A Thickness Equation for Nonwoven, Needle-Punched Geotextiles under Normal Loading
An equation to predict the thickness of nonwoven, needle-punched geotextiles under normal compressive loading is proposed. The equation is t=(t0-t8)e-as+t8 in which, t0 is the initial thickness, t8 is a limiting thickness, s is the normal stress, and a is an empirical coefficient. Comparison with thickness data obtained in multiple tests on eight different geotextiles using an in-plane, radial flow device results in excellent agreement for normal stresses up to about 372 kPa. Mean square errors are typically less than 0.017 mm. An equation for the limiting thickness, t8, is developed based on the observation that under compressive loads at the limiting thickness, nonwoven, needle-punched geotextiles have their porosity reduced to about 91% of the initial value.