Two fabrics and one membrane are geotechnical impervious materials made of plastic film and non-woven fabric. Its impermeability mainly depends on the impermeability of plastic film. At present, there are mainly two kinds of plastic films used for seepage control: polyvinyl chloride (PVC) and polyethylene (PE), which are polymer chemical flexible materials with low specific gravity, strong ductility, high deformation adaptability, corrosion resistance, low temperature resistance and good frost resistance. The thickness of the membrane is usually 0.30-2.00 mm. The main mechanism is to block the leakage channel of the earth dam with the impermeability of plastic membrane, and to bear the water pressure and adapt to the dam deformation with its great tensile strength and elongation. Non-woven fabric is also a kind of polymer fiber chemical material, which has high tensile strength and extensibility through needling or thermal bonding. At present, as long as there are composite nonwovens, there are polyester staple needle-punched geotextiles, polyester long-filament spunbonded geotextiles, flat-filament plastic woven fabrics and so on. When combined with plastic film, it not only increases the tensile strength and puncture resistance of plastic film, but also increases the friction coefficient of contact surface because of the rough surface of non-woven fabric, which is beneficial to the stability of composite geomembrane and protective layer. At the same time, it has good corrosion resistance to bacteria and chemical action, and is not afraid of acid, alkali and salt corrosion.