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 ma terial. Measurements of strain, or displacement, are typically provide d by attaching electronic sensors directly to the geosynthetic specime n. Of interest and concern, is the comparison between the measured str ain and the true (global) strain experienced by the geosynthetic. The measured strain, is influenced by the structure of the geosynthetic, t he size of the sensor, the attachment technique used for the sensor an d the type of load applied. A large wide-width strip tension apparatus was constructed to assess the differences between the global and meas ured strain for four types of strain sensors attached to geogrid and g eotextile specimens. The four sensors used were vibrating wire displac ement gages, vibrating wire strain gages, linear variable differential transformers, and bonded resistance foil strain gages. The results in dicate differences between the measured and global strain response wit h the magnitude of these differences being dependent on the sensor, th e geosynthetic material, and the type of load applied. Calibration fac tors are developed and applied to the results to achieve a match betwe en the measured and global strains.