Failure of an Industrial Residue Cover and Remediation Using the Cellular Confinement System

A large residue disposal area in the northeastern region of Brazil was required to be capped with an impermeable layer and vegetation. The residue was graded to a 35 m long 3H:1V-stable slope. The initial design had the following material layers (bottom to top): residue, 1.5 mm thick HDPE geomembrane, non- woven needle-punched geotextile, as well as 60 cm of cohesive soil and vegetation. Once half of the soil cover had been installed, a heavy rainfall-induced failure of both the soil cover and the geotextile occurred, while the geomembrane remained intact. In order to reconstruct the capping system, several options were analyzed. The final solution consisted of the following layers (bottom to top): residue, 1.5 mm thick HDPE geomembrane, non-woven needle-punched geotextile, 7.5 cm high sand-infilled HDPE-perforated Geoweb sections, as well as 20 cm of cohesive soil and vegetation. This paper describes the failure mechanism of the original solution and the remediation procedure.