Cover systems with synthetic water‐repellent soils

Abstract

A cover system is a crucial component of engineered landfills, to minimize water percolation into the underlying waste. Capillary barriers are an alternative cover system, which has been widely used in the arid and semiarid regions as no cohesive, low-permeability materials are used. However, the performance of capillary barriers in tropical climate has been unsatisfactory (breakthrough observed). In recent years, synthetic water-repellent granular materials have drawn increasing attention due to their distinctive hydraulic behavior (inhibited water infiltration and high water entry pressure), suggesting they may also be used to improve the performance of cover systems. In this study, flume tests were conducted with inclined model slopes under artificial rainfall. By monitoring the surface runoff, lateral diversion, and basal percolation and conducting water balance analysis, the performance of monolithic cover, conventional capillary barrier, and water-repellent cover systems were evaluated. The study revealed that (a) the barrier effect and diversion capacity were significantly strengthened by induced water repellency, providing a promising solution to extend the application of capillary barrier covers; and (b) cover systems can be formed using one raw material to decrease the construction cost, by using synthetic water-repellent soil as the underlying layer.