Monitoring and management of a large open pit failure
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Date
2010-09-13
Authors
Wessels, Stephanus David Naude
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Abstract
A large scale slope instability developed at an operating mine over two years,
resulting in a 4.5 million tonne collapse in July 2004.
During this period the Geotechnical personnel monitored and inspected the slope to
ensure that the safety of personnel and equipment was not compromised. Monitoring
of the slopes was done using visual inspections, conventional survey methods and the
use of the Slope Stability Radar. The details of the observations and the monitoring
results are described in this project, as well as the methods used to try to predict the
onset of failure. The Slope Strain method of predicting failure is evaluated.
An important part of the management of a failure is the control measures that are put
in place. The control measures, and how they are escalated in reaction to an
increasing risk, are discussed.
Certain trigger levels were put in place. Due to location of mining at time of collapse
the evacuation of personnel based on the trigger levels was not required. The
effectiveness of the different trigger levels is evaluated.
All slope deformation and slope failures behave differently. When no site specific
historical data is available, the geotechnical practitioner relies on available literature
to formulate guidelines and threshold levels for the monitoring, prediction of failure,
and safe management of unstable slopes. The detailed case study described in this
report is considered to be a valuable contribution to the literature in these fields. The
data contained in the report have been presented in detail since they may be of value
to other researchers and practitioners in the rock slope field