Modern Mining September 2019

SHAFT SINKING AND UNDERGROUND DEVELOPMENT

Full-scale tests have been done in Walenstadt, Switzerland, to assess the performance of the Geobrugg mesh. These have shown that MINAX mesh pro- vides a solution for high-energy demands, up to 60 kJ! Recent tests developed by the geotechnical department of Chilean state-owned cop- per mining company, Codelco, proved that the special design of high-tensile steel mesh, anchors and shotcrete, is highly suitable for protection and sup- port in underground excavations in areas with a high potential for extreme rock bursts. This series of large-scale tests provided the verification of the dynamic ground support system for El Teniente mine in Chile. At one of the platinum mines in North West Province in South Africa, aerial support is required that could act as a permanent

support application. A safe and feasible mining strat- egy was sought to eliminate the risk to people in a cost-effective way. Geobrugg’s MINAX 80/3 mesh was identified as an ideal product to meet the mine’s requirements. The mesh, with an 8 mm cable on the leading edge facing the blasting front, was used and was secured within 0,5 m of the blast face. During instal- lation, the blast-on mesh also doubled up as a robust safety net that would remain in place during the blast. The mesh and anchor combination has proved successful in containing hanging wall instabilities. Mechanised mining Deep-level mining increases exposure to rock bursts. The increased depths at which mining takes place are associated with high stresses and seismic- ity factors that need to be taken into consideration when choosing underground support regimes. Conventional ground support systems are designed primarily for static loads and cannot always provide safe working conditions for seismically active mines. Mechanised installations bring a significant reduc- tion in overall installation costs and increased safety as people are removed from the drilling face. Geobrugg’s purpose-built mechanised roll mesh handler is compatible with all standard multi-boom underground drill rigs and is operated using the hydraulic circuit normally used for the feed arrange- ment. Using the MESHA® installation handler system, the mesh can be installed up to 40 % faster than the standard practice of sheet meshing in the under- ground environment. Furthermore, miners are

not exposed to the unsupported area during the installation. Open-pit mines and quarries In surface mining operations, Geobrugg’s range of products and systems provides rockfall mitigation solutions that are not only aesthetically more pleas- ing but are easier to install and more cost-effective than conventional methods. Geobrugg’s GBE rock- fall barriers are installed in a number of local mines. All barriers are tested in Switzerland under the supervision of – and in cooperation with – research institutes and certification bodies. Energy categories for the GBE rockfall barrier series are approved in accordance with European Directive ETAG027 and bear the CE conformity marking. Geobrugg’s barriers have a considerably smaller carbon footprint than concrete or steel constructions. Attenuator The first Geobrugg attenuator system in South Africa has recently been installed in one of the diamond mines. The attenuator system combines the proven strengths of both barrier and drape systems. The barrier breaks the fall and the drape steers the rocks into a designated runout zone. Rocks and other debris accumulate at the bottom safely and can be cleared with routine periodic maintenance. Attenuators are used when the slope height is too great for a single barrier. This solution is self-cleaning and virtually maintenance-free and customers are looking at this as an alternative rockfall protection solution. 

Geobrugg MINAX ® mesh sheets connected with T3 clips.

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September 2019  MODERN MINING  45