Specific geotechnical problems issued by the closure and ecological reconstruction of tailing ponds containing radioactive wastes
|Location||International Geological Congress,oslo 2008|
|Author||Mihai, Ovidiu Sorin; Caranda, Dan|
|Holding Date||08 October 2008|
The Earth surface transformation dynamics and the evolution concerning the environment restoration specific to the uranium mining objectives make compulsory a complex approach of the issues related to the closure and ecological restoration of tailing ponds containing radioactive wastes.Taking into account the IAEA experts’ recommendations from Vienna and the new concepts trends of the environment reconstruction for the uranium mining units, the present contribution will present the consequences from geotechnical viewpoint that such an ample work involves. The case study presented in this paperwork concerns a tailing pond containing radioactive wastes, having a surface of about 20 ha the amount of radioactive waste is 2,350, 000 m3 respectively 4,512,000 t.
The main phases of this operation involve the execution of the following scheduled categories of works:
- Collection, drainage and exhaustion of technological and pluvial waters from the ponds reservation through vertical drain system; - The contaminated land surfaces relocation into the pond from the pond’s slopes;
- Pond encapsulation and ecological restoration using geotextiles; the encapsulation operation "sandwich" type includes the compulsory utilization of the following layers: geotextile layer weaved (or geogrids) in order to hinder the workers’ and equipments subsidence; draining geotextile layer, which will conduct the water contained by the waste mass drained by the draining capillar toward the coast overflow; geomaterial layer (trisoplast) 7 cm thick, vegetal soil layer of 30 cm and finally a geothermal biodegradable seeded layer of about 3 cm.
From the geotechnical viewpoint the following main issues have to be established, correlated and monitored during the time:
- consolidation of material deposited on a small depth in order to improve the mechanical resistance with a view to allowing the traffic and safety deposition of (precompression) a coverage initial layer;
- determination of versants stability during the closure works progress (initial layer placement and checking of bearing capacity for the load due to the equipments);
- Long term settlement of material deposited in pond and its impact on the "encapsulation" integrity.