Towards a Unified Unsaturated Soil Mechanics Framework for Interpretation of Frozen and Unfrozen Soils

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The thermo-hydro-mechanical behavior of a frozen soil during winter in many regions of Canada is significantly different in comparison to unfrozen soil during the remainder of the year. However, saturated soil mechanics principles are widely used in Canadian geotechnical practice ignoring influence of suction in both frozen and unfrozen soils. Recently, the UN Intergovernmental Panel on Climate Change (IPCC) suggested that global warming effects would contribute to an increase in annual temperatures of 1.5oC above pre-industrial level temperatures by 2030. This temperature rise would likely contribute to extreme floods, extended drought periods and significant variations in soil temperatures. In other words, global warming effects offer challenges to the design of geotechnical infrastructure. Through this research proposal, a unified framework will be developed for the rational interpretation of thermo-hydro-mechanical behavior of unsaturated soils taking into account frozen and unfrozen conditions including climate change effects. The short-term objectives will be directed towards undertaking comprehensive experimental studies at the University of Ottawa geotechnical laboratory on a variety of typical Canadian soils; namely, sand, glacial till, expansive soil, silty clay and sensitive clay. The results of these studies will be used in the development of a framework for the design of pile foundations in expansive soils, mechanistic models for pavements in frozen and unfrozen soils and slope stability analyses of expansive clays. The long-term objectives of this research program will be directed towards understanding the complex mechanics of the coupled thermo-hydro-mechanical behavior of various Canadian soils. Additional funding from Ministry of Transportation of Ontario (MTO), University of Ottawa and other anticipated agencies will provide partial support for some of the objectives over the next decade. Expected impact This research program is expected to be step forward towards the development of a novel framework that extends the mechanics of unsaturated soils for frozen and unfrozen soils taking account of the climate changes for the rational design of various geotechnical infrastructure. The applicant's research work from the previous Discovery grants is incorporated into the design of pavements by the MTO. Also, the applicant's earlier research on the unsaturated soils behavior is being implemented in the South Africa Geotechnical Practice manual and is widely used by the Geo-slope, commercial software developed in Canada. It is expected that some of the present studies may find place into the Canadian Foundation Engineering Manual which is proposing to include state-of-the-art developments related to unsaturated soil behavior. Finally, this research will train 3 PhD, 2 MASc and 3 BASc students, who will acquire advanced knowledge and skills in the design of geotechnical infrastructure based on the mechanics of unsaturated soils.