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Geotechnical News • December 2014
45
WASTE GEOTECHNICS
• Sequencing discharge points to
avoid prolonged drying times of
tailings beaches that could result in
cracking or significant increases in
rewetting losses once deposition is
re-activated in dry areas.
The impact of these deposition strate-
gies on water recovery in a tailings
impoundment can be significant. As
an example, the make-up water for
one of the biggest mines in Chile was
reduced by approximately 40,000 m3/
day as a result of changes to the tail-
ings deposition strategy.
Overview of the laboratory
testing procedure
Although there is a general under-
standing of the deposition strategies
that maximize water recovery in a
tailings impoundment, the question
that usually needs to be addressed dur-
ing design is: how significant will this
recovery be for the proposed deposi-
tion plan? The answer is required to
determine the size of reclaim systems
and seawater pumping systems, and
is generally a key component of the
overall mine water balance.
In dry climates, quantifying water
recovery relies on developing accurate
predictions of evaporation and infiltra-
tion from freshly deposited tailings
as these losses dictate the amount
of water that will be available in the
reclaim pond for recirculation. This is
often addressed through the unsatu-
rated soil mechanics theory, which
is complex and relies on numerical
models that can be of limited accuracy
if not properly calibrated. The labora-
tory testing discussed in this article
has been developed to provide a basis
for calibration and validation of such
Figure 1. Tailings deposition in a dry climate.
Figure 2. Integrated approach used for the prediction of water recoveries
from tailings impoundments in dry climates.
Salfate figs.indd 1
14-11-10 11:58 AM
Figure 3. Typical drying column setup.