Analysis of Factors Affecting Strain Distribution in Geosynthetics

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 quality control/quality assurance evaluation of these materials and may play a critical role in design problems. A battery of tensile tests was conducted on 12 different geosynthetics to assess the effects of seam type, puncture, and clamping techniques on strain distributions. Digital images of the geosynthetic specimens were captured during testing, and the analyses of time-lapsed images were performed using two optical flow techniques to define strain distributions within specimens as well as in the vicinity of grip locations and seam zones. The results indicated that the optical flow techniques used in this study can successfully define the distribution of strains in a geosynthetic test specimen during tensile testing. The magnitude of lateral strains was small in polypropylene wovens and geogrids, whereas it was significant in polyester wovens and nonwovens. Large strains developed in the vicinity of seams regardless of the clamping technique used. The strains at the seam zones measured with hydraulic grips were significantly higher than those measured with roller grips. Sewn geosynthetics generally experienced lower lateral strain-to-axial strain ratios. The average axial strain appears to be insensitive to puncture regardless of the type of geosynthetics considered or the clamping technique used.

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