Thermohydromechanical

Thermohydromechanical (THM) refers to the coupled physical processes involving heat transfer, fluid flow, and mechanical deformation in porous or fractured materials. It describes how temperature changes influence hydraulic properties and stresses, and how hydraulic and mechanical states affect heat transport.

In THM modeling, the key components are heat conduction or convection, Darcy flow of pore water, and deformation of the solid skeleton. Couplings include thermal expansion, temperature-dependent permeability, and changes in pore pressure due to heating or cooling, as well as phase changes between liquid water and ice in frozen soils.

The governing equations typically extend poroelastic theory to include heat transport. They combine energy conservation (heat diffusion and advection), mass conservation for the fluid phase, and momentum balance for the solid, with constitutive relations linking stress, strain, temperature, and pore pressure. Numerical solutions rely on coupled finite element or finite difference methods, and may address unsaturated conditions or fractured media with nonlinear behavior.

Applications of THM analysis include geothermal reservoir development and stimulation, underground waste disposal and CO2 sequestration, frost heave and permafrost degradation, and the stability assessment of tunnels, caverns, and embankments in thermo-hydrologically active environments.

Data and experimentation support THM modeling through field measurements of temperature, pore pressure, and deformation, along with laboratory thermo-hydro-mechanical tests on soils or rocks. Model calibration faces challenges from heterogeneity, nonlinear material behavior, and evolving fracture networks.

THM remains an active area of geotechnical and energy research, frequently integrated with chemical processes (THMC) to capture reactions under varying temperature and moisture conditions.