Apparatus and Technique for Measuring the Long-Term Transmissivity of Geocomposite Drains

The apparatus developed for measuring the change in geocomposite drain transmissivity with time in a double-liner system is presented, and the technique for monitoring changes in transmissivity with time is described. Tests conducted to evaluate the new equipment and assess the repeatability of transmissivity test results are presented. The use of the apparatus and technique is illustrated by examining the effect of the geonet core structure and manufacturing process on geocomposite drains flow rate in triplanar, triaxial, and biplanar geocomposite drains. Results show the change in transmissivity with time over a year at 250 kPa at 85°C.