This paper is hosted with the kind permission of the Universidad de Chile, Eighth International Conference & Exhibition on Mass Mining, 2020.
Cumming-Potvin, D, Wesseloo, J, Jacobsz, SW, Potvin, Y & Mooney, A 2020, 'Physical modelling of cave breakthrough into an overlying cave', in R Castro, F Báez & K Suzuki (eds), MassMin 2020: Proceedings of the Eighth International Conference & Exhibition on Mass Mining
, University of Chile, Santiago, pp. 478-488, https://doi.org/10.36487/ACG_repo/2063_32
Access to the caving column in caving mines is limited and, as a result, the amount of data that can be collected (in particular observational data) is very limited. These limitations have resulted in a situation where the mechanisms of cave propagation and breakthrough are poorly understood. Cave breakthrough is of particular importance, as it is a crucial, high-risk stage of cave development. This is exacerbated by the increasingly high cave columns being mined in recent years. Breakthrough of a cave into an existing, overlying cave adds additional challenges as the connection at depth creates high induced stresses and large scale stress redistribution, sometimes resulting in large seismic events. Since visual access to the cave column is possible with physical modelling, it can deliver important insight into the caving mechanisms evolved. This is even more critical for situations of cave breakthrough into existing caves, as they are relatively rare in industry – limiting the ability to study them. In order to better understand these cave breakthrough events, a research project sponsored by Oz Minerals was created to model such situations in a geotechnical centrifuge. Four tests have been completed to date, the preliminary results of which show a potential mechanism of cave connection which has been previously unrecognised. This involves failure of the corners around the existing overlying cave when the cave back of the propagating cave below has only reached one-half to three-quarters of the vertical height of the cave column. The analysis is only in the early stages and further work is necessary to confirm the validity of the observed mechanism and rule out the possibility that it is an artefact resulting from the test methodology. Further research will focus on more detailed analysis of the results and further tests to better understand the observations from the first four tests.
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