摘要 |
Waterproofing material, as used to line ponds, lakes and landfill waste deposit sites, comprises a core layer ( 10 ) which incorporates swellable bentonite clay arranged between respective carrier layers ( 12, 14 ). In order to reduce relative slippage between the carrier layers ( 12, 14 ) and the core ( 10 ), the carrier layers ( 12, 14 ), which are preferably of polypropylene, polyethylene or PVC are connected to each other by ultrasonic welding along lines or at intervals. This may be either direct welding ( 18 ) of the layers ( 12, 14 ) to each other, or each layer ( 12, 14 ) may be welded (at 26 ) to a flexible perforate reinforcement ( 16 ) which is embedded in the core ( 10 ). |