Western Australia’s high stress mining challenges and some recent developments in their management

Mike Sandy

This presentation will cover the challenging mining environment encountered in many of Western Australia’s underground mines, where the pre-mining in situ stress gradients are amongst the highest in the world. Coupled with changes in the way in which modern mines are developed, and significant improvements in development productivity and advance rates, some mines transition from relatively benign conditions to extreme squeezing ground behaviour and/or experience damaging seismicity over the space of a few years.

High turnover in technical staff and periodic shortages of suitably trained and experienced geotechnical engineers have added to the challenge of managing these difficult geotechnical conditions.

Over the last 25 years, several important developments have come to fruition, most notably:

Improved understanding of the role of good mine design and extraction sequencing in managing stress redistribution effects.
The increased use of engineered backfill.
Significant advances in the understanding of ground support performance requirements and design, and the availability of improved support systems for managing high deformation or damaging seismicity.
Greatly improved tools for mine design, monitoring the rock mass response and excavation performance, and for visualising data.
The implementation of formal geotechnical programmes at all WA mining operations.

Examples of mines that have experienced geotechnical challenges and the successful application of some of the recent developments will be presented.

About the speaker

Mike Sandy Principal Geotechnical Engineer, Global Lead – Geotechnical Engineering, AMC Consultants Pty Ltd

Mike consults to a wide range of mining projects in Australia and overseas, ranging from block caving, sublevel caving and large-scale open stoping to narrow vein airleg operations. He has extensive experience in geomechanics at an operational level, including ground support design, stope and pillar design in high stress conditions, mining method selection, ground conditions assessment and ground behaviour monitoring. Before joining AMC in January 1995, Mike worked at Mount Isa for eight years in positions ranging from rock mechanics engineer to Mining Research Manager. Mike also spent two years at Hilton as Planning and Geology Manager, which included prefeasibility studies for the George Fisher project. Before joining MIM, Mike worked at the technically challenging Mufulira mine in the Zambian Copperbelt for seven years where he was involved in the initial overcoring stress measurement program, stress change monitoring, pillar deformation and caving studies. Mike is a corporate member of the IOM3 (UK) and a Fellow of the AusIMM.

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