Percent light penetration of woven geotextiles and its relationship to soil slurry retention

Shobha K. Bhatia, Mahmoud Khachan, Kartheek Shivalingappa

Dans les comptes rendus d’articles de la conférence: GeoMontréal 2013: 66th Canadian Geotechnical Conference; 11th joint with IAH-CNC

Session: Geosynthetics - Drainage and Soil Filtration

ABSTRACT: Woven geotextiles are commonly used for filtration application. Several filter design criteria for woven geotextiles include the Percent Open Area (POA) of the geotextile. Commonly used technique to measure Percent Open Area (POA) of a geotextile is called Light Projection Method (COE 02215). This technique has some constraints such as the procedure is highly time consuming and operator dependent. A simple technique could be used to measure Percent Open Area (POA) is percent Light Penetration. In this study, fourteen woven geotextiles are used and for these geotextiles percent Light Penetration tests were conducted. Pressure Filtration tests were also performed to measure soil piping and finally, relationship between percent Light Penetration and soil piping was established. In addition, an excellent correlation between percent Light Penetration and Percent Open Area (POA) was found. It is proposed that the percent Light Penetration be used as an indicator of woven geotextile™s soil slurry retention performance.

RÉSUMÉ: Les géotextiles tissés sont couramment utilisés pour des applications d™évacuation et de filtration. De nombreux critères de conception de filtres pour les géotextiles tissés comprennent. le Pourcentage d'Aire Ouverte (POA) de géotextile tissé, une technique couramment utilisée pour mesurer le Pourcentage d™Aire Ouverte (POA) d'un géotextile qui est appelée Méthode de Projection de Lumière (COE 02215). Cette technique présente certaines contraintes telles que la procédure est assez prenante et dépendante de l'opérateur. Une technique simple peut être utilisée pour mesurer le Pourcentage d™Aire Ouverte (POA) est le pourcentage de pénétration de la lumière. Dans cette étude, quatorze géotextiles tissés sont utilisés sur lesquels des tests de pénétration de la Lumière ont été réalisés. Des tests de filtration de pression on été réalisés afin de mesurer la tuyauterie du sol. Enfin, la relation entre le pourcentage de la pénétration de la lumière et la tuyauterie du sol a été étudiée. En outre, une correlation excellente entre le pourcentage de pénétration de lumière, le Pourcentage d™Aire Ouverte (POA) a été trouvée. Il est suggéré que le Pourcentage de pénétration de lumière soit utilisé Commeindicateur de la realization de retention de boue de géotextiles du sol. 1 INTRODUCTION Woven geotextiles are commonly being used for drainage and filtration applications. For the purpose of design, a proper filter criterion has to be implemented to avoid failures. Several researchers have demonstrated that woven geotextile properties, such as Pore size distribution, Apparent Opening Size (AOS), Filtration Opening Size (FOS) and Percent Open Area (POA) are directly related to its filtration performance (Austin et al, 1997; Bhatia et al, 1996: Mylnarek and Lombard, 1997; Aydilek and Edil 2004). Many of the criteria currently in use for filter designs are based upon ratios of geotextile pore opening size to soil grain size (Aydilek, 2004). For effective filter performance, it is necessary that the largest pore openings of the geotextile should be smaller than the large size fraction of the soil grains to prevent soil migration, likewise, the small pore openings of the geotextile should be larger than the small size fraction of the soil to prevent blocking (Aydilek and Edil, 2004). Additionally, Percent Open Area (POA) has been recommended as an additional selection criterion for woven geotextiles by several researchers (Calhoun, 1972; Mlynarek and Lombard (1997), Aydilek and Edil, 2004). Calhoun™s criteria (1972) recommended using a woven geotextile with a higher Percent Open Area (POA), specifically the criteria prescribes a fiPercent Open Area (POA) of up to 40% for soils containing 50 % or less of particles passing the No.200 sieve or a Percent Open Area (POA) of up to 10% for soils having little or no cohesion and containing more than 50% silt by weightfl. Since Calhoun™s work, woven geotextiles design has been based on Percent Open Area (US Army Corps of Engineers, 1972). However, filter design researchers have questioned the use of Percent Open Area (POA) (Giroud, 1996). Nevertheless, a research study by Mlynarek and Lombard (1997) has shown that the Percent Open Area (POA) still proves to be an important property of a woven geotextile for design consideration and the study also showed that the Percent Open Area (POA) has a direct relationship with soil piping. Aydilek, (2004) and Aydilek and Edil (2004) also show that Percent Open Area (POA) has a direct effect on filter performance and is directly correlated with permittivity. It is important to note that the role of POA has not been explored for soil slurry retention, which is important for the woven geotextile™s performance in geotextile tube dewatering application. Several techniques have been developed to determine the Percent Open Area (POA) of woven geotextiles (Bhatia et al. 1996). A commonly used technique to measure Percent Open Area (POA) of a geotextile is called Light Projection Method (COE 02215). This technique has some constraints, such as the procedure is highly time consuming and operator dependent (Aydilek, 2004).The standard test also indicates only the actual percentage opening of a woven

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