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Building on Muskeg, Peatlands, and Permafrost

 
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Location: Thunder Bay, Ontario, Canada
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Hi all,

This is a major challenge. How to construct buildings on muskeg / peatland where there is a large percentage of water in the soil, and the action of freeze / thaw cycles eventually push foundations out of level?

The standard approach is to remove all the muskeg and replace it with some sort of fill. This is extremely labor intensive and in many Northern communities the muskeg goes down deeper than 50ft.

So I'm wondering if anyone has any bright ideas about either construction techniques that decouple the foundations from the effects of frost heave (like floating it on a giant Styrofoam pad), or stabilizing the muskeg through the action of microorganisms.

Since this stuff is high in carbon material, I'm wondering if the introduction of sufficient air and Nitrogen might trigger a more complete decomposition process.
 
master steward
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How big do these buildings need to be?  I believe in unstable areas of the Southwest US they use concrete slabs with tensioned rebar in them to maintain a flat shape as the soil shifts below.
 
pollinator
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So these are a few very different issues...

For permafrost - this is very well documented. The principle is that you need to isolate the frozen soil from the building, to prevent thaw. No thaw = no settlement (harder with climate change). The typical solution for small to medium buildings is building on stilts + some insulation. You also need to worry about any water pipes, sewer pipes, etc (one of the reasons many reserves up north rely on water trucks). A good resource is : https://nrc-publications.canada.ca/eng/view/accepted/?id=8896d31f-b220-4a29-af64-a673b9d4f2da There are also some cool projects up north where they are actively using cooling coils to prevent the permafrost from melting (which is WAY beyond the scope of what you are doing probably, and far from environmentally friendly).

Muskeg is more challenging, I've not personally worked with it. One suggestion off the top of my head that i have seen employed in soft soil is piling - drive piles down to the competent till or bedrock beneath the muskeg. There are a bunch of different types of piles, depending on the application, including some that are appropriate for smaller buildings. Not necessarily cheap, but maybe more feasible than dewatering and replacing 50 ft of muskeg! I've seen some research about the modern use of corduroy roads in muskeg to "float" overtop, but I don't recall the details of the settlement they observed, and a gravel road is much less settlement sensitive than a building.

For frost heave (in areas where the average soil temperature is above freezing, ie, no permafrost) - the typical approach is to get below the frost level, or insulate to keep the frost level from reaching the bottom of the foundation, in more northern areas. You can do some interesting things with extending insulation horizontally away from the foundation, as well as running it along the edge of the foundation. You may also want to consider adfreeze affects (tendency of soil to freeze and jack up piles, etc). They typically employ some sort of a membrane (slippery plastic) to decouple the foundation from the frozen soil. I could probably dig up some research on this too, if you're interested. There's, I believe, a very old National Research Council of Canada document that explains this very well (and innumerable textbooks, web resources, etc).

What are you thinking about building?


 
Nick Kitchener
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They recently built a 6-plex. Excavated a lot of ground for that one.

These areas are not really suitable for building on but there is little alternative.

They don't build roads up there because the combination of ground subsidence and frost heave destroys them. Buildings slowly sink.

Even in town here you see concrete stairs sitting up in the air because the ground slumps so much. Lumps of wood emerge through steel reinforced concrete driveways due to the hydrolic force created by the ground freezing in winter.

In many places up north these peat lands sit on permafrost. Foundation piles transfer heat over time and melt it, which causes the foundation to sink.
 
pollinator
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I looked at a peat bog, and figured a houseboat would be just dandy.. doesn't scale up past single family home too well though!
 
Nick Kitchener
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I'm looking into a 40ft diameter geodesic dome greenhouse incorporating aquaponics and a communal meeting area.

The 6plex construction depleted all the locally available rock and shipping materials is expensive. Both approaches aren't all that ecologically friendly either.

We need to stabalize the foundation somehow and current methods are really not great
 
Mike Haasl
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What other building materials do you have at your disposal?  Can you build a 40' diameter boat to set on the muskeg?
 
Dillon Nichols
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Mike Jay Haasl wrote:What other building materials do you have at your disposal?  Can you build a 40' diameter boat to set on the muskeg?



With it being a greenhouse, the boat idea starts to seem sketchy.. surely some insulated thermal mass below ground would be highly desirable up there.. at a glance, this seems tricky to combine with floating the thing... hm.
 
Mike Haasl
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I know, I'm just trying to help you come up with a structure that holds itself together despite shifting support underneath.  Maybe a raft of logs?  Maybe a prestressed concrete slab?  
 
Dillon Nichols
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Mike Jay Haasl wrote:I know, I'm just trying to help you come up with a structure that holds itself together despite shifting support underneath.  Maybe a raft of logs?  Maybe a prestressed concrete slab?  



Maybe sufficient insulation, could act as the floatation for the concrete?

But where the heck do you get the materials for any of that?
 
Catie George
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Ok,let's define this problem better...

Is your site on permafrost, discontinuous permafrost, or thawed ground? What's the frost depth if you are on thawed ground or the melting depth if you are in permafrost (active zone)?

