Note: This is an actual report. The client’s (contractor’s) name and the road name have been changed. VicRoads’ name remains unchanged but site and contract number identification details have been suppressed.

Ballarat Rd: Design Report

Graham Foley & Associates

Executive Summary This report contains overlay advice and a re-design of a VicRoads’ (2002) specified pavement duplication for a section of the Ballarat Rd. in Basque for which Black Contractors (Vic) P/L (‘Black’) are bidding. Black are preparing a bid for Contract No. XXXX; Ballarat Rd. (Basra Dve. to the east for 1.5 km.) which comprises:

• Application of a VicRoads’ specified overlay treatment of the existing carriageway; and

• Construction of a VicRoads’ specified new duplicated carriageway. Mr. Steve Philps contacted the author on 28 June 2003 for advice on alternative solutions to those provided in the VicRoads’ contract documents. Overlay treatment It is not possible to provide any alternative to the specified overlay treatment which would be likely to satisfy VicRoads’ Surfacing Engineers. New Pavement VicRoads have proposed a deep-strength asphalt pavement comprising 190 mm of dense-graded asphalt over a 150 mm subbase layer of cement-treated crushed rock. Modelling of this pavement using the mechanistic procedure and based on numerous design assumptions has shown that it is possible to marginally refine the composition to reduce the asphalt thickness by 15 mm to 175 mm; the lowest permissible thickness over a cemented subbase. An alternative full-depth asphalt pavement has also been designed comprising a 350 mm deep stabilised subgrade to act as a working platform and to provide structural capacity to the overlying 200 mm of dense-graded asphalt. The point of discussion is likely to be the achieving of a minimum vertical modulus of 150 MPa for the cemented layer, which may require a minimum UCS of 1.5 MPa in laboratory testing. It is recommended that:

• The VicRoads’ overlay design for the existing carriageway be adopted. • The deep-strength asphalt pavement with the 2000 MPa CTCR subbase and

reduced thickness asphalt base (175 mm) be adopted as an alternative to the VicRoads specified pavement.



CONTENTS 1. INTRODUCTION ................................................................................................ 1

2. BACKGROUND ................................................................................................. 1

3. OVERLAY TREATMENT ................................................................................... 1

4. NEW PAVEMENT DESIGN................................................................................ 1

5. DISCUSSION ..................................................................................................... 3

6. RECOMMENDATIONS ...................................................................................... 4

REFERENCES ....................................................................................................... 4

APPENDIX A: DESIGN PARAMETERS FOR BALLARAT RD. & MODELLING SUMMARY – BALLARAT RD. ORIGINAL SPECIFIED DESIGN ......................... 1

APPENDIX B: MODELLING SUMMARY - BALLARAT RD. REFINED SPECIFIED DESIGN.............................................................................................. 1

APPENDIX C: MODELLING SUMMARY - BALLARAT RD. FULL-DEPTH ASPHALT PAVEMENT.......................................................................................... 1

APPENDIX D: MODELLING SUMMARY - BALLARAT RD DEEP-STRENGTH ASPHALT PAVEMENT: EV(CTCR) = 2000 MPA. ..................................................... 1

This report has been prepared in good faith based on the information provided by VicRoads’ XXXXX XXXXXXX Region, XXXXXXX and Black Contractors (Vic) P/L and in accordance with the Graham Foley & Associates quality system.

This report has been commissioned by and for the specific use of Black Contractors only. Therefore, no responsibility or liability to any third party is accepted for any damages, howsoever arising, from the contents of this report or its use by any third party. Where such liability cannot be excluded, it is reduced to the full extent lawful.

The use of this report is not appropriate where there have been any changes in the nature of this project or the conditions present during any field investigation or site inspection.

No responsibility or liability is accepted where any part of this report is used in isolation, out of context or without consideration of the total document.

If at a later time it is found that the information previously provided to Graham Foley & Associates was incorrect, incomplete and/or conditions differ substantially from those initially reported, Graham Foley & Associates should be contacted immediately and this report may need to be reviewed and amended as appropriate.



