Winter construction, earthworks

[peterb1441]

I am facing a contractor who is proposing winter construction in a harsh environment (no permafrost), with a freeze depth of around 2m or so. My opinion is that there should be no frozen soils in any earthworks fill. Again my view, is that frozen soils are not engineered fills, but uncontrolled fills. We all know what happens after earthworks are complete, and along comes the spring thaw. The materials just lose strength. Moreover, the placing of concrete foundations on frozen soils is also a no-no. These soils cannot be adequately prepared and compacted in the frozen state. Does anyone out there have any technical references on construction in/on frozen ground? Happy New year to everybody.

 

[ptmoss]

I don't have a link handy but if you find Army Corps of Engineers, Cold Regions Research Laboratory (Hanover, NH) they have an extensive library on this topic.

 

[DRC1]

I don't disagree with anything you say. However it is possible to do site work and concrete work in the winter, and it commonly done. It is significantly more expensive than doing it in the spring, but more and more construction schedules do not allow time to wait. If the contractor give you a reasonable plan to ensure the work is done properly, You may be able to let him procede.

 

[oldestguy]

A fun subject.

It has been my experience that winter work can be done with good results if you have a good contractor, willing to do some extra work, if needed. It involves such things as discarding frozen soil and using only non frozen soil for compacted fill. Clay type soil, at proper moisture content, works better than sand apparently due to that extra moisture giving off extra heat of fusion.

However, regardless of how careful he is, it seems that the job just cannot come out right if the air temp is below 20 degrees F. If strong wind the temp limit is even higher.

Immediate compaction is required also.

So, below these temp limits don't even try.

 

[boffintech]

Hey oldestguy, Your statement could easily have been written:

"It has been my experience that winter work can be done with good results if you have a good client willing to pay for some extra work, and a good contractor will to actually perform the extra work, if needed."

If everyone the job requirements and expectations are settled upfront it shouldn't be a problem; however, it takes two to do that dance.

 

[DRC1]

We have done a lot of site and concrete winter work. a lot of times 20 is a warm day. There is significant extra cost, both in terms of additional measures needed to do the work and significant ost productivity. However, it is mportant to have every one agree to both procedures and assignment of the additional costs prior to starting the work.

 

[looksatstars]

We are doing some winter construction right now, and its a bit of a fight. I'm working as the owner and the contractor that has not done that much civil work. They hauled in frozen crushed gravel to build a small pad for a water treatment building. The pad is on top of hard bedrock. They placed the soil and compacted it hard. I warned them from the beginning that i was going to do density testing. They all thought it was going to hit 100%. I said it would lucky if it hit 90%. The tester came out and did density tests. the test results were 68%. Of course it can't be that low, so i dug up so holes and seen tiny pockets of snow in the gravel that i guess were registering as voids. The contractor couldnt believe it cuz the frozen soil looked and felt like concrete. He finally put up hoarding and heat to the soil. Now you can walk on it, and you can see your footprints. I could have talked till i was blue in the face but he had to see it before he believed it. Wish i could post pictures on here. Another soil on site that i'm not too worried about is a clay till and that reached the 97% compaction even though it was frozen as well so i think you can compact clay but well graded gravel is a no go.

 

[oldestguy]

A very common situationm with granular material. It may not stick together in clumps, etc., but if below freeing, it won't make compaction.

Shove a thermometer in it and, if below freezing, forget it.

 

[1Kat1]

Frozen soil is a big no no. The soil must be thawed or non frozen. You can do winter construction, but you must heat the soils that have backfilled and compacted. Otherwise any soil that contains frost or ice must be removed, whether it be now or in the spring. Any construction soil utilized on foundations, etc. must be free of deleterous materials, (unsuitable materials). A state or city inspector would go bezerk if they happened upon a site that had frozen materials being utilized or being backfilled on. Frozen soil will thaw and lose it's density, therefore, creating building-foundation to fail.

 

[DRC1]

Although more expensive, we have used crushed stone for fill under footings in the winter.