What’s below the surface?

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Local News

May 17, 2019 - 5:41 PM

Work to rebuild U.S. 169 continues at the Tank Farm Road interchange south of Humboldt. Dowel baskets, shown in the foreground and ramp, transfer weight across joints and help with expansion and contraction of the concrete.

A year after a seven-mile highway replacement project began on U.S. 169 between Iola and Chanute, motorists can drive a few miles on fresh, smooth pavement. 

The potholes and cracks, so common and frustrating to drivers for years, are gone. But as drivers travel along the new surface, most are unaware of what lies underneath the concrete ? and how important that material will be in keeping the road in good condition for years to come. 

The history of that stretch of U.S. 169 goes back decades and is fraught with frustration, planning, negotiation and compromise. 

The project is expected to wrap up later this summer and will extend to just north of the Allen-Neosho county line. But as work continues, there?s still much to learn about the $17.8 million project, including its history and connection to the beleaguered Kansas T-WORKS project, the makeup of the road itself and its impact on Allen County and Humboldt. 

This two-part series will examine those issues, starting today with a look at the road itself and its history. Click here for part 2.

 

Crews hope to complete a rebuild of U.S. 169 from Iola to near the Allen-Neosho county line south of Humboldt later this summer. The project was several years in the making, and includes test areas to devise better ways to keep moisture from seeping below the highway?s surface. Here, crews continue to rebuild the base south of Tank Farm Road.

 

Experimenting 

When U.S. 169 between Iola and Chanute was built in the early 1980s, engineers experimented with a process they hoped would save costs. The highway was built without dowel bars and baskets to transfer weight ? in layman?s terms, the highway relied on the concrete itself to handle the weight of heavy truck traffic without support structures recommended as the best practice for modern highway construction, according to Darrin Petrowsky, area engineer for the Kansas Department of Transportation in Iola. 

Instead, the highway used skewed joints, allowing an axle load to pass over the concrete one tire at a time instead of all at once. But those joints were placed about 30 feet apart, Petrowsky said, rather than the 15-foot recommendation now followed. 

?It was a research project,? Petrowsky, who was not part of that project, said. ?Pretty much all of our pavement from the 1990s on requires dowel bars. Experience says our limestone is not durable enough for the loads it encounters.?

Problems were worsened by water seepage. Soil in this part of Southeast Kansas typically includes more clay, shale and rock seams than other parts of the state, Petrowsky said. That increases the likelihood that water will infiltrate into the subgrade of a highway.

?Water in our subgrade is a bad thing,? Petrowsky said. ?Water creates mud, and mud doesn?t support weight.?

As demolition of the road began for the current project, contractors discovered what appeared to be natural springs under the surface. 

?We ran into a couple areas that were worse than others,? he said. ?It?s kind of normal to encounter things like that. It?s nothing we haven?t dealt with before.?

Over the ensuing years, the highway required a great deal of repairs and repaving. The pavement shifted. Motorists were frustrated by chipped, cracked pavement and potholes. 

Even so, the pavement met its expected lifespan, Petrowsky said. But after nearly four decades, the highway needed to be replaced. 

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