Temperature change induces a variety of changes in soils, including volumetric change in saturated clays and clay mixtures, changes in permeability, and special variation in fluid density leading to induced flow. The aim of this research is to investigate the fundamental interaction of temperature, water pressure, and pore fluid flow in soil through integrated experimental and computational models. The knowledge generated through this research will be utilized to optimize the design and construction of nuclear waste disposal facilities, geothermal boreholes, and other energy geo-structures. The outcomes of the research, and the results of advanced numerical model and laboratory controlled experiments, will be essential for applications of thermal-hydraulic-mechanical-chemical (THMC) modeling in civil engineering (e.g., underground structures, deep geothermal power plants, and construction in permafrost areas). The results of the experimental models can also be useful to predict the permeability changes of landfills due to chemical reactions and daily temperature variations to have a better estimation of leakage based on the temperature dependent permeability. The expected research findings may also help to improve the current design codes and methodologies for underground structures surrounding heat sources. The education and outreach activities of this project will provide both K-12 and college students from underrepresented groups with opportunities to be exposed to STEM disciplines and careers. The personnel on this project will provide guidance to graduate students considering careers in academia and research. This study also help to enhance the research literacy of the Commonwealth of Kentucky, one of the EPSCoR states.
The goal of this research is to comprehensively study temperature effects on soil behavior. Soil hydraulic conductivity varies with temperature. This happens not only because of changes in fluid density and viscosity, temperature might alter the soil fabric and porosity in both sand and clay as well. Temperature increments in unsaturated media result in drying soil and moisture content reduction close to the heat sources. However, temperature changes in saturated sand make the spatial variation in fluid mass density. Such a variation results in buoyancy-driven flow and, creates thermally driven pore fluid flow. The thermally induced pore fluid flow in sand facilitates heat transfer in the ground and results in heat convection even under hydrostatic condition. Therefore, induced pore fluid flow must be considered to accurately model the heat transfer in the ground. The interaction of heat and fluid flows needs to be investigated in high permeable soil. On the other hand, heat flow results in permeability variation and volumetric changes which will result in thermal consolidation in low permeable ground (e.g., clay). Four main tasks are planned to accomplish the research goal: (1) Predicting permeability variation of different soil types (e.g. sand and clay with different void ratios) under different confining stresses using a temperature controlled cell; (2) Analyzing volumetric changes and thermal consolidation for different temperature increments in clays; (3) Studying the effect of thermally induced pore fluid flow on soil temperature response in high permeable soil; and (4) Predicting the interaction of heat and fluid flow in porous media while considering time and temperature dependent soil and fluid properties. The outcomes of the current study will be useful for Multiphysics and flow in porous media.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
