DYNAMIC INTERPRETATION OF DYNAFLECT AND FALLING WEIGHT DEFLECTOMETER TESTS

The Dynaflect and the falling weight deflectometer are commonly used for nondestructive testing of pavements. In both cases a dynamic load is imparted, and the determination of the mechanical properties of the pavement, the base, and the subbase is normally performed by comparing the measured deflections at various points along the surface to results of static analyses that consider the subbase as a homogeneous, elastic half-space. In this paper, the displacements obtained from dynamic analyses are compared to those provided by conventional static programs when the subbase is a homogeneous soil stratum of finite depth resting on a much stiffer rocklike material and when the soil properties increase smoothly with depth, as is often the case. The results of these comparisons indicate that for certain ranges of depth to bedrock a static interpretation of the Dynaflect and falling weight deflectometer tests may lead to substantial errors. Situations in which these errors are important are more likely to be encountered with the Dynaflect than with the falling weight deflectometer.