Assessing three different mining periods through the energy release rate at the Lucky Friday mine

Authors: Armatys, M Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2465_12

Cite As:
Armatys, M 2024, 'Assessing three different mining periods through the energy release rate at the Lucky Friday mine', in P Andrieux & D Cumming-Potvin (eds), Deep Mining 2024: Proceedings of the 10th International Conference on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 271-280, https://doi.org/10.36487/ACG_repo/2465_12



Abstract:
The Lucky Friday mine (Idaho, USA) uses narrow underhand mining methods to extract stacked sub-vertical, tabular (silver, lead, zinc) ore veins from the Gold Hunter (GH) deposit within the St-Regis/Wallace Formations. The GH deposit has been in production since 1997 and has sustained full production for the mine since 2003 after withdrawing from the historical Lucky Friday deposit. The GH lies 1.5 km northwest of the latter. As of 2021, the current mining depth positions the leading mining front of the GH at 2.3 km relative to the surface. The mine front deepens by ~25 vertical metres per year at ~1,000 ore tonnes per day. Over two decades of mining have carved the current mined-out geometry, which includes several remnant pillars. When investigating the seismic output from production trends, three distinct periods arise. The first mining period (1997–2016) includes extraction done by the traditional underhand cut-and-fill mining method. The second mining period (2017–2019) presents a unique case where production was essentially reduced to incremental mining due to a work stoppage. The third mining period (2020–2021) accounts for extraction performed by the new underhand closed bench (UCB) method. Using a calibrated boundary element model, the yearly energy release rate (ERR) was calculated for each mining period and compared to the seismic energy release recorded by the mine-operated seismic system. As expected, the maximum seismic efficiency (defined as the quotient of recorded seismic energy by simulated elastic kinetic energy) per period is under 0.2%, which compares with results found in the literature. However, the three mining periods showed significant variations to infer a change in rock mass response due to the mining method. Finally, an attempt was made to fit the Lucky Friday results into the COMRO’s empirical ERR graph, showing the relationship between the frequency of seismic events per area mined and the energy release rate in longwall mining of gold reefs in South Africa.

Keywords: boundary element method, deep-mining, energy release rate, mine-induced seismicity

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