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Synthetic flocculants have been used for decades in the mining industry, particularly in solid liquid separation related to thickening. Recently, the use of these chemicals to achieve improved depositional behaviour of tailings has been trialled, and implemented at a small number of mine sites. In these early attempts, flocculant addition just prior to deposition has improved the dewatering of deposited tailings and resulted in a steeper beaching angle. This has the potential to reduce capital and operating costs for tailings management if implemented correctly. While this is a promising new technology, very little research is available on the impact of flocculants on a number of important geotechnical parameters. An experimental programme has commenced to quantify these impacts.
The increased settling rate of flocculated material provides implicit evidence of the increased apparent particle size resulting from this process. However, this increase in apparent particle size is known to be sensitive to shearing and other effects. Therefore, it is possible that sufficient confining pressures or shear would quickly break down the flocculated particles, making the geotechnical behaviour of a material indistinguishable whether flocculated or not. However, little evidence exists to support or disprove this hypothesis.
Preliminary results from a laboratory testing programme to determine consolidation properties and particle size distribution for kaolin with, and without, flocculant addition are presented. Unique sample preparation methods have been utilised in an attempt to isolate the effects of flocculant addition. Initial results indicate that the effects of flocculant addition are not noticeable upon application of relatively small effective stresses to the samples. Further laboratory testing is required to assess if this conclusion can be extended to a variety of other tailings, flocculants, and resulting geotechnical properties.
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