Infrasense Heads North, Scans 290 Miles of Alaskan Pavement

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Last month, Infrasense conducted a pavement thickness survey on 290 miles of highway connecting Anchorage and Fairbanks, Alaska. The survey used a unique Ground Penetrating Radar (GPR) system comprised of two antennas of different frequencies. This dual-frequency approach allowed Infrasense engineers to collect high resolution data for shallow pavement structure, while penetrating deeper to detect base layer activity well below the pavement surface.

Infrasense survey vehicle with dual frequency antennas

Infrasense, Inc. recently completed a subsurface pavement thickness survey of 290 lane miles of the Parks Highway between Anchorage and Fairbanks, Alaska using ground penetrating radar (GPR). The thickness investigation employed the use of two different frequency antennas, designed to achieve the optimum tradeoff between resolution and depth of penetration. The objective of the work was to accurately characterize the pavement structure while reducing the number of cores that the state typically uses. By reducing the need for cores, the entire 290 mile project section was able to be tested within the limited thaw season, allowing for more immediate planning decisions to be made. Typical pavement structure thickness data was collected with the higher resolution air-coupled radar antenna. The deeper penetrating lower frequency antenna was able to capture areas where the pavement structure was unusually deep (greater than 3 feet). All data was synchronized with a Global Positioning System (GPS) to provide coordinate locations for the detected pavement thicknesses. Data collection was performed in a single day at normal highway speeds, allowing traffic to flow without any disruption.

Infrasense has played a key role in the development and implementation of GPR for pavement assessments over the past 25 years. Currently, the most common application of this state-of-the-art technology is the determination of pavement layer thickness because, unlike traditional coring, GPR requires no lane closures and provides a timely and cost-effective means of collecting continuous thickness data. This data may be used for network-level pavement management, project-level rehabilitation design, or quality assurance of newly constructed pavements. Infrasense surveys have covered over 10,000 lane miles of pavement. Projects range in size from our recent project in Alaska to a survey of 3,500 miles for the Oklahoma Department of Transportation.

At the network level, GPR can provide layer structure data used to identify homogeneous sections and to compute the remaining life of segments of the network. Computation of remaining life enables highway agencies to optimize their programming and planning of pavement rehabilitation. A number of agencies have implemented GPR at the network level, including the California Department of Transportation (CalTrans) and the Oklahoma DOT.

At the project level, GPR data provides information that enables owner agencies and consultants optimize rehabilitation design by providing accurate information on the current pavement structure. GPR data is also used to implement pavement recycling by providing details on the thickness of the bound material and how it varies over the project length.

Many GPR pavement thickness studies focus on supporting FWD operations. Pavement strength evaluations using a Falling Weight Deflectometer (FWD) provide useful data to pavement engineers for estimating remaining life and planning rehabilitation. Accurate pavement layer thickness data enhances FWD pavement strength evaluations, since thickness data is required for calculation of the pavement moduli. During 2010, Infrasense worked with the Montana DOT to evaluate the GPR/FWD combination, and to look at the potential benefits for rehabilitation design.

For QA of new construction, GPR can be used to check both layer thickness and density. Recently the Florida DOT acquired software from Infrasense which enables their field personnel to map the density variations at the time of pavement construction, thus enabling the identification of paving problems while they still can be corrected.

About Infrasense, Inc.
Since 1987, Infrasense, Inc. has applied the most current technologies to the most difficult challenges in subsurface scanning. Infrasense’s engineers are able to nondestructively extract critical information from a diverse range of structures. The firm has conducted research to advance the field of subsurface detection, while also providing valuable information to clients across the country. Learn more about Infrasense, Inc. and its services at

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Ken Maser
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