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By H Park, L Wang

Froth flotation is one of the most widely used beneficiation processes for fine and ultrafine coals and minerals. Maintaining optimal metallurgical performance in industrial flotation operation is still a challenging task owing to the lack of an effective tool to diagnose the flotation performance in realtime. For this purpose, a number of flotation performance monitoring systems with different working principles have been developed to provide instant feedback for process control and optimisation. In this paper, for the first time, five different flotation performance monitoring systems were systematically compared through an on-site trial in a coking coal flotation plant in Queensland, Australia. The monitoring systems were used to measure (i) gas holdup, (ii) overflowing froth velocity, (iii) overflowing froth height, (iv) air recovery and (v) drag force exerted by overflowing froth, in an industrial flotation column and the outputs of these systems were collected simultaneously at a wide range of operating conditions. For each monitoring system, the best regression model describing the correlation between the system output and the flotation performance was selected from various regression models (eg linear, quadratic, power-law and logarithmic) using the Akaike information criterion (AIC). A comparison of the coefficient of determination (R2 ), residual sum of squares (RSS) and measuring accuracy at 95 per cent confidence level of the best regression models of these monitoring systems suggested that the drag sensor outperformed the other systems at a wide range of flotation operating conditions. The superior performance of the drag sensor was attributed to its distinctive design that enabled intimate sensing of variation of the overflowing froth properties. Furthermore, the drag sensor had the ability to monitor feed ash content variation when the other operation variables were set almost constant.

Aug 24, 2022

The An Shan iron ore deposit is the biggest low-grade oxidised iron deposit in China. Over the past ten years, about 120 SLon verticalring-pulsating high gradient magnetic separators units have been installed in An Shan to process oxidised iron ore. This paper describes how several plants have upgraded their old technologies to new technologies with SLon magnetic separators as the key equipment for controlling tails grades, including using reverse flotation as the key technology for iron concentrate cleaning, These plants have been modernised with beneficial results at low cost.

Jan 1, 2009

By K E. Mudzanani, T A. M Msagati, D T. Maiga, T T. Phadi, M R. Letsoal, B M. Chabalala, S W. Limani

This paper addresses critical environmental, health, regulatory and scientific concerns related to gold mining activities in the specific area of Barberton, Mpumalanga, South Africa. The paper thus calls for informed decisions to be made by the authorities to safeguard both the environment and people’s health. The novelty of this study is based on its comprehensive nature of the simultaneous assessment of both cyanide and potential toxic elements (PTEs) in tailings, while taking into account their composition variability over time. By combining these aspects, it is then possible to provide a holistic understanding of the contamination risks associated with mining tailings and thus justify the need for regular monitoring and supervision to ensure compliance against regulatory limits. Additionally, this paper considered investigating the dynamic nature of tailings, which are subject to changes in their chemical composition due to exposure to weathering by various agents. In this study, the determination of weak acid dissociable (WAD) and free cyanide in tailings was performed using a validated method employing the South African Council for Mineral Technology (MINTEK) Laboratory Cynoprobe. The PTEs in tailings were determined by an inductively coupled plasma optical emission spectrometer (ICP-OES). The results revealed that the tailings contained primarily substantial amounts of PTEs, including Fe (87 566 to 37 800 mg/L), Cu (271 to 110 mg/L), Mn (2100 to 680 mg/L), Ni (400 to 390 mg/L), Zn (180 to 68 mg/L), Cr (645 to 510 mg/L), As (450 to 128 mg/L), and Pb (up to 35 mg/L). The cyanide concentrations in tailings varied between 0.20 mg/L and 0.26 mg/L for free CN (with a mean of 0.23 mg/L in water leaching), 0.23 mg/L to 0.28 mg/L for free CN (with a mean of 0.25 mg/L in alkali leaching), 0.24 mg/L to 0.35 mg/L for WAD CN (with a mean of 0.28 mg/L in water leaching), and 0.31 mg/L to 0.39 mg/L for WAD CN (with a mean of 0.35 mg/L in alkali leaching). The measured concentration of cyanide and the PTEs was compared to the minimum permissible levels enforced by the South African Department of Water and Sanitation (DWS) and the Water Research Commission (WRC) regulations that govern the disposal of hazardous constituents into the environment. Additionally, it was observed that the concentrations of contaminants in the tailings exceeded the acceptable minimum limits for hazardous waste exposure, posing risks to the environment and human health.

