Flow analysis, transportation, and deposition of frictional viscoplastic slurries and pastes in civil and mining engineering

Backfilling and injection of granular materials into mining induced voids, separated beddings, and cracks, as either diluted slurry or concrete paste, is widely used to control coal mine subsidence. As a viable environmental solution, mine waste and rejected materials from underground coal seams are used in both backfilling and injection mine operations. During longwall mining, the grout slurry is pumped into the separated beds of the fractured rock mass through a pipeline connected to a central vertical borehole, which is drilled deep into the interburden rock strata above the coal seam. Either as dilute slurry or thick paste or cake, the fill material normally needs to travel a significant distance in a long pipeline. A blockage can occur in the pipeline when the slurry velocity falls below a certain critical threshold value, indicating a material phase change from cohesive-viscous to cohesive-frictional. In a previous study of radial flow through disks, complete analytical solutions of the required pump pressure versus fluid volume rate were presented for such slurries, categorized as frictional Bingham-Herschel-Bulkley fluids. This paper is an extension to the theory of fluid mechanics to this type of flow in uniform circular pipes. General analytical solutions were developed for complex fluids in velocity and pressure gradients and velocity and pressure as a function of pipe length, from which special and familiar equations for simpler fluids are derivable by mathematical reduction of the general equations. This study differs from the previous research in consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behavior, and implementation of a friction function to mimic behavior of the depositing and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance

New perspectives on IOCG deposits, Mt Isa Eastern Succession, northwest Queensland

A model for the formation of the iron-oxide-copper-gold (lOCG) deposits in the Mt Isa Eastern Succession involves fluids derived from late orogenic granites mixing with a fluid derived from an external source to fonn iron-rich alteration zones (commonly magnetite-rich) that contain vein stockwork, breccia, dissemination or replacement-style mineralisation. This process is inferred to be spatially and temporally associated with felsic pluton emplacement and cooling at around 1540 to 1500 Ma. This contrasts with an alternative model in which the fluids are entirely intra-basinal and amagmatic in origin. Recent studies at Osborne have highlighted a potential syn-peak metamorphic timing for mineralisation (based on 1595 Ma Re-Os dates on molybdenite and a 1595 ± 6 Ma U-Pb date on hydrothermal titanite), with no apparent proximal major intrusion. There is also a potential link between mineralisation and widespread mafic intrusive activity, which spans the entire\ud range of known mineralisation ages

Strength reduction on saturation of coal and coal measures rocks with implications for coal pillar strength

Coal and associated coal measures rocks, including shales, mudstones and sandstones, may lose significant strength on water saturation due to the absorption of water, stress corrosion or mineralogical changes to the clays within the rock matrix. As most coal seams are natural aquifers, water ingress into underground mine workings is common, and is typically controlled during mining by dewatering pumps. After a mine has closed, unless ongoing pumping is maintained, workings will flood and coal pillars and the pillar roof and floor foundations will revert to fully saturated conditions. This paper reports on a study of how flooding effects pillar strength in an abandoned coal mine in Queensland, Australia. The reduction in strength of coal and coal measures rocks between unsaturated and saturated water moisture contents has been quantified through physical testing. These strength data, along with the distribution of lithologies in a coal pillar from the mine, were used as inputs for numerical modelling of the strength reduction of a coal pillar on water saturation. It was found that the modelled pillar strength reduction could be estimated by the average strength reduction of all the lithological components of the pillar, weighted by the thickness of each lithology

Towards a framework for understanding knowledge and support for the use of geothermal energy in Australia

Australia's geothermal industry is on the verge of demonstrating large-scale direct use applications and power generation. However for many of the Australian public, geothermal energy remains a relatively unknown energy technology. This research provides early insights into the social dynamics surrounding the use of geothermal energy as a new and emerging source of energy generation in Australia. Drawing from a 2011 national survey of the public's energy technology preferences and large group workshops conducted with the public during 2008 and 2009, the paper considers public perceptions towards the development of the geothermal industry in Australia. his research shows that there is moderate support for the technology in Australia, although the results also highlight there is limited understanding of what the technology constitutes, and concerns about the impacts on aquifers and seismic activity. The early implications of this research are discussed, including the factors that may contribute to the successful demonstration in Australia for project proponents, as well as policy-makers and communities

Th‐U powered metamorphism: thermal consequences of a chemical hotspot

The Arkaroola region of the northern Flinders Ranges, South Australia, records high geothermal gradient mineral assemblages that are not spatially or temporally associated with intrusive magmatism. Cordierite-bearing schists from the base of a ~12 km thick Neoproterozoic sedimentary sequence known as the Adelaide Rift Complex directly overlie Mesoproterozoic metasedimentary and granitic rocks with regional heat production values of ~7.9 µW/m3 at 580 Ma, two to three times greater than global average values for granitic rocks. We integrate in-situ U–Pb monazite geochronology, Y+HREE-in-monazite thermometry and mineral equilibria modelling to show that rocks at the base of the sedimentary succession record amphibolite facies metamorphism at c. 580 Ma while the overlying sediments were still accumulating. Metamorphism took place under average geothermal gradient conditions in excess of 180°C/kbar (>60°C/km) that propagated to depths of at least 12 km. These thermal gradients persisted for upwards of 150 Ma, maintained by a lack of crustal erosion, and are documented by long-lived crustal anatexis. This system may be the archetypal example of Th–U powered metamorphism, recording the interplay between chemically extreme basement and thermally insulating sedimentary cover.Alexander T. De Vries Van Leeuwen, Martin Hand, Laura J. Morrissey, Tom Raimond

