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RE: Frozen soil = disturbed earth?[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Frozen soil = disturbed earth?
- From: Harold Sprague <spraguehope(--nospam--at)hotmail.com>
- Date: Sun, 22 Mar 2009 23:07:20 +0000
For every rule, there is an exception. When it comes to Alaska, there are a lot of rules and a lot of exceptions. I just got back from Ft. Greely. The rule was that it is cold. If you consider -20 degrees F with 30 mph winds as cold, then I guess that is cold. I thought it was very cold. By the same token, last January it got up to +45 degrees F. The Ft. Greely area has a frost depth of 17 feet. It gets even more difficult when you place a heated structure on frozen sub soil.
I still feel that in the lower 48, the best practice is to avoid placing a foundation on frozen soil.
Regards, Harold Sprague
Subject: Re: Frozen soil = disturbed earth?
Date: Sun, 22 Mar 2009 14:30:28 -0600
In general I would agree with you; however, there are precedents for going against this advice.
Back in the late 1970s I was involved in a proposed gas plant that was to be constructed on an island in the Mackenzie River delta where it enters into the Arctic Ocean. This island was, as delta islands tend to be, about three to five feet above sea level, hence, it was subject to flooding by storm surges. The active layer (the layer which thaws in summer and refreezes again in winter) was about one to two feet thick; below that was about 1,800 feet of permafrost. This permafrost was considered to be "ice rich", containing numerous lenses of pure ice as well as many areas where the ice content was more than 100% (calculated as weight of ice divided by dry weight of soil solids).
Construction could only take place during winter months, after the river had frozen enough to drive 30 ton trucks over the ice at a time when the temperature would be about -40 degrees (F. or C.). Site work consisted of rough grading to remove any (frozen) vegetation that could possibly be removed, spreading a few inches of gravel to create a flat surface, placing 4" of high density Styrofoam insulation (40 psi crushing strength, as I recall) and placing two feet of gravel above the insulation (to prevent crushing of the insulation under heavy wheel loads). It was a large site, 25 acres, as I recall, in order to accommodate a small airstrip, a docking area for ocean going barges, drilling sites for a number of directional drilling well sites, the plant processing facilities, off-sites, living accommodations, etc., and the 14 feet high dykes to deflect storm surges.
Of course it could only be build by placing and compacting frozen material on a permanently frozen base material, something which is generally not allowed. The principal geotechnical consultant was Jack Clark, (Dr. J. I. Clark, Ph.D., P.Eng., I believe is his correct title). He had published papers on compaction of frozen granular material, and was generally regarded as the authority on permafrost construction at the time. I'm sure if anyone is really interested, they could seek out some of Dr. Clark's publications.
Unfortunately, the project was cancelled; so it really became only a two year research project. Fortunately, I had one of the best seats in the house to observe what was going on. The reason the project was delayed was that the pipeline to deliver the gas was delayed for ten years due largely (I believe; but I could be wrong) to social and environmental problems relating to aboriginal lifestyle and land claims. That was over thirty years ago; the project is still on hold; but it probably will go ahead eventually.
I hope this didn't bore you.
H. Daryl Richardson
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- Re: Frozen soil = disturbed earth?
- From: Daryl Richardson
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