Method and apparatus for forming a geomembrane with bent spikes

A method for forming a geomembrane, comprising:

• extruding a resin sheet from a flat extrusion die so that the resin sheet has first and second opposite flat surfaces;
• feeding the resin sheet along a feeding direction through a nip between first and second chill rollers so that the first chill roller contacts the first surface of the resin sheet and so that the second chill roller contacts the second surface of the resin sheet, the second chill roller having recesses and the first and second chill rollers applying sufficient pressure to the resin sheet for causing the resin adjacent the second surface of the resin sheet to flow into the recesses;
• separating the resin sheet from the first and second chill rollers so that the resin separated from the recesses in the second chill roller forms spikes projecting from the second surface of the resin sheet;
• and
• causing projecting ends of the spikes that project from the second surface of the resin sheet to move against a convexly curved spike bending surface thereby causing the spikes to bend relative to the feeding direction of the resin sheet.