Leakage through a hole in a geomembrane beneath a fine-grained tailings

Abstract

Leakage through a 10 mm diameter circular hole in a geomembrane beneath fine-grained tailings is examined for a range of pore pressures and effective stresses. Leakage was measured in an experiment with coupled physical and hydraulic conditions to simulate the effective stresses and flow conditions near the hole. The leakage rate was as little as 0.16 L/day with 200 kPa pore pressure (10–30 kPa effective stresses) and increased only to 0.46 L/day with 800 kPa pore pressure (200 kPa effective stress). Seepage analysis of the experiment and local measurements of permeability from small samples extracted after the experiment indicate that the tailings hydraulic conductivity controlling flow was 3–6 × 10−9 m/s. Only a subtle decrease in hydraulic conductivity (less than 2 times) near the hole was found. No evidence of seepage-induced migration of fines within the tailings was found. Calculations with the parameters deduced from the experiment show that leakage from a tailings storage facilities containing fine-grained tailings can be limited to 1–2 L/ha/day with a geomembrane liner, even when containing up to five 10 mm diameter holes per hectare, as opposed to an unlined facility with 3 to 4 orders of magnitude more leakage.