Evaluation of Strain Distribution in Geotextiles Using Image Analysis

Localized strains due to production defects, seams and punctured zones significantly affect mechanical performance of geosynthetic materials. Accurate determination of localized strains becomes particularly important for QC/QA evaluation of these materials and plays a critical role in design problems. A number of geosynthetic specimens were tested in an accredited laboratory to determine strain distributions under wide-with tensile loading using image analysis techniques. Specimens were tested using both roller and pneumatic grips to identify the effects of clamping. The tensile load, cross head extensions and image frames at a specified rate were recorded during testing. The testing plan included nonwoven, low strength and high strength woven geotextiles each sewn with flat, butterfly and J-type seam to determine the effect of seaming on strain distributions. Punctured specimens were also used to simulate localized failures in field applications. Average strains were calculated at peak strength values to compare the performance of different geosynthetic specimens. The results indicated that digital image analysis is highly effective in determining the localized strains and their distributions within specimens tested with two different grips. Furthermore, the image-based strains can clearly identify the performance of different seam types and effect of puncture on specimen performance.