Geotextile Pore Structure Characterization Using Image Analysis

Filtration performance of geotextiles strongly depends on their pore structure parameters, i.e. percent open area (POA), pore opening size distribution (PSD) and constriction size distribution (CSD). Current methods of determination of pore structure parameters contain inherent disadvantages whereas image analysis can be used effectively for this purpose. Two new image-based PSD and CSD determination methods and a new imagebased POA determination method were developed specifically for woven and nonwoven geotextiles. The POAs, and a characteristic pore opening or constriction size, O95 or C95, of various geotextiles were determined using the information provided by the image analysis methods. The image-based POAs and the pore opening size of woven geotextiles were comparable to those obtained from the physical measurements and the values reported by the manufacturers. The constriction sizes of nonwoven geotextiles were comparable to the ones using the bubble point test and the values suggested by a theoretical equation. However, the image-based constriction sizes were consistently lower than the manufacturer’s reported apparent opening size, which is typically determined on the basis of the dry sieving test.