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By S M. W Rajaratnam, P Varma, T L. Sletten

Mining employees undertaking shift work are at considerable risk of experiencing sleep disturbances and circadian rhythm disruptions. In the complex, high-risk environment of mining, these sleep and circadian disruptions lead to adverse impacts on employee health, alertness and safety. Evidence-based tools that effectively target improvements in sleep health amongst shift workers are needed. Variability in work hours and individual differences in the response to shift work mean that a ‘one-size-fits-all’ solution is often insufficient in complex work environments. Currently no interventions provide tailored support for shift workers based on their rosters, personal commitments and sleep habits. Existing technologies, such as smartphone applications and watches, allow sleep monitoring, but their strategies are targeted towards night sleepers, which does not translate to shift work contexts. To address this, our team has developed an innovative digital tool that implements biomathematical models to provide automated, personalised sleep and circadian intervention strategies to optimise sleep, alertness and performance during shift work. The tool uses mathematical models of sleep and alertness regulation that provide physiologically optimal times for an individual to sleep when experiencing circadian disruption. This program of work included co-designed development of a world-first app with shift workers and the examination of the preliminary efficacy of the intervention for improving sleep, alertness and performance.

Apr 16, 2024

Many stress measuring instruments use overcoring stress-relief principles but adopt different sensing techniques. Every technique is subject to certain limitations of rock types and conditions. To investigate the performance and reliability of the instruments in field measurement, a simple and practical approach has been developed to allow comparable laboratory results to be obtained which simulate in-situ rock and stress conditions. Four commonly used devices, the USBM deformation gauge, the CSIRO HI cell,the CSIR triaxial cell and the UNSW SI cell were thoroughly tested in the laboratory. Some conclusions have been drawn as to their suitability and reliability in different field conditions. Recommendations are provided for the choice of an appropriate technique for a given rock type and condition. A new thin-wall cell that overcomes the disadvantages of earlier devices has been developed and tested. Its laboratory performance shows that it has good prospects.

Jan 1, 1990

By Brown K, Francis D

The Yallourn Open Cut Mine has recently commenced mining operations in the new East Field which will supply the 1450MW Yallourn W Power Station for the rest of its 30 year design life. The authors describe the design and implementation process followed during the rehabilitation of the areas disturbed by works associated with mining in the East Field. One area of the East Field, the old external overburden dump, has been of particular interest and is discussed in detail. A discussion on the fire protection considerations is included as these are critical and often misunderstood as being contrary to good rehabilitation design practice. Finally, the development of a master plan for the rehabilitation of the Yallourn Open Cut in general, incorporating the East Field work, is discussed.

Jan 1, 1992

By J Zhao, C E. Loo

The flame front is a narrow region in the iron ore sintering bed where coke particles combust. The maximum flame front temperature is as high as 1400°C. At high temperatures, the sinter mix components react to form melts, which facilitates material coalescence and the formation of dense sinter particles. It is well-established that flame front speed is an important factor influencing sinter productivity, sinter quality and fuel rate. In this work, the effect of suction, coke addition and mix moisture on flame front speed was studied in a pilot-scale sinter pot and also using the outputs of a recently developed theoretical model, which takes into account most of the significant physicochemical processes in sintering. Airflow through the bed has a large influence on flame front speed. A power law relationship between these two parameters means that increasing sintering airflow rate will lead to increased flame front speed, but the increases become smaller at higher airflow rates. Sinter pot test results showed that increasing coke addition decreased green bed permeability and increased flame front temperature, which resulted in increased flame front resistance and decreased flame front speed. Studies also showed that green bed properties are sensitive to sinter mix moisture level. The changes in green bed properties further influence the flame front speed and temperature.CITATION:Zhao, J and Loo, C E, 2015. Dependence of flame front speed on iron ore sintering conditions, in Proceedings Iron Ore 2015, pp 83–90 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

