Assessing Variability of In Situ Pavement Material Stiffness Moduli

Abstract

This paper describes research carried out to investigate pavement material-stiffness modulus variability. Detailed pavement surface deflection data were obtained from two sections of newly constructed flexible pavement in the United Kingdom, by performing tests with a falling weight deflectometer. The deflection data were back-analyzed using the computer program PADAL to obtain estimates of the in situ pavement layer stiffness moduli. The results were statistically analyzed to identify suitable test sampling regimes for end product specifications using the falling weight deflectometer. Results show that the mean values of key deflection parameters are not very sensitive to test spacing for a nominally uniform (as specified) pavement construction. However, more variability in the standard deviations of these parameters, particularly when data were sampled at more than 50 m centers (<10 samples) was found. Results from a statistical analysis of the layer stiffness moduli showed that mean layer stiffness moduli could be reasonably estimated from a low number of samples. However, many more samples would be required for a reasonable estimation of standard deviation of the layer stiffness moduli. For lengths of pavement around 500 m, tests would be required every 10 m.