NONDESTRUCTIVE VIBRATORY PAVEMENT EVALUATION TECHNIQUES

The U.S. Army Engineer Waterways Experiment Station (WES) has performed several studies since the Second International Conference on the Structural Design of Asphalt Pavements in an effort to develop techniques and criteria for use in the nondestructive evaluation of flexible pavements and the prediction of performance of the pavements under various aircraft loads. This paper covers the results of three studies: (1) development of criteria relating elastic deflection beneath prototype loads to performance of pavements subjected to trafficking with those loads, (2) development of techniques of extrapolation of deflections under steady-state vibratory loads to predict elastic deflections beneath static prototype laods, and (3) development of anautomated nondestructive testing system and utilization of this system in accumulation of data from airfield pavements throughout the United States that confirm the nondestructive evaluation procedures by comparison with conventional Corps of Engineers (CE) criteria. Relationships between the elastic deflection of a pavement beneath a static wheel load to the number of repetitions of that load to cause failure of the pavement have been developed for flexible pavements. These relationships were made from data accumulated over a period of years from full-scale airfield and highway test pavements. These relationships are not only important in the nondestructive evaluation procedures, but may also provide the link for theoretical treatments of layered systems to predicted performance of these systems. The multiple-wheel heavy gear load (MWHGL) test sections at WES consisted of instrumented pavements that were tested with various single- and multiple-wheel loads. Pavement deflections measured beneath the steady-state vibratory loadings were extrapolated with a fair degree of accuracy to predict deflections under static loading with the test load carts. Load-deflection ratios obtained with a large mechanical vibrator were related to performance of the test sections under traffic and to conventional pavement strength parameters. Airfield pavements throughout the throughout the United States, which provided a range of pavement types and environmental conditions, were evaluated by both nondestructive techniques and conventional test pit methods, and comparisons of these results are presented. /Author/