DEVELOPMENT AND PRELIMINARY INVESTIGATION OF ROLLING DYNAMIC DEFLECTOMETER

Abstract

A Rolling Dynamic Deflectometer (RDD) has been developed by making modifications to a vibroseis truck. The RDD can make continuous profiles of pavement flexibility or stiffness can be measured under heavy loads. The RDD employs a servo-hydraulic vibrator to apply static hold-down and vertical dynamic forces to two sets of dual loading wheels. A total force (static plus dynamic) of 150 kN (33,000 lb) can be applied to the pavement surface while the RDD is moving at velocities of 3 to 6 km/h (2 to 4 mph). Dynamic deflections of the surface are continuously recorded with an accelerometer located on a set of receiver wheels positioned mid-way between the loading wheels. The loading and monitoring systems of the RDD have been calibrated, and initial testing has been performed at the Texas Transportation Institute (TTI) pavement test facility. Eight flexible pavement sections, covering a range in flexibility, have been successfully tested. Loading frequencies of 22 and 40 Hz have been used with a wide range in dynamic loads. The RDD was able to make measurements of: longitudinal variability within each section, differences in flexibility between sections, and nonlinearities in flexibility at several sections. Finally, a comparison between RDD and FWD measurements shows the flexibilities measured by both methods are consistent with each other and closely related.