Improving Design Methodologies and Assessment Tools for Building on Permafrost in a Warming Climate

Mr. Kevin Bjella | U.S. Army Engineer Research and Development Center – Cold Regions Research and Engineering Laboratory

RC-2436

Objective

Permafrost presents significant difficulties in the design, construction, and maintenance of horizontal and vertical infrastructure in Interior Alaska where the Department of Defense (DoD) has five major installations and spends billions of dollars a year on military construction (MILCON) projects. Interior Alaska permafrost is particularly problematic because it is “warm” (near 0°C) and ice-rich with massive ice features such as wedges, lenses, and segregation ice. This makes the permafrost susceptible to thaw settlement, which can have adverse to catastrophic impacts on built structures.

The objective of this project is to develop a set of knowledge-based decision tools that will provide better information to DoD planners and engineers faced with building in this challenging environment. These tools will aid in the full spectrum of tasks related to construction in Interior Alaska, beginning with identifying favorable building sites or roadway routes using satellite/aerial imagery, characterizing the subsurface conditions using a combination of drilling, geophysical measurements, and geostatistical methods, and balancing risk and cost when matching a foundation design to subsurface conditions. Lastly, this project will address how to incorporate instrumentation into a foundation to detect early signs of foundation failure and/or thaw settlement.

Back to Top

Technical Approach

This project consists of two research components and a synthesis component. The first research component focuses on developing more systematic, cost-effective ways to produce high-quality characterizations of permafrost soils prior to construction. Current practice consists of exploratory drilling on spacings dictated (and often severely limited) by the project budget. Many geophysical methods are available to aid in subsurface characterization (ground-penetrating radar [GPR], electrical resistivity [ERT], seismic/acoustic). These techniques see little use in MILCON projects and are rarely used in concert. This investigation will focus on optimizing the combined use of all of these technologies to provide more accurate (and less expensive) assessments of subsurface conditions with improved vertical and horizontal resolution. The team will accomplish this by deploying all these tools at field plots covering the range of permafrost conditions found in Interior Alaska. At these plots, drill cores and survey measurements will be collected at a denser spacing than would be practical in normal MILCON situations, allowing for highly detailed representations of the subsurface stratigraphy and ice content. Using geostatistical methods, the team will then systematically eliminate input data, regenerate subsurface conditions, and compare to the original representation until the relationships between sampling frequency, accuracy, and methodology are determined. Guidance will then be developed on how to minimize characterization costs.

The second research component will explore the utilization of next-generation foundations in DoD permafrost construction and will create a logical system for guiding designers and engineers in selecting the appropriate foundation. This will take into account subsurface characteristics, structure longevity, risk tolerance for foundation failure, and budget. A key part of this component will be to analyze existing data (thermal and structural) from several novel instrumented foundations in Interior Alaska and Greenland. The project also will investigate how to best instrument foundations in permafrost so that post-construction thermal and structural problems can be recognized early.

In the synthesis component, the project will combine existing (but often elusive) information with the new results in a decision support system (DSS). The DSS will be a guide for designers and engineers to decide how to investigate potential sites and build the most cost-effective designs for permafrost, especially in the context of anticipated climate warming in Interior Alaska. The DSS will have map-like ArcGIS characteristics and a user-friendly “TurboTax”-like interface. Lastly, and most importantly, this work will allow for an update to the current guidance documents used by engineers and planners of DoD facilities. The Army/Air Force engineering manual UFC 3-130-04 Foundations for Structures: Arctic and Subarctic Construction supersedes TM-5-852-4 dated 15 October 1983, which was based on a monograph  published by the Cold Regions Research and Engineering Laboratory in 1980.

Back to Top

Benefits

The benefits of this work to DoD will be (1) an improved and objective methodology for selecting where to build on DoD facilities in Interior Alaska and elsewhere in the Northern tier, (2) enhanced ability to assess permafrost conditions, and (3) greater ability to match the most cost-effective foundation system to the site. In combination, the preceding will save money and should result in improved performance of infrastructure where permafrost is present. The benefits to the scientific and engineering community will be: (1) new knowledge of how to combine multiple geophysical methods and drilling when delineating permafrost and areas with high ground-ice content, (2) a decision support tool for combining geophysics, drilling, and  spatial statistics, (3) performance data on novel foundations in permafrost, and (4) a highly utilized guidance document updated to current methods and tools. (Anticipated Project Completion - 2018)

Back to Top

Points of Contact

Principal Investigator

Mr. Kevin Bjella

Cold Regions Research and Engineering Laboratory

Phone: 907-361-5171

Program Manager

Resource Conservation and Resiliency

SERDP and ESTCP

Share