How Did This Owner Realize a 70:1 ROI? Using Falling Weight Deflectometer to Evaluate Pavements Did the Trick!

09.08.15   Robert C. Rabeler, PE | More by this Author

How Did This Owner Realize a 70:1 ROI? Using Falling Weight Deflectometer to Evaluate Pavements Did the Trick!

This article is part of a series regarding lessons learned in geotechnical engineering. These are real projects with real people, but the names have been omitted to protect those involved.

Picture this: Main Street in a small Midwest community. Picturesque and quaint. Except for the deteriorating street pavement. The surface was cracking and the town thought it was in for an expensive total removal and replacement of the old concrete pavement that was overlaid with asphalt. Not only would removal and replacement be expensive, but business and downtown shopping would be disrupted while Main Street was under construction. 

Customarily, evaluation of the pavement and subgrade conditions would consist of pavement cores and soil borings. In this case, the town elected to use SME’s Falling Weight Deflectometer (FWD) to evaluate the pavement. The FWD simulates moving vehicle loads on the pavement andis tailored to meet individual project’s specific loading conditions. By applying an impulse load to the pavement, the FWD is able to measure surface deflections and analyze them to obtain the structural number (SN) of the pavement and the subgrade modulus.

SME is one of the few companies in the country that owns and operates its own FWD. SME’s FWD can simulate light car traffic, or can apply as much as 55,000 pounds of force to simulate heavy aircraft loads.

As it turned out, using the FWD was a great decision. SME found that 90% of the underlying concrete was in good condition requiring only minor patching and a new asphalt overlay. This meant that Main Street would not be totally torn up because traffic could travel on the underlying concrete pavement once the old asphalt was removed. In addition to the enormous economic savings realized because patrons were not deterred from shopping and patronizing local establishments, the town saved over $250,000– a return on investment in SME services of 70:1!

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