Pavement Evaluation Projects in California
Infrasense recently worked with NCE, of Reno, Nevada, to evaluate the pavement structure under runway 28L at the San Francisco International Airport. This project materialized after cores extracted from one of the main runways revealed uncharacteristically thin areas of asphalt, and airport engineers needed a quick and reliable method of evaluating the 11,000-foot-long, 200-foot-wide runway and identifying areas of thin asphalt cover. Because SFO is one of the busiest airports in the country, the runway closure was limited to just 6 hours; Infrasense had to be deliberate and efficient with our data collection in order to obtain all the necessary data within the prescribed timeframe.
Working within the time constraints set by the airport, Infrasense collected 4 channels of GPR data simultaneously using dual 1-GHz air-coupled antennas and dual 400-MHz ground-coupled antennas. By using two different frequencies, Infrasense was able to obtain multiple resolutions of data so that both the thin asphalt layers and deep asphalt base and supporting layers could be identified in the GPR analysis. Data was collected using GPS for positional accuracy, and allowed Infrasense to collected data at precise 6-foot intervals across the width of the runway.
In order to reduce costs to the client, only two lines of data were initially analyzed and mapped. The preliminary results highlighted areas of thin asphalt across the entire runway, and a complete analysis of all the collected data was performed; the resulting asphalt thickness profiles defined the precise limits of the thin asphalt layer that prompted this pavement structure evaluation.