Apr 16, 2024

By S L. Barbour

Measurement of the net percolation from the base of a cover system into the underlying waste material is a key component of a cover system monitoring program. The units of measure (ie a percentage of precipitation or rainfall) are simple to understand for all stakeholders, which increases the importance of obtaining representative net percolation values. In general, lysimeters are used to measure net percolation across the cover material-waste material interface; however, the design of lysimeters for cover system monitoring programs in the mining industry have typically not considered fundamental aspects of lysimeter design. Lysimeter design is typically thought of as being conceptually simple, when in reality the design, installation, and operation of lysimeters is often counter-intuitive, due to the complexities of flow through unsaturated soil systems. This paper puts forward a methodology for lysimeter design while also presenting the fundamental design variables that should be considered. Lysimeter design for differing climates, cover materials, and waste materials is discussed. Finally, the performance of lysimeter designs previously installed in the field at sites in Australia, Canada, and the United States are subjected to numerical modelling to determine whether net percolation is being measured properly.

Jan 1, 2003

A brief history of the significant haulage truck feature changes and the factors that influenced those changes during the 60's and 70's provide a basis for forecasting the changes that can be expected in the 1980's. A review of the impact factors and changing requirements that currently exist that will create changes. Define the critical requirements of a successful haulage truck design and discuss the availability of bigger engines and better electric drive componetry to provide deeper pit capability and improve reliability. The Unit Rig Trolley Assist System to provide improved productivity and diesel fuel savings and an economic analysis to evaluate the Trolley System is covered. The Unit Rig Automatic Truck System for a driverless truck is covered in concept and discussed from the point of view of the experience in a test in a New Mexico mine. INTRODUCTION A good basis for trying to forecast what is going to happen in the future is to go back a little bit in history, to see what the influencing elements were in different periods of time as a foundation for the forecast. INFLUENTIAL FACTORS IN THE 1960'S If you look at the truck development that occurred in the 1960's, there were some identifiable factors that give us insight. (See Fig. 1) Several things happened at the beginning of the 1960's. Mechanical drive haulage trucks were introduced that were

Jan 1, 1982

By Canterford J. H, Sparrow G. J, Dyson N. F

Pressure leaching of a bulk flotation concentrate prepared from a complex Cu-Pb-Zn sulphide ore was carried out at 150 and 190¦C under 1050 kPa oxygen overpressure in 1 L and 4 L titanium autoclaves to extract zinc, and to obtain residues for smelting tests and leach liquors for purification and recovery of the zinc by electrowinning. Dissolution of 95% of the zinc was achieved at both temperatures. Copper and iron dissolution and the degree of oxidation of the sulphide sulphur to elemental sulphur or sulphate depended on the temperature of the leach. At 190¦C, a jarosite (a basic iron sulphate) was the major iron-containing material in a residue that contained 17% total sulphur. Its formation was associated with dissolution of 18% of the iron. At 150¦C, oxidation of the sulphide sulphur and dissolution of the iron were significantly less. Only 7% of the iron was dissolved and a residue containing 25% total sulphur, present as a lead jarosite, lead sulphate, and elemental sulphur, was obtained. The formation of small pellets of unreacted sulphides coated with elemental sulphur caused problems during the leaching at 150¦C, and also during scale-up from the 1 L to the 4 L autoclave at 190¦C. At 150¦C the concentrate required two stages of leaching to achieve dissolution of over 90% of the zinc. These problems are discussed.

