Polyethylene expands a lot with temperature, so black HDPE heating in afternoon sun grows into wrinkles that can stand well clear of the subgrade. Waves buried under soil get folded in and can later stress crack or trap liquid, so specs limit wrinkle height and crews cover in the cool part of the day or work the waves out to the edges. At night the same sheet shrinks and can pull tight.
Waves are knee high by two o'clock, so stop the cover crew and come back at first light.
Place cover soil early in the morning when the sheet is cool and flat, and push the soil so it walks small waves out instead of folding them over.
Also heard as
- wrinkles
- thermal wrinkles
Related terms
HDPE
High-density polyethylene: the stiff, chemically resistant polymer used for most landfill and mining geomembranes.
Trampolining
Geomembrane pulled tight across a corner or the toe of a slope, leaving a gap underneath like a trampoline.
Composite liner
Barrier made of a geomembrane in direct contact with a low-permeability soil or GCL layer beneath it.
Deployment
Unrolling and positioning geosynthetic rolls in their final location before seaming or covering.