Numerical study of advective flow through composite liners

Leakage through composite liners used in landfills with a damaged geomembrane is analysed in this paper using a 2D numerical code. The main emphasis of this study is to assess the influence of the degree of saturation of the soil liner on the leakage rate in composite liners. The interface between the geomembrane and the clay liner is modelled as a high hydraulic conductivity medium. This conceptualisation is inspired by previous work on single fractures in porous media. Flow rates obtained from simulations assuming a uniform interface transmissivity are compared with leakage rates calculated using an existing analytical solution. Results reveal that: (a) the modelled flow is highly dominated by flow in the interface; (b) the initial degree of saturation of the soil liner has negligible effect on flow rates; and (c) predictions from analytical solutions and numerical results are consistent.