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1. INTRODUCTION This report contains overlay advice and a re-design of a VicRoads’ (2002) specified pavement duplication for a section of the Ballarat Rd. in Basque for which Black Contractors (Vic) P/L (‘Black’) are bidding.

2. BACKGROUND Black are preparing a bid for Contract No. XXXX Ballarat Rd. (Basra Dve. to the east for 1.5 km.) which comprises:

• Application of a VicRoads’ specified overlay treatment of the existing carriageway; and

• Construction of a VicRoads’ specified new duplicated carriageway. Mr. Steve Philps contacted the author on 28 June 2003 for advice on alternative solutions to those provided in the VicRoads’ contract documents.

3. OVERLAY TREATMENT 3.1 Specified Treatment VicRoads’ specified overlay solution; to be applied to the existing carriageway is as follows:

• The Contractor shall provide a geotextile reinforced spray seal (GRSS) followed by ultra thin open graded asphalt (UTOGA) to all pre-existing pavement….

• The Contractor shall also place additional asphalt overlay of (sic) [on] pre-existing pavement in order to correct for rutting, achieve the required design cross-fall, and achieve the design level requirements of its detailed design. The Contractor shall be responsible for all work necessary to achieve the minimum overlay requirements, correct crossfall and rutting, and adjust pre-existing pavement levels to suit the required design levels.

3.2 Discussion The above ‘specifications’ refer to placing asphalt overlay to achieve geometric design levels only, rather than achieving a structural solution. The application of a GRSS and a UTOGA implicitly recognise and reinforce that this forms a ‘surfacing solution’ rather than a structural solution. The GRSS and UTOGA is a very specific, thin and tenacious surfacing solution which can not be readily substituted. As advised late on 28th June, it is not possible to provide any alternative to the above treatment which would be likely to satisfy VicRoads’ Surfacing Engineers.

4. NEW PAVEMENT DESIGN 4.1 Specified Pavement The specified pavement for the Ballarat Rd. and cross-roads is as follows:



2Surface 40 mm size 14 Type H asphalt (320) Upper base 75 mm size 20 Type T asphalt (600) Lower base 75 mm size 20 Type R asphalt (320) Subbase 150 mm 3% CTCR1 with assumed vertical resilient modulus 500 MPa Total 340 mm This pavement is a classical deep-strength asphalt pavement with a typical thickness of cement-treated crushed rock, which is ascribed the maximum accepted unbound granular vertical resilient modulus of 500 MPa. In modelling this layer is assumed as being ‘cracked’ and therefore no ‘first life’ for cracking of this layer is allowed for. The asphalt base/subbase is an optimal composition with the minimum thickness Type R layer of 75 mm (Section 10.3.1 VicRoads 2001). The minimum cover of dense-graded asphalt above Type R asphalt is 100 mm (Section 10.3.1 VicRoads 2001) for which the above design contains 115 mm. Mechanistic modelling using the design parameters given in Appendix A show for the design reliability traffic loading a cumulative damage factor (CDF) of 0.596. A CDF of 1.0 means the design is just acceptable.

4.2 Changes to Specified Pavement Given that some modelling assumptions have not been verified (but are shown in Appendix A), a number of other pavement combinations were modelled, however the generic type pavement provided by GeoPave in Section 4.1 proved the optimum. Given the CDF was 0.596, the above pavement was modelled with 100 mm of asphalt cover to the Type R lower layer. This model produced a CDF of 0.949, which is below 1.0. The CIRCLY (Mincad Systems 2003) summary output is given in Appendix B.

