Physical and hydraulic response of geomembrane wrinkles underlying saturated fine tailings

Abstract

The effect of applied pressure on the deformation of a prescribed wrinkle, with and without a hole, in four different geomembranes (1 and 2 mm thick high density polyethylene (HDPE) and 1 and 2 mm thick linear low-density polyethylene (LLDPE)), placed on a compacted silty-sand underliner and backfilled with saturated fine tailings at 65% solids content, is investigated. For the 1 mm thick geomembranes without holes, the gap beneath the wrinkle was eliminated (but the geomembrane was excessively strained) at an applied total stress of 250 kPa, whereas for the 2 mm thick geomembranes the gap remained even under a total stress of 1000 kPa. The short-term performance was the same for both LLDPE and HDPE. For wrinkles with a hole, any gap that remained beneath the wrinkle was completely filled by tailings. The tailings migrated into the gap beneath the wrinkle partly as free-flowing slurry and partly under the applied hydraulic gradient. There was a difference in the shape of the final wrinkle depending on whether the hole in the wrinkle was present before or after backfilling with tailings. However, the same leakage was measured through a 10 mm diameter hole in both cases. With an increase in applied vertical stress, the leakage decreased.