Abstract
The article presents a novel yielding mechanism, especially designed for the rock bolt support. Mechanical rock bolts with an expansion head and equipped with one, two, four and six dome bearing plates were tested in the laboratory conditions. Furthermore, in the Phase2D numerical program, five room and pillar widths were modeled. The main aim of numerical modeling was to determine the maximal range of the rock damage area and the total displacements in the expanded room. The models were made for a room and pillar method with a roof sag for copper ore deposits in the Legnica-Głogów Copper District in Poland. Additionally, in the article a load model of the rock bolt support as a result of a geomechanical seismic event is presented. Based on the results of laboratory tests (load–displacement characteristics), the strain energy of the bolt support equipped with the yielding device in the form of dome bearing plates was determined and compared with the impact energy caused by predicted falling rock layers. Based on the laboratory tests, numerical modeling and mathematical dynamic model of rock bolt support, the dependence of the drop height and the corresponding impact energy for the expanded room was determined.
Highlights
Several mines in Poland are being operated at depths greater than 1000 m
It was found that the value of the additional force did not exceed 4% of the required bolt load capacity of 100 kN
It was found that the value of the additional force did not exceed 4% of the Characteristic structural formscarbonate of carbonate (a) stratification the (b)
Summary
Several mines in Poland are being operated at depths greater than 1000 m At such levels, the rock mass can be highly stressed causing an increase in the frequency of natural hazards, especially rock bursts. The basic way to minimize the mining losses is to cut the technological pillars to residual dimensions, while maintaining the required load capacity of the rock bolt support. The importance of this issue, results from the fact that the rock bolt support are used in the conditions of the stratified rock mass, and the occurrence of geomechanical seismic events or technological resulting from the use of explosives for the mining technology. In order to ensure full functionality of the excavation, the loads carried by the support interaction system with
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