Subgrade assessment is a crucial process that is undertaken prior to the installation of the overlying pavement layers. This process involves a visual assessment to ensure that the subgrade is suitable for the construction of subsequent pavement layers. To conduct this assessment, various methods can be used, including the use of a smooth-drum roller or a fully laden truck with a single axle carrying a heavy load.

Geotechnical engineers walk alongside the roller as it moves forward over the completed subgrade to detect and deformation, which provides a comprehensive assessment of the entire subgrade. The visual assessment is quick, inexpensive, and conducted by highly trained professionals.

Moreover, eight-tonne single-axle trucks are used to evaluate whether there is any deflection on the surface, which is an essential step in quality control. The subgrade assessment process is critical in ensuring the longevity and stability of the pavement layers and is an integral part of any construction project.

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    Frequently Asked Questions

    Proof rolling procedure as per Transport Roads & Maritime Services "Test method T198: Proof rolling test" consists of:
    1. Test the layer by operating the equipment at a speed in the range 3-10 km/h, as determined by and in the presence of the Principal’s nominated representative. The rolling pattern must cover the area or lot to be tested, with successive passes of the equipment offset laterally by 40 to 50%
    2. When standing beside the equipment, the Principal’s nominated representative, must assess the surface deformation under the roller as perceptible or not perceptible at specific locations, and as uniform or non-uniform over the area of the lot.
    All details regarding proof rolling can be found in the Transport Roads & Maritime Services "Test method T198: Proof rolling test".
    The proof roller can either be:
    • a pneumatic-tyred static roller, not less than 4.5 tonnes per tyre and 600 kPa tyre pressure or
    • a 10,000 L water tanker with internal baffles to minimise sloshing with a minimum 600 kPa tyre pressure.
    Proof roll test undertaken when a suitably sized plant such as smooth drum roller or watercart is used to 'proof' load test the ground. The engineer would walk besides the roller and check for deflection or movement.
    This is at the discretion of the suitably qualified and experienced geotechnical engineer. The proof roll test is conducted to his satisfaction.
    Proof rolling is a subjectively assessed deformation test that allows the nominated representative to judge whether the transient surface deformation under the equipment is perceptible or not.