A Framework for Evaluating Thaw Settlement in Permafrost Regions

Permafrost degradation due to climate change threatens infrastructure stability in cold regions, leading to ground subsidence, structural instability, and increased maintenance costs. Accurate thaw settlement prediction is essential for mitigating these effects and ensuring infrastructure resilience. This thesis presents a Thaw Settlement Evaluation Framework designed to support thaw settlement evaluation across different project stages and spatial scales. The research addresses key knowledge gaps by improving thaw strain estimation at the site scale and developing a new approach for assessing susceptibility to thaw strain at the regional scale. The study began with the compilation and analysis of thaw settlement test results from diverse sources, consolidating and publishing a structured dataset that includes test results, locations, index properties, and descriptions of soil and ground ice. This cleaned and compiled dataset addresses the scarcity and fragmentation of geotechnical data on permafrost and serves as a valuable resource for future studies. The data was used to explore thaw settlement behavior across soil types, evaluate empirical tools, and refine and develop new correlations where gaps existed, particularly for coarse-grained and highly organic permafrost. These improvements support more reliable thaw strain estimation for a broader range of permafrost conditions. To contribute to broader-scale thaw settlement assessments, the study developed Thaw Settlement Potential Index (TSPI), which evaluates the susceptibility of ground materials to thaw strain using key geotechnical factors such as ground ice content, surficial geology, and bedrock type. TSPI is designed for use with regional-scale datasets typically available in desktop studies. Building on TSPI, the Thaw Settlement Hazard Index (ITSH) was introduced as a regional-scale hazard assessment tool that combines TSPI with predicted changes in active layer thickness. The ITSH enables early identification of areas prone to thaw settlement, informing planning prior to site investigations. Finally, these contributions were synthesized into a Thaw Settlement Evaluation Framework, offering standardized workflows for regional-scale hazard assessments and site-specific thaw strain estimations. The framework enhances thaw strain prediction, improves access to relevant tools and data, and supports informed infrastructure design and maintenance planning. This research advances both the accuracy and accessibility of thaw settlement assessments in permafrost regions.

Name thesis:degree_name

Doctor of Philosophy (PhD)

Discipline thesis:degree_discipline

Engineering – Civil

Grantor dc:publisher.institution

Schulich School of Engineering

Year dc:date.issued

2025

Author dc:creator

• Mohammadi, Seyedeh Zakieh

Advisor dc:contributor.advisor

• Hayley, Jocelyn L.

Committee members dc:contributor.committeemember

• Moorman, Brian J.
• Priest, Jeffrey
• Khoshnazar, Rahil
• Yang, Zhaohui Joey

• Permafrost
• Thaw strain
• Thaw settlement
• Permafrost degradation
• Empirical modeling

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

en

DOI

https://dx.doi.org/10.11575/PRISM/49043

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/121453