The significance of the contact angle in characterising the pore size distribution of geotextiles

摘要

The current test method for quantifying geotextile pore structure for filtration design isnthe AOS test (ASTM D 4751). The AOS test quantifies structure using a single value, the O95 or 95%nopening size. The bubblepoint test (ASTM D 6767) is a method for calculating the pore sizendistribution (PSD) of a geotextile. Information on a number of pore sizes more completely describes angeotextile, and may allow for better filtration design criteria. An important step of the bubblepoint testninvolves saturating a geotextile sample with a wetting fluid and then expelling the fluid usingncontrolled airflow. The data reduction of ASTM D 6767 supposedly accounts for the effect of thenwetting fluid, and several different wetting fluids are allowed. Accurate knowledge of the contact anglenbetween the wetting fluid and the geotextile is essential to computing accurate pore size distributions.nEven with accurate contact angle measurement, the use of different wetting fluids yields different porensize distributions. This suggests a need to re-examine the data reduction of ASTM D 6767.