4.3 Alternative Full-Depth Asphalt Pavement Design As an alternative to the deep-strength asphalt pavement with a cemented subbase requiring a minimum of 175 mm of asphalt cover, a number of full-depth asphalt (FDA) pavements were modelled using as a construction platform, stabilised subgrade, rather than the typically adopted 100 mm of granular material. The function of the granular layer is to provide a good working platform for the asphalt paver and to achieve good compaction in the lowest asphalt layer (minimum of 75 mm VicRoads 1993). Two of the main pavement design documents used by VicRoads, Technical Bulletin No. 37 and the Manual of Codes of Practice (VicRoads 1993 and 2001) are silent on the material type required for the FDA working platform. The one requirement is that the subgrade has a CBR at the time of construction of at least 10% (Section 6.2 VicRoads 2001). Should the subgrade material be stabilised with sufficient binder to provide a heavily modified material having CBR values in excess of 40% at Standard compactive energy at say a density ratio of 98%, it is likely that in the field a Design CBR of 15% could be adopted for this layer. This meets the minimum 10% requirement for the FDA subgrade. The maximum improved via stabilisation ‘subgrade’ strength value is a CBR of 15% (VicRoads 1993). Given sufficient binder such that the material becomes bound, and is not responsive to CBR testing (i.e. exceeds the values for which the test were designed), the material’s resilient modulus will no longer be stress-dependent, and can therefore be modelled as a monolithic layer of isotropic material.

1 Cement-treated crushed rock



3Given the modified material is not a granular material; it will be unlikely to have a resilient modulus near that of even a ‘cracked’ stabilised granular material, which is 500 MPa (VicRoads 1993). The maximum vertical resilient modulus that would be accepted for a stabilised subgrade is likely to be 150 MPa2, which is 10 times the materials upper limit of CBR value; the protocol adopted by VicRoads for elastic characterisation of subgrade materials (VicRoads 1993). A Poisson’s Ratio of 0.2 is assumed for this stabilised subgrade material. Full Depth Asphalt Pavement Numerous pavement combinations were modelled using various thicknesses of stabilised subgrade and asphalt base. The optimum design is one which uses the maximum achievable thickness of stabilised subgrade likely to be achieved, that of 350 mm.

Surface 40 mm size 14 Type H asphalt (320) Upper base 85 mm size 20 Type T asphalt (600) Lower base 75 mm size 20 Type R asphalt (320) Subbase 350 mm Stabilised subgrade with min. vertical resilient modulus 150 MPa. Total 550 mm This pavement has a CDF3 of 0.98; a modelling summary is shown in Appendix C. To achieve a depth of 350 mm of stabilised subgrade, a tolerance of at least 20 mm to 30 mm should be allowed; i.e. design for and specify a 380 depth of stabilised subgrade.

4.4 Deep Strength Asphalt Design with 2000 MPa CTCR Layer Modelling was undertaken using an increased modulus for the cemented 150 mm thick granular layer with the minimum asphalt thickness of 175 mm required by VicRoads (1993 and 2001) over such layer. The first life of this pavement system in which the cemented material cracks has a CDF of 4.48 as shown on Page 1 of the summary output in Appendix D. This means that for the design reliability loading (DRL) of 27,000,000 ESAs, this first life of the pavement lasts (27/4.48) x 106 ESAs or approximately 6,000,000 ESAs. The second life of this pavement system given that the cemented layer is now considered cracked and the pavement system now has as the ‘critical’ layer, the bottom asphalt layer is shown on Page 2 of Appendix D, where the CDF is 0.95 (i.e. as for the pavement described in Section 4.2). That is the second life of the pavement is (27/0.95) x 106 ESAs or approximately 28,400,000 ESAs Using Equation 8.2 given in VicRoads (1993) it is possible to combine the two pavement lives together to produce a total life of 31 x 106 ESAs, i.e. greater than the DRL of 27 x 106 ESAs.

