【正文】 / Journal of Cleaner Production 14 (2020) 1168e1175of a hydraulic fill sample.permeable brick failures were reported later that sameyear as a result of hydraulic fill containment at theOsborne Mine in Queensland [1].The specialized barricade bricks often used for thecontainment of hydraulic fill in underground mines aregenerally constructed of a mortar posed of mixtureof gravel, sand, cement and water at the approximateratio of 40:40:5:1, respectively. Fig. 6 shows a photograph of (a), a barricade brick and (b), an underground,the walls have been constructed in a vertical plane,but the recent industry trend has been to increase wallstrength by constructing them in a curved manner, withthe convex toward the hydraulic fill as shown in Fig. 6b.Although it is known within the mining industrythat the porous bricks used in underground barricadeconstruction are prone to variability in strength properties [5], the manufacturers often guarantee a minimumFig. 6. Porous brick barricade. (a) A brick, (b) brick barricade under1172 N. Sivakugan et al. / Journal of Cleanerconstruction in a mine.value for uniaxial pressive strength for the bricks inthe order of 10 MPa [11]. Kuganathan [5] and Du?eldet al. [11] have reported uniaxial pressive strengthvalues from 5 MPa to over 26 MPa.A series of uniaxial pressive strength testsundertaken on a large sample of brick cores havedemonstrated the scatter of results, but more importantly, have highlighted a distinct variation in brickperformance when saturated, as it would occur in themines. Two identical cylindrical cores were cut from 29porous barricade bricks. One of the brick cores fromeach of the individual bricks was tested dry, and theother core was tested after having been saturatedfor either 7 or 90 days. The strength and deformationparameters (namely, the uniaxial strength, Young’smodulus, and the axial failure strain) for the wet anddry cores are shown in Figs. 7e9.Firstly, the extreme scatter between all results reitertheaverageuniaxialpressivestrengthofdrybrickstofallbetween6and10 MPa,whenthebrickmanufacturersguarantee minimum of 10 MPa. It can also be seen fromthis figure that there is a distinct loss of pressivestrength as a result of wetting the brick. There was nosignificant di?erence between 7 and 90 days soaking,implying that the strength loss occurs immediatelyupon wetting. This loss appears to be in the order ofapproximately 25%, which is notable considering thatbricksaregenerallyexposedtosaturatedconditionswhenplaced underground, and all manufacturer strengthspecifications are based on bricks that are tested dry.The sti?ness also appears to be reduced by wetting(Fig. 8). The Young’s modulus of the dry cores rangedbetween 1 and MPa. The length of time the brickswere wetted did not have a significant impact onthe magnitude of the reduction in sti?ness. The peakfailure axial strain was not reduced by wetting (Fig. 9).The cores in general failed under an axial strain of lessthan 1%.The porous bricks are designed to be free drainingand therefore, their permeability is at least an order ofmagnitude greater than that of hydraulic fill. The02468101214086421012Uniaxial pressive strength of dry core (MPa)Uniaxial pressive strengthof wet core (MPa)90 days7 days14Production 14 (2020) 1168e1175Fig. 7. Uniaxial strength of dry and wet bricks.barricade bricks have proven, over time, to satisfy thefreedraining situation, and the reduction of permeability through mitigation of fines has not been recorded.Rankine et al. [4] carried out constant head and fallinghead permeability tests on several barricade bricks andreported permeability values in the order of 3500 mm/h,three orders of magnitude greater than the permeabilityof the tailings.4. Paste fillLike hydraulic fill, paste fill falls into the category ofthickened tailings. A conceptual framework to describethickened tailings in terms of concentration and strengthis shown in Fig. 10 [12,13]. Paste fill is prised of fullmill tailings with a typical e?ective grain size of 5 mm,mixed with a small percentage of binder, in the order of3e6% by weight, and water. It is the densest form ofbackfill in the spectrum of thickened tailings placedunderground as a backfill material. The acceptance ofpaste backfill as a viable alternative to hydraulic slurryand rock fill did not truly occur until the mid to late1990s with the construction and successful operation ofseveral paste backfill systems in Canada and the BHPBilliton Cannington Mine in Australia.010 1 7 days90 days012340 1 2 3 4Young39。240。This implies that all the hydraulic fills settle to a voidratio of and porosity of 40%. The laboratorysedimentation exercise verifies this.. Oedometer testsOedometer tests are carried out on hydraulic fills todetermine the constitutive modelling parameters for theCam Clay model e one of the constitutive models thatcan be adapted for hydraulic fills when analysed usingnumerical modelling packages such as FLAC, FLAC3Dor ABAQUS. In addition, oedometer tests are useful indetermining the constrained modulus (D) from which,Young’s modulus (E) can be estimated for an assumedvalue of Poisson’s ratio using the following equation.EZ240。 continuous e?ort is made during mining toensure that it is kept above a threshold limit in thevicinity of 100 mm/h [3]. Larger permeability leads toquicker removal of water from the stope, thus improving the stability of the fill contained within the stope.Permeability tests for mine fills and barricade bricksare discussed by Rankine et al. [4]. The constant headand falling head permeability tests carried out on thehydraulic fill samples give permeability values in therange of 7e35 mm/h. In spite o