Soil is a typical multiphase porous media, of which the saturation is influenced by both subsurface and surface water. The thermal-hydro-mechanical coupling process of saturated and unsaturated soils under special climate conditions, such as cyclic freeze-thaw, evaporation, or regional hydrological conditions, can affect the hydraulic-mechanical properties of the ground or foundations, potentially inducing geohazards and geo-environmental problems. Significantly, the coupling process gives critical insight to geotechnical, environmental, and underground engineering, and as such the coupling process is a prerequisite for all such engineering, construction, and geohazard prevention.

New areas of research have been brought forward by the development and analysis of the coupling process in environmental and geotechnical engineering. However, research into constitutive theory, the chemical effect on the coupling process, mathematical coupled theory for engineering, and the coupling mechanisms is still limited. To this end, the need for detailed and systematic analysis of the coupling mechanism is most essential and urgent before undertaking engineering practices.

This Special Issue aims to publish original research and review articles on the latest developments and research in thermal-hydro-mechanical coupling of soils subjected to extreme environmental conditions. Papers submitted on new and emerging topics within the discipline are also encouraged. Theoretical papers are welcomed, and practice-oriented papers are particularly encouraged.

Potential topics include but are not limited to the following:

• Coupled hydraulic-mechanical properties of soils in the saturated-unsaturated zone
• Moisture-heat dynamics of soil and rock under freeze-thaw and evaporation conditions
• Effects of groundwater on ground improvement and deep excavation
• Effects of regional hydrological conditions on the soil coupling process
• New methods investigating the coupling process, not limited to finite-element (FEM), finite-difference (FDM), and finite-volume methods (FVM)
• Regional environmental changes
• Regional data coupling and evaluation of engineering conditions