5. DISCUSSION The design reliability factor (DRF) of 4.5 is assumed to provide a design reliability of about 95% (VicRoads 1993). The DRF incorporates various factors including some construction tolerances; viz. thicknesses achieved in the field. The specified pavement comprises 190 mm of asphalt and 150 mm of CTCR and by using the design parameters given in Appendix A has a CDF of 0.60. Refinement of this design by thinning the asphalt base layer 15 mm to 175 mm (the minimum permissible) and

2 Little et al. (1995) suggest that for lime stabilised subgrade material with an UCS of 1.0 MPa, the resilient modulus is likely to be approximately 200 MPa. At an UCS of 1.5 MPa, this increases to 400 MPa. 3 Cumulative damage factors



4retaining the 150 mm CTCR layer, the design still appears to work with the CDF less than unity; viz. 0.98. Without further detailed discussion with the GeoPave designers, it is not possible to determine if some of the new Austroads’ protocols for modelling have been adopted which differ from those in this assignment. Thus the CDF for the specified deep-strength pavement may be much closer to unity (and hence the limit) than that calculated herein of 0.60. The solution of upgrading the cemented layer to produce a modulus of 2000 MPa as described in Section 4.4 provides an extension of the life of the design from 28,400,000 ESAs to 31,000,000 ESAs (the DRL is 27,000,000). The optimum full-depth asphalt design that deletes the stabilised granular interlayer and incorporates a stabilised subgrade (of design depth 350 mm) uses 200 mm of dense-graded asphalt (of Type T (600)) which is 10 mm more than the specified design; and 25 mm more than the refined design. The point of discussion for the full-depth asphalt pavement is likely to be the achieving of a minimum vertical modulus of 150 MPa for the cemented layer, which may require a minimum UCS of 1.5 MPa in laboratory testing.

6. RECOMMENDATIONS It is recommended that:

• The VicRoads’ overlay design for the existing carriageway be adopted.

• The deep-strength asphalt pavement with the 2000 MPa CTCR subbase and reduced thickness asphalt base (175 mm) be adopted as an alternative to the VicRoads’ specified pavement.

REFERENCES Little, D.N., Scullion, T., Kota, P.B.V.S. and Bhuiyan, J. (1995). Guidelines for Mixture Design and Thickness design for Stabilised Bases and Subgrades. Texas Transportation Institute, Research Report 1287-3F, Texas Dept. of Transportation, Austin, Texas. Mincad Systems (2003). CIRCLY Version 4.1k (12 May 2003). Mincad Systems P/L. Richmond. VicRoads (1993). VicRoads Guide to Pavement Design. Technical Bulletin No. 37. Sept. 1993. VicRoads, Burwood East. VicRoads (2001). Manual of Codes of Practice; Code of Practice RC 500.22. GeoPave, Burwood South. VicRoads (2002). Contract No. XXXX. Revision No. T0 (05/06/03). VicRoads, Burwood South.



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APPENDIX A: Design Parameters for Ballarat Rd. & Modelling Summary - Ballarat Rd. Original Specified Design Original specified design is as follows: Surface 40 mm size 14 Type H asphalt (320) Upper base 75 mm size 20 Type T asphalt (600) Lower base 75 mm size 20 Type R asphalt (320) Subbase 150 mm 3% CTCR Total 340 mm

Loading Tyre pressure 750 kPa

Footprint radius 92.3 mm

Force Vertical

Configuration Dual tyre / half axle

Spacing of tyre loads 330 mm

AADT 24 Hr 2-way volume 25,000 2001

Load factor 1.0

Design Traffic Loading 6.1 x 106 ESAs EB Slow lane

Design reliability factor 4.5 Urban Main Road

Design Reliability Loading 2.7 x 107ESAs

Materials WMAPT 250C

Speed of traffic 60 kph (Table 6.15; VicRoads 1993)

Interface conditions All rough

Pavement Layer

Material description Modulus (Vert) at WMAPT (MPa)

Fatigue Constant (K)

Isotropic? ..if not..

(Degree of Anisotropy)

Traffic Multip.

Perf. Exp.

