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By William Hustrulid

The National Institute for Occupational Safety and Health (NIOSH), as part of a comprehensive program to improve mine safety through the widespread acceptance of careful excavation principles in drifting, have revisited standard drift round design concepts. Although the initial emphasis was on contour row design and providing improved design tools for blasting with de-coupled charges, the focus has broadened into the development of a general gas pressure-based drift round design approach. The concept of a damage radius (Rd) for a given explosive-hole-rock mass combination is introduced. With the damage radius as the basic building block, the blast holes are positioned on the face, beginning with the buffer row, to achieve the desired excavation size, shape and smoothness. The design of the contour row of holes is also performed using a pressure-based approach. The paper presents in some detail the overall approach and the required gas pressure-based design equations.

Jan 1, 2007

By Brockway DJ, Holmes RJ

A natural gamma-ray gauge has been devel- oped for discriminating overburden and inter- seam sediment from low ash coal located on a moving conveyor belt. It is based on the difference in natural radioactivity of the sediment and overburden compared with the low ash coal, which is detected with a highly ef- ficient "Polyscin" NaI(T1) gamma-ray detector located underneath the conveyor. Gauges have been successfully installed on the bucket wheel boom of the two coal dredgers at the Loy Yang Open Cut. They are used to warn dredger operators that they are digging overburden or sediment and that action is required to avoid the sediment or divert it to the waste dump rather than send it to the coal bunkers at the power station.

Jan 1, 1987

Vatukoula is credited with the second largest population in the Colony of Fiji. Within an area comprising 550 acres are living approximately 4,500 people. Of these, about 1,150 Fijians, 90 Rotumans, 90 Europeans, 180 Part-Europeans, 180 Indians and 30 Chinese and miscellaneous Pacific islanders are employees of the Associated Mining Companies.The remainder is made up of employees dependants with a small minority of tradespeople and Government servants, such as storekeepers, school teachers, police and post office officials.To appreciate fully the work involved in the administration of this unusual community it is necessary firstly to know something about the various types of people which compose it.The FijiansAlthough the Fijians are of Melanesian stock their physical characteristics indicate a Polynesian strain. Natives from all provinces in the Colony are to be found in Vatukoula and their varied types point to this MelanesianPolynesian intermixture. For example, there are people from Lau** and Kadavu who are tall and well built with good features and comparatively fair skins contrasting with the dark, broad featured and generally short people of the hill tribes of Ra and the coastal tribes of Bua.The Fijians, particularly the older people, are noted for their dignity, courtesy and hospitality. The young Fijians of the present generation, large numbers of whom are...

Jan 1, 1953

Vatukoula, the Fijian equivalent of gold rock, is the name of the community embracing the gold mines owned and operated by Emperor Gold Mining Company Ltd., Loloma (Fiji) Gold Mines, N.L., and' Dolphin Mines Ltd. It is situated in the Tavua Goldfields approximately five miles from the northern coast of Viti Levu, the largest island of the Colony of Fiji.The climate is sub-tropical, there being a definite wet and dry season. The wet season is somewhat variable in length but usually extends from December to March, during which time most of the rainfall for the year is recorded.Although the average annual rainfall is 71 in., more than twice this amount has been recorded. Precipitation at the rate of 5 in. per hour is not uncommon and 15 in. of rain has been registered in 24 hours. The mining methods adopted, therefore, had to suit these wet conditions.The occurrence of gold in the Tavua area has been known since 1872, but it was not until 1932 that discoveries were made which led to the formation of the present operating companies. In 1934 the Emperor Gold Mining Company Ltd. commenced operations, followed in 1935 by the Loloma (Fiji) Gold Mines, N.L., and later by the Fiji Mines Development Ltd., now known as the Dolphin Mines Ltd. Up to the end of 1951 these three mines had produced 2,501,688 tons of ore from which 1,277,881 oz. of fine gold and 347,429oz. of silver were obtained, realizing in Fijian currency £13,025,153.The three mines are situated close togeth.er on contiguous mining leases, and, although under common management, are operated as separate en,tities. Since 1944 all the...

Jan 1, 1953

By Cornelis Van Der Veen

Foundation piles, partly passing through unconsolidated compressible layers, suffer a downward drag that is called negative skin friction. The negative skin friction depends on the movement of the surrounding unconsolidated soil relative to the pile and on the friction between pile and soil as a function of that movement. The negative skin friction adds to the load on the pile. However as it is a function of the pile movement relative to the soil, the amount of negative skin friction to be taken into account to determine the allowable bearing capacity depends on the allowable pile settlement. In this paper this property is indicated by the factor µ. As under the conditions of ultimate pile bearing capacity negative skin friction does not occur, a factor of safety is introduced, which is lower than normal. Eventually a formula for the bearing capacity is given in which µ and both figure. The exact values for given circumstances have to be determined empirically. A few examples are given.

