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    Interface shear behaviour of different geomembranes with rough surfaces in Heap Leaching applications

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    Solanki, Rahul
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    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.
    URI for this record
    http://hdl.handle.net/1974/28580
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    • Department of Civil Engineering Graduate Theses
    • Queen's Graduate Theses and Dissertations
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