The authors have succeeded in providing additional rigour and clarity to the formulation and execution of the dynamic programming algorithm for optimum open pit limit determination. The inclusion of the blocks on the J + 1 column in the search for Pmax, and constraining this search with blocks assigned a value of negative infinity, ensures an optimal solution within the defmed blocks. The effect of the negative infmity blocks is to preclude mining along the diagonal blocks from the first row that they occur in. Figure 1 graphically illustrates the effects of this on the calculation of P. A practical application for constraining mining with negative infmity blocks is the case where the pit outline is defined by lease boundaries and not by the value of blocks to be removed. Any legal, social or physical constraint could be accounted for in the same way.The danger in applying this technique is that the negative infinity blocks will override any other more profitable solutions that may exist. This is in fact what has happened in the example that the authors use. If a further column is added to the left hand side (column -1) and the calculation is carried out again, a more optimal x-section can be found. (If the negative infinity values are removed the same result is obtained.) This gives a pit value of 112 as against the 108 of the authors' optimal pit. This calculation is shown in Figure 2. Lerchs-Grossman optimization is reliable only if there are sufficient columns available to allow "mining" to optimum depth of the ore body and still allow the pit to break out at the surface within the confines of the columns.This author's approach is to create enough columns each side of the lateral limits of the ore to allow the pit to intersect the surface while still within the confines of the block model. Implementing the methods discussed by the authors helps to reduce the number of columns required to achieve this.

Jan 1, 1987

Direct measurements of liquid contents in foams obtained from (x-terpineol a-T) n-pentanol (AmOH) and n-octanol (OctOH) solutions were carried out using a column of special construction. The column enables to determine the liquid contents by cutting-off foam layers of various thicknesses and measuring amounts of liquid contained in the cut-off foam layers. Liquid contents in the whole foam layers, in the top foam layers of thickness 14 ¦ 1 mm and distribution of water alongside foam height were determined. The average liquid contents were high and reached a level of 30, 35 and 40 per cent for foams formed from cc-T, AmOH and OctOH solutions, respectively. The liquid contents in the top foam layers were much smaller. They were of an order of five per cent for a-T and AmOH and 12 per cent for OctOH. On the basis of the liquid distribution alongside foam height some practical conclusions concerning possibilities of minimising amounts of liquid contained in the collected concentrate are presented.

Jan 1, 1993

By W Lu, D Wang

Study of coal oxidation at low temperatures forms the basis of investigating the inherent properties of spontaneous combustion of coal. In general, the process of coal oxidation at low temperatures is very complex, involving many factors. Experiments examining the properties of oxidation and ignition of coal have been carried out. Based upon the results of these experiments, the catastrophe properties in the process of coal oxidation are analysed and the mechanism of catastrophe is proved for the ignition of coal. A folding catastrophe model is also established for the process of coal oxidation. Results obtained show that the process of coal oxidation to ignition is discontinuous, where the coal-environment system yields structure destabilisation. The system can jump from one stable attractor to another. The research results presented in this paper help to show the irregularities of coal oxidation at low temperatures and how to pursue effective control measures.

Jan 1, 2005

By P Gardner

The Kanowna Belle gold mine in Western Australia has reached a depth of 1000 m on the way to 1300 m. A feasibility study undertaken in 2006 identified the mining of E-Block as both technically and commercially feasible. One of the major risks identified in the study was the ventilation capacity, as the existing primary ventilation system would not support the production schedule for mining and a major system upgrade would be required. Failure to provide the necessary airflow would put the project at risk. A review of the airflow requirements and infrastructure options detailed in the feasibility study was undertaken to ensure that the assumptions and design were optimised. This review recommended a minimum airflow of 206 m3/s, but by acknowledging the necessary constraints imposed by mining at depth and re-engineering the mine layout to optimise the primary ventilation circuit, this requirement was reduced to 160 m3/s. This represents a 22 per cent reduction in airflow and a reduction in capital cost that will see mining at depth become economically feasible at Kanowna Belle. This paper discusses the processes that led to a redesign of the mining layout and highlights the importance of including the ventilation network in the optimisation process.

Jan 1, 2008

Obtaining correct assays for gold determinations relies on the correct methods being chosen and the assayer being made aware of the mineralogy of the sample and its general origin. Usually when a geologist or metallurgist obtains "incorrect" gold assays the problem can be traced to poor communication between the geologist or metallurgist and the assayer.

