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Reversing Upheaval
Fri Jan 30, 2004
Listen in RealAudio 
Hi, I'm Bryan Yeaton for The Weather Notebook. Dr. Karen Henry is fighting frost
heaves.
KH: Really three conditions are required for frost heaving to form: freezing temperatures
(which we have lots of), a good water supply - and by good water supply I mean the water
table's within about eight feet of the surface; but the 3rd thing that's required - and that
New Hampshire has plenty of - is a silty soil. The Connecticut River Valley silts are
particularly good heavers. I grew up in the State of Michigan and their soils are much more
sandy. And they experience much less frost heave, even though they have just as cold
winters.
BY: Is there anything that can be done to prevent them?
KH: One way that I've studied to interfere with the water supply to freezing soil is to be a
layer of really big holes in the soil between where the freezing temperatures are and the
water supply. And those holes act as a big bulge in a straw would act to break the capillary
rise of water.
BY: Are we looking at large, crushed rock, like fist-sized or something like that?
KH: Crushed recycled glass would make a fantastic capillary barrier. There are also synthetic
materials called geosynthetics that make fantastic capillary barriers. To be effective they
have to be below the depth of freezing and above the water table in the soil.
BY: Does it affect the stability of the roadway above?
KH: A capillary barrier usually improves roadway stability; it doesn't degrade it, by any
means. And we've seen great results on some test sections in Windsor, Vermont.
Dr. Henry is a researcher at the Cold Regions Research and Engineering Lab in Hanover, NH. Our
show is supported by Subaru and the National Science Foundation. Find us online at
www.weathernotebook.org.
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