Jan 1, 2010

By Russell Levens

A strategy for prioritizing mining health and safety research by evaluating the potential for risk reduction through interventions is proposed. Mining has one of the highest incidence rates of injury and disease found in major industries. The main premise of this paper is that often the best opportunities to reduce these rates are not revealed by retrospective analysis of injury and illness data. Instead, a proactive approach is needed that accounts for risks to specific hazards that can be abated by engineering or behavioral interventions. The process proposed here begins with development of prospective interventions. The degree of reduction in risk to be expected from an intervention then is determined from statistics on the mining worker population, the expected degree of success of the intervention, and the expected change in the severity of injuries resulting from the intervention. Three disparate mining health and safety concerns are presented to demonstrate common problems in assessing risks of injury and illness and describe additional data needs. Information on events preceding injuries and illnesses and more detailed demographic data on the mining work force are needed to analyze injury and illness data more precisely. Detailed information on exposure to specific hazards is necessary to evaluate the potential for an intervention to reduce risk of injury or illness.

By David G. Dixon

A general, unsteady-state model for leaching of one or more solid reactant species from a non- reactive, porous, spherical pellet is derived in dimensionless form for the interpretation of leaching data, and for use in the design of coarse-ore leaching processes. The effects of diffusion rate, chemical reaction rate, variable reaction order, and competition between multiple solid reactants are examined using the concept of the effectiveness factor. It is shown that the model is capable of simulating both "reaction-zone" and "heterogeneous" kinetics, depending on the choice of three dimensionless parameters. Results of batch leaching tests of artificial ore pellets are presented, and their relationship to the model is discussed.

Jan 1, 1993

By L. G. Austin

The paper summarizes the current state of development of simulation models for SAG and FAG mills, and gives the results of recent investigations of the physical processes occurring in autogenous grinding. The breakage process is treated as the sum of three regions of breakage actions: normal breakage caused by nipping of particles between media (steel balls or pebbles); abnormal breakage caused by media when the particle or lump is too big in relation to the media to be readily nipped; and self-breakage resulting from the chip¬ping fracture and abrasion of the tumbling action of rock lumps. Each region of breakage action has associated specific rates of breakage and primary progeny fragment distributions. A simplified form of the model was used to predict the performance of an 8 m diameter SAG mill with L/D = 0.5 grinding a copper ore, and predicted maximum capacity and minimum kWh/ton at about 6% ball load at 25% total filling. Two FAG mills of L/D = 2 were necessary to give the same capacity, and the simulations indicated a lower kWh/ton for these mills. For this ore, both systems were technically feasible.

Jan 1, 1987

By W. R. Green, B. W. Barde

"Geological exploration involves the collection and analysis of a wide variety of information. A basic problem in interpretation is to determine the interrelationship s of the different data. A number of statistical methods can be applied to this problem, provided that subsets of data can be selected.We have recently developed a set of interactive computer programs which provide the cap ability to quickly examine a large set of data, and may be used by people with little previous computer experience. There are two main stages in using this system. First is selection of subsets of data , by applying various tests on the values of given items. This includes matching specific entries in descriptive fields, and minimum - maximum tests on numeric fields. The second stage is basic statistical analysis and data display , including histograms, 2-D scalier plots, probability (cumulative frequency) plots, and correlation matrices. All output can be viewed on a computer terminal, and important parameters changed to produce the most effective display for use in interpretation.This system has been applied to a number of different exploration problems. An example was the determination of the nature and extent of mineralization of a gold prospect in the Queen Charlotte Islands, from drill-hole data. With the aid of the computer programs , a mineralized zone was defined, and locations for further exploration identified."

Jan 1, 1984

By D. W. Horsfall

The coal-preparation techniques used in South Africa over the past ten years are reviewed, the term preparation being taken to refer to processes involving beneficiation techniques. The success of the preparation methods adopted can be gauged from the fact that, although South African coals are generally of a fairly low quality, the country is producing coals both that are used locally for the raising of steam and for metallurgical purposes, and that compete successfully on world export markets.

Jan 1, 1980

By J B. Maughan

Gas and oil seeps have been known in Quebec for more than one hundred years. These occur in three main areas which contain sedimentary rocks with a total thickness estimated to vary from 6,000 to 20,000 feet. The strata in these areas are similar in many respects to those in producing areas of southwestern Ontario and the Appalachian basin, and the prospects for finding and developing commercial reserves of oil and gas in Quebec would therefore also appear to be favourable. Little of the exploratory drilling to date has been con-ducted in a systematic manner, and most of the drilling has utilized improper or inadequate equipment. Many wells have also failed to adequately test and fully evaluate the principal zones of interest. Relatively high drilling costs have hindered systematic exploration; however, with improved portable equipment, it is expected that future wells can be drilled with greater efficiency and at less cost. Most of the mineral rights in Quebec are held by the Provincial Government, and acreage can still be leased in large blocks on favourable terms.

