Short-Term Local Tensile Strains in HDPE Heap Leach Geomembranes from Coarse Overliner Materials

AbstractLocal tensile strains in a 1.5-mm-thick high-density polyethylene (HDPE) geomembrane induced from coarse overliner soil materials intended to simulate the physical conditions at the base of a heap leach mineral extraction pad under very deep burial are reported. They were obtained from physical experiments conducted in a 590-mm-diameter pressure vessel at applied vertical pressures up to 3,000 kPa for 100 h and a temperature of 21°C. An applied pressure of 3,000 kPa corresponds to a heap leach depth of around 150 m. Three different coarse-grained overliner materials placed directly above the geomembrane and a silty sand underliner beneath the geomembrane were examined. Both the grain size and grain size distribution of the overliner affected the maximum tensile strain in the geomembrane. At an applied pressure of 3,000 kPa, the largest strain of 27% recorded for the coarsest overliner tested, which had a maximum particle size of 50 mm and 20% sand, well exceeded one proposed maximum allowable stra...