Slope movements in open pit mines

Impact of uncontrolled instabilities and the importance of an effective slope monitoring program

Dr Paolo Farina

Reliable slopes are essential to the design of an open pit mine and for its operations. However, instabilities do occur and as such, remediation requires an understanding of the dynamics at play in order to minimize risk potential for continuing mine development.

To achieve safety and maximize economic performance objectives requires an effective slope monitoring system. Nowadays most large open pit mines, as part of their slope performance monitoring program, have sophisticated and complex systems in place for near real time monitoring; as well as integrating different technologies including robotic total stations, GPS, piezometers, wire extensometers, radar, InSAR, etc. All of these sensors automatically acquire every day Terabytes of data transferred and stored, often in separate databases at the mine offices. Experience indicates that despite the availability of monitoring data and dedicated site staff in charge of the management of risk, negative and surprise geotechnical events associated with slope instabilities continue to occur in surface operations. Difficulties experienced at the operations level in the aggregation, interpretation and timely reporting of monitoring data are common and need to be corrected. Due to time limitations and sometimes from a lack of training, the slope engineer is not always able to fully exploit the informative content of the available data. This may result in the inability to correctly determine the most likely risk scenarios, in terms of volume of the material involved, potential run out distance and temporal evolution of the instability. A number of case histories of slopes where instabilities did occur will be presented in the seminar focusing on how integrated monitoring data were used to manage geotechnical risk associated with the slope movements.

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