Weathering tests for acid rock drainage prediction at the Irapé Dam, Brazil
DOI:
https://doi.org/10.14195/2184-8394_128_3Keywords:
Acid rock drainage, Static and kinetic tests, Earth-rock dam, SulfidesAbstract
The Irapé Dam, southeastern Brazil, was inaugurated in 2006, representing a milestone in Brazilian engineering due to the site adverse conditions, including steep topography and the presence of sulfides in the foundation rock, which could generate acid rock drainage (ARD). At that time the ARD problem was not well known in the construction of large earth-rock dams, which led to complementary research to control and reduce the associated environmental and engineering risks. The results of this research supported innovative engineering measures, including rock zoning, the use of impermeable geosynthetics and additives to protect the concrete structures. This paper presents complementary research on the quality and quantity of possible ARD generated with rock samples from that site. The experimental campaign involved rock sampling, petrographic and chemical characterization, both static (paste pH and NAG) and kinetic (column and Soxhlet leaching, natural and sulfate cycling). The results of the kinetic test and paste pH demonstrated no acid generation, as opposed to the NAG tests, which resulted in acid formation. The presence of sulfides in the petrographic analyses also indicated acid potential for the rock specimens. Considering these conflicting results further research is needed.
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References
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