Geomembrane strain gauge is a new kind of instrument used to measure strain of geomembrane. The key techniques in measuring large strain for the materials with low elastic modulus such as geotextiles and geomembranes were solved in the Chinese National 7th and 8th Five-Year Key Science and Technology Research Project. These techniques involved developing special method to achieve best sticking effect

seeking appropriate glue with the same lower modulus after being solidified to be compatible with geomembrane; developing new method in calibrating the gauge to get the two key parameters ( sensitivity coefficient k

and property index of geomebrane A) and solving problems in installation and protection. The gauge is reliable and durable in rigorous environment. It was used in-situ with good performance to monitor the strain of geomembrane in the 2nd-stage upstream cofferdam for Three Georges Project in May 1998.