Permeability of needle-punched nonwoven geotextiles subjected to uniaxial tensile strains

During their service life, needle-punched nonwoven geotextiles are frequently subjected to uniaxial tensile strains, which may impact their permeability behavior. The basic model of the permeability coefficient in nonwoven geotextiles was extended to the uniaxial tensile strain condition, considering the influence of the fiber orientation distribution. The model is expressed as a function of the tortuosity fractal dimension, pore size characteristics, fiber orientation, physical parameters, and tensile strain. To address errors in the results of traditional permeability tests attributed to the inhomogeneity and multiple layers of specimens, in situ X-ray computed tomography was used to acquire three-dimensional (3D) images of geotextiles during stretching. The 3D imaging technique was employed to extract the microstructure, facilitating fluid flow simulations for determining the permeability of two nonwoven geotextiles, thereby validating the theoretical method. The simulated permeability coefficient decreased slightly and then increased with increasing uniaxial tensile strain and the necking ratio. The theoretical permeability model exhibited a decreasing trend and then increases around 0.3% strain. The theoretical model accurately predicted the permeability and rate of change of geotextiles subjected to specific uniaxial tensile strains, thereby offering valuable insight into their effective utilization in various engineering applications.