In countries like Peru, located in complex and active seismic regions, it is vital to consider the seismic demand at the site during the design of earth structures. In the mining environment, leach pads and their lining system are considered more sensitive to seismically induced displacements than other mining facilities due to the possibility of tearing the geomembrane during seismic events, which can lead to environmental damage and economic detriment. Furthermore, leach pads in these regions, and particularly in Peru, are generally built within narrow valleys where the three-dimensional nature of these locations can significantly influence seismic behavior. This type of complexity requires adequate characterization and definition of the shear strength and deformational properties of the materials involved in their design. This paper presents a Peruvian case study of a valley fill heap leach pad where the design was defined by its seismic behavior, and a three-dimensional (3D) dynamic analysis was performed using FLAC 3D software (Itasca, 2012) in order to validate the 2D seismic analysis for the heap. A large set of geotechnical information was used for the analysis, which included the state-of-the-art characterization of the static and dynamic properties of the leached ore and the interface (lining system). The shear strength and deformability properties of the leached ore were defined considering a homogeneous medium and implementing a non-linear variation of these with confining stresses. The shear strength of the interface was determined by large-scale direct shear tests. The dynamic properties of the leached ore were studied using geophysical studies directly on the heap and using combined resonant column and torsional shear tests, as well as cyclic triaxial tests. The approach of Yegian et al. (1998) was used to define the dynamic properties of the soil-geomembrane interface. The results allowed the authors to validate the simplified and dynamic 2D analysis and understand the behavior of the ore and the interface in the valley during a seismic event.

HEAP LEACH MINING SOLUTIONS, 2016 • LIMA, PERU 304