Effect of connectivity of alluvial aquifers on groundwater flow and solute transport

A. BEAUDOIN; COLECCHIO, IVÁN; A. BOSCHAN

Nantes

Congreso; Congrès Français de Mécanique 2022; 2022

Université de Nantes, l'ENSAM d'Angers, l'Ecole Navale de Brest et l'Université de La Rochelle

We study the transport of a passive solute for monophasic flows taking place in 3D porous mediasamples composed of a high hydraulic conductivity (k+) and a low hydraulic conductivity (k−) facies.The k+ facies is characterized by a proportion p, and also by two connectivity parameters: aconnectivity structure type (low, intermediate, high), and an integral scale lc. The transit time tmean andthe asymptotic value of the longitudinal dispersivity 𝛼l of passive solute particles are numericallyestimated using Monte Carlo parallel numerical simulations. The results allow us to analyze theinterplay among solute transport, connectivity and percolation. The influence of connectivity on 𝛼l isevidenced mainly through a shift in the percolation threshold pc. The maximum of the transit time tmeanoccurs for p~pc (i.e. when the k+ facies spans the media sample in the flow direction), while that of 𝛼l isobtained for p slightly greater than pc. We show that 𝛼l presents a data collapse over the studiedparameters (lc, connectivity structure) if expressed as a function of p-pc, demonstrating that the stronginfluence of connectivity and percolation over flow effective properties also extends to transport.