Dissolution des évaporites : formalisation et développement de modèles numériques bi & tri-phasiques

Abstract : Natural evaporite dissolution at sub-surface can lead to cavities having critical dimensions in the sense of mechanical stability resulting in natural hazards. Geomechanical effects may be significant for people and infrastructures since the underground dissolution may lead to subsidence or collapse (sinkholes). The knowledge of the cavity evolution in space and time is thus crucial in many cases. We describe the use of a local nonequilibrium Diffuse Interface Model (hereafter denoted as DIM) for solving dissolution problems involving multi-moving interfaces within two or three phases, i.e., solid-liquid-gas as found in superficial aquifers and karsts. On one hand, a local non-equilibrium dissolution porous medium theory allows to describe the solid-liquid interface as a diffuse layer characterized by the evolution of a phase indicator (e.g. porosity). On the other hand, the liquid-gas interface evolution is computed using a classical porous medium two-phase flow model involving a phase saturation, i.e., generalized Darcy’s laws. Such a DIM formulation is suitable for the implementation of a fi nite element or finite volume numerical model on a fixed grid without an explicit treatment of the interface movement. A numerical model has been implemented using a finite volume formulation with adaptive meshing (AMR: Adaptive Mesh Refinement), which improves the computational efficiency and accuracy significantly since fine gridding may be attached to the dissolution front.
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Farid Laouafa. Dissolution des évaporites : formalisation et développement de modèles numériques bi & tri-phasiques. Rapport Scientifique INERIS, 2014, 2013-2014, pp.42-43. ⟨ineris-01869503⟩

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