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Common brattice cloths in use in Australian coal mines are compared by permeability measurements. The respective advantages of twill weave and tarpauling* weave cloths are listed, and the improvements to be obtained in the ventilation of a mine by using tarpauling cloths instead of the commonly used twill cloths are stressed. Plastic cloths are widely used overseas and are briefly discussed.INTRODUCTIONThe onset of extensive full-scale mechanization in Australian coal mines during the past few years has increased attention given to the ventilation of working places. Many inadequacies of the present system have been brought to light and not the least of these is connected with the use of brattice cloth, both in directing the flow of air around the face and in acting as a temporary sealing mechanism. A well-constructed line of brattice will only provide fair ventilation for a distance of 100 ft. Beyond this point the volume or air reaching the face falls off rapidly.Some of the shortcomings associated' with the use of brattice cloths are:1. Hurried installation, necessitated by a rapid advance, often results in poor workmanship with, consequently, an excessively high leakage rate.2. High places caused by falls of roof are difficult and time-consuming to seal.3. Curtains, in lines of brattice crossing transport routes, are difficult to maintain.4. Lines of brattice interfere with rock-dusting and clean-up of fine coal.5. Repair and maintenance of brattice consumes much...

Jan 1, 1959

By Shosei Serata

The Stress Control Method improves productivity and safety in underground coal mining. The method stabilizes the roofs and floors of mine openings in both shallow and deep coal beds, regardless of whether or not there are ground stability problems. This paper describes the means by which a tapered pillar experiment is used to collect in situ data, which is then used as input for a computer model. The resulting computer model is then used to optimize Stress Control design for the mine under study. The behavior of any underground coal mine is not elastic, as is generally conceived in the conventional view of rock mechanics, but rather is highly time-dependent and site-specific. Unfortunately, conventional rock mechanics methods based on the elastic principle are not able to capture the highly non-elastic nature of ground behavior which actually occurs. To capture actual behavior, a new method of study is required. In this regard, geomechanical study of an underground coal mine may be compared to studying the behavior of a living fish. Its true behavior zannot be understood by examining it "dead in the laboratory. It Is the "live" nature of the coal mine that is required for design optimization of the Stress Control Method in the given mine. The Stress Control Method is based on a time-dependent theory of the global behavior of the mine ground, which generally contradicts the conventional elastic theory of ground behavior. Therefore, site-specific adaptation of the Stress Control Method required a comprehensive understanding of the global behavior of the mine as a function of time and site-specific ground conditions.

Jan 1, 1986

By Lewis PJ, Halfpenny R, Craighead GA

Exploration drilling by Joint Venture partners CRA Exploration Pty Ltd and Elders Mining PNG Pty Ltd has discovered a signif- icant copper and gold deposit at the Wafi River prospect, 60km WSW of Lae in Papua New Guinea. An indicated resource of 18Mt at 2.5g/t Au using a lg/t cutoff has been delineated in Zone A. No estimate has been determined for the separate copper occurr- ence at Rafferty's Zone but the copper will be significant to the project. Metallurgical studies on the gold indicate that the primary ore is refractory to direct cyanidation giving a highly variable and inadequate response. All conventional refractory ore oxidation techniques perform well on both ore and pyrite concentrate and oxidation occurs rapidly. No metallurgical studies on the copper mineralisation have been undertaken. Hypogene covellite and chalcocite copper mineralisation is associated with an intensely quartz-stockworked, and quartz and alunite-altered intrusive. Economically significant gold mineralisation occurs in distal subhorizontal lenses, within a sedimentary host, that plunge toward the intrusive. These lenses are sandwiched between overlying quartz and alunite-altered zones and underlying quartz and smectite zones in a mixed zone of quartz, dickite, kaolinite and illite alteration. The alteration and mineralisation is classified as a high sulphidation, epithermal style resulting from the influx of hot, acid magmatic fluids. Preliminary land ownership, road access, power supply and mine infrastructure studies are in progress. The project is currently at an advanced exploration stage.

