This project will develop a model that shows impacts of permafrost cycling/degradation on military buildings. The primary objective of the project is to provide the tools necessary for engineers to incorporate thaw settlement adaptation into the retrofit of existing buildings on installations in cold regions. Current options to counteract permafrost thaw are limited and expensive; the current standard approach for mitigating the risks of damaging thaw-induced differential settlement is to simply overdesign the foundation to prevent marginal thermal impacts due to tight project constraints and allowing for the worst-case thawing scenario. This project aims to provide the basis for a more informed approach that incorporates uncertainty in time-dependent parameters—an essential capability for adapting to the effects of natural hazards on installation infrastructure.

Permafrost is soil, rock, or sediment that remains completely frozen (at or below 0°C or 32°F) for at least two consecutive years. It's mainly found in polar regions, such as the Arctic, and in high mountain areas. This project will accomplish the objectives through two components: 

1. The first is a reliability-based structural retrofit design procedure that incorporates permafrost thaw data. By directly addressing the projected thaw settlement during design of retrofits, the assumed natural hazard scenario becomes a decision variable that can be controlled by the designer, opening up new alternatives that would otherwise be ignored by the conventional, over conservative, approach. This component will take advantage of developments in the growing field of time-dependent reliability, which provides the statistical framework for evaluating reliability of systems for which the load, resistance, or both are varying in time. While it will be developed and demonstrated for design of retrofits for an existing building, this procedure will be easily translatable to design of new buildings as well. 
2. The second is a decision-support tool that uses the expected-value-of-information concept to quantitatively weigh the cost of data collection against the benefit that information can provide. Each parameter that is monitored is associated with costs—i.e., up-front cost of sensors and incorporation of mitigation measures—but may provide benefits in the form of future risks avoided by sensor-triggered adaptations. This tool is crucial for the cost-effective development of the Digital Twin (DT) that is needed to support the retrofit design procedure in the first component. More broadly, it will provide a basis for cost-effective DT implementation, which can also be used for design and retrofit of other infrastructure systems to cope with permafrost thaw. 

The tools developed will advance the value of a DT concept for infrastructure retrofit design and management under uncertainty with a specific use-case for structures on permafrost. This project is linked to a critical mission; it equips engineers with the tools to effectively adapt and retrofit infrastructure in cold regions, ensuring the stability and longevity of critical buildings on permafrost, safeguarding military assets in Arctic environments. A 2019 report to Congress by the Office of the Under Secretary of Defense titled, "Military Structures in Permafrost Areas" stated that deep foundations—the preferred option under current practice when permafrost thaw settlement is a structural concern—can add between 10%-37% to the cost of the foundation, depending on the type of building, not including potentially significant costs associated with the added difficulty of driving or drilling piles in frozen soil. This project would provide an additional option to engineers with the potential to avoid much of these extra costs through adaptable retrofit and design, without compromising the long-term reliability of the building. This additional option would be especially valuable on permafrost sites where the bedrock is too deep for an end-bearing deep foundation, since deep adfreeze piles or shallow foundation options for permafrost stability are expensive and complex. The project team plans to transfer their additional option in an innovative and usable way to empower engineers making design decisions in the Arctic. More broadly, this project would represent a crucial step toward installation resilience for the Department of War, which is critical to mission continuity in the Arctic. (Anticipated Project Completion - 2026)