Cryostructure and Uniaxial Compressive Strength of Ice-Rich Permafrost in Northern Alaska

Knowledge of ground ice type and volume in the upper permafrost are vital for engineering design in cold regions. Cryostructure, which describes the pattern of ice inclusions, is an indicator of the formation characteristics and geology of permafrost soil and affects the geomechanical behavior of permafrost. In this paper, we present field sampling of relatively undisturbed permafrost on the Arctic Coastal Plain near Utqiaġvik, Alaska. We characterize the cryostructure of the permafrost samples that were retrieved from five boreholes, which primarily consisted of organic silty sand with suspended ice inclusions. We conducted a series of unconfined compression tests under constant strain rate at temperatures of −2°C and −10°C to investigate the geomechanical behavior of selected permafrost cores. Here, we present the effects of temperature, dry density, water content, and cryostructure on the geomechanical behavior of ice-rich permafrost. Considering the effect of temperature, an empirical equation for short-term peak compressive strength is developed based on the experimental results. A quantitative example is provided to demonstrate how the varying geomechanical properties affect ultimate bearing capacity of shallow foundations in permafrost.