ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Wednesday, June 5, 1996 TAG: 9606050048
SECTION: VIRGINIA PAGE: C-3 EDITION: METRO
SOURCE: CHRISTOPHER L. BOYD STAFF WRITER
A sinkhole opened up late Monday night on southbound Interstate 81 in Rockbridge County, limiting traffic to one lane over a two-mile stretch of highway.
According to the Virginia Department of Transportation, one lane will be open between mileposts 182 and 180 until Friday, when VDOT expects to finish repairs.
Ernst Kastning, associate professor of geology at Radford University, said recent heavy rains may have been the "last straw" for the road, but they were by no means the sole cause of the sinkhole. He said sinkholes develop like a cavity in a tooth: As water "percolates" through cracks in the asphalt and down to the bedrock, earth under the asphalt is eaten away, causing an often undetectable sinkhole to form. After the hole forms under the asphalt, it is just a matter of time before the road collapses.
"We've been real lucky this far [that no one has been hurt], but it is a recurring problem that will continue to happen," Kastning said.
That's partly because the 20-plus-year-old highway has become old enough to decay, causing more and more cracks to develop. Kastning said the decay may be caused by the asphalt not being packed tightly enough when the highway was built.
For the hole to be repaired by Friday, the entire cavity must be dug out "like a rotten tooth," he said, until bedrock is reached - a depth that varies. The hole is then filled with rocks and gravel and re-covered with asphalt.
VDOT officials were unavailable to provide information on the sinkhole, such as its size.
Kastning said, however, that there is no definite size for a sinkhole. "A hole can range from a foot to an acre," he said.
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