Experimental Investigation on the Effect of Freeze-Thaw Characteristics of Soils on Behavior of a Model Steel Pile

Freezing and thawing affect the physical and mechanical properties of soils, causing deformations such as frost heave and thaw settlement. This poses risks to critical infrastructure in our society, including roadways, buildings, pipelines, and embankments. This dissertation aims to enhance our understanding of the effects of frost actions on deep foundations installed in frost-susceptible soils. To achieve this, a novel laboratory-scale testing system was developed to investigate tangential heave stress on a steel pile during frost heave of freezing soils. The system consists of seven components: an environmental chamber, a frost heave box, a constant-head water supply system, the test soil, the model pile, a data acquisition system, and an imaging system. Strain gauges, thermocouples, moisture sensors, and displacement gauges were installed on both the model pile and test soil to examine various aspects of pile-ice-soil interactions. Experimental results demonstrate that the newly developed testing system successfully simulates heaving of the pile and soil during the soil freezing process, providing a wealth of information on the thermomechanical behavior of the model pile, particularly for evaluating tangential heave stress, as well as high-definition images showing pile-ice-soil interactions. Additionally, this dissertation explores the behavior of nonplastic silt subjected to freeze-thaw cycles in an open system using the developed testing system. The test results reveal that nonplastic silt in the active layer becomes more porous, and its engineering properties change after multiple freeze-thaw cycles. Findings from the test provide not only an improved understanding of the behavior of nonplastic silt during freeze-thaw cycles in an open system but also comprehensive data and valuable insights into the behaviors of frost-susceptible soils subjected to seasonal freeze-thaw cycles (FTCs). The test system and procedures developed in this study are well-positioned to perform controlled experimental study and make significant contributions to the body of knowledge in cold regions science and engineering by investigating the effects of various parameters − such as temperature gradients, structural loads on the pile, initial soil conditions, and freeze-thaw cycle, among others − on the development of the tangential heave stress. As such, the laboratory-scale system developed in this study can make significant contributions to the foundation analysis and design in cold regions engineering and potentially provide some insights on developing climate-resilient foundation system in the Arctic region. Furthermore, new scientific findings and enabling technologies from this study can be applicable and beneficial to other regions for improving climate resiliency and adaptation capacity. Given the absence of standardized laboratory tests to assess tangential heave stress during soil freezing and down-drag during thawing, the experimental test system and procedures developed in this study has the potential to be served as a benchmark study to further develop a test standard. The high-definition images of soil sample obtained from the freeze-thaw test can be used for outreach activities to educate K-12 students and the general public on cold regions science and engineering and to raise their awareness on climate changes.

Embargo status: Restricted until 06/2025. To request the author grant access, click on the PDF link to the left.