Characterization of Geotextile Void Structure

This paper presents results from a study undertaken to quantitatively evaluate a fibrous medium containing both voids and man-made filaments. The evaluation was conducted using optical images captured from surfaces of coupons cut from resin-impregnated specimens of a needle punched nonwoven (NPNW) geotextile under various boundary load conditions. The sizes of voids enclosed by adjacent filaments were measured using optical image analysis and expressed in terms of the largest inscribing opening size (LIOS). In contrast to the dimensionless parameters of global or local void ratio, the largest inscribing opening size is useful for directly measuring the actual void size which affects properties such as the hydraulic conductivity, soil retention/migration, compressibility, and tensile strength. LIOS was particularly suitable for analyzing images containing linear or curved line segments with relatively low values of void ratio. The results showed how the LIOS distribution varies as a function of normal load and shear displacement.