soil freezing point 1

[kjo5280]

I am currently working on a land fill cover project, and we are coming into winter. The specifications say that we can’t place material on frozen ground. Does anyone have a good analysis for frozen soil calculations? This is in the Denver area, and temps are warming up well above 32 during the day. I don’t believe that the actual soil is frozen if the ambient temp is 32 degrees F. Let me know if anyone has any input or case studies to support this.

 

[CarlB]

If it has dipped only a little below freezing at night, frost should be in the upper inch. Should be easy to check by scratching the ground and looking, more reliable than calculations.

If soil doesn't need to be compacted to 95% minimum I don't see any problem with placing unfrozen fill on a thin layer of frozen ground.

 

[kjo5280]

The requirement I think is only 90 percent. I just got back to the project. We have a 2 foot layer we are putting over a liner. And the material (rubblized concrete) we now are getting ready to place on that is the concern. The spec says we can't place on frozen material and given the void ratio in the upper material, I don't believe it will be a problem in the long run. However, I have to be able to justify this somehow. The concern is frost heave in respect to undermining the compaction. I am awaiting the soil tests to see what the actual moisture content is.

 

[DRC1]

If you place material on frozen ground, the material can become mushy once it thaws. Ambient air temperature is not a good indication of frost. The soil will gai or lose heat muc more slowly than the air. thus if the night temperatue dips below for a few hours at night, there will probably be no frost. conversely, If the temperature goes above after frost has set in the ground, the warm air for a short period will not be sufficenrt to thaw the ground. If there is a thin layer of frost, it is best to remove it by back blading. If it ifs only an in ch or so, and the material is good material, youmay be ablre to work it into the fill once you backblade it. You really need to look at it and see if that will work though.

 

[oldestguy]

Keep in mind one basic thing about soil freezing. The stuff that freezes is water. Water gives off heat of fusion when it freezes. The more water, the less the depth of freezing under a given situation.

Thus, sand, with low moistur content, freezes more deeply than clay.

Thus if you have to remove the frozen layer, frozen low moisture soil is a thicker layer than high moisture material.

 

[dgillette]

kjo5280 - Just for my curiosity, did you measure the frost penetration on any of those recent cold mornings? It got down to about 20 at my place near Golden (el. 5900) once last week.

DRG

 

[kjo5280]

No frost penetration measured