Artificial Ground Freezing

[a.p.re]

Hello,
I’m a civil engineer and I’ve to deal with the feasibility study of a temporary support (during excavation of a shaft) using Artificial Ground Freezing.
More precisely, I’ve to carry out the preliminary design of the refrigeration plant that will be used to freeze the soil.
Could anyone recommend a handbook to me that deal with the problem?
Would anyone care to mention some firms capable of constructing such a refrigeration plant?
Thanks,
AP

[US Iceman]

HI AP,

Welcome to the RE forums.

There is nothing special about a refrigeration system used for ground freezing. It is simply a system used to cool a brine solution. The brine solution is cooled in a heat exchanger. Then the brine is pumped through many vertical pipes that are sunk into the ground in the required shape of the excavation.

The ground is frozen over some period of time and forms an ice barrier to reinforce the hole in the ground and to hold back ground water.

The difficult part is to develop the cooling loads due to the depth of excavation and the soil/groundwater conditions that exist on the site.

[US Iceman]

I just remembered a book on the subject of ground soil freezing you might be interested in. I have not purchased it yet...but thinking about it.

Info below from Amazon.com

Frozen Ground Engineering
About the Authors
ORLANDO B. ANDERSLAND, PHD, is Professor Emeritus in the Department of Civil and Environmental Engineering at Michigan State University and a recipient of the Distinguished Faculty Award. He is senior author of the first edition of this book and numerous papers in technical journals, as well as senior editor of Geotechnical Engineering for Cold Regions.

BRANKO LADANYI, PHD, is Professor Emeritus in the Department of Civil, Geological, and Mining Engineering at the University of Montreal, École Polytechnique. He’s coauthor of the first edition of this book and numerous papers dealing with various geotechnical subjects. He is a Fellow of the Academy of Sciences, Royal Society of Canada, and has earned numerous awards and honors for his achievements in geotechnical engineering.

Hardcover: 384 pages
Publisher: Wiley; 2 edition (November 5, 2003)
Language: English
ISBN-10: 0471615498
ISBN-13: 978-0471615491

[a.p.re]

Hi US Iceman,
thank you for the informations.
Are you interested in artificial ground freezing?

AP

[gloucesterfridg]

This has certainly tweaked my interest thats for sure..

G.F

[US Iceman]

Are you interested in artificial ground freezing?


Hi. Yes, I think this is a very interesting application of refrigeration. I have worked on several systems used for underground freezing and another used for soil remediation.

These systems tend use ammonia as the refrigerant and calcium chloride as the brine solution. The systems are mounted on trailers for transportation to the site.

Then the electricity and brine hoses are connected to the system and the brine tank filled. The most difficult thing is to drill the holes for the vertical pipes and waiting for the ground to begin freezing.;)

[BigJon3475]

Just curious.......what are the typical ratios of calcium chloride in a brine solution? ppm or mg/L...or is it dependent upon conditions needed?<tt><tt>
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[US Iceman]

The ratios as you call them are either % of mass or % of volume, which are identical for glycol's. The % is determined by the desired minimum temperature required by the fluid plus a little more for a safety factor.

It's been a long time since I worked on one of these but I seem to think the target temperature was in the range of -20 to -30°F. So whatever the % required to achieve a eutectic point of -30°F would be the right mixture.

With this temperature range the evaporating temperature would have been around -10 to -20°F.

[Contactor]

Is this any cheaper than conventional excavation methods? Surely constructing and maintaining such a plant would cost quite a bit, what are the benefits?

Thanks

[US Iceman]

Is this any cheaper than conventional excavation methods?


I'm assuming it would have to be cost-effective otherwise why do it?

This is a fairly common technique used for underground mining and excavation. This has been done for many years and the benefits are probably due to minimizing the total construction costs.

[a.p.re]

Hi Contactor,
the AGF is not cheaper than other soil reinforcement methods (for exemple jet grouting or injections). However, in some cases the AGF beomes the best solution because of the site conditions. For exemple, if you have to excavate the by-passes of a twin-tube tunnel (i.e. the connections between a tube and the other) and it is impossible to drill from the ground surface, you can freeze the soil from one of the tubes. Furthermore, the AGF is "clean" because it has no impact from an environmental point of view.

AP