Design Of Flexible Pavements


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Presentation given to Ergon Energy Civil Conference 2011 at the Picnic Bay Surf Life-saving Club.

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Design Of Flexible Pavements

  1. 1. Design of Flexible Granular Pavements Presenter: Bill Hutton
  2. 2. Pavement Types <ul><li>Flexible Pavements: </li></ul><ul><ul><li>Consist of Unbound Granular Materials, typically with a thin bituminous surface. </li></ul></ul><ul><ul><li>Also Includes pavements consisting of substantial thickness of bitumen bound materials and even cement stabilised materials </li></ul></ul>
  3. 3. Pavement Types <ul><li>Rigid Pavements: </li></ul><ul><ul><li>Those consisting of Portland Cement concrete </li></ul></ul>
  4. 4. Pavement Types <ul><li>Types of Flexible Pavements: </li></ul><ul><li>1.  Conventional </li></ul><ul><li>2.  Asphalt Surfaced </li></ul><ul><li>3.  Deep Strength </li></ul><ul><li>4.  Full Depth </li></ul><ul><li>5.  Modified Full Depth </li></ul><ul><li>Conventional and Asphalt most commonly used and most relevant to Zone Substations or Depot Roads. </li></ul>
  5. 5. Structural Analysis <ul><li>Pavement design is essentially a Structural Analysis problem! </li></ul><ul><li>Structural Adequacy determined by one of two methods </li></ul>Road Classification Pavement Material Standard Modified Local Urban Roads & Rural Roads Empirical Mechanistic State Highways & Urban Arterials Empirical Mechanistic Freeways, Motorways & Major Arterial Roads Not Applicable Mechanistic
  6. 6. Structural Analysis <ul><li>To design a pavement we need to know: </li></ul><ul><ul><li>Subgrade Strength or bearing capacity </li></ul></ul><ul><li>      Measured by the CBR test.  Typically CBR 2-3 for clays and </li></ul><ul><li>        15% or greater for sandy soils.  Used directly in the empirical </li></ul><ul><li>        design procedure </li></ul><ul><ul><li>Pavement Material Characteristics; and </li></ul></ul><ul><li>      Need to know what materials are available.  Generally used Type 2.1 for top 150mm </li></ul><ul><li>        with Type 2.3 below.  For deep pavements, may also have a deep layer of CBR15 </li></ul><ul><li>        material </li></ul><ul><ul><li>Design Traffic Loading </li></ul></ul><ul><ul><li>No. of equipvalent standard axles that traverse the design lane over the pavement </li></ul></ul><ul><ul><li>design life </li></ul></ul>
  7. 7. Design Traffic Loading <ul><li>  The Standard Axle loading is defined as an axle with dual tyres loaded to 80kN (8.2 tonne). </li></ul>
  8. 8.   Design Traffic Loading <ul><li>  Loads on other axle configurations that cause equivalent damage to the standard axle </li></ul>Axle Configuration Designation Load, P (kN) Mass (tonnes) Single Axle, Single Tyre SS 53 5.4 Tandem Axle, Dual Tyre TAD 135 13.6   Triaxle, Dual Tyre TRD 181 18.5
  9. 9. <ul><li>To determine the damaging effect of loads other than the standard load for an axle type, the following equation is used: </li></ul><ul><li>Doubling the axle load causes 16 TIMES the damage </li></ul><ul><li>This equation applied to each axle/axle group on a vehicle can be used to calculate the ESA for that vehicle </li></ul>  Design Traffic Loading
  10. 10.   <ul><li>  </li></ul>  Design Traffic Loading
  11. 11.   <ul><li>  </li></ul>  Design Traffic Loading
  12. 12.   Design Traffic Loading
  13. 13.   Design Traffic Loading
  14. 14.   Design Traffic Loading
  15. 15.   Design Traffic Loading 150mm
  16. 16.   Design Traffic Loading
  17. 17. Geometric Design Considerations Earthworks – 1:200 Residential – 1:400 Industrial Concrete – 0.5% Longitudinal (0.3% if required) – 1% Cross Fall Asphalt – 2% Cross Fall Minimum Chip Seal – 3% Cross Fall Minimum Kerb & Channel – 0.3% Longitudinal Table Drains with Grass Invert – 0.75% (0.5% min). Table Drains with Conc. Invert – 0.35% (0.3% min).
  18. 18. Case Study 1 – Granite Vale Road
  19. 19. Case Study 1 – Granite Vale Road
  20. 20. Case Study 1 – Granite Vale Road 250mm -75 material with Geo-fabric 150mm Type 2.3 CTB with 3% Cement
  21. 21. Additional Reading & Questions <ul><li>Austroads Design Guides </li></ul><ul><li>Mainroads Technical Specifications </li></ul><ul><li>Townsville City Council Ausspec Guidelines </li></ul><ul><li>Questions??? </li></ul>