Leakage through Holes in Geomembranes below Saturated Tailings: Fid-Bau Portal

Leakage through Holes in Geomembranes below Saturated Tailings

Rowe, R. Kerry / Joshi, Prabeen / Brachman, R. W. I. / McLeod, H.

Experiments conducted to quantify potential leakage from holes in two geomembranes [1-mm-thick linear low-density polyethylene (LLDPE) and 2-mm-thick high-density polyethylene (HDPE)] placed on a silty-sand [underliner hydraulic conductivity ( $k_{UL}$ ), $1.1 \times 10^{- 7} \leq k_{UL} \leq 1.2 \times 10^{- 5} m / s$ ], or pea gravel ( $k_{UL} = 1 \times 10^{- 2} m / s$ ) underliner (foundation/subgrade) and covered with saturated fine tailings at 65% initial solids content are discussed [tailings hydraulic conductivity ( $k_{T}$ ), $2.9 \times 10^{- 8} \leq k_{T} \leq 1.6 \times 10^{−6} m / s$ ]. Tests results show that the overlying tailings, with a $k_{T} < k_{UL}$ , filled the geomembrane hole and had a larger effect on flow through the hole than the underliners examined. For the tested conditions, leakage through 10 and 20-mm-diameter holes were essentially the same whereas the leakage through a 1.5-mm-diameter hole was three orders of magnitude lower. Introduction of a $580 g / m^{2}$ nonwoven needle-punched geotextile (GTX) layer between the geomembrane and tailings increased the flow by approximately 60%. A gap below geomembrane hole attributable to a stone on the underliner filled with tailings, which flowed through the hole. The evidence of fines migration through the hole, from the tailings to the underliner is discussed.