FILTRATION AND CLOGGING PERFORMANCE OF GEOTEXTILES

Abstract

Geotextiles have been widely used in soil structures for separation, filtration, reinforcing and drainage. They are often used to provide reinforcement and filtration for retaining walls and embankments. While reinforcement is an important function expected from geotextile systems, filtration is another function that is critical for the long-term performance. Geotextile filters are rapidly replacing graded granular filters as the standard of practice in geotechnical design The objective of this study is to predict the behavior of the geotextile filter, to calculate its long term performance for the locally available soils (Solani sand and clayey soil) using three different geotextiles (two nonwoven and one woven). Importance of long term behavior of geotextiles is considered in view of development of these materials for a number of applications where long life duration and safety are essential. Nonwoven geotextiles are commonly used in filtration applications. In this research work the long-term performance of needle-punched nonwoven geotextiles used as filters in coastal and river bank applications is evaluated. Filtration tests on soil-geotextile filter systems are conducted in the laboratory in order to evaluate the filtration and clogging performance. A laboratory test program has been executed to evaluate the filtration performance of two different nonwoven geotextiles in combination with locally available Solani sand and clayey soils. For comparison, these geomaterials has been also tested with one single-woven geotextile. The present work describes the concept and details of the test method called the fine fraction filtration (F3) test and presents data on three different geotextiles which were evaluated using three different soil types. This is useful test where the upstream soil particles are not in intimate contact with the geotextile filter. To differentiate the liquid flowing conditions, soils in intimate contact with the geotextiles are tested using constant and falling head permeameter apparatus. Geotextiles when used in filtration applications, decrease in permittivity (which means increase in clogging) with time has been observed. It has been observed that the non-woven geotextiles behaved better in all filtration applications than woven geotextile. At equilibrium, higher permittivity of geotextile-soil system, than the soil alone was observed. For geotextiles in contact with soils higher permeability was observed with increasing the number of layers of geotextile.