This paper discusses the difficulties associated with the potential exploitation of the deep multi-seam resources east of the Daarby fault in the Waterberg coalfield using bord and pillar and longwall mining. Figure 1 illustrates the location of the Waterberg coalfield relative to other coalfields in South Africa, while Figure 2 shows the areas containing deep and shallow resources. The Waterberg resources are expected to contribute to South Africa's future energy requirements, and are

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... exploited at the Grootegeluk open pit mine. Grootegeluk produces coal mainly for a power station, with the higher quality product supplied as metallurgical coal. The deposit is technically unique and challenging, being a multi-seam coal deposit with a total of 12 seams over a thickness of 110 m as shown in Figure 3 , including Zone 5. There is currently limited knowledge on the multi-seam mining of the deep Waterberg resources. Multi-seam mining utilizing the bord and pillar method has been practised in South Africa before, but at a depth of less than 100 m in the Witbank coalfields. Multi-seam mining in thin seams has also been performed in the Natal coalfields at a depth of less than 160 m, but mostly using bord and pillar mining and secondary mining (partial pillar extraction). However, past experience with multi-seam mining at depths greater than 250 m in South Africa is limited. It is therefore critical to review multi-seam mining experience in other countries where the depth of mining is greater than 250 m. South Africa has over 19 recognized coalfields as indicated in Figure 1 , only 10 of which are producing coal. The Central Basin, constituting the Witbank, Highveld, and Ermelo coalfields, is responsible for over 80% of the run-of-mine (RoM) production (Chabedi and Phillips, 2012). The Witbank and Highveld coalfields together account for over 75% of the RoM and the Witbank coalfield alone accounts for over 55% of the RoM produced over the past 20 years (Prevost, 2011). In the past 30 years two major seams (No. 2 and No. 4 seams) have been exploited in the Witbank and Highveld coalfields because of good mining conditions, i.e. horizontal, shallow seams from 2-6 m thick at depths of less than 150 m. Although the No. 2 seam occurs at a greater depth than the No. 4 seam, it was exploited first because of its higher export value. The mining This paper discusses the difficulties associated with the potential exploitation of the deep multi-seam resources east of the Daarby fault in the Waterberg coalfield. The resources occur at a depth greater than 250 m and the thickness of the coal is roughly 110 m, but the top 50 m comprises coal intercalated with shale and the bottom 60 m contains five seams with sandstone and shale partings. Various factors affecting multiple seam mining at these great depths are discussed with reference to lessons learned from local and international experience on multi-seam mining. Field geological and geotechnical data was utilized to assess the stability of the roof of the seams. There is no specific rock mass rating for the Waterberg area, therefore approximate coal mine roof rating (CMRR) values were used to propose appropriate support strategies. Analysis of Multiple Seam Stability (AMSS) was used to analyse the strength of the parting or interburden between the various seams, the mining sequence, and the interaction between the various seams. The research indicated that it is possible to mine seams with a low CMRR at high mining rates using longwall mining, although support for gateroads is expected to be expensive, time-consuming and onerous to install, and will impact gateroad development rates. It will not be possible to simultaneously mine zones in close proximity and failure of the interburden is predicted, thus dangerous mining conditions are anticipated. However, it will be possible to mine just two of the eleven zones using longwall mining. multi-seam mining, Waterberg, coal mining, longwall, coal mine roof rating (CMRR), Analysis of Multiple Seam Stability (AMSS).