Scientists Aim to Freeze Chena Hot Springs Ground
Fairbanks Daily News-Miner (AK); September 8, 1998
Scientists have decided it’s time to freeze that asphalt-buckling villain permafrost in its tracks.
At a test site on Chena Hot Springs Road, construction crews are installing grids of carbon dioxide-filled steel pipes – called thermosyphons – engineered to carry away heat from below the road’s surface. The intent is to freeze the permafrost permanently.
“Chena Hot Springs Road hasn’t been built in a perfect place,” said John Zarling, a retired University of Alaska, Fairbanks mechanical engineering professor. “The section we’re working on is essentially floating. It’s thawed down 16 feet, it’s just soup underneath that road.”
“But the road is there, so you have to try to do the best you can with it.”
By definition, permafrost is permanently frozen ground. But areas of it melt and refreeze in an annual cycle that causes the ground to heave and sag, warping and cracking the road.
Less than one year after completion of the first half of the Chena Hot Springs Road project, for instance, crews had to patch an area of the road where they discovered too late some massive ice.
It’s a chilling problem.
The Alaska Science and Technology Foundation awarded a $130,000 research grant to scientists from UAF, the Army Corps of Engineers and the Anchorage-based Arctic Foundations, Inc. to find ways to stabilize ground under building and road projects.
Another $50,000 in federal and state funding – a drop in the bucket on the $10.3 million, seven-mile road project – will cover installation at the 200-foot test area, said Rod Anderson, the Department of Transportation’s construction engineer for the Chena Hot Springs Road project.
The systems developed by engineers – three designs using similar principles will be tested at the site – attempt to eliminate permafrost thawing.
The technology is similar to steam-boiler systems people used to heat their homes in the 1930s and 1940s. The same principle is also used on some space satellites and in the piles supporting the trans-Alaska oil pipeline, said Zarling.
It’s all about evaporation and condensation. Ed Yarmak, chief engineer for Arctic Foundations, likened the process to condensation that gathers on a bathroom mirror when steam from the shower contacts the cool glass surface.
The system will operate only in the winter, when the ground is colder than the air. The warmth of the ground will boil the carbon dioxide, which will rise to condensers – posts than can be seen above ground on the side of the road – then be returned to the liquid state.
The net effect is to transfer heat from the ground to the air – and keep the permafrost frozen.
To track how well the systems work, construction crews also are installing temperature-sensing devices at the site, located near the Steele Creek Road intersection.
If the data proves the systems successful, the technology could be used on future projects where ground has inherent permafrost problems like those near Bennett Hill, the troublesome section paved last year about 2-1/4 miles out Chena Hot Springs Road.
“That would have been the ideal place,” Anderson said. “Years ago, the pioneers established routes going to different areas. Even though it’s not necessarily a desirable place to build a road, we’re kind of stuck with the one that was chosen originally.”