Jan 1, 1989

By P Revell, G Wilkie, P Walters, L Keeney, F Faramarzi

Grade Engineering® is a value-driven strategy aiming to maximise benefits by exploiting intrinsic grade variability of ore deposits. It utilises a multitude of separation techniques to remove low grade material before being introduced to post-blast size reduction processes, i.e. crushing and grinding. At an operational scale, Grade Engineering® techniques can be implemented at the drill-and-blast stage, to control the degree of fragmentation in accordance with the spatial distribution of valuable minerals across an ore domain through differential blasting. It can also exploit intrinsic textural and breakage characteristics of a given ore type to reject uneconomical barren material at coarse sizes, which is known as Natural Deportment. Grade Engineering® can also be employed in the deliver stage of the mining value chain through sensor-based bulk and particle sorting. Each strategy is therefore highly dependent on the responsiveness of an orebody to available techniques. That is, the extent to which Grade Engineering® drivers would be capable of unlocking potential values of currently un-amenable orebodies depends on how detailed the heterogeneous nature of ore domains can be described. This paper considers exploring possible linkages between deportment characteristics of an ore and its competence when broken in a range of energy inputs at a particlebased level. Accordingly, potential opportunity may lie in exploring whether the intensity of input energy (or degree of fineness) can be used as a lever to improve or ‘unlock’ ore amenability to Grade Engineering® techniques. Implications from such a detailed approach offers new opportunities to enhance Grade Engineering® gains through engineering ore competence variability.

Nov 10, 2020

By García B., Wolff E.

The pellet qualities primarily depend upon the thermal profile and gaseous environment during induration. During the induration of the pellet, it undergoes physical as well as chemical changes. Physical changes are mostly due to sintering and chemical changes are due to carbon burning inside the pellet. The effect of carbon on sintering is investigated on a single pellet scale using an optical dilatometer. Sintering is a complex process that involves transportation through various mechanisms. Sintering is quantified in terms of sintering ratio and the kinetic parameter, exponent ‘n’, under isothermal conditions is deduced using the power law equation. The value of n can be used to estimate the sintering mechanism at different isothermal temperatures. Also, the activation energy is calculated using the empirical Arrhenius equation. The activation energy of 0 per cent coke and 1 per cent coke-containing pellets are 531.0 kJ/mole and 552.6 kJ/mole respectively. The order of magnitude of activation energy suggests the same mechanism in both cases. Although the mechanism of sintering is the same, 1 per cent coke-containing pellet sinters more at any isothermal temperature.

Jun 17, 2024

By D Giddings, S A. Silvester, S Pickerin

Underground fires represent a constant threat to the safety of underground personnel. Miners in the immediate vicinity may face intense heat, blinding smoke, toxic fumes, fall of ground and other direct effects of a fire. However, the vast majority of victims never actually see the fire, and are overcome either by deadly fumes in the ventilating current or by asphyxiation. The mine ventilation system, which maintains a sustainable atmosphere to the working places, can transport products of combustion with equal efficiency. Miners who are remotely situated from a fire may be forced to evacuate considerable distances, through dense smoke and fumes, or even become cut-off from escape. Additionally, miners may become confused by unfamiliar ventilation characteristics caused by fires. Conveyor belts are widely used for transporting minerals in mines as well as in many other industrial situations. Because they contain large amounts of polymeric materials their use in certain environments, especially coal mines, but also in steel works, power stations and other enclosed areas must be controlled to minimise the fire risk. Over last nine years there have been 60 fires in underground mines in the UK alone and that of these, half have been associated with conveyors. This paper summarises the results obtained from a recent research project that has developed a preliminary computational thermal and fluid dynamic model to represent the spread of flame along a typical conveyor belt used in UK deep coal mines. The results of these models have been calibrated against a series of experimental tests performed within a surface fire test gallery. An improved knowledge of the burn characteristics and rate of release of the products of combustion from conveyor belt fires will assist in the development of better fire detection and fire fighting techniques.

