In a course of 3 weeks (28 August-12 September), Geological and Mining Engineering year 2 students together with a few members of staff of Botswana International University of Science and Technology set off on a field trip to 4 mines around Botswana. Through these tours, students were taught about general safety, processes and handling of products in the mines. Interaction of students and miners.
On the 28th of August, Mining and Geological Engineering Year 2 students of Botswana International University of Science and Technology set off on a trip to Morupule, Bela Bela Quarries on the 29th of August and finished off their tour with Karowe Mine and Orapa on the 10th and 12th of September respectively.
With the Karowe and Orapa which are both diamond mines, permits were made for everyone including the lecturers who were guarding the students too. A lot more mines had been scheduled to be visited during the set time period but unfortunately that could not happen due to some major measures.
The sole purpose of these mine tours/site visits was to introduce students to more practical procedures than that of the classroom and give them a feel or rather surface experience of their life careers after graduation. In this way, it gives the students more clarification, new ideas, and better understanding on content they are taught in the classroom. Additionaly, these mine tours was also a way to give us the students a bit more motivation to work harder and become better and greater engineers on our set lifetime careers.
Morupule mine is a coal mine situated on the western far side of the Palapye village/area. The coal mined in Morupule is used to power the country of Botswana with electricity. The coal in the mine also gives a helping hand in powering Namibia as well. Underground mines are found in which the Room and Pillar mining method is used to extract the coal ore from the ground. The ore is extracted across a horizontal plane, creating horizontal selections of rooms and pillars. For ventilation in the underground mine, exhaust fans are used in the rooms and brattices are used. The air flows from the fans in an upcast and downcast and these are controlled by brattices which are partitions built between columns of a sub-surface mine to direct air for ventilation. Moisture is also introduced into the mine to trap dust and avoid cases of suffocation. The fresh air circulated around the mine reduces the methane content to 0.18m3/ton.
The depth of the underground mine from the earth surface is 112.85m and contains a seam thickness of 7.89m.
A continuous miner mines which Remote-controlled is used to work in the underground mine. The machine mines out the coal from the underground beds. The ore is the loaded onto a shuttle and hauled right away. The coal is then dumped into feed-breakers which reduce the coal into smaller sizes for efficient transport. Conveyors or cars (railway wagons) transport the coal out from the mine to the processing plant. After the coal is brought up to the surface by conveyors, it undergoes a process that removes sand and mud. Thermal coal goes for communition and sizing for fines, then for separation by immersing the coal in a solution of water and tiny magnetite particles. The different elements distinct naturally. The coal floats while the other ores, called tails, sink to the bottom. The coal is then arranged into stock piles according to customer’s preference.
The Bela-Bela quarries are situated a few kilometers from the capital city of Gaborone. Bela-Bela operates on a 2-shift basis for 24 hours. The first shift starts at 12pm and ends at 12 midnight when the second one starts. The quarry began its processes in 2004 and the life expectancy of the mine is 15 years from now. An open pit is used to extract and mine brittle granite which is the most abundant rock there can be used for building aggregates such as concrete, crusher dust/ river sand, gravel and roadstones of different dimensions.
The dimensions of the mining pit are 1.8 kilometers wide and 1.2 kilometers across with benches of bench heights of 12 meters and standard bench widths of 15 meters.
The burden and spacing dimensions are 2.3 meters which is the lateral distance on centers between holes in a row. The burden is the distance from a single row to the face of the excavation, or between rows in the usual case where rows are fired in sequence. Many parameters influence burden; hole diameter or charge diameter. Parameters such as hole depth and charge length are the derivatives of the bench height.
Karowe mine is a diamond mine owned by the Lucara Diamond Corp. located in Letlhakane, Botswana. Surface open pit/cast mining is used to extract the diamond. Diamonds which are the major contributor to Botswana’s economy. The Karowe Model Diamond Mine started its operations in 2012 and the life expectancy of the pit is 6 years from the present date. The pit is to be transformed into an underground mine by next year using the block caving mining method for the next 20-30 years.
The mining pit covers a distance of 800m from South to North, 700m from East to West and reaches a depth of 324m deep. The height of the constructed 12m each and only 1 double bench at 24m. The Basalt bed dip at an angle 60? and 48? on Sandstone bed to prevent and minimize damage and danger from rock falls.
Drilling: Drilling may be initially used to discover or explore further very detailed rock layers around where you are working at. But mainly the drilling process is carried out to create presplits in the ground for efficient and controlled blasting.
The first Kimberlite that was bearing diamond to have been discovered in the country of Botswana 15km form a village called Letlhakane in 1967. The Orapa mine situated 240 km west of Francistown was then opened in 1971 by the first president of Botswana, His Excellency Sir Seretse Khama. The income brought to by diamond sales has been used to develop Botswana throughout the years to what it is today. Orapa Diamond pit is also known as the AK1 owned and managed by Debswana, uses surface open pit mining (truck and shovel) to extract the diamond ore.
Currently Orapa is mining at a depth of 300 metres and is expected to reach 450 metres by 2026. It is 1.8km from North to South and about 1.2km from East to west.
The mining process in Orapa mine is represented by four main operations: drilling, blasting, loading and hauling. Holes are drilled to explore the focus bed for exploration and also injection of emulsion explosives are used which are advantageous in cost, safety and ease of use. They can also be used as water gel/slurry and due to wet holes as a result of underground water from boreholes, AK1 uses them. Conventional blasting operations comprise of drilling holes, placing a charge and a detonator, detonating the charge and hauling the blasted material. The emulsion explosive is an electric detonator used when there are wet rocks. A haul road is located at the side of the pit, forming 3 ramp ups which trucks drive, carrying ore and waste rock. It takes about 50 minutes for one loading to reach the stock piles from the mine.
Safety is achieved through mandatory standard to make particular safety or information features on diamonds compulsory for legal supply of the product into the market. The use of Personal Protective Equipment also known as PPE to protect everyone working or visitinf the mining area and these can include items such as safety helmets, gloves, eye protection, high-visibility clothing, safety footwear and safety harnesses.
Rockfalls, Blasting, Radiation, Chemicals, Wildlife, Electricity.
An important result of the mine tour consisted in familiarizing students with mining environments from an intense, 3-week study tour.
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