Telfer Gold Mine is located in the Great Sandy Desert and consists of both open pit and underground operations, including a mature sublevel cave (SLC). Changes to SLC design, with the addition of several sublevels, have resulted in an increased cave influence zone, with particular impact on the 4650 to 4600 Decline. This increased cave influence was identified during the planning stage risk assessment for the additional sublevels and a monitoring plan with associated trigger action response plans (TARPs) were included in the cave major hazard management plan (CMHMP). Once TARPs were triggered, ground support upgrades and a planned bypass were initiated for a section of the main decline. High underground temperatures and difficult work conditions resulted in the bypass activity being delayed until temperatures subsided. Due to the delays with bypass development and ongoing progression of deformation at a faster-than-expected rate, access through the original section of decline needed to be maintained for a greater length of time and with higher-than-expected deformation rates. Both a tactical ground support upgrade and a risk management plan based around monitoring data were used to maintain safe access through the main decline until the bypass was complete. Monitoring data showed a clear cause and effect between SLC production and deformation, allowing SLC production holds to be used as a key control.

Many mines experience squeezing ground conditions due to orebodies located in weak rock masses. Often, the conditions leading to squeezing ground are not recognised or underestimated at the feasibility stage, leading to significant difficulties in mining the deposit, high costs and lost resources. There are a number of processes to determine the potential existence and degree of squeezing ground. Feasibility study to determine the rock mass behaviour will significantly reduce the risks associated with mining such deposits. In many cases, it is not possible to prevent squeezing occurring; however, good planning at the feasibility stage can provide the means to control the ground to allow economical extraction. The aim of this paper is to present an approach to maintain access development in squeezing ground identified during the feasibility study. Much is written about squeezing ground, but mainly about how to solve a problem that has already occurred (Potvin & Hadjigeorgiou 2008; Sandy et al. 2007). The aim of this paper is to give guidance for planning and management solutions for a deposit that will likely encounter squeezing ground conditions. The paper will also discuss operational requirements that need to be considered at the pre-production stage. The paper reviews ground control schemes aimed at controlling movement before and during stoping. It is based on experiences and research conducted at mines experiencing squeezing ground conditions and reviews considerations in design and monitoring to mitigate outcomes associated with squeezing rock masses. 2 Defining squeezing ground A number of definitions of squeezing ground are available. Potvin and Hadjigeorgiou (2008) listed a number of definitions as part of the Australian Centre for Geomechanics Squeezing Ground Task Force. Several of these are shown in Section 2.1. Section 2.2 describes how to recognise rock mass conditions that may lead to squeezing ground.

Telfer gold mine consists of both open pit and underground operations, including a mature sublevel cave. Changes to mine design, the addition of subsequent sublevels, level footprint and increasing depth have all resulted in a changing seismic hazard, which is managed using a combination of seismic exclusions zones and dynamic ground support. The seismic hazard associated with high-stress slot development and production is well understood, but the progression of seismic activity into areas of low expected seismic hazard required a systematic upgrade to support. A common theme is that changes to mine design have resulted in additional and changing seismic hazards, with areas of existing infrastructure no longer adequately designed or supported for the future expected demand. Understanding how changes to mine planning, addition of sublevels, footprint size and depth all effect the evolving seismic hazard, have been key to managing the hazard.

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