Pore Size Characteristics And Filtration Properties Of Geotextiles Subjected To Tensile Strains

As filtration materials, the geotextiles are widely used in water conservancy, civil engineering, port, shipping and other fields. To ensure the effective filtration applications, the pore sizes of geotextiles typically need to meet several criteria, including retention, permeability, and anti-clogging capabilities. Pore size characteristics are important parameters in filtration applications. The filtration applications of geotextiles are usually subjected to tensile loads, whereas the characteristic pore sizes are commonly tested and determined in the unstrained condition, which results in the failure of filtration applications despite the satisfaction of design criteria. The cause of the failure in filtration applications is the influence of tensile strain on pore size characteristics. And the phenomenon of the failure is the influence of tensile strain on filtration properties. Hence, it’s important to study the analytical and experimental relationship among tensile strain (T), pore size characteristics (O), and filtration properties (F) of the geotextiles.1) The analytical relationship between tensile strain and pore size characteristics (the relationship of T-O) have been established. Depending on the two-dimensional structure of woven geotextiles, analytical solutions have been proposed to predict the pore size characteristics of woven slit-film geotextiles under certain uniaxial and biaxial tensile strains. The strained percent open area (POA) and equivalent pore size can be calculated based on the physical properties of the geotextiles and the tensile strains. When it comes to nonwoven geotextiles, the analytical solutions under uniaxial tensile strains have already been proposed to predict the characteristics pore size and the pore size distributions, which are the equations of uniaxial strained equivalent pore size by Wei She (2011), and the equation of uniaxial strained pore size distributions by Rawal(2011). Depending on the three-dimensional structure of nonwoven geotextiles, the analytical solutions about the equivalent pore size Obi95and pore size distributions PSDbi subjected to unequal biaxial tensile strains have been proposed.2) The experimental relationship between tensile strain and pore size characteristics (the relationship of T-O) have been established. The pore size parameters of three woven slit-film geotextiles subjected to several levels of strains were measured by image analysis. The uniaxial and biaxial strained pore size parameters of needle-punched nonwoven geotextiles have been tested by dry sieving. The experimental results were compared with the analytical predictions. The analytical results correlate well with the experimental results, and the pore size parameters change approximately linearly with tensile strains.3) The experimental relationship between tensile strain and filtration characteristics (the relationship of T-F) have been established. Gradient ratio tests are carried out to study the influence of uniaxial tensile strain on the filtration properties of geotextiles. Four kinds of geotextiles (two needle-punched nonwoven and two slit-film woven) are employed in the tests. The flow rate through the geotextiles, quantity of soil passed the geotextile, and the gradient ratio were analyzed depending on the filtration criteria. The variations of filtration characteristics agree with the influences of tesile strains on pore sizes. The relationships between pore size characteristics and filtration characteristics (the relationship of O-F) have been established qualitatively.4) The variations of passion’s ratio of geotextiles subjected to tensile strains have been involved in the analytical solutions of pore size. Hence, image analysis was adopted to determine the passion’s ratio of eight kinds of woven and nonwoven geotextiles. The strained passion’s ratio equations of incompressible and compressible materials have been proposed by Giroud(2004). The experimental results of passion’s ratio were compared with the equations.