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1 2023

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Underground testing of load bearing capacity of rock bolting as part of the verification of its proper selection

Lubryka Dariusz, Madziarz Maciej

Mining Science

2023

Vol. 30

63--82

The results of an underground study of the interaction of expansion bolts with the rock mass, aimed at the improvement of rock bolting selection principles in copper ore mines in the LGOM (Legnica and Głogów copper industry district) area are presented in this paper. Although the grouted bolts are generally suitable for use in most types of rock mass, expansion bolting still accounts for a significant share of underground mine workings in two of the three LGOM copper ore mines. This is mainly due to the simplicity of installation and the resultant higher bolting performance, which, among other things, has its economic benefits. Based on the research carried out, it was concluded that in conducive geo-mechanical conditions, mechanically fixed bolts work correctly with the rock mass, however, the correct selection of the bolt design for specific roof conditions is crucial. In order to verify the proper interaction of expansion bolts of different designs with rock mass with varying properties, 6 typical designs of expansion bolts used in the LGOM mines were selected and 7 underground test sites were prepared where the bolts had been installed. The tests were performed in a crosswise manner, i.e., each tested bolt design was tested on each of the test sites. For the mentioned 42 bolt-rock mass systems, the underground performance tests of rock bolting were performed immediately after its installation and then, after 1 and after 2 years from installation. Based on the results of the tests, the selected expansion bolts of different designs were evaluated for proper interaction with rock mass of varying properties.