The crustal scale architecture of the Eastern Succession, Mount Isa: The influence of inversion

The three-dimensional crustal architecture of the eastern part of the Mount Isa Inlier is investigated from serial cross-sections constructed using geological map data, revised chronostratigraphy, gravity, magnetics, worms (multiscale wavelet edges of potential field data) and seismic data. The top part of the crust consists of rift and platform type metasediments that were deposited in three cover sequences from 1850 to 1610 Ma. These rocks constitute the Mount Isa Eastern Succession, and they were intruded by mafic–felsic plutons, dykes and sills of various ages before and during the Isan Orogeny (ca. 1.6–1.5 Ga). The Eastern Succession overlies a felsic metamorphic basement, which in turn sits on a tonalitic–gabbroic lower crust. The depositional basin architecture for the Eastern Succession was controlled by major N–S trending structures that penetrated the lower crust, and accommodated E–W extension. These structures also underlie major upper crustal structures such as the Mitakoodi Culmination and Snake Creek Anticline that were formed by contraction in the Isan Orogeny. Positive inversion may therefore have been a key process in the evolution of the eastern part of the inlier, and governs its architecture at the crustal scale. Inversion involved reactivation of basement-penetrating structures, which localised contractional structures in the cover sequences above, as well as influencing pluton emplacement. The felsic metamorphic basement may have been penetratively deformed during inversion. The spatial association between the basin-controlling and contractional structures suggests that either early extensional displacements were completely reversed by later contraction, or that much of the Eastern Succession has remained essentially parauthochthonous relative to the basement

The crustal scale architecture of the Eastern Succession, Mount Isa: the influence of inversion

The three-dimensional crustal architecture of the eastern part of the Mount Isa Inlier is investigated from serial cross-sections constructed using geological map data, revised chronostratigraphy, gravity, magnetics, worms (multiscale wavelet edges of potential field data) and seismic data. The top part of the crust consists of rift and platform type metasediments that were deposited in three cover sequences from 1850 to 1610 Ma. These rocks constitute the Mount Isa Eastern Succession, and they were intruded by mafic–felsic plutons, dykes and sills of various ages before and during the Isan Orogeny (ca. 1.6–1.5 Ga). The Eastern Succession overlies a felsic metamorphic basement, which in turn sits on a tonalitic–gabbroic lower crust. The depositional basin architecture for the Eastern Successionwas controlled by major N–S trending structures that penetrated the lower crust,\ud and accommodated E–W extension. These structures also underlie major upper crustal structures such as the Mitakoodi Culmination and Snake Creek Anticline that were formed by contraction in the Isan Orogeny. Positive inversion may therefore have been a key process in the evolution of the eastern part of the inlier, and governs its architecture at the crustal scale. Inversion involved reactivation of basement-penetrating structures, which localised contractional structures in the cover sequences above, as well as influencing pluton emplacement. The felsic metamorphic basement may have been penetratively deformed during inversion. The spatial association between the basin-controlling and contractional structures suggests\ud that either early extensional displacements were completely reversed by later contraction, or that much of the Eastern Succession has remained essentially parauthochthonous relative to the basement

Non-urban water infrastructure prioritisation - a technical report from the CSIRO to the Queensland Government Department of State Development

The objective of this study was to provide a standardised high-level assessment of non-urban water infrastructure proposals, in a manner that assists in prioritisation of non-urban water infrastructure in the Queensland Bulk Water Opportunities Statement whole of government review process. The prioritised list of projects can then be used to guide further assessment of the highest ranked projects on a whole of government basis, or by individual agencies. From a list of 69 potential water storage developments that have had some level of assessment by government or been subject to public discourse, 13 developments were short-listed and then appraised using multi-criteria analysis (MCA). MCA was selected because it allows for the evaluation of decision problems beyond the reach of traditional benefit cost analysis (BCA). MCA is able to consider a broader set of tangible and intangible criteria than BCA. It has a track record of successful applications in water management in Australia and internationally. The approach undertaken was intentionally rapid, and involved assessing existing proposals rather than generating alternative ones. Where there was insufficient detail to assess a proposal, assumptions were made based on the best available information. Seven broad categories were evaluated as part of the MCA: i) water demands; ii) project costs; iii) project benefits; iv) project impacts; v) project risks; vi) project readiness; and vii) project commerciality. Based on a set of basic principles, each category was further disaggregated into a series of criteria groups, resulting in a total of 27 criteria across the seven categories. Importantly each criterion was independent of all others. Categories and criteria were selected in conjunction with representatives from key Queensland Government Departments. Methods were devised for each criterion for consistently assigning scores across the 13 water development options. For consistency in this analysis, each option was assessed primarily for supplying water to agricultural areas, although potential demand from other nearby industries was also considered. As part of the MCA process, criteria are typically assigned weights to indicate the relative importance of different criteria and categories. In this project criteria weights were not assigned, rather the criteria weights will be subsequently assigned by the user according to key stakeholder’s explicit objectives. Importantly, this prioritisation does not constitute a ‘pre-feasibility assessment’ and does not replace the need to develop a business case or to undertake regulatory requirements for approval (such as environmental impact assessment). Rather, its purpose is as an exploratory tool to facilitate discussion about the relative merits of alternative water development proposals and how they may be modified so as to achieve better proposals or better regional economic outcomes. The MCA was performed using the Multi Criteria Analysis Tool (MCAT). This report provides the technical documentation explaining the criteria used to populate the MCA and the assumptions and rationale for assigning ratings to each criterion, for each of the short-listed water storage developments