A case study: managing decline deformation in an active sublevel caving operation

Abstract

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.

Undercutless caving at Newcrest: towards the next generation of cave mining

“…A large regional fault (Graben Fault) exists in the eastern flank of the main orebody, which is intersected by mine development. Reef and shear units cut the entire mine stratigraphical sequence generating frequent and pervasive jointing decreasing the overall rockmass strength making it amenable to caving (Woods et al 2019). Intact rock strength is generally very high (greater than 200 MPa), except for the major ore units (around 80 MPa), with RMR values ranging from 50 to 60 (Woods et al 2019).…”

“…Reef and shear units cut the entire mine stratigraphical sequence generating frequent and pervasive jointing decreasing the overall rockmass strength making it amenable to caving (Woods et al 2019). Intact rock strength is generally very high (greater than 200 MPa), except for the major ore units (around 80 MPa), with RMR values ranging from 50 to 60 (Woods et al 2019). The Telfer underground operation consists of three separate and distinct mining areas (Figure 5b).…”

Mining Ground Deformation Estimation Based on Pre-Processed InSAR Open Data—A Norwegian Case Study

“…The deformations that develop around the mine can be classified into three zones that are parallel to the mined mineral deposit [5]. These are: the caved zone, which occurs above the mining operation; the fracture zone, characterised by parallel cracks that develop in the rock mass Minerals 2023, 13,328 2 of 16 as it moves towards the caved zone; and the continuous deformation zone, which is the area where terrain deformations due to mining activity can be observed (Figure 1). The cracks define the limit between the continuous and the discontinuous subsidence zones [6].…”

“…Prior studies related to sublevel caving mining focused predominately on the monitoring and modelling of deformations in underground workings for draw control and underground stability analysis [5,11], as well as underground mine planning and safe caving operation [12][13][14].…”

“…The application of satellite data for systematic monitoring of surface movements and the analysis of the full extent of the influence of sublevel caving mining that includes the continuous deformation zone have so far attracted less attention [9,13,15]. Thus, the main aim of our study is to estimate the continuous deformation zone associated with sublevel caving mining of steeply inclined iron ore deposits based on the processing of openly available satellite permanent scatterer InSAR (PSInSAR) data in a geographic information system (GIS).…”