Jan 1, 2005

By T Kojovic

"The index A*b, determined from the Julius Kruttschnitt Mineral Research Centre (JKMRC) drop weight tester (DWT) results, has become well-known in the mining industry as a reliable measure of ore hardness in impact or crushing, having the inferred units of t/kWh. This index evolved from a long history of comminution studies at the JKMRC, including the development of the now superseded JKTech twin-pendulum, the industry standard JK Drop Weight Tester (JKDWT) and the faster alterative JKMRC rotary breakage tester (JKRBT). A reduced version of the DWT, the semi-autogenous grinding mill comminution test (SMC test®), also provides estimates of the A*b though the testing of only one particle size at five specific energies. Experimental determination of A*b using the above devices/tests requires samples, with sufficient mass, to be sent to designated laboratories, registered to conduct such tests. This protocol is fine for bankable and commercial testing, where material characterisation data is used in conjunction with machine specific data in modelling and simulation, and power based calculations. However, for comparative testing, where results are required at the time of sampling (eg for plant troubleshooting or spot-surveys), or for rapid ranking of geometallurgical samples, these existing tests simply do not provide a timely, viable and cost-effective solution. In order to address this critical void in the realm of comparative testing, a new device has been developed, exploiting a central feature of single particle impact testing – that the A*b can be reliably estimated using one precise low energy test. This device, for which a patent is currently pending, called the HIT (Hardness Index Tester), has been precision engineered to allow users to break narrowly sized fragments at a set specific energy, in a safe and easy manner. The manufacturing materials have been chosen carefully to ensure compatibility with the intended use and portability to any site, whilst minimising cost. The device is supplied with a novel quality assurance / quality control (QA/QC) feature, to ensure that the targeted potential energy is consistently delivered. The product from the HIT breakage test can be quickly sized using a single screen to determine the mass per cent undersize, from which the A*b index is calculated directly at site – eliminating the need to send the raw data off-site for analysis. On presized fragments, a single test using 20 fragments takes less than five minutes to complete, and the results are immediately available. The HIT is currently being tested at a major mining laboratory in the US and the results to date have proved it can deliver on all fronts. This paper describes the new prototype device, which offers users a low cost in-house mechanism for estimating the A*b at any mine site, with potential applications on fragments up to 25 mm from drill core, blast chip rejects or the grinding circuit feed. It also outlines the results of field tests carried out by an objective third party mining group and compares the results with those from current industry standard tests conducted on the same material.Citation:Kojovic, T, 2016. HIT - a Portable Field Device for Rapid Testing at Site, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 9–16 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By G Byrne

Long-term water management is typically ignored in mine closure planning. A review of 73 mine closure plans dating from 2007 to 2013 shows that, on average, relinquishment is proposed to be achieved in 11 years. A separate review of 57 mines in actual closure shows that only five have so far achieved relinquishment with an average closure period of 14 years after production cessation. The remaining 91 per cent of sites in closure have an average closure duration to date of 21 years - and still going.A common issue among those sites in closure is water management, with a further common issue being acid and metaliferous drainage (AMD). Of the closure plans that were reviewed only one site had allowance for long-term (>50 years) of water treatment. Of the sites in actual closure 25 per cent have reported that they expect such long-term water treatment, with many acknowledging that in perpetuity treatment is probable.Clearly there is a gap between what is being allowed in closure plans and the reality of closure. There are a number of factors leading to the optimism of the closure plans, including unrealistic assumptions, pressures to reduce closure cost provisions and the technical complexity of many AMD issues.Long-term water management is a reality that needs to be acknowledged and addressed. If addressed early in the mine life cycle the impacts for mining companies can be reduced.CITATION:Byrne, G, 2013. Long-term water management - the forgotten legacy of mine closure, in Proceedings Water in Mining 2013 , pp 163-168 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By P Hatherly, H Gurgenci