Jan 1, 1964

By Nasib Al Habib, Hooman Askari-Nasab, EUGENE BEN-AWUAH

In-pit crushing and conveying (IPCC) is getting popular in deeper open pit mines as a suitable alternative to truck haulage because it offers a lower operating cost due to shorter haulage distance and less truck requirement. Semi-mobile in-pit crusher, currently the most popular IPCC system, is relocated every two to five years, and the short-term plan needs to be updated accordingly. To the best of our knowledge, short-term planning with IPCC is an area of research that has yet to be explored extensively, and hardly any model can generate a shortterm extraction sequence considering an IPCC. This research work proposes a mixed integer programming model to develop a short-term production plan within a time horizon of 12 months. The model's objective is to optimally allocate shovels to minimize the cost of material handling and maximize revenue subject to meeting plant requirements, maximum allowable tonnage variation and IPCC location constraints to achieve production and NPV targets set by the strategic plan. The proposed model will be implemented in an iron ore mine case study for verification. The model is developed and solved using MATLAB. The comparison of results between scenarios with and without IPCC justifies the use of IPCC in large open pit mines from a short-term perspective.

Jun 25, 2023

By K. Baba

Liberation of valuable minerals from a gangue matrix during size reduction of multiphase mineral particles is an important objective in mineral separation processes. A methodology for the prediction of volumetric grade distribution from one dimensional, linear intercept image analysis is being developed using a transformation function to describe the relations hi p between the linear and volumetric grade distributions. As part of this research effort it has been found that a transformation function, derived from Monte Carlo simulations of irregularly shaped particles, mainly depends on the volumetric grade and the dispersion density, i.e., the number of nuclei (or grains) per particle. A possible mathematical form for the transformation function is described in detail.

Jan 1, 1985

Many sampling standards arrive at a value for the prescribed sample mass by assuming a specific relation between the sample mass and the relative standard deviation of the fundamental error and assigning a value to the tolerated coefficient of variation. In order to obtain an equation that provides a relation between the minimum sample mass and the particle properties, many different models for the drawing of a sample have been developed. Here, a model for the drawing of a sample is proposed which can be considered to be a generalisation of the model used in GyÆs sampling theory. Using simulations, it is illustrated that the generalised model can lead to a better correspondence with actual sampling processes.

Jan 1, 2005

By Bhattacharyya A. K

A strata parameter is introduced to include the deformation characteristics of the undermined strata in the prediction of subsidence movement. By using the strata parameter and mining factors as parameters, a nomogram for predicting the maximu

Jan 1, 1994

By R C. A Minnitt

The two methods for calibrating the parameters K and (alpha) for use in Gy’s equation for the fundamental sampling error (FSE), the duplicate sampling analysis (DSA) and the segregation fractionalised analysis (SFA) are described in detail. A case study using identical broken reef material from a Witwatersrand-type orebody is calibrated using the DSA and SFA methods and the results are compared. Classically, the form of Gy’s equation for the FSE raises the nominal size of fragments given by dN to a power of 3. Gy’s formula is a theoretical formula applicable in the case when fragments are randomly collected one by one, which is obviously never the case. This is because the fragment shape factor (f) and the granulometric factor (g) were introduced to take care of this anomaly. More recent formulae, such as those suggested by François-Bongarçon and Lyman, are empirically based formula. A later modification of Gy’s formula raises dN to the power ? (alpha), the latter term being calibrated with the coefficient K in the DSA and SFA methods. The preferred value of ? (alpha) for low-grade gold ores used by sampling practitioners in the mining industry is 1.5. A review of calibration experiments for low-grade gold ores using the DSA and SFA methods has produced values of K that vary between 70 and 170 and values of alpha in the range 0.97 to 1.30. The average value for alpha is found to be 1, rather than 3 as originally proposed in the classic form of Gy’s equation or the industry preference for 1.5. It is suggested that for low-grade gold bearing ores, the equation for the FSE should raise dN to a power of 1. Such an equation for the variance of the combined FSE plus the grouping and segregation error, now referred to as the short-term component of the quality fluctuation error (QFE1), greatly simplifies the characterisation of gold ores, which now only requires the calibration of K for a given mass and established fragment size. The implications for the heterogeneity test from the generalised equation are that provided the fragments have been screened to within a narrow size range, any particular size will return a value for K that is acceptable for use in the sampling nomogram.CITATION:Minnitt, R C A, 2017. A generalised form of Gy’s equation for gold ores – empirical evidence, in Proceedings Eighth World Conference on Sampling and Blending , pp 331–350 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

