Prof. Hanène Souli came to EPFL on September 29, 2015. She gave a presentation entitled “Effects of particles migration on the properties of some geomaterials (clays and granular materials)”.
In the presentation, the interest was focused on the study of the effect of the migration of particles on the properties of two geomaterials via two different mechanisms:
- in granular materials, the transport of fines by a water flow, a phenomenon called “suffusion”,
- in clays, the transport of water and pollutants by an electric field.
In the first case, the objective of the study carried out on binary mixtures of sand and gravel was to (i) establish new suffusion criteria, and (ii) follow the evolution of the mechanical properties of the materials when suffusion occurred. Suffusion was simulated by reducing the amount of fines in the samples. Undrained triaxial tests were carried out to measure its effect on the strength of the samples and the evolution of the amplitude of the contractive and dilative phases. The results highlighted a clear relation between these parameters and the changes in the void ratio of the specimens.
In the case of clays polluted by heavy metals, electrokinetic was used to depollute the soils. The application of the electrical field causes several phenomena to occur: displacement of the heavy metal ions, electroosmosis, changes in pH, precipitation, etc. The electrokinetic study was carried out on mixtures of carbonate and kaolinite, artificially polluted by lead at different concentrations. In addition to the electrical parameters, the evolution of the structure after the eletrokinetic treatment was analyzed.
Even if, these two phenomena are completely different, the migration of particles causes changes in the porosity and fabric of the studied samples. As a consequence, the mechanical and physicochemical properties of the samples are largely influenced.