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Abstract: Results from physical experiments are presented to assess the possible puncture of a 1.5-mm-thick HDPE geomembrane and, if not punctured, the maximum tensile strains in the deformed geomembrane from intentionally placed stone particles in an underlying compacted clay liner when subjected to applied vertical stresses. The influences of applied pressure, clay water content, stone size, stone burial depth and protection layer on the geomembrane tensile strains are reported. Except in one test conducted to a pressure of 2000kPa, the geomembrane was not punctured in the short-term tests conducted; however, it was subjected to local indentations and tensile strains from the underlying gravel particles that may exceed proposed allowable long-term strain limits. Tensile strains for the specific 35mm stones tested when initially flush with the clay surface were negligible, even up to pressures of 1000kPa, provided the initial water content of clay was 12%. Increases in water content or stone size were found to increase the tensile strain. Placing the clay at the lower limit of acceptable water content was found to be beneficial in terms of reducing strains from buried stones; however, this was also found to make the geomembrane more susceptible to stone particles sitting on top of the clay surface and hence careful site inspection is required to remove all visible stones that sit on top of the clay surface. [Copyright &y& Elsevier]

Abstract: A method to record the shape, size, and spacing of gravel contacts that act on a geomembrane from an overlying granular drainage layer is presented. The gravel contacts acting on a 1.5-mm thick, high-density polyethylene geomembrane are then quantified for two poorly graded, angular gravels (GP1 and GP2 with nominal grain sizes of 50 and 25mm) with compacted clay beneath the geomembrane and when subjected to an applied pressure of 250kPa. The geomembrane indentations and strains are also reported. Five types of contacts were defined: point, edge, area, perimeter and composite. Point contacts were the most frequent and, along with edge contacts, caused the steepest indentations and the largest strains. The average spacings between gravel contacts were found to be 55mm for GP1 and 37mm for GP2. Without a protection layer, the largest tensile strains in the geomembrane were 32 and 16% for GP1 and GP2, respectively. A nonwoven needle-punched geotextile was found to reduce the contact pressure acting on and the resulting strains in the geomembrane. However, none of the geotextiles tested (with masses up to 2240g/m2) were able to limit the tensile strains below proposed allowable levels for long-term strain even for the short-term conditions examined. [Copyright &y& Elsevier]