Electromagnetic, thermal, hydraulic and mechanical characterization of frozen soils having different initial thermal and hydraulic properties

This research focuses on the investigation of the coupled electromagnetic, thermal, hydraulic, and mechanical properties of frozen geomaterials subjected to thermal gradients. Accelerated subsurface warming in the cold regions exacerbates the temporal and spatial evolution of frozen ground properties which necessitates the accurate characterization of frozen geomaterials. Existing studies often focus on isolated external effects, such as thermal conductivity or mechanical strength under frozen conditions at constant temperatures, without considering the complex interdependencies between these properties. Therefore, the main objective of this research is to investigate the coupled relationships between thermal, electromagnetic, and hydraulic properties of frozen soils under varying temperatures and their impact on the mechanical properties. Laboratory experiments were conducted using capacitance sensors and Electrical Impedance Spectroscopy to characterize the effect of initial degree of saturation, initial dry density, temperature, and applied frequency on the bulk electromagnetic properties - specifically dielectric constant and electrical conductivity - of sand, silt, and clay soils. The dielectric permittivity values from the measurements were used to calibrate the physics-based models for estimating the water content and ice content of soils at different temperatures below 0°C. The estimated water contents were plotted against temperature to establish soil freezing curves. A set of laboratory experiments were performed to characterize the thermal properties of soils during the freezing and thawing process and a new methodology for measuring ice content during freezing and thawing was introduced. The latent heat during the phase change of water was quantified and used to predict the ice content. The results from the latent heat calculations were consistent with ice contents estimated from the capacitance experiments. Direct simple shear tests were performed at temperatures below 0°C on soil samples having initial degrees of saturation identical to the soil samples prepared for previous experiments. This allowed for an in-depth evaluation of how ice content, as indicated by the soil freezing curves, influences the shear strength of frozen soils. The results from this study demonstrated the significant impact of initial degree of saturation, temperature, and soil type on the thermal, hydraulic, electromagnetic, and mechanical properties of frozen soils. An increase in the initial degree of saturation resulted in a higher dielectric permittivity, electrical conductivity, latent heat, ice content, and the shear strength at temperatures below 0°C. Decreases in soil temperature initiated the phase change and it resulted in decreasing dielectric permittivity, electrical conductivity, and a significant increase in the shear strength. A further decrease in the temperature continued to increase the shear strength of frozen soil due to an increase in ice content as expected. For the same initial water contents, clay and silt soils exhibited lower ice contents, but higher shear strengths compared to the sand. Based on the results of shear strength tests, an integrated failure criteria using Mohr-Coulomb model and soil freezing curve was developed for frozen sand. The approach followed in this research is an important step towards advancing our understanding of how the coupled effects of thermal gradients, initial degree of saturation, and soil type influence the electromagnetic, thermal, hydraulic, and mechanical properties of frozen soils under thermal gradients. By providing a detailed characterization of the frozen soil properties, more accurate predictions of soil behavior under changing environmental conditions can be achieved. The results from this research contribute to long-term sustainability by enhancing the ability to assess and mitigate the impact of changes in climate trends on frozen soil stability, ultimately supporting more resilient infrastructure development in the Arctic and cold regions.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Abhinav, Anshu

Contributors dc:contributor

• Baser, Tugce
• Sychterz, Ann
• Al-Qadi, Imad L
• Olson, Scott Michael
• Xiao, Ming

• Frozen soils
• electromagnetic properties
• thermal properties
• mechanical properties
• soil freezing curves

Statement dc:rights

• Copyright 2025 Anshu Abhinav

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129667

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129667