Steady-state drainage in a liquid collection system with two different slopes

Abstract

Liquid collection layers are commonly used as part of modern landfills. These collection layers are often composed of two sections with different slopes. Design methods are presently available for limited cases where there is no drain at the connection between the two sections. This paper presents a computational solution based on the Dupuit assumption to calculate the maximum liquid depth and provide the liquid profile for the drainage systems comprising two different slopes. A case study showed that, in most cases, the maximum depth of the downstream section is determined by the total horizontal length of the two sections, the slope of the downstream section, and the inflow rate. The application of a geocomposite in the downstream section can significantly reduce the maximum liquid depth in both the upstream and downstream sections of the drainage system. The application of a geocomposite in the upstream section can only influence the maximum depth in the upstream section of the drainage system. Simplified procedures are proposed that can estimate the maximum depth in the upstream and downstream sections if the drainage layer consists of one material.