AUTC project number: 410018
William E. Schnabel (UAF)
Roads and bridges constructed in permafrost areas are often damaged when the thermal state of the soil changes. Characterizing soil subsurface conditions and designing for them is key to constructing a road or a bridge. Geophysical methods such as electrical resistivity tomography and ground-penetrating radar, currently under-utilized in arctic subsurface investigations, could be powerful and relatively inexpensive tools for infrastructure planners. Current research indicates that using ERT and GPR together as part of a geophysical survey can effectively map the extent of ice wedges, ice lenses, massive ice, and talik (a layer of year-round unfrozen ground within a permafrost area). This effort by scientists at the University of Alaska (Anchorage and Fairbanks campuses) and Laval University will describe four case studies in which geophysical surveys are implemented into subsurface investigations along road and bridge alignments being conducted by ADOT&PF. Although results will be used to augment existing ADOT&PF projects, the team's primary goal is to provide guidance on making ERT and GRP a routine component of characterizing arctic and subarctic soils. The four case studies will produce initial information for a database describing geophysical properties characteristic of permafrost and talik conditions in Alaska. Thereafter, previous and new reports on the geophysical properties observed in other frozen environments in Alaska can be added to assist in interpreting future geophysical surveys. This project will provide protocols for carrying out and interpreting arctic/subarctic geophysical surveys, as well as guidance for selecting the appropriate methods and estimating survey costs.