Falling/Heavy Weight Deflectometer Reliability

Abstract: The Federal Aviation Administration hosted a Falling/Heavy Weight Deflectometer roundup in 2010 and 2011 where several participants tested newly constructed and instrumented flexible and rigid pavement sections. While the F/HWD remains the ultimate choice for testing the pavement structural capacity, there is room for enhancing decades-old technologies. Initial evaluation performed on data collected at the centers of the Portland cement concrete slabs reveals that (1) significant differences in deflections exist between all devices, and some or all of these differences can be attributed to the variations in durations of the applied load pulses, (2) unrealistic negative deflections are noticed which may impact the accuracy of the backcalculation results, especially for the deep foundation layers, (3) irregular signals, such as noise and double peaks, are present in the data and are due to mechanical or electronic factors, (4) raw deflection sensors readings should be made available to allow for potential re-analysis as the technology advances, (5) the reliability of measurements needs to be improved to better quantify the layer properties and evaluate the pavement structural capacity, (6) testing should follow standard procedures, and (7) static backcalculation is unreliable because different F/HWDs, applying loads with varying durations and producing distinct deflections, results in different layer moduli for the same pavement structure, among other influencing factors. Ultimately, there is a crucial need to advance the current calibration procedures and improve the precision and accuracy of measured loads and deflections across the entire testing duration, rather than solely focusing on the peak responses.