High Resolution Seismic Monitoring in Open Pit Mines

Project Leader: Phil Dight

Having commenced in early 2005, this ACG project aims to demystify the intricate processes of slope failure in active Australian open pit mines. With industry support the project seeks to minimise the financial and safety risks associated with the potentially catastrophic slope failures by early detection and analysis of the microseismic warning emitted by the failing rock.

The project is well underway with an ESG system currently recording data at BHP Billiton Nickel West's Mt Keith operation. Installation of an ISS system at Xstrata's Black Star Open Pit (Mt Isa) is in the advanced stages.

At Mt Keith, a staged approach has been adopted, with three small-scale 6-sensor trial arrays installed at strategic locations around active mining areas. The plan is to identify the most active of the three sites and expand this array to a full-scale trial 24-channel network, consisting of 4 triaxial and 12 uniaxial sensors.

The 319 Level trial site was the first to have an ESG Paladin continuous monitoring system installed and commissioned in March 2005. Seismic events that have been recorded since monitoring commenced indicate a positive outlook for monitoring and accurately locating deep seated failures through cluster analysis using the ACG's MS-RAP software.

Planning for the installation of a 24-channel ISS system at the Black Star Open Cut at Mt Isa is at an advanced stage, with the seismic system hardware ready for installation. The Black Star Open Cut commenced operations towards the end of 2004 and thus is in the early stages of development. The chosen monitoring site is on the east wall at the final pitwall position, which Xstrata have deemed critical from an infrastructure perspective.

The Black Star site offers a unique opportunity to monitor, from a stress/deformation perspective, the progression of the pit floor with depth, and the interaction with underground voids. The pit wall is extensively monitored with movement detection extensometers, which will provide the necessary correlation data for linking seismic activity with physical deformation.

Sponsors

Acknowledgements

The significant contributions made by the project sponsors BHP Billiton Nickel West, Xstrata Zinc and The Minerals and Energy Research Institute of WA (MERIWA), both towards project justification and funding, and the efforts of the site personnel, are greatly appreciated.