With the depletion of the mineral reserves that can be mined by surface mining, demand for highly productive and safe underground mines will increase. Underground drill and blast techniques continue to be refined but true æmass productionÆ is difficult to achieve. As is evidenced by the longwall mining of coal, alternative mining methods based on mechanised mining can meet the expectations but the issues of how to effectively cut strong rocks, how to define the orebody and how the mechanised miners can be automated and maintained all need to be addressed. CMTE is working in all of these areas. We believe that the oscillating disc cutter may provide the long sought-after breakthrough in mechanised rock cutting. Disc cutters are one of the most robust designs of cutting tool and the cutters attack the rock in a manner which effects direct tensile breakage. The internal cutter drive and the inertial damping mean that the already low cutter forces are not all transmitted back to the machine, making it possible to design lightweight, flexible mining systems. For orebody delineation drill monitoring, drillhole logging and geophysical imaging are key procedures being developed at CMTE. To automate mining machines, work is progressing well in the development of systems for autonomous vehicle navigation and mining robotics. A strategic contribution to maintenance issues is being made through the development of procedures for automatic analysis of used oils, monitoring the strength of mechanical structures, and operating point optimisation.

Jan 1, 1998

By S Nkwanyana, I Govender

Batch experiments in a 0.6 m diameter mill have shown that improvements of about 13 per cent in the efficiency of energy utilisation can be realised in ball mills by replacing 25 per cent of the ball charge by an equivalent volume of cost-free critical size pebbles from AG/SAG mills. For a mill of a given size, speed and charge filling, the rate of size reduction of ore particles depends on (i) the frequency of grinding media collisions (ii) the probability of capture of ore particles between the colliding grinding media (iii) the probability of fracture of the captured particles. The probability of fracture depends on the magnitude of collision energy. The distribution of collision energy into shear and impact events determines the relative strengths of attrition breakage and impact breakage. The efficiency of energy utilisation depends on which of the two mechanisms of breakage is more desirable in a particular milling stage. In this paper collision data from a series of DEM simulations of a mill charged with steel media and a mixture of steel media and pebbles is presented in energy spectra and spatial distribution maps. The data provides the necessary detail to elucidate the improvements in the efficiency of energy utilisation in ball mills when using a mixture of pebbles and steel media.

Aug 24, 2022

By K Peters, C McKenzie

New Zealand has an established history of gold production beginning with the gold rushes of the 19th century in the Coromandel, Nelson/Marlborough, West Coast and Otago regions. Despite this, the number of significant modern hard rock gold operations has been limited in recent years due to a lack of sustained exploration capital and not limited geological prospectivity.The New Zealand Government is actively encouraging explorers to invest in New Zealand through a series of targeted promotional visits, more importantly through the acquisition of precompetitive regional geophysical data. Data collection has been completed over the prospective Northland epithermal district and a large portion of the South IslandÆs west coast that is prospective for both orogenic gold and intrusive related gold.Analysis of new data has been an important component in aiding the generation of exploration targets from prospectivity modelling. Determining the prospectivity of an area involves reviewing all the available data and analysing it with respect to the most up-to-date mineral system model for the mineralisation style of interest. Using the weights of evidence modelling approach, the most prospective areas for epithermal gold-silver, orogenic gold and intrusion-related gold have been identified. The key exploration parameters relevant to each mineral system are first represented spatially and then statistically combined into a single prospectivity map. New potentially economic deposits could be found by focusing exploration on targets identified from these models. The prospectivity modelling approach can greatly reduce the risk involved in mineral exploration.CITATION:Peters, K and McKenzie, C, 2013. New Zealand gold potential - using mineral prospectivity modelling to evaluate gold-bearing mineral systems in an underexplored country, in Proceedings World Gold 2013 , pp 479-486 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By A M. Sardo, D E. Sinnett

