Common practice and innovations in talings dams using geosynthetic tubes
Abstract
This paper demonstrates innovative concepts for building tailings dam embankments with the help of geotextile dewatering tubes and introduces the corresponding stability considerations. Geotextiles tubes were originally developed for the purpose of dewatering of sewage and sediments. In combination with carefully selected flocculation aids almost every type of sludge can be dewatered, stored safely and the required storage volumes reduced. Another focus of this paper is a new development combining the advantages of geosynthetic mattresses and geotextile tubes intended for the use in protection and sealing as ballast layers on tailings dam embankments.
Conclusion
In this paper early concepts about the utilization of geosynthetic dewatering tubes in tailings dams have been presented. This innovative methodology enables the increase of the storage capacity in the pond by using tailings as embankment fill material in tailings dams. The transport and installation of imported granular fill materials is reduced significantly by the deployment of this methodology. The principles of the dewatering process and the dimensioning of dewatering tubes with regard to the required tensile strength and filtration properties of the fabric was demonstrated. In recent dewatering projects stacking of tubes has been carried out successfully (Wilke & Breytenbach 2016). Practical experience with the construction of the main components of a tailings dam built with geosynthetic dewatering tubes with particular reference to the downstream raising method was introduced in the paper.
In order to mitigate the possibility of failure design should consider the main failure modes. The lack of design guidelines specifically developed for dewatering tubes can be compensated for by combination of existing guidelines dealing with the design of tailings dams, encapsulated sand containers (Bezuijnen & Vastenburg 2013) and geosynthetics in retaining structures or slopes (EBGEO 2010 or other national guidelines). In future stability analysis (analytical or numerical), fields trials or laboratory tests should be used to study the behaviour of stacked dewatering tubes. Verification of the analytical models is essential in order to improve on the reliability of the stability analysis of tailings dams built with dewatering tubes. Geomembrane protection/ballast layers for upstream tailings dams slope protection can deliver significant benefits and could improve the durability of tailings dams in the long term.