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By T Howard, J E. Everett

BHP Billiton Iron Ore has replaced the conventional product quality control batch system at Yandi with the Continuous Stockpile Management System (CSMS) centred on a fully integrated æcontinuousÆ stockpile flow from mine planning through to port reclaiming. With increasing tonnage rates, tight operational coupling associated with the original batch system caused production interference which achieved final product quality but in an increasingly inefficient manner. This innovative approach places a continuous emphasis on product grade control and takes full advantage of the most appropriate blending opportunities of the mine to port planning and production system in order to reduce the natural variability of the ore to an acceptable level. To implement continuous control, product variability throughout the process is classified as long-term and short-term. Long-term variability is best controlled through the monthly mine planning process which determines monthly grade targets while taking into account optimum mine development. In the past, attempts to control long-term variability were made at the port through selective stockpiling and reclaiming which reduced operational efficiency. Short-term variability is best controlled around the monthly mine grade target by daily mine production scheduling, train sequencing, stacking into port stockpiles of appropriate size and systematical stockpile reclaiming. The implementation of the new system has maintained customer accepted shipping grades and has provided significant improvements in resource utilisation, operational efficiencies and costs.

Jan 1, 2002

By B. M. Larsen

IN endeavoring to put the art of the steelmaker on a more scientific basis, as a means of securing closer control of the product, we must be severely critical of the basis of any theory we use. In particular, we must be careful to distinguish between factors that are primary and those of only secondary importance. The concentration relations that determine the slag-metal equilibria, which are usually more or less closely attained, are of course of primary significance, but a clear picture of the whole process requires that the actual rates of the several reactions be taken properly into account. At the high temperature of the steelmaking furnace, all reactions might be thought to be very rapid, but some of them in fact are not; the essential causes of this condition are important to a proper understanding of the process. This paper aims to present, and to justify, the viewpoint that the most significant reaction is the oxidation of carbon in the metal, the progress of which determines the oxygen pressure levels in slag and metal and produces stirring effects, all of which influence the course of the process as a whole. REACTION RATES AT STEELMAKING TEMPERATURES General experience in reaction rates makes it almost certain that at steelmaking temperatures equilibrium is attained practically instantaneously when the reactants are well distributed in a single liquid phase -that is, in the so-called homogeneous reactions. The actual slowness of some of the reactions in the open-hearth furnace must therefore be attributed to a relatively slow rate of diffusion within the slag or metal phase, which limits the rate at which the reactants can meet each other in the liquid steel or at its surface. That the reactions can be made to go with great rapidity, by proper mixing and stirring of the reacting phases, is indicated by the following illustrations: I. In the Bessemer process there is intimate contact between air and the whole mass of metal, and the reactions are complete in a few minutes. 2. Perrin1 has demonstrated that by pouring liquid steel into slag contained in a deep ladle, and thereby producing almost a slag-metal emulsion, the phosphorus or oxygen content of the steel is adjusted immediately. 3. Barret, Holbrook and Woods observed a quite rapid rate of desulphurization when powdered calcium carbide was stirred vigorously into liquid iron. 4. When a spoonful of liquid steel is poured into a mold containing aluminum wire, the formation and precipitation of alumina occurs in the fraction of a second required to freeze the surface layer of the tiny ingot. The first three examples all show that any means of increasing the effective surface between slag and metal and promoting intimate mixture of the reacting phases, thereby obviating the limitation imposed by diffusion, will enhance the speed of the steelmaking process.

Jan 1, 1941

As mining operations in the United States (US) have become more productive, controlling the dust exposure of mine workers has become more challenging. In response, US mining operations are applying basic controls at elevated levels and are looking to emerging control tech­nologies in an effort to better control airborne respirable dust levels. The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) conducts research to develop and/or improve control technologies that reduce the respirable dust exposure of workers in underground coal mines. The goals of this research involve optimizing the use of water sprays and ventilating air, as well as, evaluating emerging control tech­nologies. An overview of dust controls typically utilized in underground US coal mines will be provided. An update on ongoing PRL research efforts that are evaluating new control technologies will also be presented.

Jan 1, 2008

By W. C. Smith

Even with conservative mine planning, rib instability can progress from a nuisance to a major safety hazard. This Bureau of Mines paper examines the mechanisms of progressive rib failure in high mine openings and discusses techniques to control rib slabbing. A field test site in a longwall mine was instrumented to investigate rib behavior during mining. While data analysis showed minor pillar dilation. sporadic zones of progressive rib instability were detected that culminated in eventual rib failure. The failure occurred despite conservative pillar dimensions and shallow depth. Models were used to demonstrate the mechanisms of rib failure and then evaluate the influence of support and other mine-related parameters on rib behavior.

