Investigation of thin flexible pavement response between traffic and the falling weight deflectometer (FWD)

The Falling Weight Deflectometer (FWD) is commonly used to evaluate structural characteristics of pavements. The FWD simulates vehicular loads at typical highway speeds and the data is used to back-calculate layer moduli and design overlays (among other functions). In routine testing, the only data obtained is on the surface of the pavement, which leaves potentially significant behaviors within the pavement undetected. The focus of this paper is to present the analysis of a heavily instrumented, full-scale flexible pavement that was subjected to vehicular traffic and FWD loads under controlled testing conditions. Statistical analysis and finite element modeling separately demonstrated that the responses produced by the FWD were, in general, lower than those from corresponding vehicular traffic, and this behavior was more pronounced with depth. Finite element modeling resulted in traffic asphalt strain, base pressure, and subgrade pressure responses exceeding FWD responses by factors of 1.27, 1.76, and 2.43, respectively. Similarly, a statistical analysis resulted in factors of 1.36, 1.66, and 2.39, respectively. Additional analysis showed the deflection from FWD loading would have to be increased between 1.3 to 1.6 times to produce corresponding vehicular traffic stress states.