Poiss. ratio

Surfacing Asphalt Type H (320) 3500 0.003660 Y 1.1 5 0.4

Upper Base Asphalt Type T (600) 5300 0.003020 Y 1.1 5 0.4

Lower Base Asphalt Type R (320) 3500 0.004260 Y 1.1 5 0.4

Subbase 4% CTCR (deep-strength asphalt (DSA))

2000 0.000979 Y 1.9 8 0.2

Subbase 3% CTCR (full depth asphalt and post-cracked phase of DSA)

500 NA Y NA NA 0.2

Subgrade Stabilised to DCBR of 15% 150 NA Y NA NA 0.2

Subgrade Given DCBR of 4% 40 0.008511 No (2) 1.5 7.14 0.45



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APPENDIX A: Modelling Summary - Ballarat Rd. Original Specified Design

CIRCLY Version 4.1k (12 May 2003): Job Title: Ballarat Rd_01

Job Title: Ballarat Rd Original Design

Damage Factor Calculation

Assumed number of damage pulses per movement: One pulse per axle (i.e. use NROWS)

Traffic Spectrum Details: ID: Ballar01 Title: Ballarat Rd_01

Load Load MovementsNo. ID1 ESA750 2.70E+07

Details of Load Groups:

Load Load Load Load Radius Pressure/ ExponentNo. ID Category Type Ref. stress1 ESA750 ESA750 Vertical Force 92.3 0.75 0.00

Load Locations:Location Load Gear X Y Scaling ThetaNo. ID No. Factor1 ESA750 1 -165.0 0.0 1.00E+00 0.002 ESA750 1 165.0 0.0 1.00E+00 0.00

Layout of result points on horizontal plane:Xmin: 0 Xmax: 400 Xdel: 10Y: 0

Details of Layered System:

ID: Ballar01 Title: Ballarat Rd FDA Original Design

Layer Lower Material Isotropy Modulus P.RatioNo. i/face ID (or Ev) (or vvh) F Eh vh1 rough Asph3500 Iso. 3.50E+03 0.402 rough Asp5300 Iso. 5.30E+03 0.403 rough Asp3500R Iso. 3.50E+03 0.404 rough Cement0500 Iso. 5.00E+02 0.205 rough SubCBR4A Aniso. 4.00E+01 0.45 2.76E+01 2.00E+01 0.45

Performance Relationships:Layer Location Performance Component Perform. Perform. TrafficNo. ID Constant Exponent Multiplier1 bottom Asph3500 ETH 0.003660 5.000 1.1002 bottom Asp5300 ETH 0.003020 5.000 1.1003 bottom Asp3500R ETH 0.004260 5.000 1.1005 top Subgrade02 EZZ 0.010520 7.140 1.500

Results:

Layer Thickness Material Load Critical CDFNo. ID ID Strain1 40.00 Asph3500 ESA750 1.81E-05 2.97E-302 75.00 Asp5300 ESA750 -5.10E-05 4.09E-023 75.00 Asp3500R ESA750 -1.23E-04 5.96E-014 150.00 Cement0500 n/a n/a5 0.00 SubCBR4A ESA750 4.36E-04 5.48E-03



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APPENDIX B: Modelling Summary - Ballarat Rd. Refined Specified Design

CIRCLY Version 4.1k (12 May 2003)

Job Title: Ballarat Rd Original Design 100 mm AC over Type R layer.



Traffic Spectrum Details:

ID: Ballar02 Title: Ballarat RdLoad Load MovementsNo. ID1 ESA750 2.70E+07






ID: Ballar02 Title: Ballarat Rd



Results:

Layer Thickness Material Load Critical CDFNo. ID ID Strain1 40.00 Asph3500 ESA750 1.70E-05 2.97E-302 60.00 Asp5300 ESA750 -4.83E-05 3.10E-023 75.00 Asp3500R ESA750 -1.35E-04 9.49E-01

4 150.00 Cement0500 n/a n/a5 0.00 SubCBR4A ESA750 4.85E-04 5.27E-02



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APPENDIX C: Modelling Summary - Ballarat Rd. Full-Depth Asphalt Pavement

CIRCLY Version 4.1k (12 May 2003) Job Title: Ballarat Rd Stabilised Subgrade 350 mmE = 150 MPa Design




ID: Ballar03 Title: Ballarat Rd.








