Emplaced Geotechnical Characteristics of Hydraulic Fills in a Number of Australian Mines

Abstract

Hydraulic fills used in Australian mines have similar grain size distributions whilst having quite different specific gravity values, typically in the range of 2.7-4.4. When produced and distributed in slurry at 65-75% by solid content, they settle to produce fills with similar geotechnical characteristics. The fills under investigation have been found to settle, in the laboratory, to a dry density of about 0.56 · specific gravity, a saturation water content of about 17-34%, and a porosity of 37-49%. A quick estimate of the optimum water content that gives the minimum porosity may be obtained by locating the intersection of the saturation curve and minimum porosity line, which may simply be done on a water content vs. porosity plot. However, transportability of the slurry requires it to be mixed at water content substantially greater than the optimum water content. As the tailings settle out of suspension, they settle to relative density of 50-80%. This paper shows that the current empirical relationships relating relative density and N-value to friction angle for sands will significantly underestimate the friction angle of the hydraulic fills. Based on limited experimental data, a unique relationship between relative density and friction angle is proposed for hydraulic fills placed in some Australian mines.

Underground Mine Backfilling in Australia Using Paste Fills and Hydraulic Fills

“…Herget and deKorompay [12] suggested that the hydraulic conductivity should be greater than 100 mm/hour to ensure good drainage. Rankine et al [4] studied 24 different hydraulic fill samples that were sedimented in the laboratory and reported hydraulic conductivity values in the range of 1-40 mm/hour, very much less than the threshold suggested by Herget and de Korompay [12]. All these mines operated satisfactorily, with no serious drainage problems reported.…”

“…The geotechnical characteristics of Australian hydraulic fills have been studied extensively by Rankine et al [4] and Sivakugan et al [5]. In the absence of any fine clay fraction and cement binder to absorb the water, there will be substantial excess water present when the slurry settles within the mine stope.…”

“…Based on laboratory tests on hydraulic fills from several mines, Rankine et al [4] and Sivakugan et al [5] showed that the when the hydraulic fill slurries undergo self-weight consolidation, they settle to a porosity of about 40 % and relative densities in the range of 40-70 %. Pettibone and Kealy [7] reported relative densities in the range of 44-66 % at four different mines in the United States.…”

Numerical Investigation of Stress Distributions in Stope Backfills

“…Pirapakaran and Sivakugan [10] compared numerical models of arching effects in a stope backfill in narrow and circular stopes and compared their results with available analytical solutions. More field tests and numerical modeling results on stress distribution and arching effects are found in the literature [29][30][31][32][33][34][35].…”

Study of Drainage Through Hydraulic Fill Stopes using Method of Fragments

“…Access drives are provided at more than one level and they are closed by barricades made of very porous concrete bricks as shown in Figure 1 to retain the hydraulic fill. Rankine et al (2004) discussed the geotechnical characteristics of hydraulic fills from some Australian mines.…”