This study uses the Q Method to examine how those living in former metal mining landscapes value this heritage and their preferences for the long-term management of mine waste. Such sites are often perceived as derelict or degraded, and of very little value. It is therefore assumed that their reuse, for example for development or recovery of metals, is likely to be beneficial. There are around 5,000 former metal mines in England and Wales, many of which are protected for their ecological, geological or cultural value. The Q Method is particularly suitable for issues where there is no consensus of opinion. We asked 38 residents of six mining areas in England and Wales to ‘sort’ a series of statements based on their resonance with the resident’s perspective; this is the Q sort. The statements covered a range of opinions of the mining legacy, its value and options for its management with a particular focus on the potential for metal recovery from the wastes. Analysis of the Q sorts revealed five perspectives on the mining heritage. All placed a high value on the cultural and ecological value of this heritage, however, they differed in their priorities for long-term management. For example, emphasis was placed on either nature conservation, cultural heritage, water quality or the opportunity for job creation through reworking the mines. Cutting across these themes there were also differing perspectives on the role of experts and local people in shaping the future management of the wastes. This research suggests that the views of local people are nuanced; they value their mining heritage but opinion is split on the most effective way to manage these sites especially where there is an impact on water quality.CITATION:Sinnett, D E and Sardo, A M, 2018. Former metal mining areas in England and Wales – local residents’ preferences for the management of wastes, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 126–134 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By Stevenson I, Dickinson W, Taylor R. N

Despite flash smelting's widespread use little is known about the actual processes taking place in flash furnace shafts and comparatively few reports of sampling campaigns have appeared in the published literature. his paper reviews the previous reports of the use of horizontal trough samplers and analyses their expected collection efficiency. In the light of the deficiencies revealed by this analysis an isokinetic sampler was produced and a vertical sampling technique was also developed to obtain samples from directly below the burners in the shaft of the flash furnace at the Kalgoorlie nickel smelter. Comparison of the sizing of the samples obtained with the horizontal trough and isokinetic samplers confirmed the theoretical analyses and showed that the trough samplers were not collecting the fine particles. Besides providing data to validate mathematical models of the burners and shaft, chemical analyses of the shaft samples showed that the coal in the charge was reacting preferentially and that the plume of at least one of the burners was being deflected from its axial position. In the region directly below the burner there was evidence that the disperser on the burner was imparting more momentum to the coarser particles and that these were concentrating in the outer regions of the particle plumes issuing from the burners.

Jan 1, 1992

By A Marton

Concerns with crest losses have seen changes to a number of design and operating parameters to retain the integrity of the wall and the berms of the Kidston Gold MinesÆ Eldridge Pit. Until trials began in 1999 most final wall designs utilised large diameter blastholes up to the presplit row to achieve the wall angle. The berm crests were being lost, wall support requirements were increasing and affecting mining schedules and several fault areas were putting pit access at risk. Standard designs had been determined during the early mining years and while periodic modifications had been made there was a need for major blast pattern revision. This paper traces the development of wall control blasting programs over the years, relating designs to the geology and the evidence in the walls with the theories of the day and includes the recent trials that were conducted in what is a most unforgiving geology. Trials and improvements to ensure the walls were safe were conducted even as the mine neared its economic life. Instrumented monitoring of trials blasts has greatly increased the understanding of the damage criteria and enabled rapid revision of designs. Recent changes included reduction in presplit energy, charge redistribution and use of smaller blast holes for the trim patterns. Determination of a minimum proximity-to-final wall limit for production blastholes, establishment of the correct standoff to berm crests and walls and selective use of presplitting techniques for protecting crests have resulted in cost effectiveness, improved bench crest retention and an overall reduction in visible wall damage.

