What is Permafrost?

If you’re looking to break ground on a new construction project in Anchorage or anywhere that experiences frigid temperatures, you may be wondering, “what is permafrost?” Permafrost forms when the ground in an area remains at or below freezing temperatures (0°C, 32°F) for two or more years. It may impact the most immediate ground layers, or it can form anywhere from several inches deep to thousands of feet deep.

Far from just a cold or snowy layer on top of the ground, permafrost impacts the integrity of structures and creates many challenges that must be overcome to complete a successful construction. Learn more about permafrost engineering, design, and construction below.

Challenges of Permafrost Engineering, Design, and Construction

Now that we’ve given some basic parameters and covered the definition, concerns of permafrost construction arise naturally. Whether you’re gearing up for a public, commercial, or residential job, permafrost can create many challenges and potential hazards. Working with an experienced geotechnical engineer from the start will allow you to identify the extent of the issue and begin to plan to counter the impact.

Successful permafrost engineering, design, and construction are wholly reliant on assessing risks and taking proper precautions. When working with permafrost, geotechnical engineers will conduct site investigations to collect data to determine if a site is thaw stable or not. If not, plans must be made to ensure that construction doesn’t disrupt the integrity of the soil. Working with a geotechnical engineer from the start is the best way to plan for risks and complete a sound and cost-effective build. However, geotechnical engineers can contribute and advise regardless of your current building phase.

Potential Permafrost Hazards

You may be wondering what hazards can result from building in an area where permafrost is present. Unfortunately, permafrost can lead to a number of problems. As reported by the Alaska Division of Geological & Geophysical Surveys, permafrost covers nearly 85% of the state of Alaska. So, if you’re planning to build in the state, or in a similarly cold region, permafrost must be dealt with. The key to building on it is to maintain the status of the foundation. A practical way to approach this is: “If it’s frozen, keep it frozen; if it’s thawed, keep it thawed.” Construction can disturb the soil, so proper planning is key. If a building is constructed that gives off too much heat, the permafrost can thaw and a building could sink.

Thawing can be mitigated by a number of temperature control techniques. A structure can be elevated to allow cooling air to pass beneath the structure to keep the soil frozen. Additionally, thermopiles and thermosyphons can be used to regulate the temperature of the soil. A more active approach can be taken wherein refrigeration systems can be installed. Depending on the goals of the build, the site conditions, and the type of structure, different temperature regulating techniques may be deployed.

Along with thawing, permafrost can also expand and cause frost heave. Solidifying structures with critical reinforcement can mitigate damage caused by subsurface shifts. Building on permafrost is no easy task — subsurface changes of any kind can threaten the integrity of a build. Working with a geotech to plan for the specific risks found at your site is critical.

Consult With Central Geotechnical Services

Beginning a permafrost construction project can seem incredibly overwhelming. Working with the right team to create an effective plan will ensure that the build is successfully completed. Here at Central Geotechnical Services, we’ve worked on projects in diverse environments and can offer our services to help improve construction at any phase. Whether you’re looking to talk shop on a potential project, or if you want to discuss concerns on an ongoing job, contact us today. Our highly-skilled team can offer insights to help you complete your project in an efficient and safe manner.