Jan 1, 1991

By Keith A. Heasley

In the past, numerous displacement-discontinuity (DD) models of stratified rock masses have been proposed using a homogeneous isotropic elastic overburden. In this paper, it is postulated that a laminated overburden model might be more accurate for describing the displacements and stress in these stratified deposits. In order to investigate the utility of using a laminated overburden in a DD model, the fundamental mathematical basis of the laminated model is presented and graphically compared with the fundamental behavior of homogeneous isotropic elastic overburden and with field data. Specifically, the stresses and displacements surrounding an idealized longwall panel as determined from the laminated overburden model are presented and compared with results from the homogeneous isotropic overburden and with measured abutment stress data. Also, the remote displacements and surface subsidence as calculated by the laminated overburden model are compared with homogeneous isotropic calculations and with measured subsidence data. The results of this investigation show that the laminated overburden is more supple, apt to propagate displacements and stress further, and better able to fit observed data than the classic homogeneous isotropic overburden. Ultimately, it is suggested that the laminated model has the potential to increase the accuracy of displacement and stress calculations for a variety of mining situations.

Jan 1, 1996

By M. Fan

Froth flotation is the most widely-used method of separating fine coal, especially coal with coking properties. However, froth flotation is not efficient for treating ultrafine coal and coarse coal particles. Our previous fundamental test results demonstrated that cavitation-generated nanobubbles can significantly improve coal and phosphate flotation performance over a wide particle size range. In this study, the effect of nanobubble on the flotation performances of different particle size fractions of coal was investigated using a bank of 10-liter flotation cells, a specially designed 50 mm inside diameter column and a 152 mm inside diameter column. It was found that nanobubbles that were either directly formed on or subsequently attached to the surface of coal particles during coal froth flotation process improved flotation efficiency. The use of nanobubble in a bank of mechanical cells flotation and column flotation significantly increased the flotation recovery at a given product grade. Nanobubbles increased the flotation rate constants of different coal particle sizes. The presence of nanobubbles in flotation slurry could extend the lower and the upper particle size limits for effective coal flotation.

Jan 1, 2012

By Stephen C. Tadolini

The U.S. Bureau of Mines, in cooperation with the Cyprus- Plateau Mining Company, has conducted research to provide an alternative to traditional secondary support systems in a two-entry, yield pillar gate road. As recent as two years ago, it was impossible to imagine a gate road supported solely with internal high-strength resin-grouted cable supports that would virtually eliminate the necessity for crib or concrete external supports. The support system evaluated consisted of 1.6-m (5-ft) full-column resin-grouted bolts and 4.8-m (164) long cable supports installed in conjunction with wire mesh and "monster-mats." Cable loading and roof deformations were monitored to evaluate the behavior of the immediate and main roofs during first and second panel extractions. The stress and loading histories for the panels and yield pillar were monitored to evaluate the stress transfer and pillar performance in conjunction with the roof and floor behavior. The test results indicated that the designed support system successfully maintained the roof during the extraction of two longwall panels and dramatically reduced the cost of secondary support. This paper will describe the theory of a cribless support system, the advantages of cable supports, and present the pillar, roof, and floor measurements made to assess the support performance during longwall retreat mining.