The strategy of adjusting operating conditions to maintain optimum process performance as the feed quality varies - adaptive optimisation - is being investigated by computer simulation of chemical processes for the treatment of ores. Those ore-process systems that are most likely to yield substantial benefits from adaptive optimisation are being identified as a guide to the selection and development of systems for practical application. The generalised mathematical representation of the cost structure, ore quality variations, process kinetics, reactor characteristics and operating variables for ore-process systems is described. Results are summarised for temperature, reagent concentration or residence time as the manipulated variable. For almost all systems, adaptive optimisation was economically beneficial, although a few exceptions have been identified where there is a significant synergistic effect between poor-performance and good-performance materials in a blended feed. The sensitivity of the benefits of adaptive optimisation to a range of economic and technical factors is summarised.

Jan 1, 1985

By Jackson D. G

Iron ore mineralisation in the Paraburdoo environs is known to extend almost continuously over a strike length of 55 kilometres. Six formations of the Mount Bruce Supergroup con- tain high grade mineralisation in varying degrees of importance. Ore is currently being mined from the Joffre and Dales Gorge Members of the Brockman Iron Formation, with smaller, less significant amounts, occasionally taken from the lowermost units of the Weeli Wolli Formation and the upper parts of the Mount McRae Shale. Regional mapping has demonstrated the existance locally of a major unconformity at the base of the Wyloo Group sediments out- cropping south of the minesite. The basal con- glomerates at the unconformity are sometimes mineralised at Paraburdoo. A supergene enrich- ment process controlled by structure, strati- graphy and topography is the only one which can satisfactorily explain the disposition and chemistry of the Paraburdoo iron orebodies.

Jan 1, 1979

By C. B. Manula

Languages such as SIMSCRIPT and GASP have reduced the programming skills required to build simulation models, but not to a level where these can be used by a busy engineer or manager unless he has extensive programming experience. In an attempt to make simulation a more readily available tool, Sanford (1969) structured a generalized materials handling model (UGMHS)* for underground coal mining. The majority of materials handling systems consist of a set of moves and a set of pieces of equipment required to execute the moves. UGMHS gives a technique for describing and classifying the elements in these sets and then a technique for simulating the interactions of these elements as the materials handling system operates. To apply the model, the user simply furnishes data parameters and a fixed set of orders to the computer for his own problem. This new philosophy of dynamic simulation as applied by UGMHS was demonstrated in the paper by Sanford and Manula (1973). A dynamic model of underground coal mining was presented for the purposes of systems design and selection of equipment for a completely new operation and the analysis of existing ones for possible alterations, additions, and general improvements. The main differences between this application and its predecessors is the ability to transport material from multiple mine faces to multiple mine destinations and the ready adaptability to a wide variety of mine layouts. The second difference that characterizes the model is the deterministic simulation of equipment moves according to their mechanical capabilities and the physical profile of the mining scheme. Here, the computer generates performance data in the absence of time studies to compare equipment rather than operator performance.

Jan 1, 1974

By J. C. Johnson

The problem of estimating pillar capacity in coal mines has motivated development of a variety of empirical equations. Most of these equations have arisen from experience and a very limited set of measurements that have, necessarily, been focused on particular regions or coal fields. Their applicability is often limited to a specific range of pillar sizes. This is of particular concern in the design of large gateroad pillars and small barrier pillars between panels. The result has been a variety of equations and equation coefficients that can calculate load estimates to size pillars. Inclusion of these equations in more sophisticated loading models, such as boundary element methods (e.g. LaModel and MULSIM) has been hampered by absence of a function that describes specific variation of coal strength within the pillar. A singular exception, to our knowledge, is a function corresponding to the Bieniawski pillar strength equation. Because of this, it is the only coal strength criteria inherently available in most boundary element models. This paper presents a general method for deriving local coal strength, as a function of distance from the pillar rib, for an arbitrary pillar strength equation. Integration of this function provides the strength of pillar regions, or cells, needed for boundary element models. The method is demonstrated for the Bieniawski, Maleki and Holland-Gaddy equations. The Maleki and Holland-Gaddy equations contrast strongly with Bieniawski as strengths are extrapolated to large pillars and barriers. This development provides a tool for incorporating any of the proposed empirical equations into a boundary element model, thereby allowing the analyst to choose the most appropriate equation for a particular region, coal seam and/or pillar size.

Feb 23, 2014