Evaluating the integrity of HDPE geomembranes in high-stress heap leaching projects

¹ Chair, IGS Chile. CEO, Axios Engineering SpA, Chile.
² Geotechnical Engineer, Axios Engineering SpA, Chile. MSc Candidate in Seismic and Geotechnical Engineering, University of Chile.

^* Corresponding author: andres.leon@axiosingenieria.cl

Abstract

The success of heap leaching projects is highly dependent on the design and construction of the liner system, including the selection of suitable overliner material, representing a significant part of project capital expenses. This paper presents results from two recent studies at one of the largest copper leaching operations in Chile, which aimed to expand the secondary leaching process and to explore challenges in expanding a lowgrade oxide dump leach. Large Scale Puncture tests were developed to evaluate HDPE geomembrane performance under maximum heap leach loads. The first study subjected the geomembrane to loads equivalent to 120 meters with 2” maximum size overliner material, revealing no puncture failures, only minor yielding. In the second study, simulating loads of up to 235 meters, mild to moderate yielding occurred for heights up to 180 meters, whilst for heights of 225 and 235 meters, major yielding was presented, showing that reached the limit of the puncture failure due to increased load or deformation over time. The study concluded that the recent HDPE geomembranes manufacturing are more resistant and can withstand higher loads and an overliner with a maximum grain size larger than 1.5” without puncture failure, although deformation may still occur.