Jan 1, 1995

By Zachary Q. Maassen

The purpose of this paper is to highlight the environmental benefits of properly managing slurry waste as it is generated on site. The following projects will be used to illustrate the importance of proper onsite waste management. Project: Jet Grout Backflow Dewatering The goal was to dewater the backflow directly onsite to produce a dry, solid waste and reusable water. The backflow spoil was pumped directly to the dewatering system as it was generated. Utilizing mechanical separation equipment and flocculation polymer the waste volume was reduced by 44%. Due to the site footprint and high volumes, slurry waste removal and onsite processing were the only two feasible options. Onsite dewatering proved to be the environmentally beneficial option as it eliminated the need for slurry waste hauling and disposal. The benefits of utilizing a dewatering system are listed below: Project: Soil Mixing Spoil Recycling for Slurry Wall Construction In this application the spoils generated contain bentonite mud, cement mixture and organic ground soils. The goal of this project was to process the backflow mixture to recover reusable bentonite mud and separate the soil as a dry, stackable waste product. The treatment system replaced the traditional method of vacuum truck extraction and facility disposal. The environmental benefits of properly handling the backflow is a decrease in fresh water usage, bentonite additive reduction, and the reduction of CO2 emissions. The paper will consist of a project scope, technical equipment and process description, environmental impact reduction calculations and lessons learned for each project.

Jan 1, 2018

By J. Searra, M. Aboagye

"For new mining projects or for medium- to long-term areas of existing mines, drilling data is invariably on a relatively large grid. Direct estimates for selective mining units (SMUs), and also for much larger block units, will then be smoothed due to the information effects and the high error variance.The difficulty is that ultimately, during mining, selection will be done on the basis of SMUs on the final close-spaced data grid (grade control), which will then be available, i.e. the actual selection will be more efficient, with fewer misclassifications. However, this ultimate mining position is unknown at the project feasibility stage and therefore has to be estimated. This estimation is required because any cash flow calculations made on the basis of the smoothed estimates will obviously misrepresent the overall economic value of the project, i.e. the average grade of blocks above cut-off will be underestimated and the tonnage overestimated for cut-off grades below the average grade of the orebody. Similarly, unsmoothed estimates will be conditionally biased and will give even worse results, particularly in local areas of short- and medium-term planning or mining.This paper presents a case study of indirect post-processing and proportional modelling of recoverable resources designed for mediumand long-term mine planning at the Gold Fields’ Tarkwa Mine in Ghana. The case study compares long-term indirect recoverable mineral resource estimates based on typical widely spaced feasibility data to the corresponding production grade control model as well as the mine production. The paper also proposes certain critical regression slope and kriging efficiency control limits to avoid inefficient medium- to longterm recoverable estimates, and highlights the danger of accepting block estimates that have a slope of regression less than 0.5."

Jan 1, 2015

Samples weighing O· 2 g are digested with 2 ml of 72 per cent perchloric acid for 2 hr at 180°C, and then diluted to 10 ml. with water. After settling, an aliquot of clear solution is reduced with ascorbic-citric acid, and then a zinc dithiol solution is added to form a coloured molybdenum complex which is extracted with petroleum spirit for comparison with standards.Concentrations down to 2 p.p.m. may be analysed at rates up to 150 determinations per day.

Jan 1, 1970

By Eric Schraml

Wardrop Engineering and the Placer Dome?s Campbell Mine Design Team utilized leading edge directional raise boring techniques and an innovative, remote controlled application of steel fibre reinforced shotcrete ground support to achieve improved mine ventilation and a superior, safety focused secondary emergency egress. While more standardized methods may have provided a sufficient solution to either the requirement for a ventilation raise or for a traditional escape ladder way, innovative methodology ensured both objectives were met with a single, enhanced solution. Placer Dome committed to provide a solution that minimized energy consumption, optimized air delivery and facilitated an escape way focused on minimizing the negative physiological aspects associated with mine evacuation. The project was successful in providing a new airway, returning 47 m3/s (100,000 cfm) from the 39 Level to 30 Level, minimizing risk to the raise equipping crew and providing a fully equipped escape hoist. The resulting secure escape environment provided an efficient means of evacuating personnel working at depth without necessitating a potentially dangerous exhausting climb to surface. The project has substantiated, that optimized safety focused design can be achieved without jeopardizing project economics.

