Mining in focus
The equipment will be sized to meet the requirements set out by the mining schedule and the capacity of the plant .
ramps , spirals , as well as loading and tipping points are influenced by the size of the trackless equipment and the effective safe operating slope angle .
The layout of a mine or quarry is also affected by legal and legislative constrains , such as the property limits of the approved mining rights area and servitudes associated with public roads and infrastructure , for example power- or waterlines . The presence of protected flora and historical sites or graves might also influence the layout .
Economic factors
At the end of the day , the aim of all operations is to make a profit . Economic factors will determine the viability of operating a quarry or open pit . The grade of material might be good , but if there is no demand or if the cost of extracting it is too high , it will not be worth developing it .
Evaluating the costs associated with a quarry or opencast mine can be done using techno-financial modelling . The different costs relate to establishing and running of the operation . Capital expenditures ( capex ) refer to the cost associated with establishing the mine or quarry . This pertains to the expenses of conducting the front-end studies , such as the appointment of EPCM consultants and contractors to do the various feasibility studies , trade-off studies , and optimisation studies and designs .
Operating costs ( opex ) are the costs associated with the day-to-day running of the operation . This is the actual nuts and bolts required to run the mine or quarry . It entails everything from the salaries , the fuel , and service of trackless equipment , to the water and electricity of the plant .
Marketing considerations relate to having a market for the product being produced . In the case of an opencast mining operation , it would entail having an offtake agreement in place before the first ton of material is processed . In the case of a quarry , market condition will be driven by construction and associated property development . Dimension stone operations , on the other hand , are at the mercy of the current trends , such as marble versus granite countertops .
The selection of mining equipment is usually done to determine the equipment best suited to the type of material , size of the operation , and on-site processing requirements . The mining equipment selection will include everything from the blasthole drill rigs , excavators , and front-end loaders to haul trucks . The equipment will be sized to meet the requirement set out by the mining schedule and the capacity of the plant . Open pits and quarries use trackless mining , and trade-off studies will usually be done to determine the benefit of using certain brands of heavy vehicles , based on the production specifications . Correct selection of vehicles will also have an impact on the capital layout and operational costs .
The on-site plant set-up will be determined by the level of beneficiation or processing that is required of the product at the mine gate . Quarries may require only basic crushing and screening equipment , whereas opencast operations may require more sophisticated washing plants . The operator has the option of having a fixed capacity plant for the life of mine or flexibility by using a modular plant set-up . As with the trackless equipment , the plant equipment selection is based on the requirements of the operation and optimising it as far as possible .
The rate of production is influenced by commodity or product price and demand . Locating infrastructure in terms of the cost impact it has on the mine is another factor that needs to be kept in mind when doing the plant design and selection . The placement of the entire infrastructure , from the offices , parking bays , and workshops to plant , needs to be optimised . This includes distance from the mining or quarrying operation , without sterilising portions of the deposits , and proximity to the access road ( s ) for road transport to market delivery or shipping points . b
About the authors
Nicolaas C Steenkamp is an independent geological / geotechnical consultant , while Breton Scott is the managing director of Bowline Professional Services .
Bowline Professional Services provides consultation services during the planning and front-end development of opencast or quarry operations and has a unique service offering called ‘ Mine in a Box ’. This concept fast-tracks ( without shortcuts ) the design and development processes to bring a small-scale mine into production as early as possible .
[ 36 ] MINING MIRROR SEPTEMBER 2018