Trends of large scale direct shear strength results for LLDPE-HDPE geomembrane/soil Interfaces
Date
2013Author
Ale, José
Rodríguez, Martín
Román, Claudio
Preciado, Humberto
Sánchez, Marsy
Metadata
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The mining industry is developing at a fast pace in the South America region, and demands the construction of important and larger mining structures such as: tailings impoundments, heap leach pads, rock waste facilities, etc. Heap leach pads by design, must contain leached mineral solutions through properly designed engineered liner systems. As part of the geotechnical design of a heap leach pad, a geotechnical characterization of the geomembrane-soil interface must be conducted. This characterization is performed by large scale direct shear (LSDS) testing, using confinement pressures which simulate the weight of the ore stacking in the leach pad. The types of geomembrane mainly used in the mining industry are the high and linear low density polyethylene (HDPE and LLDPE, respectively), single side textured (SST), and of variable thickness (1.5 and 2.0 mm). Many authors have studied the responses of geomembrane-soil interfaces (Koener et al., 2005; Koerner et al. 2007; Thiel, 2009; Parra et al., 2010; Breitenbach, 2011), and analyzed their strength envelopes considering linear and nonlinear geometries (Parra et al., 2012). This paper compiles LSDS test results obtained in Peru, and other data available in the existing literature, and analyzes their trends and range of values. Results from HDPE and LLDPE single side textured geomembranes are presented, with the textured side in contact with the underlying soil, and using confinement pressures of up to 800 kPa, which are equivalent to about 45 m of ore stacking. The results show a consistent trend in the residual shear strength envelopes of different types of geomembranes, regardless of geomembrane thickness. For high pressures, this trend could be non-linear. The values of adhesion range from 26 to 53 kPa, and angles of internal friction range from 16° to 26° for HDPE interfaces, and adhesion between 15 and 35 kPa, and angles of internal friction between 12° and 24° for LLDPE interfaces.