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Rough surf: Frost heave makes drivers seasick

Add this to the list of annoying winter weather maladies: frost heave.

Like it's not enough to white-knuckle it to work, skidding on snow and ice, now you also have to worry about knocking a tooth loose surfing road waves.

Blame frost heave. Here's what happens:

The bone-chilling cold causes the ground to freeze a foot or so down, far enough that it won't thaw all winter.

Then comes a couple of warm days, a nice spell that causes snow to melt, maybe a little rainfall.

Water trickles through the cracks in the pavement, seeps through the upper layer of earth that's close enough to the surface to thaw a wee bit, then hits the frozen wall.

Temperatures drop, and that trapped moisture freezes, pushing the pavement up around the fissures in the pavement and creating a concrete washboard that rattles your bones and sends your teeth clacking and your chassis chattering.

Once the weather starts to warm, you might see the phenomenon in action.

"In the springtime, you'll start to see the road weeping," Whiteside County engineer Russ Renner said. "Moisture weeps out of the cracks, and you'll see water on the pavement on a warm, sunny day, because the ground is still frozen and the water has no place to go but back up through the cracks."

Trisha Thompson, acting operations engineer in the Illinois Department of Transportation's Dixon office, says frost heave happens every winter, to some extent.

It occurs mostly on the old two-lanes, built around the beginning of the last century with poor subgrading that doesn't drain well and tends to hold moisture, she said.

The good news: The ruptured roads should flatten back out once the world thaws back to normal.

In the meantime, the problem can be alleviated by grinding the road surface, but too much grinding can result in a dip after the road settles back to normal, causing an even bigger problem, Thompson said.

"Unless it's an extreme safety issue, we don't tend to do a lot of grinding," she said.

Except for the usual Sisyphean task of trying to keep the cracks sealed, few repairs should be needed – although "that's hard to predict entirely," Renner said.

"We kind of wait until things settle down," he said, "then go out and find what's wrong and fix it."

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