Surface erosion effect on tailings

Abstract

Due to the high water consumption in process plants, the shortage of water, and its increasing cost in many regions in the world, maximum water recovery from tailings prior to transportation and placement in the tailings storage facility is a necessary outcome for many existing and proposed mines. There are also many other advantages to considering dewatered (thickened, paste, or filtered) tailings as a tailings management option, including improved geotechnical performance, reduced closure/reclamation costs, and even enhanced permitting expediency. Some properties of dewatered tailings are well understood and proven in an operating environment, whereas others can be defined by standard test procedures, for example, dry density, slump, rheology, and permeability (amongst others). However, some critical parameters, especially performance data, cannot be defined by standard tests and the database on operating dewatered tailings facilities is limited. These parameters include the definition of deposition slopes, erosion effect (hydraulic and wind), post-depositional re-saturation behaviour, and liquefaction susceptibility. The inability of some designers to appropriately identify these critical parameters has led to poor performance with some dewatered tailings facilities. Even though some of the largest mines and tailings deposits are located in dry areas, they are exposed to extremely large hydrology events (such as the 'Invierno Altiplánico' in the desert in northern Chile). These events may produce significant damage and excessive erosion on the tailings surface. The objective of this paper is to show the importance of the hydraulic erosion effects and how they could impede or even reverse reclamation work.