The intrinsic in-plane (IP) permeability (K||) and through-plane (TP) permeability (K⊥) of nonwoven geotextiles were measured experimentally. Also, the realistic 3D images of the samples were acquired by the nondestructive μCT technique and their microstructural characteristics were measured. This information was used to simulate virtual fibrous structures resembling the microstructure of geotextiles. The flow of fluid was then simulated through realistic and virtual structures and K|| and K⊥ were calculated. The experimental and predicted results were compared with each other and those of some empirical, analytical and numerical studies. A non-linear relation between both the K|| and K⊥ and geotextile porosity was observed.
It was found that for the same porosity, coarser fibers provide higher K|| and K⊥ and this is more pronounced at higher porosity values. It was observed that by increasing the IP fiber orientation in the flow direction, K|| increases exponentially, while K⊥ is independent of IP fiber orientation.
The anisotropic permeability ratios of samples were calculated and it was established that nonwoven geotextiles show highly anisotropic behavior with λ tending to unity with the increase of geotextile porosity.
It was shown that K⊥ increases with the increase of fiber orientation through the thickness direction.