In-Plane Flow of Four Geosynthetics for Landfill Drainage
The in-plane flow behavior of four geosynthetics, including three geonets and one geocomposite, for landfill drainage applications was investigated. Laboratory testing was performed to evaluate the effect of boundary material (cover material), hydraulic gradient, applied normal compressive stress, and time on the flow rate. The boundary materials investigated were a geomembrane, geotextile, sand, clay, two geosynthetic clay liners, and foam rubber. Testing was performed at hydraulic gradients from 0.03 to 1.0, with normal compressive stresses from 25 to 930 kPa. The highest flow rate was obtained with the geonet or geocomposite between two geomembranes. The flow rate was lower for the other configurations materials due to intrusion of the boundary material into the flow path. The type of soil used as a boundary material did not have a large effect on the flow rate. Foam rubber appears to be a suitable replacement for soil as a boundary material for flow testing. The flow rate was found to decrease with time due to creep of the geonet or geocomposite core and additional intrusion of the boundary material. Design implications based on the test results are addressed.