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Geotechnical News • June 2013
www.geotechnicalnews.com
WASTE GEOTECHNICS
effect of the presence of sand on the
consolidation behaviour, Standpipe
1 was filled with mature fine tailings
from Syncrude, and Standpipe 2 was
initially filled with a mixture of fine
tailings and sand (48% sand). How-
ever, because the consolidation prog-
ress of Standpipe 2 was similar to that
of Standpipe 1, and the fact that field
applications of CT potentially would
use more sand, in November 1984
Scott and Dr. Norbert Morgenstern
decided to empty Standpipe 2 and fill
it with a new fine tailings and sand
mixture (82% sand). From that point
on, Standpipe 2 was known as Stand-
pipe 3, and its contents, over time,
were similar to that of today’s CT.
Scott, who is a Professor Emeritus at
the University of Alberta, has been
actively involved with the standpipe
experiment over the past three decades
and trained several graduate students
who have gone on to be experts on
tailings management in the oil sands
industry. Gord Pollock completed his
Master’s research under the super-
vision of Scott and was involved
during the early years of observing
the standpipes. “A unique part of the
experiment was simply its scale: the
columns are 10 metres tall – or three
stories high – and being able to handle
all of the material was a challenge,”
says Pollock.
During the initial observations, the
research team saw that the MFT was
not responding as expected. “The
material appeared to be densifying
throughout the height of the column
and without any change in effective
stress, which was the earliest indica-
tion that MFT didn’t consolidate like
normal slurries. Rather, there appeared
to be some type of creep behaviour
occuring”, Pollock says.
According to Dr. Silawat Jeeravi-
poolvarn, whom Scott had mentored
and co-supervised during his gradu-
ate research involving the standpipes
20 years later, the MFT compression
mechanism is complex in that the
current large strain consolidation test
(and ensuing result) cannot be directly
applied with the finite strain consoli-
dation theory to predict its behaviour.
“The prediction of the compression
behaviour of this material likely
requires consideration of the time
dependent effect that is not properly
accounted for in both characterization
and theory,” says Jeeravipoolvarn.
He says a significant aspect about the
experiment was the ability to monitor
the standpipes over a long-term period
under a well-controlled environment.
“No other standpipe containing oil
sands tailings has been monitored
successfully this long; thus, it provides
Amarebh Sorta working on deconstructing one of the
standpipes.
One cubic meter containers for collecting mature fine
tailings samples from the standpipes.