Physical and Numerical Modelling of a Two-Well Tracer Test at the Laboratory Scale

Abstract.

Two-well tracer tests were performed at the laboratory scale on a large hand-compacted Bruxellian sand sample (about 2 m³), using electrical sensors buried in the soil and placed in piezometers to monitor solute concentrations. First, heterogeneity within the soil was investigated using simple one-dimensional transport experiments. Deduced perme ability values showed some non-negligible variations, that had to be taken into account when interpreting two-dimensional experiments. A numerical model was then developed under Modflow®, in order to simulate two-well tracer test recovery curves under heterogeneous soil conditions. Comparison of numerical results and experimental data highlighted the need for a sufficiently refined measurement grid, as phenomena occurring in zones where fewer sensors were installed were not well simulated.