Jan 1, 1986

The interfaces between the Broken Hill ore lenses and the enclosing wallrocks are, on a broad scale, parallel to metamorphic layering in the wallrock gneisses and quartzites. In detail, however, the concordant contacts are interrupted by piercement structures, formed by plastic injection of ore into the wallrocks during metamorphism.These discordant bodies vary from minor projections measuring less than I m long, to major ore shoots ("droppers") as much as 60 m long. The intrusive bodies consist of fragmented ore and wallrock in amatrix of recrystallised sulphides. Wallrock fragments have been altered to manganese-rich and calcium-rich mineral assemblages. The injected ore is enriched in sulphides compared with the parent ore, and there has been enrichment in a number of minor elements.Piercement structures formed during the waning phase of high grade metamorphism, when incompetent ore was injected plastically under pressure into the wallrocks, particularly at fold crests. Adjacent to the "droppers", retrograde schists developed as a result of shearing along the ore-wallrock interface.

Jan 1, 1976

By Denisov GA

Conventional processes for disintegration of ores are characterised by low selectivity and cause damage to the components of their structure. It affects their liberation and recovery which are connected also with the inevitable formation of extreme fines. In the world practice recently came into view 4 trend to grinding of materials within a thick layer (in a bed layer), which provides a substantial selectivity of liberation, for example, of kimberlite. The degree of diamond preservation in the final product is highly increased. However, this method causes a considerable overgrinding of material. A new method of intralayer vibro-impulse breaking of materials providing an easily adjusted force acting at the layer and timely removal of product size grains from the grinding chamber has been developed in Russia.

Jan 1, 1993

By Standish N

The heterogeneous reactions of carbonaceous materials with oxidising gases are basic to all combustion phenomena and to many gasification processes. The carbon- carbon dioxide reaction at elevated temperatures (Reactivity) plays important roles in many metallurgical operations like iron blast furnace and ferro-alloys smeltings, zinc and lead smelting, alumina reduction, cupola operation and direct reduction processes. The stoichiometry but not the mechanism of the reaction between CO2 and carbon is represented by the equation (Boudouard reaction) CO2 + C 2CO (1) This reaction is more complex than that between carbon monoxide and metal oxides, which involves essentially a transfer of oxygen from the oxide to carbon monoxide to generate carbon dioxide without any change in gas volume, whereas the volume of the product gas of Equation (1) is twice that of the reactant gas. In the present paper an attempt has been made to review critically the reactivity measurements of various carbonaceous materials in carbon dioxide atmosphere. Steps in C-CO2 reactions, surface reaction mechanism, role of mass transfer on reaction kinetics, dynamic oxygen exchange reaction and rate equations and rate controlling steps are discussed. Various methods of reactivity measurements with their pros and cons are also presented. Effects of pertinent process variables on the reactivity of carbon are also described in detail.

Jan 1, 1986

By D S. Stewart, K W. Keskimaki

In 1999, the Henderson Mine commissioned the Henderson 2000 project - a new truck haulage level, a new underground crusher and a 24 kilometre conveyor system to replace a 23-year old rail haulage system. Henderson has been able to continuously improve in almost all aspects of its rubber-tired mining. The rail haulage system represented one of the last barriers to continuous improvement to the overall plant performance. Many of the lessons learned in other areas of the mine were utilised to design the truck level. This paper chronicles the benchmarking, equipment selection and design of the level. Areas covered will include haulage trucks, level layout, ore chute design, traffic control, road design and crusher layout.

Jan 1, 2000

By B Shen

The Wambo Rail Spur located near Singleton, New South Wales, Australia, runs for approximately 14 km linking the Mt Thorley rail loop and the Wambo Coal Mine. The project involves a 260 m long tunnel in weathered sedimentary and intrusive materials. The tunnel has a low cover and runs under a main highway. This second paper on the project looks into one aspect of the tunnel in detail: the use of shotcrete arch as the primary support for part of the tunnel excavation. The use of shotcrete instead of steel arch, formulation of the material specification, construction sequencing, installation at the excavated face and material testing for verification related to this facet of the project will be discussed in this paper. The tunnel opened in April 2006, and two years on, we briefly reflect on the impact of this design decision on the overall project.