Layer Lower Material Isotropy Modulus P.RatioNo. i/face ID (or Ev) (or vvh) F Eh vh1 rough Asph3500 Iso. 3.50E+03 0.402 rough Asp5300 Iso. 5.30E+03 0.403 rough Asp3500R Iso. 3.50E+03 0.404 rough Cem_150 Iso. 1.50E+02 0.205 rough SubCBR4A Aniso. 4.00E+01 0.45 2.76E+01 2.00E+01 0.45

Performance Relationships:Layer Location Performance Component Perform. Perform. TrafficNo. ID Constant Exponent Multiplier1 bottom Asph3500 ETH 0.003660 5.000 1.1002 bottom Asp5300 ETH 0.003020 5.000 1.1003 bottom Asp3500R ETH 0.004260 5.000 1.1004 bottom Cement2000 ETH 0.000280 18.000 1.0005 top Subgrade01 EZZ 0.008511 7.140 1.500

Results:

Layer Thickness Material Load Critical CDFNo. ID ID Strain1 40.00 Asph3500 ESA750 1.59E-05 2.97E-302 85.00 Asp5300 ESA750 -5.73E-05 7.28E-023 75.00 Asp3500R ESA750 -1.36E-04 9.84E-014 350.00 Cem_150 ESA750 -na -na5 0.00 SubCBR4A ESA750 3.25E-04 3.07E-03



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APPENDIX D: Modelling Summary - Ballarat Rd Deep-Strength Asphalt Pavement: EV(CTCR) = 2000 MPa. First-Life Calculation CIRCLY Version 4.1k (12 May 2003)Job Title: Ballarat Rd Original Design but with Ev=2000 MPa












Layer Lower Material Isotropy Modulus P.RatioNo. i/face ID (or Ev) (or vvh) F Eh vh1 rough Asph3500 Iso. 3.50E+03 0.402 rough Asp5300 Iso. 5.30E+03 0.403 rough Asp3500R Iso. 3.50E+03 0.404 rough CemV2000 Iso. 2.00E+03 0.205 rough SubCBR4A Aniso. 4.00E+01 0.45 2.76E+01 2.00E+01 0.45

Performance Relationships:Layer Location Performance Component Perform. Perform. TrafficNo. ID Constant Exponent Multiplier1 bottom Asph3500 ETH 0.003660 5.000 1.1002 bottom Asp5300 ETH 0.003020 5.000 1.1003 bottom Asp3500R ETH 0.004260 5.000 1.1004 bottom CemV2000 ETH 0.000978 8.000 1.9005 top Subgrade01 EZZ 0.008511 7.140 1.500

Results:

Layer Thickness Material Load Critical CDFNo. ID ID Strain1 40.00 Asph3500 ESA750 1.13E-05 2.97E-302 60.00 Asp5300 ESA750 -3.05E-05 3.13E-033 75.00 Asp3500R ESA750 -5.52E-05 1.09E-024 150.00 CemV2000 ESA750 -1.28E-04 4.48E+005 0.00 SubCBR4A ESA750 3.10E-04 2.15E-03



2 Second-Life Calculation CIRCLY Version 4.1k (12 May 2003)

Job Title: Ballarat Rd Original Design but with Ev=500 MPa (cracked CTCR)














Results:

Layer Thickness Material Load Critical CDFNo. ID ID Strain1 40.00 Asph3500 ESA750 1.70E-05 2.97E-302 60.00 Asp5300 ESA750 -4.83E-05 3.10E-023 75.00 Asp3500R ESA750 -1.35E-04 9.49E-014 150.00 Cement0500 n/a n/a5 0.00 SubCBR4A ESA750 4.85E-04 5.27E-02

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