Study on the Anti-seepage Performance of Compacted Tailing Sand-Bentonite Mixture in Landfill Cover System

Abstract

Purposes To achieve the reuse of solid waste, the feasibility of using compacted tailings-bentonite material as an impermeable material for landfill cover system is explored in this study. The maximum dry density values of tailings-bentonite mixtures with varying bentonite contents are determined through compaction tests. Methods Saturated permeability coefficients of the tailings-bentonite mixtures were measured by using a consolidation permeameter. Additionally, the pore characteristics of the samples were analyzed through mercury intrusion porosimetry and scanning electron microscopy tests. Finally, the service performance of compacted tailings-bentonite mixture in cover systems was investigated by using numerical simulations. Findings The results reveal that the maximum dry density of the tailings-bentonite mixture first increases and then decreases with increasing bentonite content, reaching the maximum of 1.94 g/cm3 at 10% bentonite content. The permeability coefficient of the compacted tailings-bentonite mixture decreases with the increase of bentonite content. A bentonite content of 10% or higher satisfies the permeability requirement for the impermeable layer, i.e., ks=5.61×10-10 m/s, ≤10-9 m/s; in this case, an impermeable layer with a thickness of 10 cm meets the requirement that annual percolation ≤30 mm. Additionally, setting a certain slope to facilitate lateral drainage can effectively reduce the percolation through landfill cover system.

Keywords

• landfill cover system
• tailings
• bentonite
• permeability
• percolation