Effect of geosynthetics on the hydraulic performance of leak-detection systems

The hydraulic performance of a leak-detection - secondary leachate collection system below a composite liner consisting of a geomembrane (GM) over a geosynthetic clay liner (GCL) is studied using the finite element method. The effect of the initial conditions in the underlying foundation layer (e.g., compacted site soils), distance from the leakage point to the drainage point, properties of the GCL, hydration history of the GCL, and the presence- absence of a foundation layer are examined. The interaction between the GM-GCL interface, GCL foundation layer in- terface, and the underlying geocomposite is investigated. The time for leakage to be detected is shown to be highly de- pendent on the material below the composite liner, the initial degree of saturation of the material, and the distance between the hole wrinkle and the drainage point in the system. Under some circumstances this could result in leakage not being detected for a considerable period of time. Predicted leakage is shown to be similar in magnitude to that re- ported in field monitoring. A comparison of an analytical solution for steady state conditions with the numerical solu- tion shows excellent agreement.