1,720,969 research outputs found
Evaluation of the tailings basins pollution potential
No full textTailings basins within mining areas may represent potential sources of environmental
contamination for soil and underground water. In fact, the disposed muds are typically characterized by high
concentration of heavy metals and other possibly dangerous compounds. The tailings basins built in Europe
before the legal implementation of the EU Directive on the landfill of waste (Directive 99/31) were not
provided with impermeable barriers. In such conditions, during the initial period of the basin life the liquid
phase in the disposed residue filtrates throughout the solid phase under a unit vertical hydraulic gradient,
reaching the soil underneath; afterword, when the accumulated mud forms an impermeable layer at the
bottom of the basin, the same mud, under the load of the superimposed new strata, consolidates, ejecting
liquids throughout the bottom. The article discusses the implementation criterion aimed at evaluating the
conformity of old tailing basin to the new regulation on landfill of waste and a method for the calculation of
the rate of polluted liquids released through the bottom of a tailing basin during its operative life and after its
closure
The Use of Eelectroosmotic Techniques to Improve Safety Conditions of Abandoned Tailing Dams
No full textA 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
Fugitive dust emissions due to the disposal of dried red mud.
No full textThe recent change in the red mud storage practices poses a major concern with respect to the emission of suspended Particulate Matter (PM). With reference to a red mud tailing located in Sardinia, the article discusses the potential hazard of air pollution posed by the conversion of the disposal method from lagooning to dry disposal. A first estimation of airborne dust concentration for the two fractions PM10 and PM2,5 has been carried by means of a Gaussian atmospheric dispersion model, on the basis of the emission factors defined by US EPA. The results found for the long-term period (a calendar year) proved that the disposal of a dried residue does not pose relevant concern regarding air quality. As regard the PM10 short-term concentration, the possibility to exceed the limit value for more than 35 days in a calendar year can be avoided by adopting a work organization based on the use of wheel loaders of greater capacity
The unique landfill site and the mine void backfilling as solutions for the environmental safety of the abandoned mine areas
No full textabandoned mining districts of Sardinia in which contaminated materials both from mining excavations and mineral processing plants are accumulated. Remediation solutions based on the relocation of the materials in new and engineered dumps or on materials treatment are not appropriate due to the huge volume of the deposits (the whole amount has been estimated in 70 Mm3). It appears particularly workable the use of a small number of the compromised major sites as “accumulation centres” in which materials from the other smaller abandoned areas of the same district, can be placed.
This strategy has important advantages related to some typical elements of the mining areas i.e. the presence of tailing basins, often having significant surface extension, and the existence of mining voids both on the surface and underground.
The use of these surfaces and volumes as “accumulation centres” introduces important technical matters referred mainly to the need of ensuring pollutants containment, to the embankments stability and to the safety condition of surface and underground voids during and after backfilling operations.
The paper discuss the issues related to the selection criteria of the sites to be used as “accumulation centre” and proposes some technical solutions aimed at obtaining their permanent and global safety conditions
Application of electroosmotic technique to realize impervious barriers for the insulation of abandoned tailing dams
No full textThe design of hydraulic barriers: integration between rational and observational methods
No full textHydraulic barriers can be used to control and prevent the migration of pollutants from contaminated sites to the surrounding area. Their barrier design requires a deep knowledge of the geological, geotechnical and hydrogeological characteristics of the site. Data collection and hydrogeological modeling can be very expensive, especially in complex geological conditions. Furthermore, despite the significant amount of data to be collected and the economic resources engaged, the resulting conceptual model of the site might not result sufficiently detailed as to allow a reliable design of the barrier. An alternative approach is represented by the implementation of subsequent observational phases alternated to the actual design and construction phases, so that the barrier design results the optimum for the specific site under consideration. This integrated design methodology (rational and observational) is discussed in the article with reference to a major case study located in Sardinia (Italy)
Use of low cost stone wool products in the construction of sanitary landfills and tailing dams
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Criteri geotecnici di progettazione delle opere di marginamento delle falde inquinate: il caso di Portovesme
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