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High-tensile mesh systems provide safer working environment underground

5th April 2013

By: Zandile Mavuso

Creamer Media Senior Deputy Editor: Features

  

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The increasing depth of ore extraction in the South African mining industry leads to new challenges in hard-rock underground mines, with conventional ground-support systems, which can often not withstand rock-bursting ground caused by seismicity, becoming ineffective in highly stressed environments.

This, and a higher demand for resources, require that ore be extracted faster, which often results in a heightened need for safety and a higher degree of mechanisation for ground support, mesh systems developer and producer Geobrugg tells Mining Weekly.

The company believes that its Tecco G80/4 and the Deltax G80/3 high-tensile chain-link mesh systems are ideally suited to deal with such issues by providing surface support for underground operations and increased labour safety.

“Our mesh is produced from high-tensile steel wire. The wires vary in thickness of
2 mm, 3 mm and 4 mm. For example, the Deltax G80/3 is manufactured from
3-mm-thick high-tensile steel wire. The Deltax G80/3 is also light, as it spreads its weight at 1.45 kg/m², with the wire’s tensile strength at 1 770 N/mm², compared with mild steel, which offers about 500N/mm²”, Geobrugg MD Bart Schoevaerts explains.

He adds that it delivers a strong strength to weight ratio, which is appreciated by the miners, as the mesh is light and easy to transport and install.

“Dynamic testing has showed that the Tecco G80/4 is able to absorb energies of up to 12 kJ for every 1.5 m². This is equal to stopping a rockburst mass of 1 000 kg, which was previously accelerated from 4.5 m/s to 5 m/s. In similar conditions, welded wire mesh showed energy absorption capacities of about 2 kJ,” Schoevaerts says.

He adds that the Tecco G80/4 can be used as a replacement or extension of shotcrete, fibrecrete or cable lacing. The Tecco mesh system is made of high-tensile 4 mm wire, absorbs dynamic rock impacts and was developed to withstand the heavy loads of rocks. Because of its 4 mm thickness, it offers significantly higher static and has the capacity to prevent rockfalls, compared with mild steel weld mesh or brittle shotcrete.

Schoevaerts notes that one of the challenges facing deep-level mining is that pressure on production is high and applying a mechanised installation of roof support can help miners. “For nonmechanised operations, the product will also contribute to further reducing risk in the case of a rockburst or a fall-of-ground situation and, as such, it will potentially reduce the fatal-ities caused by heavy rockfalls underground,”

The mesh system is supplied in rolls and when installed with the Rock Mesha handler installation, installation time can be reduced by up to 30% to 40% by unrolling the mesh through parallel bolting. In comparison to shot- or fibrecrete, no curing time is required.

“The Deltax G80/3 is blast resistant and has excellent anti- corrosion properties, which offer you an extended life cycle of up to four times more than galvanised mild steel products. So, gone are the days of having to resupport because the current support has rusted away,” explains Schoevaerts.

“All our meshes are patented and manufactured by in-house designed machines. Together with the Rock Mesha Handler, customers can move to a fully mechanised installation of roof support, resulting in significantly increased safety and savings on time and costs,” he says.

The company believes that the system also reduces labour costs, as only one operator and machine are required for installing the mesh system. There is also less mesh consumption because it does not overlap in cross section and eliminates mesh repairs after blasting.

“Our meshes are chain-link-type mesh, which offers the client easy installation and transportation. “The wires of the mesh are bent over and double-twisted in such a way that the connection is as strong as the mesh itself, which guarantees excellent shear and impact resistance,” says Schoevaerts.

Geobrugg says it has installed the mesh system for gold miner Goldfields, diamond mining company Petra Diamonds and gold miner AngloGold.

Geobrugg currently manufactures its products in Switzerland, China, Japan, Australia and the US, but plans to start manufacturing its products locally in 2014.

Edited by Megan van Wyngaardt
Creamer Media Contributing Editor Online

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