That Sinking Feeling

Why is that building sinking into the dirt?

Writing and describing Permafrost, Frostjacking and Frostheave in Northern Climates

If it’s frozen, keep it frozen. If it’s thawed, keep it thawed

-First rule of arctic engineering.

Not only does a structure build in northern climates have to survive the harsh elements, but it has to be able to interact with the phenomenon of permafrost. When permafrost is not taken into account during construction, warmth from the structure causes it to melt. This in turn causes the soil beneath to collapse. Then subsidence of the structure occurs.

I decided to write this blog post to help people understand this phenomenon when they are looking through pictures of Alaska and see the building leaning and sinking.

Alaska Permafrost information and Map

https://dggs.alaska.gov/hazards/permafrost.html

Permafrost

As mentioned in the website above permafrost is defined as a ground with a temperature that remains below freezing for more than 2 consecutive years. Most of the southern half of Alaska (including Chicken, where our cabin is located) is a region of discontinuous permafrost.

Construction in Discontinuous Permafrost

This creates a quandary to the rule above. How does one keep something frozen and thawed at the same time? In the region of discontinuous permafrost, where the soil may be expanding, thawing and melting at different rates, this leads to heave and jacking if not done properly.

This is also problematic where you have different soil types that absorb moisture, then freeze and thaw at different rates. The City of Dawson, built on the mudflats of the Yukon and Klondike rivers is notorious for this type of subsidence and jacking. In the winter, the ground would freeze solid, but in the summer, the streets would turn into a quagmire of sloppy mud and gravel as the different soil types thawed and subsided.

Some of my civil engineering friends can discuss at length the various gravel types used for construction and their merits when it comes to cold region application. But for the purpose of this blog, I will stick to what we did for construction of our cabin.

Digging Down

The soil has to be dug down to gravel and the permafrost must be melted completely before construction. When we built our cabin, we spent 2 years moving earth, shoveling gravel, compacting and allowing the permafrost to melt beneath where we planned to build the structure.

Construction

Due to the size of the structure, we built it on jacks to allow for leveling later. We also waited another year to install windows. This not only allows for the gravel beneath the structure to settle, but the expansion and contraction of the logs themselves as they dry out and acclimate.

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Gold Rush Structures

Due to improper construction and a lack of understanding of managing permafrost, many structures from the era of the Alaska-Klondike Rush are subsiding into the earth. At the time they were built, the miners cared more about digging gold from the ground than building structures that would last. In Dawson, the conditions created by the freeze cycle of the soil from the Yukon and Klondike Rivers wreaked havoc on the buildings. What flooding and subsidence did not destroy, fires did.

Thanks for reading! My next post I will be talking more about our building plans and alternative energy project in the interior of Alaska this summer. My Alaskan horror novella, The Dark Land, is available on Amazon.