Thermal and Thermo-hydro-mechanical analyses in PLAXIS Finite Element Software: validation and application to Deep Waste Galleries and Energy Piles

Coupled Thermo-Hydro-Mechanical (THM) processes are prevalent in a number of geotechnical engineering applications. Coupling temperature changes (T), groundwater flow (H) and mechanical deformation (M) affects the response of both geologic systems and overlaying structures. Generally speaking, the understanding of the mechanical behaviour of a soil allows predicting its responses under loading, to quantify its settlements and to analyse its stability. Due to the complex nature of soil as a composite material, soil mechanics involves a number of processes in which its three constituents (solid skeleton, water and air) are interacting with each other. For a number of engineering purpose, the coupled multi-physical behaviour of soils subjected to varying temperature and degree of saturation is of wide interest. Modelling coupled processes in fully or partially saturated porous materials under gradients of pore pressure, temperature and deformation by means of finite element numerical analysis may facilitate the design and optimise the performance of a broad range of geotechnical engineering applications. Therefore, to understand and predict the mechanical behaviour of saturated or partially saturated soils by means of numerical methods, the full triply-coupled thermo-hydro-mechanical process needs to be studied and deformation, unsaturated groundwater flow and heat transport need to be simultaneously analysed. A fully coupled formulation with implicit discretization scheme has been implemented in PLAXIS 2D Finite Element software to perform robustly THM analyses. The purpose of this research is to validate thermal and thermo-hydro-mechanical analysis in PLAXIS 2D finite element software and to contribute to enhancing the capability to model multi-physics couplings in geomaterials by means of finite element methods. Several simple examples and case studies are modelled in PLAXIS 2D and then validated by comparison with analytical, numerical and experimental results.