This paper presents the physical stability analysis of cover systems with geosynthetics that could be placed in the closure of slopes for tailings and mine waste storage facilities and heap leach pads. A geosynthetic liner as part of cover systems, allows to avoid the acid rock drainage and reduces the risk of contamination of the ecosystem. This geosynthetic must be waterproof and has a high durability, which provides advantages when compared with traditional cover systems that use a layer of low permeability soil. In addition, geosynthetics are useful when borrow source of low permeability soil is not available close to the project or is very far, or when the compaction become a difficult process due to steep or very steep slopes.

Although cover systems with geosynthetics have advantages over traditional soil cover systems, stability problems can happen such as soil cover slide down over the geosynthetic which could be caused by own weight, seismic forces or seepage forces (pore water pressure), which increases the repair and maintenance costs. The design of cover systems for mine facilities is getting more common, therefore, criteria and tools that help in the geotechnical analysis and design are necessary, even more considering that physical stability is affected by rainfalls and seismic events that are frequent where most of mines are located.

This paper evaluates the conditions of physical stability in cover systems that include LLDPE geomembrane and geosynthetic clay liner (GCL) placed on slopes between 1.5H:1V and 3.5H:1V. In order to analyze the stability, shear strength of the interfaces generated by geosynthetics has been estimated by large scale direct shear laboratory testing, considering low normal stress (less than 50kPa), typical in cover system. Subsequently, a parametric analysis is performed in three types of cover systems in order to know the influence of the design variables on the factor of safety to be obtained. Different soil properties, geometric configurations and service conditions has been considered. Based on the parametric analysis, a maximum seepage, maximum seismic acceleration and the necessary geogrid reinforcement tension are recommended for each slope inclination and type of cover system analyzed. Also, based on a reliability-based approach, design charts in function of failure probabilities are proposed, which will be useful for preliminary design of cover systems in mining projects.