Modern Mining January 2023

COMPANY PROFILE

Geobrugg targets zero harm The mining industry in South Africa had been working to find new ways towards the realisation of zero harm. Geobrugg offers highly specialised know-how in this field. Although our South African of fice based in Lanseria has only been in the country for a decade, it can rely on more than 65 years of experience in steel wire process ing offered by our head office in Switzerland. Our team of dynamic people can provide technical support on various flexible rockfall mitigation systems. The BRUGG Group is one of Europe’s largest steel rope and associated product manufacturers.

G eobrugg is at the forefront of upgrading or reassessing the safety of a mining operation. Traditional support and reinforcement systems such as shotcrete reinforced with electro welded mesh or fibercrete used in underground mining are limited in their capability against dynamic loads. The development of diamond-shaped light weight steel wire meshes MINAX of very high strength in recent years has offered alternative design solutions. In order to fully understand the behaviour and capacity of various ground support systems using these MINAX meshes, Swiss company Geobrugg has carried out many full-scale dynamic tests at its test centre in collaboration with universi ties and mines from all parts of the world. The need to increase energy dissipation capac ity in the support system, designs of different mines have been present for many years. With this goal in mind, systematic studies have been carried out,

Round spike plate on MINAX mesh.

aiming to improve the performance of single ele ments and complete reinforcement systems. In addition, the development in recent years of dia mond-shaped lightweight steel wire membranes of very high-tensile strength, has greatly boosted this trend. These powerful flexible solutions, combined with suitable anchors, have undoubtedly been a huge step towards solving situations where protec tion against dynamic load is imperative. To prove the suitability of support systems with high-tensile steel mesh and bolts, and to analyse their bearing behaviour, a large-scale test centre was commissioned in Walenstadt, Switzerland. On a test rig, it is possible to apply large energies to variable ground support systems with variable bolt patterns and meshes with a total support area of 3.5 m x 3.6 m in a full-scale manner. The test site is instru

Blast-on mesh installation.

mented by load cells, high-speed video analysis and accelerom eters. It could be shown that a combination of high-tensile steel mesh with a specific bolt pattern can result in high-energy capac ity surface support. Distribution of the impact loads during the stopping process to the different elements of the bearing support system depends on the strength and flexibility of the mesh and the bolt resistance and its pattern. Given the characterist ics of a structure that attempts to reproduce the conditions of a mine, boundary conditions are generated that do not allow a direct correlation of the results obtained in the test with the results expected at the mine. However, they allow compari sons between systems/elements of fort i f icat ion and help to

52  MODERN MINING  January 2023