Abstract:
The mining industry is currently facing rock related accidents accounting for in excess of 50% of all fatalities occurring in the underground mines (Daehnke et 2001). Falls of ground still account for around 35% of all fatalities in underground South African. mines as shown below (Ferreira, 2012).
In Uganda, most of the gold mines are at small scale mining level and they are still using timber for supporting which is external and passive. At Greenstone Resources Limited, the main tunnel is divided into drives which tend to the north. and south direction, measured from the main tunnel point as 28 m North, 28 m South, 45 m North and 45 m South of the shaft. The southern drives have minimal and randomly placed supports inform of timber, but the northern drives have not been supported because the rock is a bit strong for working.
During my Industrial training at Greenstone Resources in June 20.14, I observed a variety of accidents in underground workings in relation to rock falls which were normally caused by the instability of the rocks and the poor timber supports. The existing randomly placed timber supports are weak and others have rotted away because of the percolating water since the mine is located at 54m and the water table. is approximately at 36m.
Prom the Cost point of view, Bolts and Timber have the cheapest cost so they were chosen for further analysis
From the Results of RMR and Guidelines- for excavation and support of 10 m span rock tunnels (After Bieniawski 1989) it shows that it is a fair Rock which requires Systematic bolts 4 m long, spaced 1.5 - 2 m in crown and walls with wire mesh in crown. However, RMR is used for design of supports in development galleries so due to limitations of its application, other approaches were considered.
After analysis of factor of safety; Rock Bolts are considered because their factor of Safety is approximately equal to 1.2 while that of Timber is less than 1.2.
