MDOT, MSU researchers tackle potholes from the soil up

Lansing State Journal, 28 April 2016
R.J.Wolcott

This story has been updated with additional information from MSU professor Gilbert Baladi

LANSING – Two Michigan State University researchers think they’ve found at least one solution to one of the most despised seasons in Michigan.

Pothole season, brought on by freezing and thawing on roadways in the months before summer, is exacerbated by heavy trucks.

Until now, state officials have relied on the calendar and visual observation as much as anything in applying restrictions to when heavy trucks can use local roads.

There’s a better way, according to MSU doctoral student Pegah Rajaei, who with professor Gilbert Baladi and the Michigan Department of Transportation spent three years and $184,000 coming up with a better way to protect roads.

“Even being a couple days late (with load restrictions) can result in damage to the roads,” Pegah said.

Relying on a couple days of warm weather to make restriction decision is problematic, said Scott Greene, manager of MDOT’s utilities coordination, permits and agreements section.

“We had a situation in early March where we had some really nice days,” he said, “but it was still frozen underground.”

Cracks formed by this freezing-thawing cycle get expanded by heavy trucks and machinery on local roads with softer soil or fewer drains for water, said Richard Endres, a project manager within MDOT’s geotechnical services section.

Currently, MDOT uses visual inspection of roads and frost tubes buried underground to decide when load restrictions are needed. However, the timing of these inspections may not correlate with the start of the thawing season, Baladi said, and visiting more frequently would be expensive and time consuming.

““The problem with sending people out is you need enough time to inform the trucking companies that load restriction signs will be posted,” Rajaei said.

Rajaei and Baladi developed a formula that accurately predicted the measured frost depth under roads over the last few years. The formula uses the daily high and low temperatures and some easily obtained soil characteristics. That data can be used as an input in another model to predict thaw depth beneath roads as well as a guide on when to post and remove load restrictions. Ensure load restrictions are in place at the appropriate time can decrease costs to the trucking industry as well as preserving roadways, Baladi said.

Bill Conklin , director of the Ingham County Road Department, prefers tried-and-true methods.

“We’ve consistently found the best way to do this is to look at the roads themselves,” he said. “To see when the roads are starting to thaw and when they’re done.”

More than 800 miles of roads in Ingham County have seasonal weight restrictions, Conklin said. While numerous studies on seasonal restrictions have been done over the years, he said his department will continue to use staff inspections of roadways for instituting restrictions.

“We’re making observations and using our best judgment,” he added.

MDOT is waiting on more results before changing any of its policies, said spokesman Dan Weingarten, but the research holds promise, officials say.

MDOT has expanded its number of stations with sub-soil sensors from 25 to more than 50 since researchers began working.

“Wherever we have weather stations measuring soil temperature and we know soil type under the road, we can model how deep the frost goes,” Endres said.

The report cost $184,000, 20% of which was funded by MDOT, with the Federal Highway Administration  picking up the rest of the tab.

A frost model has been developed and tested, the next step is the development of accurate thaw model and then merging the two models. MDOT is installing more ground temperature sensors and the MSU researchers are collecting additional data on the soil of rural Michigan roadways.

Contact RJ Wolcott at (517) 377-1026 oremail hidden; JavaScript is required. Follow him on Twitter@wolcottr.

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