19 Jul 2024

Permafrost and Groundwater Characterization at the Proximity of the Landfill, Fort Wainwright, Alaska

Abstract: This report summarizes a site investigation at the vicinity of the landfill, a discontinuous permafrost site, at Fort Wainwright, Alaska. The objective of this effort was to characterize the permafrost extent and groundwater flow at the study area, and to compare newly collected subsurface characteristics with historical datasets. The main tasks for this effort included lidar and remote sensing analyses, geophysical investigations, a tracer dye study, contaminant trend analysis, and installation of soil temperature sensors. Findings included changes in stream channels and watershed boundaries, and elevation losses (0.2 m to 1 m) east and northeast of the landfill. From frost probe measurements, we found that depths to permafrost were up to 1.5 m deeper in 2021 than in 2010 where the difference in depth ranged from 20% to more than 350%. Furthermore, we detected a reduction in lateral permafrost extent from geophysical datasets. The groundwater flow direction, as detected through the dye study, was south to southwest. Dye was detected up to 2,300 m from the injection point. Groundwater travel times, as calculated from the dye study, varied greatly. For upcoming historical comparisons, it is recommended that data collections are performed using similar methods as described in this study.

17 Jul 2023

Testing Expedient Ground Anchor Solutions for Guyed Towers in Remote Cold Regions: Considerations for Cold Remote Regions with Limited Tools

Abstract: Ground anchors connected to guy wires for tower structures in cold climates suffer from frost heaving, which causes loss of wire tension and subsequent structural instability. It is necessary to understand what ground anchors are available to resist this tendency yet are still capable of expedient installation in remote areas. To that end, three metal, traditional ground-anchor types (arrowhead, bullet, and penetrating auger) and one novel polyvinyl chloride (PVC) T-post anchor were evaluated in frozen gravels and frozen silts at a research facility in Fairbanks, Alaska. Criteria included installation capability, failure loading, and removal ability. Additionally, expedient installation techniques for use in field conditions were also demonstrated. All three traditional ground anchors failed to penetrate frozen gravels. The penetrating auger also failed to penetrate frozen silts, but the arrowhead and bullet anchors did penetrate frozen silts with difficulty. The PVC anchor is capable of being installed only in a predrilled pilot hole. Under flexural load, the arrowhead anchor cable failed at 3686.72 lb, and the bullet anchor cable failed at 1753.44 lb. The PVC slid out of its hole at a direct-pull force of 1978.24 lb and failed under flexural stress at 202.32 lb.

22 Jul 2021

Sublimation of Terrestrial Permafrost and the Implications for Ice-loss Processes on Mars

Abstract: Sublimation of ice is rate-controlled by vapor transport away from its outer surface and may have generated landforms on Mars. In ice-cemented ground (permafrost), the lag of soil particles remaining after ice loss decreases subsequent sublimation. Varying soil-ice ratios lead to differential lag development. Here we report 52 years of sublimation measurements from a permafrost tunnel near Fairbanks, Alaska, and constrain models of sublimation, diffusion through porous soil, and lag formation. We derive the first long-term in situ effective diffusion coefficient of ice-free loess, a Mars analog soil, of 9.05 × 10⁻⁶ m² s⁻¹, ~5× larger than past theoretical studies. Exposed ice-wedge sublimation proceeds ~4× faster than predicted from analogy to heat loss by buoyant convection, a theory frequently employed in Mars studies. Our results can be used to map near-surface ice-content differences, identify surface processes controlling landform formation and morphology, and identify target landing sites for human exploration of Mars.