Creep Behavior of Ice-Rich Warm Peaty Soils along the Trans Alaska Pipeline System at Lost Creek, Alaska

Abstract

In Interior Alaska, a slope underlying the Trans Alaska Pipeline System has recently experienced downslope movement, which is attributed to a buried frozen, ice-rich peat layer. We performed a field investigation of the site including coring and sampling, and conducted a suite of laboratory tests including mechanical tests at temperatures between -0.56°C and -5°C to quantify the secondary creep behavior and to estimate the impact of soil cooling on the creep deformation. We tested a variety of soils, including ice-rich silt, silty peat, and peat with the majority having an organic content of 10% or greater. The results indicated that temperature has a strong control on the resulting time-dependent mechanical properties. Here we provide secondary creep power law relationships for these soils. The analysis indicates that cooling the soils can be effective in reducing creep movement; for example, cooling by 1.1°C from -0.56°C to -1.67°C results in an order of magnitude reduction in the shear deformation rates. These results are significant as they add to the limited amount of work done on the time-dependent mechanical behavior of ice-rich peat and organic soils at warm sub-freezing temperatures.