Evaluating the Strength and Performance of Backfill Support in Deep Level Gold Mines


  • Fhatuwani Sengani School of Mining Engineering, The University of the Witwatersrand, Johannesburg
  • Tawanda Zvarivadza School of Mining Engineering, The University of the Witwatersrand, Johannesburg
  • Rinae Netshithuthuni School of Mining and Environmental Geology, University of Venda, Thohoyandou




CCT, FPT, UCS, backfill, deep level gold mines, support


The backfill operations at the deep level gold mine consist of a Cyclone Classified Tailings (CCT) Plant as well as a Full Plant Tailings (FPT) Plant with both producing cemented backfill. Due to the high demand of backfill at the mine, including a backlog of voids that need to be filled, both the CCT and FPT Plants are being operated at the moment. The mine will require an increased capacity of backfill going forward, with monthly throughputs in the order of 200 000 to 250 000 tonnes being required. The current mining methods includes destress cuts, long hole stoping as well as drift and fill mining with cemented backfill as a support medium. These concerns have led to the review of the entire backfill operations of the mine with a need for optimising, reducing costs and reducing operational complexity going forward. The research provides strength test work (solids density, particle size distribution, slurry pH, temperature, conductivity, freely settled bed packing concentration, permeability, particle micrographs, water quality, mineralogy, boger slump tests, cement mortar tests (ISO bars), and unconfined compressive strength (UCS) tests) and audit the current backfill operations at the mine. The data showed that both materials had similar top particle sizes of approximately 500 μm. The CCT has a d30 and d10 of 63.4 and 18.2 μm, respectively, compared to the FPT with a d30 and d10 of 13.1 and 3.1, respectively, which is significantly finer. The freely settled bed packing concentration by volume was calculated from the volume of the freely settled bed formed by a known volume of solids. A slurry sample was allowed to settle for 24 hours in a measuring flask. The actual solids volume was determined from the dry mass of material and the solids density. The results were as follows: CCT 45.2 %v (69.1 %m) and FPT 40.0 %v (63.8 %m).