Development of a Rolling Dynamic Deflectometer for Continuous Deflection Testing of Pavements

1998Project Summary Report (9/96-8/97)PDFTech ReportFHWA/TX-99/1422-3FDeflectometersDeflection testsStiffnessVibrationVibrators (Electricity)Airport runwaysNondestructive testsLoad testsDeflectometersMobil equipmentNondestructive testsPavement deflectionsPavement testsRunwaysStiffnessTest methodsVibrationVibrators(Machinery)United StatesTexasUniversity of Texas at Austin. Center for Transportation ResearchBay, James A.Stokoe, Kenneth H. IIUniversity of Texas at Austin. Center for Transportation ResearchTexas. Dept. of Transportation. Research and Technology Transfer SectionUS Transportation CollectionA rolling dynamic deflectometer (RDD) was developed as a nondestructive method for determining continuous deflection profiles of pavements. Unlike other commonly used pavement testing methods, the RDD performs continuous rather than discrete measurements. The ability to perform continuous measurements makes RDD testing very effective for quickly characterizing large sections of pavement while simultaneously providing a comprehensive picture of the pavement condition, with little danger of missing critical pavement features. RDD testing is performed while the RDD vehicle travels at speeds of up to 1.5 mph (2.4 km/hr). Continuous deflection profiles determined with the RDD can be used to: 1) assess the overall stiffness of a pavement; 2) differentiate the relative stiffnesses of different regions; 3) detect cracks, joints, and weak regions; 4) assess the performance of cracked or jointed regions; 5) delineate the regions of the pavement influenced by joints and cracks; and 6) identify areas where additional discrete testing should be performed. The RDD is a powerful tool having the potential for: 1) designing pavement repairs and retrofits, 2) estimating the remaining life of pavements, and 3) functioning as a quality assurance and quality control system during the construction of new pavements. The RDD was constructed by modifying the electrohydraulic loading system on a Vibroseis truck. The RDD applies large sinusoidal dynamic forces to the pavement through specially designed loading rollers. The resulting deflections are simultaneously measured by rolling sensors designed to minimize the influence of noise caused by rough pavement surfaces. Distance measuring and data acquisition systems were designed to record the forces applied to the pavement and the resulting dynamic displacements; these systems also track the position of the RDD. The RDD was used to determine continuous deflection profiles at two sites on Interstate Highway 10 over a total length of 21 mi (33.5 km). These results were used to assess the condition of the pavement and to design an overlay. The RDD was also used to test runway and taxiway airport pavements at the Dallas-Fort Worth International Airport as part of a project to predict the remaining life of the airport pavements. Finally, the RDD was used in a stationary mode to dynamically load bridges and bridge foundations. All testing except the bridge project is presented in this report.85