Jan 1, 2001

By J Rostami, T Afshar, M Sharifzadeh

Accurate estimation of rock load and selection of types of ground reinforcement to match post-failure behaviour of rock mass are important issues to assure tunnel stability. This paper focuses on the main factors affecting rock load to evaluate the capabilities of the existing models for prediction of rock load. Rock mass properties, project features and excavation method, as well as ground conditions and stress condition were found to be the key factors affecting the magnitude of rock load. Field data from tunnels of about 37.5?km driven in several geological structures in non-squeezing ground was used in this study. An in depth statistical analysis was performed on data to find correlations between the input parameters and measured/observed rock load. A weighting system was proposed to obtain the proper contribution of each factor for estimation of rock load in tunnelling through various ground conditions. The new classification system offered predicted values for rock load that were in a good agreement with the actual field measurements. The high disturbance factor (D>0.4) was the prime factor which controlled the rock load. Rock mass quality was the second key factor influencing rock load, which could be estimated by GSI, GSIresidual , especially when combined with tunnel depth.CITATION:Afshar, T, Sharifzadeh, M and Rostami, J, 2014. Estimation of rock load for tunnels with different disturbance factors, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 3–8 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By F T. Suorineni

Empirical methods are deeply rooted in geomechanics. This is a consequence of the recognised complexity of the nature of the rock mass. The usual assumptions of material continuity, homogeneity, isotropicity and linear elasticity often assumed for soil, concrete and steel are difficult to justify in a rock mass except for mathematical convenience. These assumptions form the bases for most mechanistic, analytical and numerical methods in geomechanics. Believers in empirical methods argue that the complexity of the rock mass and its interaction with structures developed in it is adequately accounted for in empirical methods, which compensate for our ignorance.Franklin (1993) defines empirical design as quantified judgement based on experience. He further states that empirical methods often prove ‘closer’ to the ‘truth’ than the apparently more precise predictions of theoretical analysis, adding that based on real data empirical methods provide a standard against which theoretical predictions are measured and can be judged. This paper takes a critical look at the common empirical methods in geomechanics – rock mass classification systems (Bieniawski, 1973; Barton, Lien and Lunde, 1974; Hoek, 1994a), Laubscher block caving design rules (Laubscher, 1994), the stability graph (Mathews et al, 1981), pillar design equations (Salamon and Munro, 1967; Hedley and Grant, 1972; and their derivatives), pillar design chart (Lunder and Pakalnis, 1997) and failure criteria (Hoek and Brown, 1980; and its derivatives). The common thread in the application of these methods is that in most cases they are often applied blindly without an understanding of the underlying assumptions and database limits. This paper emphasises that users of these methods need to know the underlying assumptions, database limits and inherent hidden risks that are often unmentionable for their satisfactory use. Finally, suggestions are provided for the efficient use of empirical methods and how they can be improved.CITATION:Suorineni, F T, 2014. Reflections on empirical methods in geomechanics – the unmentionables and hidden risks, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 143–156 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By K L. Olzard

At the WMC Resources Phosphate Hill operation, monitoring the quality of the ore delivered by the mine to the beneficiation plant is of prime importance to ensure the fertilizer is produced cost-effectively through the various stages of production and meets customer quality requirements. P2O5 and Fe2O3 are among the critical-to-quality elements. Fe2O3 is a key performance driver as it is an impurity that adversely impacts some of the chemical processes. The ore is supplied to the plant on a conveyor belt that is equipped with an automatic sampler. Increments are taken off the flowing ore stream at regular time intervals. A variographic experiment was conducted to investigate sampling strategies capable of estimating ore properties over a 12-hour shift to a nominated level of precision. The combination of individual increments into a shift composite was included among the strategies that were assessed. The experiment involved collecting data at regular time intervals and preparing variograms to characterise the feed-grade variability on the conveyor belt. Duplicates were also collected to assist in quantifying the precision of the subsampling stages of the sampling protocol and assay accuracy was monitored with matrix-matched standards. Various sampling schemes were evaluated by combining geostatistical techniques and the sampling theory of Pierre Gy. The following parameters were varied: the number of increments, the increment-size reduction leading to the composite, the masses of the subsequent sampling stages and the number of analytical determinations. This paper describes the planning of the variogram experiment, the various phases of data collection and the methodology used to process the data. It discusses the development of some of the sampling schemes that were considered.

Jan 1, 2005