Frost propagation

[hollowstemhead]

All,

Looking to increase my knowledge of frost action, especially in terms of how frost behaves and propagates horizontally. It seems as though the growth of ice lenses is usually explained as behaving predominantly vertically through capillary action in frost susceptible soils, resulting in vertical heaving and whatnot. Does anybody have any experience with sidewalls of cuts or sidewalls of soils behind retaining structures having troublesome frost action? Do ice lens and frost propogation occur predominantly vertically rather than horizontally? Thanks for any insight or case studies you can pass along. Happy New Year to all.

 

[jhoulette]

I can't recall much about frost action behind a retaining wall or similar structure. I believe this is due to drainage always being specified and using free draining soil where practical.

Jim Houlette PE
Web:

http://www.evstudio.us

Online Magazine:

http://www.evstudio.info

 

[oldestguy]

Frost heaving goes in the direction of least resistance.

I have seen many a house basement wall shoved in by frost.

While the subject of capillary action is used by some to explain frost heaving, it more likely is due to combinations of other mechanisms, such as clay electro-chemical actions. You can see that's as far as I have progressed in soil chemistry.

To use the theory of capillary action you need an air-water interface and that is not always the case for frost action.

 

[cntw1953]

Just guessing here.

I think frost heave has something to do with grain size, void ratio, water content, and temperature. It is not true that soil will frosen wherever it has the potential for capillary action, the depth counts. Surface water in soil with lots of fines tends to perform worser than uniform coarser soil because of smaller/tighter void ratio - lack of space to accomodate the volume expansion, or particle realignment (by roll over).

The expansion should be all around with the fast, and the most in the direction of sharpest temperature drop.

Chemistry? Oh, my worst enemy. But I believe it has something to do with water attratciveness (affinity) of soil of different types.

 

[hollowstemhead]

Thanks for the input everyone. My curiousity was sparked by a discussion in the office about a permanent soldier pile and lagging wall we did construction observation for (northeast US). The wall was tied back into the retained silty till soils, and finished with a shotcrete facing. There was concern by the design team about frost penetrating horizontally, into the vertical face of the cut, behind the lagging, and how this would effect the wall performance. Has anybody had any experience with a similar situation?

 

[jhoulette]

I knew I saw something on this before. I just remembered reading one of the UNIFIED FACILITIES CRITERIA (UFC) for design of military buildings in the extreme cold.
Below is a great resource of most if not all the UFC publications. Scroll down and find UFC 3-130-04 I think that is the publication that will help you out. Good luck!

http://www.wbdg.org/ccb/browse_cat.php?o=29&c=4

Jim Houlette PE
Web:

http://www.evstudio.us

Online Magazine:

http://www.evstudio.info

 

[aeoliantexan]

Excuse me for being late to the conversation. I have seen retaining walls deflected several inches by frost action. My interpretation is that in frost-susceptible soils, moisture migrates (due to capillarity)in the direction of heat flow and forms an ice lens along the freezing front. As the freezing front migrates deeper, additional ice lenses form. The lenses displace soil, so the volume increases even if the moisture content remains constant (layers of ice and dry soil take up more space than the moist soil). Of course, if additional moisture can migrate from the unfrozen zone, the moisture content can increase, and the volume change is even greater.

Behind a cold wall, the heat flow can be horizontal, and the ice lenses vertical, so the wall can be pushed laterally.

The same process can form ice lenses parallel to a slope. When the soil melts, the slope sloughs.

 

[iandig]

Just to add a couple of points to the on-going discussion. Water migrating through the material via cappilary action can and does have an impact on frost heave. When samples of sub-base are tested for frost heave, they are placed in a freezer cabinent, with the top 2/3 in the cold section, and the base of the sample sitting on a pourous disc, which it self sits in a water bath at 4ºC. The cabinent is reduced in temp to less than -18ºC (sorry, can't remeber the exact range) and kept at this temperature for 5 days. As water in the sample freezes, the sample begins to heave, however it is water drawn up through the sample and subsequently causing additional heaving which determines whether or not a sample will fail (more than 15mm heave, the sample is frost suceptible).
Therefore, not only is it important where the cold front is, but also the ability of the soil to draw in additional water which increases the level of heave.
For the first time in years, with the cold winter in the UK we are seeing frost heaving of pavements, so bit of a 'hot' topic at the moment.