The use of polymeric geosynthetic barriers (GBR-P) such as geomembranes in water proofing systems of tailings dams has been increasing in the last few years. When placed at the foundation of the dam, this barrier can reduce the slope embankment stability due to the low shear strength at the barrier-embankment or barrier-foundation interface, which might become a potential sliding surface. This paper will present an evaluation of the stability of a gold tailings dam where a 1.5 mm thick high density polyethylene (HDPE) geomembrane layer was placed at the reservoir bottom, the upstream dam slope and the foundation of the dam to prevent contamination of soil and groundwater. The dam will be built in seven stages, with the downstream raised method and has a maximum depth of 115.0 meters. Limit equilibrium deterministic and probabilistic analyses were performed to study the influence of the polymeric barrier placed at the foundation of the dam on the slope stability. The input data used in the analyses are based on laboratory tests performed using the embankment dam material (cyclone underflow tailings) and geosynthetics (texturized geomembranes and non-woven geotextiles) in different stages of their lifespan: virgin specimen, after one month and after eight months immersed in the gold tailings fluid). Results show the most important factors that influence the stability of the dam when it concerns to the polymeric barrier and how the slope factor of safety and probability of failure vary with different strength conditions applied to the geosynthetics material and its interface.
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