Jan 1, 2008

By Wright S

Single pellets of mixed lead-zinc concentrate containing up to 20 % lead were roasted in the temperature range of 800-1100¦C. Variables studied included pellet size (from 9-8 to 3-2 mm diameter), gas flowrate past the pellet (from 0.05 to 5 ms t), composition of the atmosphere and the effect of additives such as zinc oxide and silica. After defined periods of time, the pellets were removed from the furnace, quenched and submitted for chemical, XRD, SEM and microprobe analysis. The oxidation of the zinc sulphide followed a shrinking core model. Temperature measurements showed that very high pellet temperatures were experienced at the start of an experiment but after 5-10 minutes these approached a constant temperature. The lead loss from the pellets was then constant with time. Thermodynamics predicted the presence of two bands of lead material in the reacted layer of the pellet. These were found in practice. The lead loss from the pellet occurred from the outer oxysulphate layer via the vaporization of lead oxide polymers. The vapour pressure of PbO, and the loss of lead, was dependent on temperature and bulk gas concentrations of SO2 and 02. At 1100¦C the addition of silica greatly reduced the loss of lead from the pellet. Physical factors such as pellet diameter and gas flowrate past the pellet affected the particle dynamics. These results were found to vary in accordance with the predictions of the Froessling equation.

Jan 1, 1989

By Andrews B. S

The sinter plant at the Sulphide Corporation's Cockle Creek works produces a feed for the company's Imperial Smelting Furnace. The feed contains lead and zinc oxides and all the fluxes necessary for furnace operation. The quality of this feed is a major factor in furnace performance and the considerable flexibility of operation possible at the sinter plant has been used in efforts to achieve optimum operating conditions.Operating data is processed daily and information gathered from this source has led to three of the four improvements described.These improvements have resulted from elimination of gas recirculation, reduction of sinter returns sizing and alteration of ignition conditions and main layer fuel loading.

Jan 1, 1964

Tasker (1985) has detailed the accepted practices for constructing polygonal blocks of influerrce in the estimation of ore reserves. Further he suggests that users might fall into traps such as omission or overlap when determining the area of influence for each sample point.As an example of these types of errors Tasker (1985) describes under "Coverage ofthe Area" how 25 per cent of the exploration area will not be included in an equiangular triangular grid where hexagonal blocks of influence are used.The introductory suggestion of Tasker (1985) of "incorrect procedure" by Rudenno (1983) (and Armstrong (1983)) reiterated around the Figure 2a of Tasker (1985), is based on the brief description of the polygonal area of influence by Rudenno (1983). That description is not too different from that given by King, McMahon and Bujtor (1982).

Jan 1, 1985

Esso Australia Ltd. operates a large natural gas producing system in the Gippsland Basin, supplying gas to the Gas and Fuel Corporation of Victoria, the State Electricity Commission of Victoria and several industrial customers. Gas reaches the Longford processing plants from three offshore platforms via a network of large diameter pipelines, which must be protected against the formation of ice-like hydrates. When gas production commenced in 1969, methanol was used to inhibit hydrate formation in the offshore pipelines. However, later investigations showed that the methanol was causing excessive degradation of molecular sieve in the onshore gas-processing plants. (Molecular sieve is used to remove water and H2S from the gas prior to further processing to remove heavy hydrocarbons.)

Jan 1, 1982

In October 1993 it was decided to undertake the fourth phase of mining at Big Bell. This decision followed the exhaustion of open pit reserves in January 1993. Two stages of mining were proposed for the new underground mine. The initial stage would mine the remnant ore, consisting of the rib and crown pillars and lower grade ore on the hangingwall and footwall side of the old open stopes, which were mined from the 1930s to 1950s. Most of the old open stopes were backfilled with either deslimed mill tailings or development mullock, both of which were economic to recover. However, the mineable ore from this resource was difficult to evaluate. The second stage focused on mining ore outside the remnant areas and was initially proposed as a Core and Shell method under a caving hangingwall. This method has since been superseded with sublevel caving, in part due to the very high and deviatoric stress conditions encountered at Big Bell and the relatively long mining cycle required for open stoping. The problems and challenges discussed in this paper will cover the identification of remnant ore reserves, dewatering the old workings, and remnant mining.

Jan 1, 1998

By Warren M

Many Australian tunnelling and mining companies regularly investigate different methods or equipment in an attempt to keep ahead of their competition. Sometimes the result is a new approach or process which wins a tender or provides an advanced solution to a problem.The Australian Government has a policy of encouraging forward thinking among Australian companies and provides a range of incentives. One of these incentives is currently available retrospectively to 1985 - 86, and the registration process is relatively simple with only one form to be completed. Companies who investigate methods of raising productivity could be reimbursed for the costs of the investigation.

Jan 1, 1993