Abstract
Because of the large number of practical applications using the in-plane hydraulic properties of bulky geotextiles, there exists a need for a suitable test method, which should eventually be standardized. The method developed here measures the parallel flow of water in a constant head device using relatively large rectangular specimens measuring 61.0 by 30.6 cm (24 by 12 in.). The device can support normal stresses on the geotextile up to approximately 144 kPa (3000 lb/ft2).
The basic parameter measured is transmissivity (the in-plane coefficient of permeability times the geotextile's thickness), which behaves as a strongly exponential decreasing function with increasing normal stress. A wide variety of needled nonwoven geotextiles were tested with transmissivity values ranging between 0.062 to 0.14 cm3/s/cm (0.004 and 0.009 ft3/min/ft) fabric. Tests on multiple layers of fabrics showed an increase in transmissivity roughly proportional to the thickness of the total number of layers. When the thickness was eliminated from the transmissivity values, it was seen that the in-plane coefficient of permeability was equivalent to that of a coarse to fine sand and was highest for a single layer of fabric and decreased as the fabric layers increased.
As a final comment, the need for geotextile transmissivity test standardization is noted and highly recommended.
