Creep Deformation of Ice-Rich Silty Permafrost Under the Interactive Effects of Solid Fraction, Temperature, and Axial Stress

Ziyi Wang , Ming Xiao, Matthew Bray, Margaret Darrow, Dmitry Nicolsky, Xiaohang Ji

Permafrost degradation influences permafrost’s creep deformation and stability, posing
challenges for existing and future civil infrastructure in cold regions. The secondary
creep rate is the controlling parameter for the design of civil projects. Solid fraction,
temperature, and axial stress may interactively affect creep deformation rate of ice-rich
silty permafrost; yet their interactive effects are not well understood. In this study, field
samples of relatively undisturbed permafrost from the upper 1.5 meters of the Arctic
Coastal Plain near Utqiaġvik, Alaska were first retrieved and analyzed. We conducted
constant stress creep tests, unconfined compression tests, and unfrozen water content
tests to assess the mechanical and physical properties of the permafrost cores. From
these tests, mathematical relationships between secondary creep rate and volumetric
solid fraction, temperature, and axial stress were proposed based on Glen’s flow law.
Combining the experimental results and mathematical relationships, we quantitatively
investigated the interactive effects of solid fraction, temperature, and axial stress on
creep deformation. The research yields the following findings. (1) Increasing volumetric
solid fraction can either increase or decrease permafrost creep rate depending on
temperature and axial stress. (2) At lower temperatures and lower axial stresses, for
example, -10°C and 500 kPa, increasing volumetric solid fraction enhances
permafrost’s resistance to creep and decreases creep rate. (3) Increasing temperature
increases unfrozen water content and diminishes the strengthening effect of increasing
solid fraction. This diminishing effect caused by unfrozen water content is amplified at
higher solid fractions. (4) At warmer temperatures near the melting point and higher
axial stresses, for example, -2°C and 1000 kPa, permafrost at higher volumetric solid
fractions is more susceptible to creep deformation with an increased creep rate.