The Use of Eelectroosmotic Techniques to Improve Safety Conditions of Abandoned Tailing Dams

A considerable number of tailing dams is scattered all over the abandoned mining districts of Sardinia. Some of them are actually huge and represent dangerous sources of contaminant diffusion in soil and underground water. Due to the volume of the basins, the best remediation strategy appears to be the construction of low permeability barriers both at the basin bottom and along its perimeter, aiming at the hydraulic insulation of contaminants. Barriers can be realised by consolidating the contaminated material at the bottom and at the perimeter of the basin in order to obtain the reduction of the material porosity and, consequently, an effective decrease of its permeability. Electroosmotic techniques can be used as a mean to induce consolidation in selected volumes of accumulated mineral waste. The application of an electric potential difference between two points in a saturated soil produces, in fact, a hydraulic flow that induces faster material consolidation. The paper deals with the environmental safety conditions of the abandoned tailing dams and illustrates the experimental apparatus able to simulate the consolidation process under simultaneous application of a static load and an electric potential difference. The final results of the experimental activity are presented and discussed in order to evaluate the applicability of the proposed technique.