Jan 1, 1991

Control dust generated during undercutting in salt mines without causing ore-solubility problems that result from excessive water use. Approach A foam generator was developed to provide a reliable foam to control dust on cutting machines used in mining water-soluble ores. The system was designed to keep total foaming agent/water mixture flowrates below the flow-rates characteristic of water-only systems. The foam generator consists of a reservoir to hold the premixed agent and water, a metering pump, and a small compressor to aerate the mixture. The system is compatible with all cutting machines. How It Works One of the current wet-bar techniques, the through-the-bar trickle system, pumps water through a pipe in the cut-ting bar to its tip placing the water behind the kerf. If the pipe conducted foam effectively the foam would be released in the kerf where it would mix with the cuttings and the dust produced by the chain. For improved foam delivery, however, it is recommended that the pipe be replaced with an external channel welded along the top of the bar. This provides excellent dust control while avoiding the accumulation of copious quantities of foam in the heading. The system is very simple. The foam generator is a 50-gallon tank filled with a mixture of water and foaming agent. The mixture is pumped through a wye fitting to a second line where it is mixed with compressed air, (300

Jan 1, 1984

By K. C. Ko

The pit slope angle dictates the economics as much as the depth of the pit. Steeper slope provides more ore reserves, at the same time, the steeper slope presents higher probability of instability and associated maintenance problems. While large open pit mines mostly belonged to nonferrous metals in the past, other mines are becoming deeper as the mine economics permits deeper mine operations, Such minerals include coal, uranium, phosphate, and others. There are some basic differences between an open pit slope and slopes that are encountered in usual civil engineering work such as dam embankments and highway cuts (Figure 1). The stability of the civil engineering slope changes continuously with time due to ground-water movements, weathering, etc. But the stability of the open pit slope (Figure 2) changes more drastically day-to-day or even hour-to-hour, These changes occur because not only is the slope geometry being continuously changed by the mining operation, but also different geology and geologic structures are being exposed on the slope. Even when a particular slope area is not presently being mined, excavation in adjacent areas can affect the general condition of that slope area. A pit will experience some slope failures during its life.

Jan 1, 1977

By John W. Tieman

Research on processes to remove sulfur oxides from flue gas has been in progress for many years. Pioneers in this field were the British who, in the early 1930's, installed a full-scale flue gas scrubbing unit on a 120 MW boiler using alkaline water from a Thames estuary plus chalk. Since that time, various methods have been studied by many investigators. Federal laws covering air pollution started with the 1955 Air Pollution Control Act. With the advent of the Air Quality Act of 1967, and subsequent publishing of criteria and available technology for control of sulfur oxides in January 1969, the clamor for information on commercially available control techniques to remove sulfur from fossil fuels has rapidly increased.

Jan 8, 1972

By Q Liu

Open stoping is one of the widely adopted methods in underground bulk mining. In this method, fanned or parallel holes are often drilled from a top sill down to a sublevel in the ore zone and blasted ring by ring into a stope for excavation. A mass stope blast may involve blasting rock from multi-level drift rounds and displacing the muck to specific locations in order to allow safe and easy access for ore removal. This paper presents a strategic mass stope blast that took place at a large lead and zinc underground mine in eastern Canada. The blast consisted of more than 800 holes drilled in six blocks from three different sublevels. The challenge lay in the control of ground vibration and muck movement using precise timing to complete the blasting within 6.5 seconds. During this time span, sufficient voids were created in each level to allow the muck to move from the upper to the lower levels in sequential order across the six mining blocks without bridging. This paper describes stope blast simulations using a discrete element computer code for modeling blast-induced rock displacement as well as the application of electronic detonators. These detonators provided the means to accomplish the desired firing sequence including a drop raise blast at the start of the mass blast. The modelling concept is also described in the paper.

Jan 1, 2005

By M. Grave

Rock Engineers are required to design safe cost effective support systems and stoping layouts for their respective mines. As each stope has its own unique environment, continual re evaluation is required in all stopes to maximize extraction and achieve value from the support standard. This paper presents numerical modelling used to plan early mining within the shaft pillar and a reevaluation of an existing stope support standard.

Jan 1, 2009

By Yingzin Zhou

Partial backfilling can be used to reduce and control surface subsidence damage caused by longwall mining or pillaring operations in room-and-pillar mines. The use of partial backfill as opposed to total backfill minimizes the cost associated with such efforts. By com- paring surface subsidence, strains, and slopes, the effectiveness of partial backfilling including the amount, geometry, and location of backfill are demonstrated. Results show that it is possible to arrange a given volume of backfill in its geometry and location so that optimum effects are achieved in controlling vertical movement, surface slope, and curvature.

