A dynamic gradient ratio test apparatus

Abstract

The soil-geotextile filtration mechanism is a complex process which depends on physical compatibility between the geotextile and the soil to be retained. Several methods have been proposed by researchers for assessing the filtration behaviour of soil-geotextile composite systems under steady state conditions. The Gradient Ratio (GR) test is the most commonly used method for measuring filtration compatibility of soil-geotextile systems. This paper describes the design of a modified GR permeability test apparatus to overcome disadvantages associated with traditional GR test devices. The apparatus can perform filtration tests under static and dynamic conditions and can be used to evaluate the filtration compatibility of fine-grained soils with geotextiles. The apparatus is incorporated within a triaxial testing system, hence representative field stress conditions can be applied to test specimens. Some exemplar GR tests performed on coarse and fine-grained soils with a non-woven geotextile are presented in this paper. Unidirectional dynamic loads are applied within the filtration tests to replicate highway traffic loading. Test results show that dynamic loading affects the filtration behaviour at the soil-geotextile interface by increasing the fine particles migration towards the geotextile, but that, for the soil evaluated here, this effect was small.

Filtration performance of non- woven geotextiles with internally-stable and -unstable soils under dynamic loading

“…Very little research has been done to assess the filtration performance of geotextiles under highways and railways (Bell et al, 1982;Hoare, 1982;Alobaidi and Hoare, 1996, Fatahi et al, 2011, Kermani et al, 2018. Apparatus used to test filters have lacked control over stresses as well as precision of measurements (Khan et al, 2018). In addition, the internal stability of soils has not been taken into account.…”

“…Test specimens were prepared in a dynamic GR apparatus (Khan et al (2018); see Fig. 4) which can accommodate samples 50mm in diameter and 100mm high.…”

The role of geosynthetics in reducing the fluidisation potential of soft subgrade under cyclic loading

“…Dry and wet sieving, hydrodynamic sieving, mercury intrusion porosimetry, image analysis, and bubble point methods are commonly used to evaluate the pore size distribution of geotextiles (Aydilek et al 2002;Bhatia & Smith 1996); the different methods used to define soil and geotextile filtration, retention, and clogging criteria have also been studied earlier (Bhatia & Huang 1995;Faure et al 2006;Ghataora et al 2006;Ghosh & Yasuhara 2004;Palmeira et al 1997;Palmeira 2009;Xiao & Reddi 2000). The Gradient Ratio (GR) and Hydraulic Conductivity Ratio (HCR) are the common methods used to determine the permeability, hydraulic conductivity, and filtration capacity of geotextiles (Khan et al 2018;Palmeira & Gardoni 2000;Williams & Abouzakhm 1989). To evaluate the filtration of soil geotextile systems, the GR method is mainly used to describe the relationship between the hydraulic gradient across the soil geotextile interface and the hydraulic gradient that develops within the soil.…”

Laboratory evaluation of the filtration behavior of three filters wrapped around drain pipes in fine tailings based on a radial flow test

“…In the last few decades, fibrous filter materials have gradually replaced traditional granular filters due to their advantages of easy installation, space savings, and the versatility achieved through variations in fabric design/manufacture. [8][9][10] In the filtration process, filter performance is influenced by various parameters, including the physical properties of the soil (the particle type, concentration and size distribution) and the structural parameters of the fibrous filter (manufacturing process, opening size and thickness). 11,12 Koerner and Koerner 13 found that nonwoven geotextiles were easily clogged in cohesionless fine-grained soils based on a survey of 69 field failures involving geotextile filters.…”