Today’s technology is making inroads into better pavement engineering, with companies like Resource Intl., www.resourceinternational.com, Columbus, Ohio, dedicating resources to the study of structural conditions.
The company recently conducted numerous investigations in Ohio using a JILS-20HF FWD – GPR integrated system. This nondestructive pavement evaluation was used on Interstate 75 in District 1 of the Ohio Dept. of Transportation, www.dot.state.oh.us, Columbus, Ohio, as well as for evaluation of newly constructed Ohio Turnpike projects.
The evaluation uses a data integration and analysis system to merge FWD (falling weight deflectometer) data and GPR (ground-penetrating radar) data with digital video images of surface conditions and global-positioning coordinates. At the core of these projects is the falling weight deflectometer, which evaluates the structural condition of pavements and the stiffness or the modulus of various layers and to determine overall structural strength.
As part of this research, engineers use GPR to: determine continuous pavement layer thickness, detect voids under pavement, evaluate base material, map zones of asphalt stripping, and locate construction defects and changes in pavement structure.
The flexible FWD/GPR system is capable of collecting data on aggregate, asphalt and concrete-surfaced roadways, airport runways, and parking lots. Engineers gather deflection and radar data with a minimal disruption to traffic, and analyze the collected information with a variety of specialized software tools to provide their clients with findings and recommendations. The two nondestructive, noninvasive test instruments provide engineers with objective assessments of the pavements’ structural condition so that good rehabilitation decisions can be made. These two instruments are used to provide forensic information regarding early failure of new pavement sections.
Core data is localized and cannot represent the entire average thickness of different materials unless a considerable amount of core samples are taken. However, GPR surveys provide continuous layer thickness data along the entire length of the tested pavement. The analysis results of the GPR data allow the user to break the pavement into homogeneous sections and provide pavement layer thicknesses for each section, which increases the accuracy of the FWD deflection data back-calculations.
As part of Resource Intl.’s FWD/GPR system, there is also integration of high-resolution digital cameras and a GPS unit for a more complete and accurate analysis of the pavement being tested. The digital images are played forward and backward to help the user to interpret the structural analysis results.