Jan 1, 1990

By William Catron

BECAUSE the rich La Colorada orebody of the Cananea Consolidated Copper Co. does not outcrop at surface, after its discovery (by churn drill) and before mining was begun, a large amount of development work was done to learn the shape and extent of the ore and to provide for eco-nomic and effective mining. As these openings progressed, the actual shape of the orebody became known and with this knowledge came the realization that mining this rich and unusual deposit without loss of ore or danger to workmen presented several difficult problems. This paper will describe one of these problems; namely, the handling of an inverted cone-shaped core of barren rock, on the periphery of and below which the ore occurred. It was clear that as the ore was mined out from around and under this inverted cone of rock, weighing about 3,000,000 tons, it would hang over the workings, held suspended only by its own tensile strength and threatening to crash into the stopes below with disastrous results to men and mine. The method of mining developed during the years 1928, 1929 and 1930 anticipated and provided for the eventual collapse of this core of rock. In November 1936 the core settled clown gradually on the edges of the stopes, descending a total of about 50 ft. vertically. The men in the stopes had ample to warning and no lives were endangered. There were no air blasts in the mine. The core broke loose from its top support at the 500-ft. level along old fracture planes and evidently is crushed to the ninth level. Movement was of short duration; the following shift went to work in the stopes as usual. No ore was lost.

Jan 1, 1938

By William Catron, Cyril U. Colledge

BECAUSE the rich La Colorada orebody of the Cananea Consolidated Copper Co. does not outcrop at surface, after its discovery (by churn drill) and before mining was begun, a large amount of development work was done to learn the shape and extent of the ore and to provide for economic and effective mining. As these openings progressed, the actual shape of the orebody became known and with this knowledge came the realization that mining this rich and unusual deposit without loss of ore or danger to workmen presented several difficult problems. This paper will describe one of these problems; namely, the handling of an inverted cone-shaped core of barren rock, on the periphery of and below which the ore occurred. It was clear that as the ore was mined out from around and under this inverted cone of rock, weighing about 3,000,000 tons, it would hang over the workings, held suspended only by its own tensile strength and threatening to crash into the stopes below with disastrous results to men and mine. The method of mining developed during the years 1928, 1929 and 1930 anticipated and provided for the eventual collapse of this core of rock. In November 1936 the core settled down gradually on the edges of the stopes descending a total of about 50 ft. vertically. The men in the stopes had ample warning and no lives were endangered. There were no air blasts in the mine. The core broke loose from its top support at the 500-ft. level along old fracture planes and evidently is crushed to the ninth level. Movement was of short duration; the following shift went to work in the stopes as usual. No ore was lost. GEOLOGICAL STRUCTURE The shape of the orebody is illustrated in Fig. 1. The geology of the Colorada orebody has been described by V. D. Perry1 and by W. G.

Jan 1, 1938

By Ron Jessulat

"IntroductionBrunswick Mining and Smelting Corp. Ltd. is a IO 500 tid base metal producer. Development is carried out by Jarvis Clark MJM-21 3-boom development jumbos, using Tamrock E400, 410 and 550 pneumatic drills. Typical drift size is 13 ft by 18 ft with a 12-ft advance per round. Blast holes are 1 ½ in. in diameter while reamed holes are 3 in. in diameter. AN/FO is the principal blasting agent, being loaded by C-I-L model60R intermediate loader. The detonators are NONELS and DETINELS. Sulphide dust explosions occur during blasting when dusts from certain minerals such as pyrite and pyrrhotite are ignited by name from the detonating shots. The result is a secondary unwanted explosion with a characteristic shock wave and name front that are very destructive to mine services such as ventilation ducting, electrical cable, and ventilation control doors.A typical reaction in the Brunswick orebody occurs according to the chemical formula:4FeS 2 + IIOs-2Fe2O3 + 8SO2 + 3458--(Enright , 1988)The hematite (FeO3) is deposited as a red dust in the blast area while the toxic sulphur dioxide gas (S00 contaminates the underground workings . The presence of S02 gas disrupts production until it is purged from the area by the mine ventilation system or dissipates slowly in those areas where the vent ducting has been melted by the name front or torn down by the shock wave.Sulphide dust explosions exact a high economic toll. Direct costs in damaged materials and wages are probably exceeded by the value of lost production and disruption to the mining cycle. In addition, the health and safety concerns associated with sulphide dust explosions cannot be ignored."

Jan 1, 1993

By R. N. Chakravorty, R. J. Kolada

Explosions of methane in coal silos and coal ships is an ever present hazard. Recent investigations have shown beyond question that considerable accumulations of methane do occur in coal storage silos and numerous recent explosions in coal transport shipping strongly indicates that the same conditions also exist in ship storage holds. Investigations have shown that the main concentrations of methane occur within the actual coal pile. Within this region normal silo and ship ventilation systems are ineffective. The main 1ine of defence is therefore to exclude potential sources of ignition or to place the coal in an inert atmosphere, or both. This paper presents the results of a methane survey of all operating silos in Western Canada. These results demonstrate that a serious and widespread hazard of explosion exists. This paper also discusses various methods by which this hazard may be reduced including methods of venti1ation, inertization, microbiological control and early warning systems.

