Arctic Infrastructure Ingenuity: Engineering keeps old and new-buildings stable and safe.

AuthorOrr, Vanessa
PositionENGINEERING

Companies that specialize in Arctic construction spend years perfecting their craft under the harshest conditions. As in many cases in Alaska, logistics plays a huge part of any undertaking.

"Any sort of development starts with the question, 'How do you get there?'" says Jim Campbell, PE, principal engineer and president of PND Engineers, Inc. "Almost any project that you want to build in the Arctic requires that you build roads. While a small number of projects are roadless, most are not."

"Building roads to some of these sites is no trivial task, either," adds PND Principal and Lead Geotechnical Engineer Torsten Mayrberger, PE. For example, on one oil and gas project a company found a considerable amount of oil, but it required a 100-mile access road over extremely rugged terrain and fourteen bridges to reach it. "In that case, it was so expensive to get to the resource that the company had to weigh the costs to determine if it could still be profitable."

Logistics also affects where a project can be built, especially in cases where soil conditions are unknown, according to Jeremiah Holland, PE, senior geotechnical engineer at DOWL. "Much of the work in the Arctic is done in remote locations where companies may not know the subsurface conditions," he says. "Before we can start any design, we need to go explore the area with a drill rig or other tools. This requires personnel and equipment, which drives project costs up quickly."

He gives the example of prospective projects around Nome. "On the shoreline, the soil could be thawed, while on the tundra it may be frozen five feet down," he says. "That's why we drill; it's a challenge to know what we're dealing with."

Building on Permafrost

According to Holland, designing for a building on permafrost is inherently complicated. "You're putting a warm building on frozen ground, which gives you two options--you either protect the permafrost or you thaw it," he says. "In most cases, we go with protecting it, especially in areas where permafrost is pervasive."

In order to keep the ground frozen, buildings may be constructed at-grade on refrigerated gravel pads using passive thermosiphons or elevated above ground on thermopiles. Passive thermosiphons and thermopiles are long, sealed, steel pipes installed into the ground beneath the structure, with radiator fins or the top few feet of the thermopile exposed to cold air at the surface. Natural convection forms as pressurized gas exposed to cold winter air chills to liquid and drops down to the warmer permafrost.

DOWL recently provided geotechnical engineering design and recommendations for...

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