Global Road Technology Hardstand Designs

Global Road Technology Hardstand Designs

Hard Stand – Similar to conventional pavement design, Heavy Duty pavement design has been developed for non-standard vehicles for Ports, Haul Roads and Hardstand.

The method of structural design has been developed by the recognised road agency – British Ports Association and has been further referenced in Mincad’s HiPave which focuses around site specific heavy duty pavement variables including wander and proximity factors.

Typical Hardstand, the three common heavy duty pavement configurations include:

• Configuration A – Permeable – Typically comprises a paver based structure, allowing surface water to penetrate through the joints entering the moisture insensitive subbase and gradually draining through a semi-permeable subgrade
• Configuration B – Semi Permeable – Is similar in nature to a permeable configuration excluding the permeable subbase, at this point, sub surface drains or a impermeable membrane is placed to discharge this moisture into local swale or stormwater drains
• Configuration C – Impermeable – This configuration is designed to encourage surface drainage and reduce the likelihood of water entering the pavement. The surface drainage is paramount to prevent pooling of water and localised failure.

Where an impermeable pavement is desired, consideration must be given to crossfall and methods of surface drainage, which can be undesirable for loaded off-road trucks, reach stackers, forklifts and other heavy vehicles.

The selection of each pavement configuration is typically based on the site conditions and the availability of drainage infrastructure.

In terms of designing pavement thickness, there are several key steps that must be followed to satisfy both rutting and fatigue requirements on hardstands. These include:

• Step 1: Determine the critical load of the critical vehicle – this includes calculating the ‘worst case’ wheel load of the design vehicle when loaded
• Step 2: Determine any dynamic factors – This includes giving an allowance to dynamic factors of braking, accelerating and turning.
• Step 3: Determine proximity factors – Calculating the proximity factors with reference to insitu subgrade supports
• Step 4: Determine the appropriate Standard Equivalent Wheel Load (SEWL) and no. of passes – calculate the effective number of SEWL’s per pass of the design vehicle, giving consideration to wander of the wheel loading and container distribution (if appropriate).
• Step 5: Determine a standard base thickness – using material equivalency factors for empirical charts outlined in the British Ports Manual or adopting relevant design properties for mechanistic design to determine the required thickness to achieve the desired number of passes

Other considerations given to heavy duty pavement design include the abrasion resistance under repetitions wheel loads, turning and screwing and the damage caused by long-term storage of loaded container corner plates.

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