Experience with the application of the spectral analysis of surface waves method on a falling weight deflectometer time history

Abstract

Falling Weight Deflectometers are commonly used in pavement diagnostics and the outputs of measurements are a basis for pavement performance evaluation. Usually, a surface modulus of a pavement is determined or the modulus of a pavement layer is back-calculated using maximum values of a load force and measured deflections. A Falling Weight Deflectometer time history contains data describing a total response of a pavement to a load in time domain. The theory and principles of the Spectral Analysis of Surface Waves method were applied to these measurement outputs to determine Rayleigh wave velocity and a compression-tension modulus of a pavement. The problems with the determination of travel time of a wave were identified. The calculated compression-tension modulus differed noticeably depending on a used distance between receivers. Analysis showed the depth of the propagation of a wave or the bulk density of an investigated area is probably not a reason of the difference in the values of the compression-tension modulus calculated for the various distances of receivers.