SPECIALIST EQUIPMENT
MINE BACKFILL: one size fits all?
Martijn-K Mannot-Russell & Zlatko Martic explore the relationship between backfi ll and production
I
n the past, at many mining sites utilising backfi ll methods there may have been a tendency to focus more on the mining production than the backfi ll element. For cut & fi ll operations, the success of the mining operation also relies heavily on the success of the backfi lling operations. In fact the mining, mineral processing and backfi lling methods are inextricably interlinked, with an immediate eff ect should one of the processes be disrupted. T e total cost of mining operations depends on the all processes being well connected and part of the total net present value (NPV) of the mine.
It means that backfi ll optimisation needs to be evaluated as a part of the total mining cycle. Backfi ll cost and benefi ts are related to the cost of the binder but also essentially, to the effi ciency, production rates, energy costs, total tailings and water management and maintenance costs (wear and tear). T ere are several types of mine backfi ll and
to avoid any misunderstanding, it is worth clarifying what each type is. Cemented rock fi ll (CRF) is rock, aggregates
from external sources or waste rock from footwall/development drives placed in the stopes, fi ne tailings with binder pumped into them to fi ll any voids and bind the backfi ll or sprayed onto the rocks that are on the trucks dumping close to the stope and placed by LHDs.
Cemented hydraulic fi ll (CHF) is backfi ll material consisting of a fl uid mix of classifi ed tailings or sand and binder pumped into stopes fi tted with barriers to allow the drainage of excess water to pass through. Tailings or sand are classifi ed to enhance dewatering process (drainage) and excess amount of water is needed to permit fl owability/transportability of CHF. During the drainage certain amounts of fi nes and binder are drawn with the water, causing inhomogeneity of the fi ll and loss of cement with the water. T e solid faction separates out with the excess water being pumped out to surface or re-used elsewhere in the mine. ‘Grout pack’ fi ll is a typical South African
development from the narrow reef stopes of the gold and platinum mines as an alternative to the traditional support methods using timber. T ese bags or pillows are fi lled with CHF. Cemented paste fi ll (CPF) is the latest
Cemented hydraulic fi ll placed onto bulk fi ll CRF 30
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backfi ll system, using full tailings stream from run of mine or dry excavated tailings. T is
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