Interpretation problems and reliability of falling weight deflection (FWD) measurements on three layer systems

The structural life of a road section can be determined through a process of falling weight deflection measurement. If only one deflection measuring point is available on the road section involved it is vital to avoid potential error sources in the determination of the structural life. If several measuring points are available on the road section, the errors will be averaged to some degree. The paper deals with two aspects of processing the results of the falling weight deflection measurments: - premature break off of an iteration process with curve-fitting of the various model parameters. Particularly in the case of pavements with bound roadbase such disruption can apparently of the structural life; - the number of repetitive measurements per measuring point needed to limit the effect of the random measuring error with deflection curve measurement on the calculation of the structural life. The effect of random measuring error can be eliminated by performing a minor amount of repetitive measurements.