Upgraded Seismic Pavement Analyzer Undergoing Field Tests in Florida

Remember the seismic pavement analyzer (SPA)? The device, which was developed under the Strategic Highway Research Program (SHRP), was designed to automate and replace several time-consuming and complex methods of evaluating asphalt and portland cement concrete pavements.

But when SHRP ended, the SPA had seen only limited field testing and wasn’t ready for routine use. Since then, however, the prototype device has been upgraded to be "more user-friendly, more accurate, and more rugged," says Soheil Nazarian of the University of Texas at El Paso, one of the developers of the prototype SPA.

The Federal Highway Administration (FHWA) last year awarded a contract to Florida A&M University and Florida State University (FAMU-FSU) to conduct comprehensive field evaluations of the prototype SPA. Assistance is being provided by Nazarian and Mark Baker, who also participated in development of the prototype and now heads Geomedia Research and Development.

The study has several objectives:

• Test the SPA’s ruggedness.
• Compare the accuracy and repeatability of the results of the SPA with the results from ground-penetrating radar, core samples, and the falling weight deflectometer (FWD).
• Determine if any modifications or improvements are needed.

The study will also evaluate the SPA’s effectiveness in specific pavement management applications. "There is an absolute need for equipment to characterize the pavement surface layer to determine remaining life and for diagnostic purposes," says Jamshid Armaghani of the Florida Department of Transportation (DOT), who is managing the project. "There is no equipment that accomplishes that now. The only option is computer models. Because computer models determine pavement layer properties from FWD test results, they may not represent the true properties of the materials.

"These field tests will provide a good indication of how well the SPA measures the properties of pavement layers. Even if we find out it’s not ready for implementation, what we learn could be a stepping stone to future research."

For more information on the evaluation in Florida, contact Jamshid Armaghani of Florida DOT (phone: 352-337-3200; fax: 352-334-1648), or Kamal Tawfiq at FAMU-FSU (phone: 904-487-6121; fax: 904-487-6142).

For more information on the SPA, contact Celso Gatchalian at FHWA (phone: 202-366-1342; fax: 202-366-3988; email: celso.gatchalian@fhwa.dot.gov).

What Is the Seismic Pavement Analyzer?

The SPA is a small trailer equipped with eight transducers and two pneumatic hammers. The trailer is towed to the test site, and the hammers and transducers are lowered to the pavement surface. The hammers then strike the pavement, producing vibrations that are picked up by the transducers, which relay the data to a computer onboard the vehicle towing the SPA. The test is almost fully automated and only takes about 1 minute.

The data are analyzed by a computer software program, which then generates a report describing the condition, thickness, and stiffness of the pavement; any defects in the pavement subgrade; and other properties that are directly related to pavement performance.

The device could be used to pinpoint the location of problems in the pavement or subgrade. It could also reveal the severity of a problem, which would help engineers then select the best maintenance or repair method. In addition, it could be used to test how well a repair or maintenance treatment is working.

The seismic pavement analyzer automates and replaces several time-consuming and complex methods of evaluating asphalt and portland cement concrete pavements. This closeup shows the device’s two pneumatic hammers and three of its eight transducers.

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