Assessment of static performance of welded mesh along mesh overlap used at Kiirunavaara mine
Abstract Localized failure of mesh, i.e., the mesh was cut or torn by rock blocks as a result of a seismic event, was observed at LKAB’s Kiirunavaara mine. This is especially common along mesh overlap where mesh sheets are joined together. However, the performance of welded mesh along mesh overlap i...
| Published in: | IOP Conference Series: Earth and Environmental Science |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
IOP Publishing
2023
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1088/1755-1315/1124/1/012093 https://iopscience.iop.org/article/10.1088/1755-1315/1124/1/012093 https://iopscience.iop.org/article/10.1088/1755-1315/1124/1/012093/pdf |
| Summary: | Abstract Localized failure of mesh, i.e., the mesh was cut or torn by rock blocks as a result of a seismic event, was observed at LKAB’s Kiirunavaara mine. This is especially common along mesh overlap where mesh sheets are joined together. However, the performance of welded mesh along mesh overlap is not well understood. A series of tests was conducted at the laboratory at Luleå University of Technology, Sweden. The tested mesh sheets are made of 5.5 mm diameter wires welded along orthogonal directions spaced on a grid of 75 mm by 75 mm. The mesh sheet(s) was placed on a steel rig and fixed with bolts with spacing of 1.0 m by 1.0 m. A 300 mm loading plate made of concrete was placed underneath the mesh and pull/push load was applied on the mesh through the plate. For comparison purpose, the loading plate was placed at the mesh center following a dice five pattern as well as in the middle between two bolts (overlap position). The force-displacement curves of different test configurations were measured and failure modes of the mesh were observed. Laboratory test results show that the load-carrying and deformation capacity of the mesh is highly dependent on the load spreading and loading position relative to the holding points. When the mesh overlap was loaded, it shows: i) the highest stiffness; ii) the highest rupture load; iii) lower residual load-carrying capacity; and iv) the lowest deformation capacity. Two failure modes were observed in the conducted tests. Heat affected zone failure is the most common one and the second is the tensile failure along wires. Based on the laboratory results, an optimized mesh layout and bolting pattern was suggested for the Swedish underground mines. |
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