The purpose of this research is to investigate the factors which affect the performance of the loading and hauling equipment at Skorpion zinc mine, Namibia and also to find possible solutions to eliminate them, so tha...The purpose of this research is to investigate the factors which affect the performance of the loading and hauling equipment at Skorpion zinc mine, Namibia and also to find possible solutions to eliminate them, so that the weekly Zinc Oxide and ex-pit waste tonnages required could be produced. This is due to the high demand of Zinc on the market. The investigation on road conditions was focused on the effects of rolling resistance, grade resistance and road widths from the road between bench 540 in pit 103 to the Zinc oxide medium grade stockpile. Cycle time data were obtained by time and motion study of the load/haul/dump cycle from bench 540 loading site to the stockpile. The data used for equipment matching by queuing theory (excel modelling) was obtained when the loaders where loading Arkose at different loading sites. The effects of different weather conditions i.e. mist, rain and wind on production where determined by collecting actual shift production tonnages and comparing with target shift production targets during this conditions. The results produced from time and motion studies show that the haul trucks have an average availability of 80.4% and utilization at 49.7% which are very low when compared to the benchmark value of 89% and 69% for availability and utilization respectively. Decline in performance time is caused by factors such as daily safety meetings, lunch breaks, blasting, tools break down and the daily machine service. Rolling resistance is also one of the factors affecting production time at the mine. The rolling resistance of different segments was determined by roughness defect scores (RDS). From calculations, it is clearly seen that if the RR could be reduced to 2% on every road segment, then each cycle period per truck can be reduced by 1.24 minutes. This will increase the production of the haulers and decrease the operating cost. It was recommended that the wearing course of the road surface be treated with a bitumen based dust suppression product in order to keep the surface’s rolling resistance to an absolute minimum (i.e. RR = 2%) [1]. The current average hauling road width is 15.987 m while the correct road width at Skorpion Zinc Mine must be 21.35 m to prevent bunching of trucks. It is therefore recommended that the haul roads be widened to 21.35 m width per segment.展开更多
A quantitative research was conducted at Tschudi mine, Tsumeb, Namibia with its main drive being to determine the influence that density and blast parameters has on the performance of a blast. The factors that are mos...A quantitative research was conducted at Tschudi mine, Tsumeb, Namibia with its main drive being to determine the influence that density and blast parameters has on the performance of a blast. The factors that are most vital to the fragmentation process are classified into three namely: explosive parameters, rock parameters and blast geometry. Rock fragmentation is dependent on two main factors, the rock properties which are uncontrollable and the blasting parameters that can be manipulated to give maximum efficiency. The selected variable quantities, density, charge length, volume of blast and mass of charge per hole were recorded after observation, determined via laboratory testing or calculated from their known equations. The main objective is to develop a model to predict blasting performance, and this will be achieved with the use of the Kuz-Ram model. The proposed equation related mean expected fragmentation size (calculated using the Kuz-Ram fragmentation model) to the actual fragmentation. Blasting parameters namely: burden, spacing, and charge quantity that are not included in this study were measured or calculated on site to facilitate the inputs of the Kuz-Ram model. A specialized software package SPLIT Desktop was used to estimate the actual mean fragmentation by analyzing scaled images from the post blast muck pile. The Microsoft Excel regression analysis correlated the two intact rock properties with the blasting efficiency. The expected mean fragmentation and the actual fragmentation were then used to determine the blast performance, defined as the percentage ratio of the actual mean to the expected mean. The blast performance showed a good relationship with density (R2 = 0.81971), with performance of the blast reducing with an increase in density. The performance also dropped with increase in charge length. The blast performance and mass of charge/explosives per hole relationship showed a correlation of (R2 = 0.56195), but the results were disregarded. Lastly the volume of the blast had a direct relation to the blast performance (R2 = 0.80897) and it would be logical to state that, the two are directly proportional to each other.展开更多
文摘The purpose of this research is to investigate the factors which affect the performance of the loading and hauling equipment at Skorpion zinc mine, Namibia and also to find possible solutions to eliminate them, so that the weekly Zinc Oxide and ex-pit waste tonnages required could be produced. This is due to the high demand of Zinc on the market. The investigation on road conditions was focused on the effects of rolling resistance, grade resistance and road widths from the road between bench 540 in pit 103 to the Zinc oxide medium grade stockpile. Cycle time data were obtained by time and motion study of the load/haul/dump cycle from bench 540 loading site to the stockpile. The data used for equipment matching by queuing theory (excel modelling) was obtained when the loaders where loading Arkose at different loading sites. The effects of different weather conditions i.e. mist, rain and wind on production where determined by collecting actual shift production tonnages and comparing with target shift production targets during this conditions. The results produced from time and motion studies show that the haul trucks have an average availability of 80.4% and utilization at 49.7% which are very low when compared to the benchmark value of 89% and 69% for availability and utilization respectively. Decline in performance time is caused by factors such as daily safety meetings, lunch breaks, blasting, tools break down and the daily machine service. Rolling resistance is also one of the factors affecting production time at the mine. The rolling resistance of different segments was determined by roughness defect scores (RDS). From calculations, it is clearly seen that if the RR could be reduced to 2% on every road segment, then each cycle period per truck can be reduced by 1.24 minutes. This will increase the production of the haulers and decrease the operating cost. It was recommended that the wearing course of the road surface be treated with a bitumen based dust suppression product in order to keep the surface’s rolling resistance to an absolute minimum (i.e. RR = 2%) [1]. The current average hauling road width is 15.987 m while the correct road width at Skorpion Zinc Mine must be 21.35 m to prevent bunching of trucks. It is therefore recommended that the haul roads be widened to 21.35 m width per segment.
文摘A quantitative research was conducted at Tschudi mine, Tsumeb, Namibia with its main drive being to determine the influence that density and blast parameters has on the performance of a blast. The factors that are most vital to the fragmentation process are classified into three namely: explosive parameters, rock parameters and blast geometry. Rock fragmentation is dependent on two main factors, the rock properties which are uncontrollable and the blasting parameters that can be manipulated to give maximum efficiency. The selected variable quantities, density, charge length, volume of blast and mass of charge per hole were recorded after observation, determined via laboratory testing or calculated from their known equations. The main objective is to develop a model to predict blasting performance, and this will be achieved with the use of the Kuz-Ram model. The proposed equation related mean expected fragmentation size (calculated using the Kuz-Ram fragmentation model) to the actual fragmentation. Blasting parameters namely: burden, spacing, and charge quantity that are not included in this study were measured or calculated on site to facilitate the inputs of the Kuz-Ram model. A specialized software package SPLIT Desktop was used to estimate the actual mean fragmentation by analyzing scaled images from the post blast muck pile. The Microsoft Excel regression analysis correlated the two intact rock properties with the blasting efficiency. The expected mean fragmentation and the actual fragmentation were then used to determine the blast performance, defined as the percentage ratio of the actual mean to the expected mean. The blast performance showed a good relationship with density (R2 = 0.81971), with performance of the blast reducing with an increase in density. The performance also dropped with increase in charge length. The blast performance and mass of charge/explosives per hole relationship showed a correlation of (R2 = 0.56195), but the results were disregarded. Lastly the volume of the blast had a direct relation to the blast performance (R2 = 0.80897) and it would be logical to state that, the two are directly proportional to each other.