May 1, 2002

By C. Scheffer

This paper describes a model that can simulate the behaviour of a pneumatic intensifier that is generally referred to as an ?air pump? (AP). The AP is used in many South African underground mines, and utilizes compressed air with pressures between 0.3?0.6 MPa to pump water up to pressures of 12?18 MPa. The high pressure water is used in numerous underground mines to pressurize props and roof bolts that act as safety and roof support devices. The simulation model reproduces the intensifier's operation under various conditions and therefore can be used to investigate the AP's sensitivity towards environmental conditions, design parameters (such as spring stiffness, plunger diameter, nozzle diameter etc.) and operating conditions. Model validation by comparison with laboratory experiments showed good correlation. The model can subsequently be used to investigate design changes aimed at improving the AP's performance and reliability over a wider range of operating conditions.

Jan 1, 2005

A number of impending and actual pit wall failures have been observed and documented, which have been interpreted to initiate on newly generated structural features. This infers failure through intact rock. Failure mechanisms have been postulated resulting from circumferential stress, extensional strain and brittle flexure. These will be discussed in the context of the failures and the associated monitoring. The implications of failure initiating on ?unknown? features has a significant impact for deep open pit mines where designs are based on the expected structural regime. Being able to anticipate such failures is important for design. Equally important is management of such changes as they arise. In this context, monitoring using high resolution microseismic techniques will be discussed as a means of providing early warning of such failures.

Jan 1, 2006

By Stephen C. Tadolini, Dennis R. Dolinar

The risk of injury caused by minor roof falls continues to increase in underground mining. Most ground control injuries result from small rock falls that occur in a supported area, but do not involve the failure of the support system. In the roof, these are the "skin failures" that occur between previously installed primary or secondary bolting systems. To minimize skin failures and the associated accidents, several devices were designed and tested in the laboratory to maximize stiffness, minimize material thickness and weight, and ease material storage and handling on roof bolting machines. The goal of this project was to design and evaluate devices that can be installed with traditional primary or secondary roof supports, and that are easy to handle/install under temporary or previously supported roof.

By C. E. M. Meskers

Electronic and Electric Equipment contains a range of components made of a wide variation of metals, plastics and other substances. Up to 60 elements can be found in complex electronic equipment: base metals, precious metals and special metals in circuit boards and batteries. Because of its amount WEEE represents a considerable metal resource with a higher special and precious metal content than found in ores. The Umicore integrated smelter and refinery recovers and supplies back to the market 17 different metals from EEE. Pre-treated materials enter state of the art, material and energy efficient metallurgical processes for environmentally sound recovery of metals and treatment of off gasses and hazardous substances. The organics in the feed function as reducing agent and alternative energy source during smelting for precious metal recovery. Lithium-ion batteries are treated using a dedicated process. As a result the environmental footprint of metals produced from EEE is much smaller than primary production.

Jan 1, 2009

By Jamie D. McEwan

To cater for the future introduction of 12 car trains, London Blackfriars railway station is being extended from the north end to span across the River Thames. Following the demolition of existing buildings, a number of challenges had to be overcome including working adjacent to a live railway line, above live London Underground tracks and working in small restricted spaces. Trains entering and exiting two lines of track at the bridge's north end of track meant that access was difficult due to the location and proximity to existing infrastructure. The site was very much constrained and congested and there were also a series of works in place to maintain passenger flows so as not to inconvenience the travelling public. The site had been developed many times in the past resulting in a number of obstructions that would require removal during the piling work including old brickwork, reinforced concrete, redundant railway sleepers and track and existing concrete and timber piles. A number of solutions had to be devised to overcome these obstructions. Piling works were undertaken during the day and at night to meet programme.

