###### Abstract
An example of this is the use of geomembranes as hydraulic barriers in mining tailings reservoirs, instead of using a compacted clay layer (CCL) to prevent percolation and consequently environmental contamination by metals. Geomembranes are geosynthetics with low permeability and are therefore used as hydraulic barriers [22; 28]. They are flat, thin, and flexible materials that can be either bituminous or polymeric [28]. Polymeric geomembranes can be of various compositions, including high-density polyethylene (HDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), polyvinyl chloride (PVC), chlorosulfonated polyethylene (CSPE), chlorinated polyethylene (CPE), ethylene propylene rubber (EPDM), and polypropylene (PP) [28; 29]. Geomembranes can also be classified based on their contact surface, such as textured or smooth. The choice of geomembrane type to be used will depend on the project, which should take into account the type of application and the boundary conditions. HDPE geomembranes are typically composed of 96-97.5% polymer resin, 2-3% carbon black additive, and 0.5-1% other additives such as antioxidants and stabilizers [29; 30; 31]. The polyethylene in geomembranes has crystalline lamellae, where the layers are orderly, folded, and packed, and amorphous regions, with a disordered form. The properties of polyethylene depend on its structural arrangement. Therefore, any alterations due to aging/degradation (when the inter-lamellar connections in the amorphous zone may break down), or variations between geomembranes, can lead to different performance and durability characteristics [29]. Also, there are different processing methods to obtain the final geomembrane product, such as flat die extrusion and blown film extrusion, which might influence the characteristics and properties of the final material. As a result, several different chemical and mechanical properties might be found between HDPE geomembranes, although all of them have the same objective, which is to meet the minimum values required by the standards and design specifications [30]. To ensure that geomembranes effectively mitigate environmental impact, focused on their application to mining reservoir dams, it is crucial for them to meet the minimum performance requirements specified in the design. Therefore, it is essential to study the durability of these geosynthetics when they are applied in the field. The degradation of a geomembrane typically consists of three stages. The first stage involves the depletion of antioxidants in the material until they reach their residual value. The second stage marks the onset of polymer degradation, though no significant changes in its mechanical properties are observed at this point. The third and final stage is characterized by measurable changes in the mechanical properties of the geomembrane, leading to its nominal failure [29; 30; 31; 32; 33; 34]. Nominal failure is when a selected physical property, such as the tensile elongation or strength at break, is reduced to 50% of its initial value or the minimum value specified by the standard GRI GM13. Although it is a conservative approach, the literature presents various studies that evaluate the durability of geomembranes based on the premises of the GRI GM13 standard [34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45]. It is important to highlight that geomembranes do not always follow these three stages, as their performance can vary depending on their composition, the manufacturing process, and the boundary conditions to which they are subjected. For example, ref. [44] observed that, in that specific case, the antioxidants in the material did not reach their residual value before measurable changes in its mechanical properties were observed. Various degradation mechanisms can affect geomembranes when they are exposed to field conditions depending on the environmental factors. These mechanisms include degradation by ultraviolet (UV) rays, temperature, chemical or biological action, and oxidation, among others [31; 33; 46].