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Design of Flexible Granular Pavements Presenter: Bill Hutton

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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>

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Pavement Types <ul><li>Rigid Pavements: </li></ul><ul><ul><li>Those consisting of Portland Cement concrete </li></ul></ul>

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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>

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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

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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>

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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>

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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

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<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

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<ul><li> </li></ul> Design Traffic Loading

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<ul><li> </li></ul> Design Traffic Loading

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Design Traffic Loading

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Design Traffic Loading

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Design Traffic Loading

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Design Traffic Loading 150mm

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Design Traffic Loading

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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).

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Case Study 1 – Granite Vale Road

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Case Study 1 – Granite Vale Road

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Case Study 1 – Granite Vale Road 250mm -75 material with Geo-fabric 150mm Type 2.3 CTB with 3% Cement

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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>