frost depth in crushed stone 1

[engrj]

I have a project where a 6 inch dia water line will be buried in # 57 crushed stone. The thickness of stone layer could be as much as 7 feet.

Local codes require the frost depth to be 3' feet.

Question: At locations where the pipe is buried in ASTM # 57 stone, is the frost depth still 3 feet, or should it be deeper

 

[BigH]

engrj: Sorry, I don't know what #57 crushed stone is. I don't work in States. Still, I have see references to these in the past. Where can I find the gradations, etc. of various crushed and natural aggregates using the numbering system you reference? You would have the same problem in Ontario where we use Granular A, Granular B Type 1 or Type 2, etc. unless you had the codes. Thanks if you have the time to help.

 

[jheidt2543]

Any areas where the waterline passes under a road, the line should be deeper or insulated. Here in the upper midwest U.S., most codes call for water pipes to be buried 6' deep to the top of the pipe, while building foundations only go to 4' below grade. While this works in the vast majority of cases, there are documented cases of frost penetration deeper than the 6' under heavily traveled roads.

Check with some of the local utilities or cemetaries in the area, they generally have a pretty good handle on the depth of frost.

 

[RDK]

Codes are generally very conservative.

In this part of Canada codes and common practice usually say 2.4 m with 2.7 under roads. I have seen water and sewer lines as shallow as 1.5 m and they still do not freeze.

One factor is the amount of flow. If this 150 mm waterline will have a considerable flow 24 hours a day, it won’t freeze even if placed on top of the ground.

If codes are 3’ and you are 7’ and the line will have some flow all the time then I don’t think you will have a problem with the fill type.

Still the best advice is to talk to some people who actually excavate the lines to repair or modify in the winter and get an idea of actual frost depths in your area. Its always good to talk to the trades, they know the practical side better that you ever will.



Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[dik]

Rick:
In the Lindsay, Ontario area, frost penetration is 4', and I've seen it go down 7'. In Winnipeg, Manitoba, the frost penetration is typically 6' (I've put in fence posts and found frost a 3' in July) and I've seen it go down 13' in a parking lot near Polo Park...

 

[SirAl]

Frost penetration is dependant upon the thermal conductivity properties of the soils/pavement and the climate at your location. Frost will penetrate gravel to deeper levels than it will clay, silt, or sand. Based upon information from local road authorities in Alberta, frost probe installations have shown frost penetation as deep as 11 to 12 feet below road top in northern portions of the province. The design aids that I have used relate air freezing index with soil type to estimate frost penetration depth. The U.S. Army Corps of Engineers have undertaken pioneering research on this topic. I don't know if the following link will get you to a relevant document. However, every civil engineer should have this site bookmarked.

http://www.usace.army.mil/publications/eng-manuals/cecw.htm

This site is a gem!