HIGH PROFILE
to be liquid. The typical seismic
movements recorded from
between December 2016 and
February 2017 are as shown in
the main image above. The area
of the water movement – shown
in blue, is approximately 250 m
wide (across the dam), and
extends into the water reservoir
some 350 m. The main area for
seismic activity shown as red is a
line extending into the water
reservoir some 150 m.
It should be noted that these
locations were uncertain, and
prior to the changes discussed
above. Typical data recorded
after the changes, and also after
the system, was relocated to the second step
from the bottom of the tailing dam, as shown in
the image above.
“The body of liquid movement is of the same
area and size as before. Note it is to one side of
the dam. This happens due to the fact that the old
mine pit has a natural body of water closer to the
right abutment of the dam – this was, in fact, one
of the reasons Germano Pit was chosen for the
tests in the first place, to check if the monitoring
system would be accurate enough to detect this
peculiarity. Some of the red seismic events are
due to random activity outside of the dam (trucks
and the like) and should be ignored as should any
single events not forming a line or cluster.”
There appear to be two seismic lines running
from near sensor ‘B’, and this needs some further
investigation, to establish the true nature of the
event. For these dams, it would be proposed to
monitor with three sensors to enable a
triangulation of event location to be 100%
accurate. This is a technique already deployed in
Australia for monitoring large open pit walls.
“For future installations, it is recommended
that a minimum of three sensors are deployed to
confirm and improve the location accuracy. The
location of water to the dam wall
would then be able to be
accurately measured and
displayed. The addition of the
third sensor will allow tri-
angulation of the source of the
events. This technique does not
require accurate wave detection
of primary and secondary (or
surface waves) time of arrival
differences. This will resolve any
remaining uncertainty about the
locations.”
“For information, this
technique was deployed in
Australia where drilling
confirmed the event locations
provided by the SureWave
system (aquifer with moving water near a side
wall). It is strongly recommended that the dam is
monitored permanently. The system is setup and
able to be observed daily via the remote
connection and visually checked for any changes
or significant events. It should also be established
if the seismic activity within the Germano Dam is
typical of these types of dams.” IM
This article is based on a paper by Breno Castilho,
Samuel Carneiro of Samarco Mineração and
Philip Shaw of SureWave Technology
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JUNE 2019 | International Mining 65