Effect of unequal biaxial tensile strains on the filtration behaviour of continuous filament needle-punched nonwoven geotextiles

Abstract

The effect of unequal biaxial tensile strains on the filtration behaviour of continuous filament needle-punched nonwoven geotextiles was investigated via gradient ratio tests. The filtration behaviour of four groups of unequal biaxial tensile strains were examined, including the gradient ratio (GR), permeability of the soil-geotextile system, mass of soil loss, and permittivity of pure geotextiles. The strains in the machine direction of a geotextile in the four groups were the same, ranging from 10% to 30%, with the ratios of the strain in the machine direction to that in the cross-machine direction set to 1, 2, 3, and 4, respectively. It is shown that for the same strain ratio, the GR value at the time of test termination (GRt) increases with increasing strain, and the permeability of the soil-geotextile system, permittivity of pure geotextiles, and the soil loss decrease with increasing strain. For the same strain in the machine direction, there are general decreasing trends for the GRt value and soil loss with increasing strain ratio, and the permeability of the soil-geotextile system and permittivity of pure geotextiles under equal biaxial tensile strains are higher than those under unequal biaxial tensile strains.