Frozen soil has a rheological behavior close to the soft rock category and the rate-dependent behavior of frozen clay soil is complex and affected by a number of factors (i.e. clay mineralogy, void ratio, stress history, pore fluid salinity, and available interlayer unfrozen water). Large number of experimental studies illustrated the rate-dependent mechanical behaviors of frozen soil. Nevertheless, there were limited studies on constitutive modeling of the time-dependent stress-strain behavior of frozen clay soils at different frozen temperatures. The objective of this study is to numerically investigate the time-dependent behavior of frozen clay soils at temperature ranges from -2oC to - 15oC. The Drucker-Prager model is adopted along with the Singh-Mitchell creep model to simulate time-dependent uniaxial compression behaviors of two frozen sandy clay soils. The constitutive modeling is validated against a series of experimental uniaxial compressive test results, where results show that a high deformation rate tends to generate brittle failure with post-peak softening behavior and a low deformation rate result in a diffuse failure associated with strain hardening.

The infrastructure in the Canadian Arctic has been influenced by climate change in the past decades. Timber piles, traditionally used as the primary pile type in the Arctic, are particularly vulnerable to climate change and other environmental impacts. The serviceability of timber piles is impaired by the seasonal temperature change that leads to subsidence and heave of the piles, and the pile shaft materials are being decayed by physical, chemical and biological actions. A technique is needed to refurbish damaged timber pile foundations in the Arctic. Among various remediation methods, the wood blocking system is often adopted in Northwest Territory owing to cost-effectiveness and efficiency. The present paper shows a wood blocking system for the remediation of timber piles supporting a three-story apartment building in Inuvik, NWT. The natural topsoil was removed and refilled with compacted coarse gravels. The wood blockings were located on the new filling material. Four sides of the wood piece stack were arranged to enclose the damaged pile and two pairs of the wood wedge were adapted between the floor beam and the wood piece stack. Although this technique is common, monitoring of the performance has been rare. To validate the workability of the wood blocking system and provide early warning for excessive building movement, a field monitoring program consisting of 6 Linear Potentiometers was deployed in October 2019. The movement data has been collected and transferred with a cellular modem via the mobile network. The ground temperature and air temperatures can be obtained from existing monitoring programs in Inuvik. By combining the measurement of displacement and temperature of more than a 6-month period, the factors that dominate the performance of wood blockings and the building will be identified in the present paper.

Cement has been widely used to modify soft and problematic soils in North Europe, Japan, and the USA for decades via a deep mixing method. Nonetheless, most of the published research was limited to clays with high moisture content, low cement content, ambient condition, and short-term stability. The present research investigates the engineering properties of Edmonton cliff clay treated with a high content of Portland cement served as a deep mixing foundation for heavy load and subjected to severe weather conditions in the long-term point of view. The cement content is higher than 20% and the cement-treated clay would suffer freeze-thaw cycles during its lifespan due to the seasonal temperature changes. This paper presents a series of laboratory tests of soilcrete specimens subjected to freeze-thaw cycles. The specimens of cement-treated clay (i.e., soilcrete) were cured for more than 28 days. A temperature control device was assembled to conduct the 3-D freezing and thawing on the cylindrical specimens at the target temperatures. Isotropically consolidated-undrained tests were used to measure the stress-strain relationship of soilcrete specimens under a confining pressure varying from 100 kPa to 3 MPa. The permeability of soilcrete specimens with various consolidation pressures, freezing temperatures, and curing days were determined. The microstructures of cement-treated clay failure planes and external surfaces were inspected using the scanning electron microscope. The porosity of cylindrical samples and porosity distribution among them were determined by the computed tomography images. The results of these tests show the strain-softening behaviour of specimens. The cohesion of specimens remained very strong at the residual state. The new image analysis method predicted porosities that matched the estimated values.

Screw micropiles have been recently introduced to North America as a new foundation type. The screw micropile is a steel pipe pile, threaded and tapered along its lower segment. It is installed using torque thus eliminating the need to excavate, or refill with concrete. Due to the unique characteristics, screw micropiles have major advantages such as lightweight, large capacities, reusability, and rapid installation, compared to conventional straight-shaft piles. Screw piles may present a better solution for arctic foundations that currently rely on drilled and backfilled with slurry or gravel straight steel piles, because conventional piles used in the Canadian Arctic require time-consuming freeze-back. However, currently there are no guidelines for use of screw micropiles in permafrost regions. The present research investigated the engineering behaviour of screw micropiles subjected to short-term loading conditions in frozen ground using the cold room facilities at the University of Alberta.
In the present research, segments of full-size screw micropiles with a shaft diameter of 89 mm were loaded under constant displacement rate in frozen soils to investigate the axial pile capacities and load-transfer mechanism. The effects of salinity, temperature, ice content and pile shaft shape upon the time-dependent deformation of model piles are being examined. Preliminary testing results showed that the pile capacities decreased with the increase in temperature and ice content. The torque when installing the piles was recorded and used to infer the torque required for field installation. The failure pattern of the piles was observed to be located along the edge of individual threads; this pattern suggests that the pile capacities may be greater than conventional smooth piles in the Arctic.