Environmental Engineering Reference
In-Depth Information
Figure 19.6.
Tailings discharge by spigotting.
Figure 19.7.
Tailings discharge from a single pipe.
It is usually preferable to discharge the tailings from the dam embankment, so that the
tailings cover the storage area in the vicinity of the dam and potentially reduce seepage. If
it is desired to blanket the base of the storage with tailings as shown in
Figure 19.41(b)
,
it
is necessary to spigot progressively from all round the storage, moving the main discharge
line up the slope as the tailings rise in the storage. In the case of upstream or centreline
type construction (see
Section 19.5
)
, it is essential that the tailings are discharged from
the embankment and the water pond kept small and well away from the edge of the
embankment.
19.3.2
Cyclones
When tailings dams are to be constructed of tailings by the upstream or centreline meth-
ods, it is common to separate the coarse fraction of the tailings from the fine fraction or
“slimes” by use of cyclones.
Figure 19.8
shows a typical cyclone. The “whole” tailings are fed under pressure into
the cylindrical cyclone. The coarser particles separate from the fines by centrifugal force
(there are no moving parts) and spiral downward through the conical section as “under-
flow”. The finer fractions and most of the water rise to the top outlet as “overflow”.
The performance of a cyclone depends on many factors, including the particle size, spe-
cific gravity, clay content of tailings, size of cyclone, pressure etc. and advice should be
sought from the cyclone manufacturer as to how effective they are likely to be.
