Composite geomembranes are made by bonding a plastic film, which serves as the base for waterproofing, with non-woven fabric. Their waterproofing performance primarily depends on the waterproofing characteristics of the plastic film. The plastic films commonly used in waterproofing applications worldwide include polyvinyl chloride (PVC), polyethylene (PE), and ethylene/vinyl acetate copolymer (EVA). These are high molecular weight, flexible chemical materials with low density, high extensibility, high adaptability to deformation, corrosion resistance, and good low-temperature and anti-freezing properties. The service life of composite geomembranes is primarily determined by whether the plastic film retains its waterproofing and water-separation functions. According to the Soviet National Standards, polyethylene films with a thickness of 0.2 meters and stabilizers used in hydraulic engineering can operate for 40 to 50 years under clean water conditions and 30 to 40 years under wastewater conditions. Therefore, the service life of composite geomembranes is sufficient to meet the dam waterproofing requirements.