AGS Technical Evening: Western Australia’s high stress mining challenges and some recent developments in their management

Western Australia’s high stress mining challenges and some recent developments in their management, by Mike Sandy, Principal Geotechnical Engineer, Global Lead – AMC Consultants Pty Ltd

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.