PAVEMENT EVALUATION WITH THE FALLING WEIGHT DEFLECTOMETER

A pavement evaluation method has been developed on the basis of elastic theory by which structural properties of a pavement can be derived from the surface deflection and the shape of the deflection bowl under a test load. The method generally expresses the structural quality of an existing pavement in terms of effective layer thicknesses and Young's moduli for the materials. Results are better with instruments using short loading times, like the Falling Weight Deflectometer, than with slow-speed instruments like the Benkelman Beam. The Falling Weight Deflectometer has proved to be an accurate, reliable and simple instrument for pavement evaluation. The force level and loading time adequately represent actual traffic. Values of effective asphalt layer thicknesses derived from the deflectometer results showed good agreement with values obtained from cores or construction reports. The structural properties derived from deflection measurements can be used in the Shell Design Charts to determine a required overlay thickness.