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The Loadman portable falling weight deflectometer (FWD) is a device for measuring the elastic modulus of pavement materials. The Loadman applies an impact force to the surface of the pavement layer being tested. The device measures the resulting deflection and calculates the corresponding elastic modulus using Boussinesq theory.

The Loadman shows significant potential as a very useful tool for the pavement engineering practitioner, particularly since the AUSTROADS pavement design procedures were adopted by Transit New Zealand in 1995.

The objectives of this study, carried out in 1997 to investigate the use of the Loadman FWD, were:

• determine the accuracy and repeatability of the Loadman, for measuring elastic moduli for both subgrade and compacted aggregate materials
• determine its zone of influence, both vertically and laterally
• determine limitations of its use.

Keywords: elastic modulus, falling weight deflectometer, FWD, New Zealand, pavement, pavement design, road, testing