1040 Geomembrane: This geosynthetic made of 1.5 mm double textured HDPE (high density polyethylene) was used to encapsulate the reservoir and contain the flow. Based on PNN (net neutralization potential) analyses, this reservoir had a potential to generate acid drainage, making it necessary to reduce the infiltration levels of non-contact water with the acid-generating material. The geomembrane used follows an international standard specification GM13 of the GSI (Geosynthetics Institute) that guarantees good mechanical performance, due to its high resistance to chemical and biological degradation, as well as its high resistance to ultraviolet rays. Nonwoven geotextile: This material made of PP (polypropylene) with a grammage of 270 g/m2 was placed under and over the geomembrane for puncture protection purposes. The profiled slopes could present puncture zones that could damage the geomembrane during the process of installing the geosynthetics and filling the cover materials. Geocell: The geocell, made of HDPE followed the GSI GS15 standard specification, with dimensions of 100mm in height and 508mmx475mm in opening. The purpose of the geocell was to improve the short- and long-term stability conditions of the cover on the 2H:1V slope. This cover was made of 75mm of granular material for drainage of precipitation infiltration and 150mm of topsoil for vegetative growth with native species. The geocell contributes to generating a macrocorrugation along the slope, the geocell walls increase the stability influence of the cover beyond 100 mm thickness, which made it unnecessary to confine the cover in its total height. The geocell type considerations were a function of slope steepness, geotechnical parametric of the cover material and final total thickness of the closure cover. Biaxial tensor: This tensor made of high-strength PET (polyester) was used to support the geocell filled with cover material on the slope. It was anchored in trenches built on each slope sidewalk, in which the entire set of geosynthetics was anchored, i.e., the geomembrane, geotextile and tensor. PET is a material that shows low deformation over time when subjected to a constant load, making it an ideal material for a structure whose closure life is projected to be hundreds of years. 1.5 Coverage Installation Procedure. Once the slopes of the reservoir were shaped and profiled to achieve physical stability, the geotextile and geomembrane were installed. Immediately proceeded the biaxial tensor anchored in a trench was progressively placed on the sidewalk in the planned areas. The geocell was then installed on the slope. They provided backfill stability and facilitated gravel placement for large areas and long slope sections. Figure 3 – Geocell and geogrid installation. Next, the granular material was placed for drainage purposes of the flow through the topsoil (see Figure 4), which discharged into perforated pipes placed transversally to the slope, and these into concrete collector boxes. Finally, topsoil was placed on top of the gravel for vegetation purposes with native species.
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