Comparative Evaluation of Geotextile Pore Sizes Using Bubble Point Test and Image Analysis

Abstract

Abstract Analysis of the filtration performance of a geotextile filter necessitates accurate information about the size distribution of geotextile pore openings. The effectiveness of the bubble point test in determining the pore and constriction sizes of geotextiles was evaluated. The characteristic woven geotextile pore and nonwoven geotextile constriction sizes, O95, were determined for a variety of specimens and compared with both the manufacturers' reported AOS values, and with those determined from the two previously developed image-based procedures and theoretical equations. The results indicated that the O95 sizes of woven mono and multifilament geotextiles determined by image analyses compared well with the AOS values, whereas the same observations were not made for the bubble point-based O95 sizes. The O95 constriction sizes of various nonwoven geotextiles obtained by the bubble point test were not comparable to the manufacturers' reported AOS values, indicating the limitation of ASTM D 4751 in determining constriction sizes. A direct method, such as image analysis, may be a better approach for determining the pore sizes of woven geotextiles, whereas the bubble point method should be preferred to determine constriction sizes in a nonwoven geotextile. Recommendations are made in regard to improvements in the current ASTM standard on bubble point testing.