As a novel solution, I just heard about an airport built on ground where they knew it was going to settle. They incorporated basically jacks between the foundation and the structure so they could continuously raise and lower parts to keep the building straight. Very creative.

I think you are talking about thawed ground, and I am guessing a frost depth of 3+ m?  If so, it doesn't matter if you transfer heat to the foundation area, just insulate like crazy to keep it from ever freezing beneath your building and pile to solid ground. In any foundation design, the goal is to prevent freeze thaw cycles from ever happening.  In my experience, once you get to 1.5 m of frost depth or more, insulation starts being crucial to save costs in foundation design.  The issue in the thawed ground is 1) keeping things from freezing and 2) finding that solid ground. From the piles, you can build an insulated raft at surface, possibly even larger than your building so you can have walkways, etc. It's basically a giant version of the house on stilts concept, and is used for bridges and other very large structures. Possibly not a cheap solution though. This is an oldie but a goodie for explaining foundation design .... https://nrc-publications.canada.ca/eng/view/object/?id=e690da64-8b5b-40f2-a653-6cb36641738d , also this one http://web.mit.edu/parmstr/Public/NRCan/CanBldgDigests/cbd081_e.html

The issue with "raft" ideas is the squishable nature of muskeg with its high organics and the variability of the water content. Picture a peat bog or a swamp ... Even assuming you can make the raft large enough and structure light enough it doesn't just sink,  unless you can keep it from thawing, you will get massive differential settlement or heave. Picture a boat not brought out of the water for the winter, except with "water" that doesn't have equal water content.  

It sounds like you may need engineering advice specific to your location. I would look for a firm with experience with construction for the various ring of fire developments or other muskeg developments. If the community can't afford that or you want novel, possibly impractical solutions.... Maybe talk to a university with a decent structural or geotechnical engineering program.... they are often looking for good design projects for their upper year students, and this one might hit a lot of "good project" buttons.


 
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The answer is simple, but expensive for muskeg...drive piles into the ground until it hits bedrock. That is how they secure bridge piers and foundations for buildings.

I was a welder in construction in my early days, and I was assigned to a pile driving crew. Piles are 40 feet long so they would drive them down, I would weld on another 40 foot H-Pile, and then drive them down again. At times we would drive them 300 feet until we hit bedrock. Typically they are driven every 5 feet or so basically the bridge or building is on steel stilts that extend down until they are sitting on bedrock.

A person can do the same thing with wooden poles because wood does not rot under the soil because there is no oxygen after 12 inches of depth. if you do not believe me, look at a rotted fence post, it actually rots at the ground line, not deep down.

The real problem of building on muskeg, permafrost or peat is NOT in how the building is supported, but rather with the percolation of a conventional septic system. Where I live, we have no building codes, BUT we do have to have permitted septic systems and they cannot be built in wetlands or on bedrock. A person can import rock to allow the percolation test to pass, and thus "make it what it ain't", but it is prohibitively expensive to do.
 
Nick Kitchener
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Yeah I considered an oil rig kind of concept where you have a floating platform and piles that act as stabilizers  / keels to keep the thing upright and level. Not too sure how that would work in a semi-fluid though.

Another thought is to excavate down, lay a plastic sheet to prevent moisture wicking up, then laying in a thick layer of wood chips (like 10ft thick), another layer of plastic to prevent moisture entering in from the top or sides, and capping it with a concrete pad. The wood chips will squish, but I noticed while reading up on freezing index literature that woodchips are actually pretty good insulators. They do compress, but they might act like suspension in a vehicle to absorb varying upward pressure from underneath. It's an expensive experiment to have go wrong though.
 
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Can you build it above ground so the soil is not altered in the sence od thawing. Piles with a deck 4 ft about the ground?
 
John C Daley
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This may helpbuilding on frozen ground
From the above website, this note stands out;

Engineers sometimes solve this problem by preventing the ground under the building from getting warm. They put the building on top of a steel frame, a few feet above the ground, so cold air can flow under the house. The cold air stops the permafrost from thawing. Another way to stop damage from thawing permafrost is to thaw the ground first. This method makes the ground more stable to build on. Then there is no danger of the ground beneath the new structure refreezing, because the structure keeps the ground from freezing.



from webpage

quote]Thermosyphons: This newfangled technology consists of large cylinders, drilled deep down into the permafrost, which extract heat from the ground and release it into the atmosphere. They don’t require energy and have no moving parts; instead, they use a liquid-vapour system and heat transfers. These are being used more and more in construction in the North, and some folks have an amazing amount of faith in the technology. The federal government is relying on them to keep arsenic in Yellowknife’s Giant Mine frozen and out of the groundwater in perpetuity. But in 2013, when Iqaluit’s new RCMP detachment began to sink, the engineer behind it went to the press saying the two malfunctioning thermosyphons had been deliberately sabotaged. So if you plan on building with these puppies, but want to keep out enemies, maybe build a tall fence around them as well.
thermosyphons
 
So I left, I came home, and I ate some pie. And then I read this tiny ad:
Food Forest Card Game - Game Forum
https://permies.com/t/61704/Food-Forest-Card-Game-Game
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