Digital Image Analysis to Determine Pore Opening Size Distribution of Nonwoven Geotextiles

The filtration performance of a geotextile is controlled by its pore opening size distribution (PSD). Current methods for determining PSD are mostly indirect and contain inherent disadvantages. Recent technological advancements in image analysis offer great potential for a more accurate and direct way of determining the PSD of nonwoven geotextiles. A new and accurate method of image analysis for PSD determination of nonwoven geotextiles is presented in this paper. The image analysis method was developed using various mathematical morphology algorithms to provide a complete PSD curve for each geotextile. The two characteristic pore opening sizes, O95 and O50, were determined from image analysis and were compared to the results from laboratory tests, analytical equations, as well as manufacturer’s reported apparent opening sizes (AOS). The image-based O95 pore opening size of various geotextiles was comparable to the manufacturer’s reported AOS as well as to those determined from the laboratory dry sieving test. However, the measured O50 pore opening size was lower than the one determined using the analytical equations developed by two previous researchers. Overall, the image analysis method presented provides a unique and accurate method that can measure fiber thickness and pore opening sizes in a cross-sectional image of a woven geotextile.