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Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
compacted embankment, and a finer fraction that is placed
behind the constructed embankment. The underflow is usually
placed at water contents of around 6 to 10%. At these values,
the variation of PANDA resistance is less severe (as shown in
Table 1) for material that represents the coarser end of tailings
from Chilean copper mines. It may be for this reason, reinforced
by the reproducible nature of material prepared using
mechanical cyclones, that the PANDA has found such
widespread application in Chile. In jurisdictions such as
Australia, where the upstream (rather than the downstream)
method is widely used, tailings are placed as full-stream
tailings, and any segregation that occurs is due to natural sorting
processes that occur on the tailings beach. The water content is
also likely to be more variable than tailings placed used the
downstream technique, so the type of results shown in Table 1
may be much more important. Much more work clearly needs to
be done to determine the effect of initial moisture content on
penetrometer resistance for a range of tailings types.
6 DISCUSSION
The mining industry is acutely aware of the need to
continuously strive to minimise risks associated with all aspects
of its operations. Failures of TSFs still occur with unacceptable
regularity. There is at least one major failure per year
somewhere in the world. The consequences of a TSF failure can
be catastrophic, with multiple fatalities often occurring and
significant environmental damage being almost assured.
Therefore any procedures that can be implemented to reduce the
likelihood of such events are likely to be embraced by the
industry, as long as the outcomes are consistent, not
prohibitively expensive and readily available.
The PANDA penetrometer provides an approach that
potentially satisfies these requirements. It has the major
advantage of portability, as it can be carried, set up, and
operated by a single operator, relatively little training is
required, and the test itself is quick. It means that multiple
profiles can be tested in a single day, tests can be carried out on
embankment
slopes
(unlike
most
machine-mounted
penetrometers) and the equipment is relatively inexpensive.
Disadvantages are that, outside of Chile, the equipment is
unproven in application to tailings facilities. Sensitivity to in-
situ moisture content is also not well understood and requires
significant further study. However, given the potential
advantages of the method, it is certainly something that is worth
pursuing and it is to be hoped that suitable field study sites can
be found to investigate the method fully.
7 CONCLUSIONS
Risk minimisation is a key consideration for all mining
operations. Perhaps because they are not part of the profit chain,
tailings storage facilities, and the stability of these facilities,
does not always receive the attention they warrant. With
decreasing mineral grades, coupled with more and more
efficient mining methods, the volume of new TSFs continues to
grow apace. The potential consequences of failure of one of
these facilities grows in a similar fashion, and any technologies
that might help reduce the potential occurrence of a TSF failure
is worthy of consideration. Such a technology, it is suggested in
this paper, is the use of a relatively simple penetrometer, the
PANDA penetrometer.
The PANDA penetrometer is now widely used and accepted
in Chile. The experience gained in this country should be
investigated and the potential application to other jurisdictions
determined. It will be necessary to carry out extensive
confirmatory studies, which must include thorough
investigations of the effect of in-situ moisture content on
penetrometer resistance.
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