Coupling Hydrodynamics and Geophysics with COMSOL Multiphysics : First Approach and Application to Leachate Injection in Municipal Waste Landfills

Electrical Resistivity Tomography (ERT) is increasingly used to investigate moisture distribution in Municipal Waste Landfills, especially when leachate is injected in waste to enhance its biodegradation. It is proposed here to theoretically assess the quality of ERT mapping, using COMSOL Multiphysics' simulations of both hydrodynamical and geophysical aspects. Leachate injection is simulated using COMSOL's Porous Media and Subsurface Flow module which produces the effective saturation distribution. Virtual current injection following ERT principles is then performed on this variably saturated domain using COMSOL's AC/DC module, to produce the electric potential field and to derive the apparent resistivity distribution. The apparent resistivity data set is then inverted with a specific code to reconstruct a calculated resistivity model, which is finally compared to the initial field of effective saturation. Notable distorsions are evidenced, especially in the lower part of the so-called saturation bulb.