TRANSACTION PAPER

An effective face support system to minimize rockfalls

N.D.L. Burger^I; A.J. von Wielligh^I; P.R. de Wet^I; R.W. Ottermann^II; J.C. Visagie^III

^IDepartment of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria
^IIBusiness Enterprises@ UP, Pretoria
^IIIDuraset, A Business Unit of AVENG Africa Ltd

SYNOPSIS

An effective prototype face support system to minimize rockfalls in rockfall-prone mines was developed and patented during a project sponsored by the Mine Health and Safety Council (MHSC). An experimental development model (XDM) roof support unit was developed and evaluated. Mines with rockfall problems in the face areas can use the roof support system to reduce fatalities and injuries in the face area of stopes.
The roof support system consists of two similar support units connected to each other via two crank mechanisms. Each unit consists of a headboard supported by a 'wishbone' structure (top and bottom leg). In the first design a threaded bar with struts similar to a scissors jack keeps the legs apart. (In the final version that was field trialed, the threaded bar mechanism was replaced with a hydraulic cylinder). All the components are manufactured from steel. To move the system forward the first support unit is collapsed, the second remaining in the loaded position. The first unit then hangs from the second unit to which it is connected. The first collapsed unit is then manually cranked forward and prestressed. If the required position is still not achieved, the other unit is released and moved forward.
The specification for the system was determined and presented at a workshop with industry participants. Different concepts were developed and evaluated against the system specifications. A technology demonstrator was then developed and tested on surface. The technology demonstrator development process included detail design, building and testing of components and subsystems, design reviews and the building and commissioning of the technology demonstrator. The testing of the technology demonstrator was done in a 500-ton hydraulic press, in a mock-up stope and underground. A risk analysis, in which technical, logistical and economic aspects were assessed, was done to determine the critical areas of the system.
During the next phase of the project working prototypes were developed for underground tests and evaluation. This process indicated that it was necessary to adjust the system specifications and a redesign was called for. In an iterative process test units were built for purposes of evaluation, specification verification and field trialing. After the successful conclusion of the trials the equipping of a complete production stope started for purposes of integrating the system into the current mining process.

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References

1. ADAMS, D. Review of Face Area Support Projects, Rockfall workshop, Westonaria, June 2006.         [ Links ]

2. ROBERTS, M.K.C., DAEHNKE, A., ARCHEAMPONG, E., VAN ZYL, M., and JAGER, A.J. Rock engineering specifications-GAP 708. First completed by Roberts on 5 June 2000, then modified by Roberts et al. on 8 June 2000. MHSC Project GAP708 Report, Department of Minerals and Energy, Johannesburg, 2000.         [ Links ]

3. BURGER, N.D.L., OTTERMANN, R.W., VON WIELLIGH, A.J., HANDLEY, M.F., and FOURIE. G.A. Effective Roof Support for Tabular Stopes-GAP 813. August 2002. MHSC Project GAP813 Report, Department of Minerals and Energy, Johannesburg, 2002.         [ Links ]