Steady Drainage of Landfill Covers and Bottom Liners

To design a drainage system for a landfill cover or bottom liner properly, the engineer must be able to estimate the maximum saturated depth over the barrier for any proposed configuration. This paper presents an analytical solution for steady drainage on a sloping impervious barrier with no flow across the upstream boundary. Based on the Dupuit approximation, this solution defines all possible phreatic‐surface profiles. The shape of the phreatic‐surface profile depends on the values of three dimensionless parameters: the barrier slope, the ratio of the vertical inflow rate to the hydraulic conductivity of the drainage layer, and the ratio of the saturated depth at the downstream boundary to the maximum drainage distance. Several distinctly different types of profiles are possible. A graph is provided for determining the maximum saturated depth directly.