Coupled Thermo-Hydro-Mechanical Numerical Modeling of Evolving Fractures in Rocks

We present a numerical technique capable of handling evolving fractures in rocks triggered by coupled thermo-hydro-mechanical (THM) phenomena. The approach is formulated in the context of the finite-element method (FEM) and consists in introducing especial (high-aspect ratio) finite elements in-between the regular (bulk) finite elements. We called this method the mesh fragmentation technique (MFT). The MFT has been successfully used to model mechanical and hydro-mechanical problems related to drying cracks in soils, fractures in concrete, and hydraulic fractures in rocks. In this paper, we extend the MFT for tackling non-isothermal problems in porous media. We present the main components of the mathematical formulation together with its implementation in a fully coupled THM computer code. The proposed method is verified and validated using available analytical, experimental, and numerical results. A very satisfactory performance of the proposed method is observed in all the analyzed cases. These results are encouraging and show the potential of the MFT to tackle THM applications involving fractured rocks. A clear advantage of the proposed framework is that it can be easily implemented in existing numerical FEM codes for continuous porous media to upgrade them to tackle THM engineering problems with evolving discontinuities.