Influence of Geotextile Structure on Pore Size Determination

Abstract

Filtration performance of a geotextile is related to its capacity to retain soil particles over time without clogging. A pore size determination such as the filtration opening size (FOS) is used to assess the geotextile's filtration behavior. Standard hydrodynamic methods use a soil with a uniformity coefficient (Cu) greater than 6, with the coarser particle size value at least twice the estimated FOS value, and with a d10 four times smaller than the FOS value. The filtration opening size determination, using such a soil, is greatly influenced by the size of the coarser particles and by their fraction. Pore size has been overestimated because of these factors and because of the curve continuity. The soil nature of the gradation curve and the quantity of soil used in the test may distort pore size determination, hide some phenomena, and lead to errors in interpretation. The geotextile structure can be characterized by the mass per unit area, thickness, density of fibers, fiber diameter, porosity, and fabrication process. This report includes the first results of a laboratory study performed at the Polytechnical School of Montreal, the University of Liège, the University of Grenoble, CEMAGREF (Antony, France), ENEL (Milano, Italy) and the Ontario Ministry of Transports (Toronto, Canada) on the interaction between geotextile structure and filtration opening size (FOS).

Constriction Size of Geotextile Filters

“…where d f = fiber thickness; n = porosity; t = geotextile thickness; = dimensionless parameter; and O f = filtration opening size and is usually given by the nearly largest constriction size of a particular geotextile (e.g., C 95 ). Comparisons of with the data of 52 laboratory tests published by Rigo et al (1990) indicated that the use of = 10 is reasonable (Giroud 1996). The fiber thickness ͑d f ͒ was measured from the captured images and an equation given by Wayne and Koerner (1993) was used to determine the porosity ͑n͒…”

Hydrodynamics of soil immobilization in the immobilized soil bioreactor

“…The nonwoven geotextile is a highly porous material. Since this material has a wide pore size distribution-between several microns and approximately 300 p m (Silva and Bhatia, 1993;Rigo et al, 1990)-it is expected that different-sized soil particles could be entrapped in these pores, and therefore be fixed in space. (Strictly speaking, nonwoven geotextile has no pores with a determined length and diameter such as are in rigid porous materials like the ones used in catalysis.…”

Filter Performance and Design for Highway Drains

“…According to Rigo et al (1990) geotextile properties playing an important role in filtration are: fiber diameter, fabric thickness, fabric density (mass per area), fabric porosity and filtration opening size. Among these properties, the opening size has been found in various types of laboratory tests a key parameter in control of geotextile filter performance.…”