Jan 1, 2011

By Peter Hatherly

As a discipline, geophysics covers an enormous range of scales and applications - from planetary geophysics through to the monitoring of acoustic emissions of rock samples. Although it is not a core discipline within the mining industry, geophysics has a useful role in providing information on the nature of the rock mass and the way it is responding to the mining process. For coal mining purposes, geophysical studies mainly seek to - delineate boundaries between the coal and the various layers within the surrounding strata - determine the physical properties of the rocks in-si tu, and - monitor the response of the rocks to the mining process Some of these applications may be associated primarily with mine planning, but once a mine is underway, most geophysical results can be used for the purposes of ground control. For example, insights into the nature of a geological fault mapped by a 3D seismic reflection survey will be relevant to determining support requirements while mining through it. In some instances there are parallels in the use of geophysics by the petroleum industry. Seismic reflection and wireline logging techniques have mainly been developed for petroleum exploration where their on-going development continues to provide spin-offs for the coal industry. The 3D seismic survey techniques that we now routinely employ were in their infancy 25 years ago and, almost certainly, the high quality borehole scanning tools that are now available would not have been developed without the need for petroleum well evaluation. Mining has also led to the development of specific techniques. An example is microseismic monitoring for the management of roof conditions during longwalling, and also the prediction of rock and coal bursts. The use and success of this technique have grown greatly over recent years. Another example lies with the use of geophysical wireline logs to predict rock strength and in rock mass classification. Coal seams also provide an unusual geophysical situation in that they form seismic and electromagnetic waveguides. The in-seam seismic and radio imaging methods have been developed to exploit these geological properties. In this paper I address the development and application of geophysical methods such as these with a particular emphasis on their role in ground control. We will see that there have been many developments over the past 25 years but we should also think about the future and how geophysics needs to be developed. From a miner?s perspective, one obvious area of need is in the detection of voids in the vicinity of current mine workings, be they old workings or karsts within nearby carbonate beds.

Jan 1, 2006

By Wilfrid Comeau

While researching for a theme lecture (Comeau, 1993l) on: 'The Mechanics and Physics Explosives', the author of Energy Transfer in Rock Fragmentaion by was confronted with many conflicting concepts regarding: the current explosive rock fragmentation theories, the physical principles governing energy transfers, the mechanical properties of rocks, and observations and data from full scale rock blasting.

Jan 1, 1995

By M. A. Trevits

The National Institute for Occupational Safety and Health (NIOSH), in partnership with the Mine Safety and Health Administration (MSHA), is conducting research to test, evaluate, improve or modify coal mine fire-fighting strategies and methodologies through large-scale tests. Since wood is the second most abundant fuel available during a coal mine fire, it was decided that series of large-scale wood crib fire tests were needed to measure the products of combustion and to observe the capability of commonly available direct application fire suppression equipment, namely, fire extinguishers, water and gas-enhanced foam. This paper discusses the wood crib fire tests, provides insight into the products of combustion and describes observations made during the application of the fire suppression agents.

Jan 1, 2009

By Hannan J. C

In New South Wales, development applications for major coal mining proposals are determined by the Minister for Planning and Environment and applications for mining leases and other mineral titles are dealt with by the Minister for Mineral Resources. The environmental conditions placed on the development consent, the coal mining lease and the approvals and licences under the pollution control legislation, amount to a substantial component of any new project's planning and commissioning considerations.An outline is presented of the framework within which various approvals are granted and conditions for environmental management are imposed upon mining projects. The principles and concerns, as perceived by the regulatory authorities, on which the majority of approval conditions are based are also outlined.No attempt has been made to analyse the extent to which these principles or standards are achieved in practice, nor to discuss the degree to which some of the conditions are achievable with the current status of technology and economics in the coal industry.

Jan 1, 1987

By Pengfu Tan

A thermodynamic model has been developed to predict the distribution behaviors of Cu, Fe, S, O, Pb, Zn, As, and heat balance in a lead blast furnace. The modeling results have been validated by the plant data of a lead smelter in Asia. The model can be used to predict for any set of controllable process parameters such as feed composition, smelting temperature, degree of oxygen enrichment and volume of oxygen-enriched air. The effects of the blast air, industrial oxygen, and coke charge on the distributions of Cu, Fe, S, O, Pb, Zn, As, and heat balance, and on the lead loss in slag have been presented and discussed.

Jan 1, 2005