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

Geotextiles were widely used as the filtration materials in civil engineering, water conservancy, transportation, environmental engineering and other fields. As an important parameter in filtration application, the pore size characteristics are commonly determined in the unstrained test at present, whereas a large amount of testing data show that the filtration applications of geotextiles are usually subjected to tensile loads to some extent. For there is no any research on change of the geotextiles pore size in biaxial tensile strains condition, the paper proposed a theoretical formula based on the previous studies, which can predict the change of the pore size and the filtration performance of a geotextile. Furthermore, the formula was verified by a pore size test in biaxial tensile strains condition.1) The theories about the pore size of non-woven geotextiles with a complicated space network structure are mainly divided into two categories. Based on the two analytical models, the analytical solutions about the equivalent pore size O95and pore size distributions (PSDbi) subjected to equal biaxial tensile strains are proposed in this study.2) The non-woven geotextiles were equal biaxial-stretched using a biaxial elongation apparatus, in which a special fixture was used to maintain the tensile strain. The biaxial strained pore size distributions curves were tested by dry sieving, which can eliminate electrostatic effect, and the characteristic pore size parameters were obtained. The experimental results were compared with both the theoretical models to validate the theoretical models. Both the theories can well predict the change of the pore size of a non-woven geotextile under equal biaxial tensile strains.3) Depending on the two-dimensional structure of woven geotextiles, analytical solutions about the strained percent open area (POAbi) and the equivalent pore size are obtained under certain equal and unequal biaxial tensile strains. Three types of woven geotextiles with different mass per unit area were biaxial-stretched using a biaxial elongation apparatus. The pore size characteristic parameters of the geotextiles under several levels of strains were measured by image analysis, including POA, PSD and the characteristic pore sizes (O95、O50、O30).The experimental data were compared with the results obtained by the proposed analytical solutions to verify that the analytical solutions can well predict the change of the pore size of a woven geotextile. The comparisons of the experimental data with the results obtained by the theories under equal and unequal biaxial strains indicate that the unequal biaxial strains have a greater effect on the pore size of the geotextiles. Moreover, the study summarized the change rule of the woven geotextiles under biaxial strains.