Jan 1, 1987

By A. J. Rigby

Refractory linings in converters or anode furnaces used to over-oxidize the blister copper will suffer rapid deterioration, due to prolonged contact with copper oxide-rich slag. Nitrogen stirring with COP KIN porous plugs and use of SEMTECH OPC in converters and anode refining vessels can considerably reduce both refractory wear and processing times. In addition, careful control of the vessel atmosphere and the use of real-time optical process control minimize both slag volume and contact time with the vessel refractory.

Jan 1, 2005

By Karsten Beckhaus

Barrier walls in levees and dams are designed and constructed for new structures and for rehabilitation or upgrade of existing structures to control seepage. Construction methods applied are often deep soil mixing with a cementitious slurry or excavating a trench and refilling it with a plastic concrete. This paper explains the technical background of jointless cementitious barrier walls inevitably developing thermal tensile stresses and how these stresses can be controlled. The theoretical background of thermal stresses is explained based on experimental and numerical studies of essential factors. Although a low cracking risk is generally inherent, risk mitigation measures should be taken to thermal cracking and to ensure the permanent function of such walls as a low-permeability and high-deformability barriers.

Sep 8, 2021

By Ronald C. Bethard, Kenneth W. Ely

The liberation of methane during underground coal mining causes serious safety concerns. During a mining cycle, with mechanized mining equipment, thousands of cubic feet of methane are released from coal seams, discharged to return air courses, and vented to the atmosphere through mine fans. This has been the traditional way of removing the explosive hazards of methane gas from the mine. Through horizontal and vertical degasification techniques, this hazard can often be handled in an equally safe and much more profitable manner. Basically, degasification allows for the controlled reduction of inseam methane content of coal prior to its mining. It is the responsibility of mine management to evaluate these degasification programs and ensure that the program itself does not introduce some new risk to the mining process. The removal of methane gas from underground coal mines using horizontal and vertical degasification is a relatively new concept. Products and systems used in degasification continue to evolve. Site conditions vary also, so no one system or equipment can be said to be the safe answer for degasification in all situations. A constant process of cooperation and evaluation by mining and degasification management should result in a safer and more profitable mine.

Jan 1, 1989

If a fire occurs outby an underground coal mine section, the immediate safe evacuation of miners from the working section should always take precedence. Unfortunately, in many cases, the dedicated escapeways (escape routes) for the evacuation of the miners become contaminated by the byproducts of fire from the adjacent entries. The purpose of this paper is to present the ventilation-control process that would keep the escapeway free from contaminants and, thus, available for travel. A few scenarios of mine fires in longwall development panels are analyzed and discussed. To perform these studies, a mine fire simulator (MFS) was used. This (MFS) provides a dynamic representation of the fire's progress (in real time) and gives a color-graphic visualization of the spread of oxygen, combustion products and temperature of the gases throughout the ventilation system. Also presented and discussed are ways in which the MFS can be used as a training and teaching tool for miners and, particularly, for ventilation and safety specialists.

Jan 1, 1997

If a fire occurs outby an underground coal mine section, the immediate safe evacuation of miners from the working section should always be the first action during the rescue operation. Unfortunately, in many cases, the escape-ways (escape routes) dedicated for miners' evacuation are contaminated with fire byproducts from adjacent entries. The purpose of this paper is to present the ventilation control process that will maintain the escape-way free from contaminants and available for travel. Several scenarios in a different section on ventilation system arrangements are analyzed, discussed and presented. To perform these studies, the author used a mine-fire simulator, which provides a dynamic (in real time) representation of the fire's progress and also gives a display, a color-graphic visualization, of the spread of combustion products throughout the ventilation system. Presented and discussed in this paper, also, are ways in which the mine-fire simulator can be used as a training and teaching tool for miners and, particularly, for ventilation and safety personnel.

Jan 1, 1993

By Z X. Zhang

Ground vibrations from the blasts of the LKAB mine at the Malmberget town had reached 18-19 mm/s from year 2000 to 2002. From 2004 to 2010 the maximum vibrations had been reduced to 9 mm/s and most vibrations lowered to about 5 mm/s, indicating that the technical measures used in the mine are effective in vibration control. The major measure that has always been used in Malmberget mine is the method called Changing Initiation Sequence (CIS in short). Another method named Dividing Ring Blasting (DRB in short) is often applied to some special blast rings in the mine. Both methods have been proved to be successful in vibration reduction, and they do not need any additional costs. Because of the two methods, both maximum vibrations and average ones have been reduced by around 50% since 2004.

Jan 1, 2012