In-Isolation Strain Measurement of Geosynthetics in Wide-Width Strip Tension Test

Field and laboratory scale studies of geosynthetic behavior typically require an assessment of strain across a region of the geosynthetic material. Measurements of strain, or displacement, are typically provided by attaching electronic sensors directly to the geosynthetic specimen. Of interest and concern, is the comparison between the measured strain and the true (global) strain experienced by the geosynthetic. The measured strain, is influenced by the structure of the geosynthetic, the size of the sensor, the attachment technique used for the sensor and the type of load applied. A large wide-width strip tension apparatus was constructed to assess the differences between the global and measured strain for four types of strain sensors attached to geogrid and geotextile specimens. The four sensors used were vibrating wire displacement gages, vibrating wire strain gages, linear variable differential transformers, and bonded resistance foil strain gages. The results indicate differences between the measured and global strain response with the magnitude of these differences being dependent on the sensor, the geosynthetic material, and the type of load applied. Calibration factors are developed and applied to the results to achieve a match between the measured and global strains.