Improving efficiency of truck haulage system in an open pit mine - a case study at Ghana Manganese Company (GMC), Nsuta - Wassaw

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This thesis work investigated the performance of the truck-shovel haulage System for the open-pit operation at Ghana Manganese Company (GM C). The present haulage operations were studied and time and motion studies conducted to establish the distribution parameters of the cycle time for the truck haulage operations at Hill B, Hill D south crest and the Stockpile. The resultant statistics and truck breakdown and repair times were used to simulate the truck-shovel haulage operations using SIMAN IV. The results generated from the SIMAN Summary Report were used to construct confidence intervals and plot bar charts. The results revealed that at the present existing haulage system, the average quantities of materials hauled per shift are 2208 tonnes of carbonate ore, 2193 tonnes of carbox ore and 2170.5 tonnes of Ballast Waste. It was also found out that the shovels operating at the various pits and stockpile were underutilised. Average shovel utilisation per shift at Hill B. is 42.6% and at Hill D south crest is about 46.3%. Similarly the average shovel utilisation at the stockpile is 49%. The results also showed that the truck queuing at shovels are very minimal. A truck queue at a shovel 26 to 38 minutes of the 8 hour shift. An alternative method for improving the operation was considered by looking at two possible areas observed to be shortcoming. Each case was applied to the original operation and simulated to see the effect on production. The results showed that when the number of trucks is increased from 10 to 13, the achieved average shovels utilisation are increased. The average shovel utilisation at Hill B is 54.2% and at the stockpile is 63%. Similarly at Hill D south crest the shovel utilisation is 51.4%. On the other hand the carbonate ore hauled per shift is 2834 tonnes, the carbox ore is 2824 tonnes while the ballast waste is 2317 tonnes per shift. The results also revealed that when maintenance was improved to about 20%, the average tonnage of materials hauled per shift increased. The tonnage of carbonate ore increases from 2208 to 2408 tonnes per shift. The carbox ore also increased from 2193 to 2336 tonnes per shift while the waste material hauled increased from 2170.5 to 2317 tonnes per shift. Similarly the shovels utilisation were also increased. The average shovel utilisation at the Stockpile, Hill B and Hill D south crest pits are 50.6%, 47.3% and 47.2% respectively. The combined results of the alternative arrangement also revealed that the material hauled per shift was increased. For carbonate ore is 3169 tonnes and the carbox ore tonnage is 3242 tonnes. The waste material hauled is 3125 tonnes. Similarly, the shovels utilisation also improved. At Hill B the average shovel utilisation is 69.6% and at Hill D south crest is about 67%. The shovel utilisation at the stockpile is 72.4%.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Science in Mining Engineering, 1998