HYDRAULIC PERFORMANCE OF GEOSYNTHETIC LINERS IN LANDFILLS AND TAILINGS STORAGE FACILITIES
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The effects of holes in a geomembrane on leakage through the base liner of a modern municipal solid waste and mine tailings storage facilities was examined. First, the performance of overlapped seams below a geomembrane wrinkle was evaluated for seven geosynthetic clay liners (GCLs; three requiring and four not requiring field-applied supplemental bentonite at the longitudinal seam). For seams parallel to a wrinkle, the performance depended on the width of the seam relative to the wrinkle. With both ends of the seam confined under vertical stress from the deformed wrinkle, there was no evidence of flow along the seam. For seams perpendicular to a wrinkle, it was observed that the availability and distribution of seam bentonite, needle-punching pattern of the GCL, applied vertical stress, and GCL type can all significantly affect the flow along the unstressed section of the seam. With 400 g/m of supplemental bentonite piled along the centre of the seam, the effect of having a wrinkle on flow was largely reduced to a point where the leakage was no larger than that through a single panel of GCL. Second, leakage through geomembrane holes in a mine tailings configuration was examined for three silty-sand tailings and four underliners (underliners ranging from silty-sand to pea gravel). The effect of different tailings, different underliners, different geomembrane type and thickness, different hole sizes, different applied stresses and heads, a nonwoven geotextile cushioning layer, and gap beneath a geomembrane hole (due to a wrinkle or stone on the foundation) on leakage are reported. The hydraulic conductivity of the tailings had largest effect on flow with a maximum measured flow (without piping) of 8.5 lpd for the cases examined. Free-flowing tailings slurry or that migrating under the applied hydraulic gradient filled any gaps beneath the geomembrane hole. There was evidence of fines migration from the tailings, through the hole, and to the underliner or geotextile. Although there was no effect of geomembrane thickness on flow, the 1-mm-thick geomembrane wrinkles were deformed to an extent that the inner sides were in contact at an applied stress of 250kPa, inducing excessive stains in the geomembrane.