Interface shear behaviour of different geomembranes with rough surfaces in Heap Leaching applications
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Authors
Solanki, Rahul
Date
Type
thesis
Language
eng
Keyword
direct shear test, ageing, interface shear, heap leach pad, geotextiles, geomembranes, geocomposite drain, textured geomembranes, geomembranes with rough surfaces.
Alternative Title
Abstract
The interface shear strength properties of the different geosynthetic layers of the liner system are examined
for heap leach pads applications. A series of large scale direct shear tests is used to examine the
effectiveness of four geomembranes (GMBs) with different surface roughness with different soil subgrades,
geotextiles (GTXs) with different mass per unit areas, and a geocomposite drain (GCD) at moderate to high
normal stresses.
Four different subgrades, including sand, two different coarse-grained underliners, and clay
representing the layers directly underlying the GMB liner in heap leach pads, are used to examine the shear
strength of the GMB-Subgrade interfaces at normal stresses between 50 and 1000 kPa. It was found that
increasing the normal stresses can change the mechanisms contributing to the shear resistance at the
interface. This resulted in a statistically insignificant increase in the interface friction of the GMB-Granular
soils interfaces when using GMBs with surface roughness relative to the smooth GMB. Furthermore,
depending on the type of subgrade, establishing the shear envelopes over a wide range of normal stresses
may over/underestimate the shear strength at the field stresses even when linear regressions present the best
fit for the data.
The effect of using GTX cushion to protect the GMB liner from excessive punctures at high stressed
zones of the pad on the interface shear behaviour of the liner system is investigated by examining different
GMB-GTX interfaces. Using GMBs with high surface roughness and/or decreasing the mass per unit area
of the GTX increased the peak friction angles of the GMB-GTX interface. However, the shear strength of
these GMB-GTX interfaces was still lower than the shear strength of most of the GMB-Subgrade interfaces
even when the smooth surface of the GMB was in contact with the subgrade. Additionally, while preageing
the GTXs to low mechanical properties prior to the direct shear experiments was found to increase the peak
interface friction angles of different single layer GTXs due to the softening of geotextiles, it resulted in aniii
internal failure of a heat bonded two-layer GTX at low shear displacements. This was due to the reduction
in the bond strength between the two layers of the GTXs due to chemical degradation of the GTX.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.