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Assinder, P. | Breytenbach, M. | Wiemers, Dipl. - Ing. J.

Utilizing geotextile tubes to extend the life of a Tailings Storage Facility

Resumo

As environmental legislation becomes more stringent, the required capital and operational in-vestment for the construction and operation of mine Tailings Storage Facilities (TSF) is increasing significantly. The paper describes the system of geotextile tubes filled with tailings to create structural elements to enable the use of filled tubes to create extensions/rises for new and existing TSF's. Tubes can be placed as a new dam foundation or stacked on top of existing tailings dams, resulting in dam embankments comprising filled geo-textile tubes, which leads to increased storage capacity for the mine operator and a subsequent expansion of the life of TSF's. Additionally, it is possible to use a broad range of tailings within the geotextile tube due to the potential to dewater the fills with flocculation agents, if required, during the filling process. The construction process is described and the required geotechnical stability aspects explored.

Conclusão

In this paper concepts about the utilization of geo-textile dewatering tubes to form the embankments of tailings dams have been presented. This innovative construction methodology enables the increase of the storage capacity in the pond by using the tailings as embankment fill material within the tailing dams. The use of dewatering geotextile tubes has a large poten-tial to lower the transportation and installation of im-ported granular fill materials and the associated capi-tal expenditure and carbon footprint. The principles of the dewatering process and the dimensioning of de-watering tubes with regard to the required tensile strength and filter stability of the fabric was demon-strated. In recent dewatering projects experience in the high stacking of dewatered geotextile tubes has successfully been undertaken (Wilke 2015). With re-gard to practical aspects the main components of a tailings dam built with geosynthetic dewatering tubes as well as the downstream construction method were also introduced. In order to avoid any performance failures of a tailings dam embankment constructed with dewatering geotextile tubes, a precise design considering the main failure modes is required. The current lack of design guidance can be compensated with a combination of existing guidelines dealing with tailings dams, encapsulated sand containers and geosynthetics in retaining structures. It is considered that methods of apparent cohesion and/or tensile strength design approaches, coupled with appropriate numerical modelling, will provide sufficient design robustness to prove the safety of such structures. The undertaking of further research, comprising further stability analysis (analytical and numerical), test fields and laboratory tests, will improve our knowledge of the behaviour and interaction of stacked dewatered geotextile tubes to form dam em-bankment structures. The knowledge of these subjects remain essential for the stability analysis of tailings dams built with dewatering geotextile tubes and new research will continue to be published through 2016.