【正文】 in flowhave turbulent flow (velO2 m/s).!2 m/s partial settling occursNo critical pipeline flowvelocity, . no settlingin pipeflow Laminar/plug flowyield stress Minimum yield Stressend elutriation Filter/centrifugeNoneNone/insignificantgh HighNonet InsignificantImmediateVery lowProduction 14 (2020) 1168e11757e35 mm/h.There is significant scatter in the uniaxial strengthand Young’s modulus of porous barricade bricksmeasured in the laboratory. Uniaxial strength decreasesby about 25% as a result of wetting the brick. Sincethese bricks are always subjected to wet conditionswithin the mine, the strength and Young’s modulusvalues of wet bricks should be used in the design ofTownsville: The Australian Institute of Mining and Metallurgy。240。 accepted 3 June 202026 April 2020of a mine operation. In the Australian mining industry, wherebackfills deployed. Many accidents reported at hydraulic fillof their behaviour and barricade bricks. This papercarried out in Australia on more than 20 di?erent hydraulic fillsis also provided, and the usefulness of numerical modelling as4 (2020) 1168e1175band as shown in Fig. 1. Along with them, the grain sizedistribution curves for a paste fill and a cementedhydraulic fill are also shown. It can be seen that thecemented hydraulic fill falls within the same band as thehydraulic fill. The addition of a very small percentage ofcement has a limited e?ect on grain size distribution.Paste fills generally have a much larger fine fraction thanhydraulic fills or cemented hydraulic fills, but havenegligible colloidal fraction finer than 2 mm.2. Hydraulic backfillsHydraulic fills are simply silty sands or sandy siltswithout clay fraction, and are classified as ML or SMunder the Unified Soil Classification System. The clayfraction is removed through a process known as desliming, whereby the entire fill material is circulatedthrough hydrocyclones and the fine fraction is removedand then sent to the tailings dam. The remaininghydraulic fill fraction is reticulated in the form of slurrythrough pipelines to underground voids.Over the past decade there has been a steady increasein the solid content of the hydraulic fill slurry placed inmines in an attempt to reduce the quantity of water thatmust be drained and increase the proportion of solids.The challenge posed by a high solid content is that itbees di?cult to transport the slurry through thepipelines due to rheological considerations. Currently,solid contents of 75e80% are mon, althougheven at 75% solid content, assuming a specific gravityof for the solid grains, 50% of slurry volume iswater. Therefore, there is opportunity for a substantialamount of water to be drained from the hydraulic fillstope.To contain the fill, the horizontal access drivescreated during mining are generally blocked by barricades constructed from specially made porous bricks(Fig. 2). The access drives, which are made large enoughto permit the entry of machinery during mining, areblocked by the barricades during filling. The drives areoften located at more than one level. Initially, the drives0102030405060708090100 1 10 100 1000 10000Grain size (181。 Mining。1222。1C255y222。1175N. Sivakugan et al. / Journal of Cleaner Production 14 (2020) 1168e1175barricade walls.Paste fill contains at least 15% of grains finer than20 mm, and the e?ective grain size (D10) is in the order of5 mm. The 3e6% binder improves the strength and thusstability significantly. The large fine content within thepaste fill enables most of the water to be held to thesurface of the grains, and therefore drainage is not aconcern in paste backfilling.AcknowledgementsSeveral mines have contributed cash and inkindto the research discussed in this paper. Their supportis gratefully acknowledged. Senior Technical O?cersMr. Warren O’Donnell and Mr. Stuart Petersen assistedin most of the laboratory test work carried out on thebricks and hydraulic fills. Our regular discussions withMr. Richard Cowling of Cowling Associates were veryvaluable throughout our mining research.References[1] Grice T. Recent mine developments in Australia. In: Proceedingsof the 7th international symposium on mining with backfill(MINEFILL)。March/April, 2020. p. 45e50.[12] Robinsky EI. Thickened discharge e a new approach to tailingsdisposal. Canadian Mining and Metallurgical Bulletin 1975。 2020.p. 218e24.[5] Kuganathan K. Mine backfilling, backfill drainage and bulkheadconstruction e a safety first approach. Australia’s miningmonthly February, 2020。s modulus of wet core (GPa)Young39。1Cy222。 received in revisedAvailable onlineAbstractMine backfilling can play a significant role in the overall operationsafety is a prime consideration, hydraulic systems are the most monmines worldwide have mainly been attributed to a lack of understandingdescribes the findings from an extensive laboratory test programmeand several barricade bricks. A limited description of paste backfillsan investigative tool is highlighted.Journal of Cleaner Productionbinding agents such as cement, and their characteristics* Corresponding author. Fax: C61 7 47751184.Email address: (N. Sivakugan).09596526/$ see front matter C211 2020 Elsevier Ltd. All rights reserved.doi:mine backfilling in Australia. Rankinea, . Rankineay, Townsville 4811, AustraliaBox 5874, Townsville 4810, Australiaform 2 June 2020。 Backfills。Laboratory sedimentation exercises at JCU laboratories, during which hydraulic filling processes weresimulated, showed consistently that when slurry settlesunder its selfweight, the relative density of the fill is inthe range of 40e70% (Fig. 3). Similar observations weremade by Pettibone and Kealy [9] at selected mines in the1170 N. Sivakugan et al. / Journal of Cle