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By John P. Weir

The planning of an underground mine for successful extraction of a bedded deposit in sedimentary rocks requires the integrated evaluation of many interdependent problems. The development and coordination of feasible solutions are the responsibility of the mining engineer. One of these problems will be discussed herein; this is the design and .layout of mine workings to secure effective control of the strata above and below the deposit. The objective is the simplest possible repetitive system permitting safe maximum recovery at optimum cost. Mining conditions to be encountered must be predictable. The best mining equipment is ineffective unless strata are controlled. Conversely, a mining layout is only of academic interest, if equipment can not be adapted to work it with adequate provision for ventilation, compliance with mining laws, proper ingress and egress and other practical requirements. Strata control, then, is but one of the mining engineer's problems, and the solutions must be worked out concurrently with solutions to other problems. Dr. Karl F. Fetters in his introductory remarks before the Fourth International Conference on Strata Control and Rock Mechanics at Columbia University said that mining engineering ?has come from the stage of empiricism backed by intuitive reasoning, to where it is based on fundamental scientific and engineering principles?. The standard curriculum in mining engineering now reflects such a change. In common with other branches of engineering education, less and less emphasis is placed on practical skills and more and more on broad scientific education. Science, research and the quest for basic truth are stressed, while descriptive courses and the teaching of specific skills are limited.

Jan 1, 1966

By J. C. Martin

Equations for three-phase, three-dimensional, compressible flow (including capillarity) are reduced to two-dimensional relations by a partial integration. This reduction allows three-dimensional flow problems to be treated with mathematics for only two spatial dimensions. The results can be used to formulate flow equations for two-dimensional reservoir simulators in which the effects of capillarity and fluid segregation in the third dimension are represented. Such reservoir simulators would retain many of the aduantages of two-dimensional simulators while simulating three-dimensional effects. The principal restriction of the method is that the thickness of the reservoir should be small, compared to the distance across the reservoir. INTRODUCTION In recent years, computers have been used to calculate the performances of many reservoirs. Most of the detailed calculations, however, are based on finite difference solutions of the flow equations, and present day computers are seldom able to handle a sufficient number of cells to produce entirely satisfactory solutions, even for reservoirs represented by two-dimensional arrays of cells. The situation becomes much worse when one wishes to approximate the reservoir by a three-dimensional array. A great saving in computation or a more detailed solution can be obtained for many reservoirs by using the partial integration of the equations of flow presented in this paper. The integration reduces the three-dimensional equations to two-dimensional relations; and, for studies of two-dimensional flows in vertical cross-sections, the equations are reduced to one-dimensional relations. Most reservoir performance calculations currently are based on one- or two-dimensional flow re1ations.l-3 In some cases flow in the third dimension is approximated by assuming a particular type of vertical saturation distribution, such as gravity segregation.l.2. The relations developed in this paper approach those for segregated flow as the capillary pressures approach zero, and they approach those for uniformly distributed saturations as the capillary pressures are increased. For this analysis, the ratio of the reservoir's thickness to the maximum distance across it must be small. The capillary pressures between the oil and water should also be small compared to the maximum pressure difference in the reservoir. This requirement is met by most reservoirs. It is assumed that the capillary-pressure curves are well defined, whether or not hysteresis effects are included. Also, the reservoir must have sufficient vertical permeability to allow the fluids to segregate. The results presented here provide a firm theoretical foundation to Coats' et aL5 assumption of vertical equilibrium and extend the relations to three-phase flow. Coats' assumption of vertical equilibrium, which he verified by calculations and experiment, is developed here mathematically from basic flow equations. DISCUSSION SATURATION AND PRESSURE DISTRIBUTIONS Appendix A presents a mathematical analysis of fluid flow in reservoirs where the ratio of thickness to maximum distance across the reservoir is small. The results indicate: (1) that the fluids along any line perpendicular to such a reservoir's upper surface are in static capillary equilibrium (vertical equilibrium); (2) that, to a first approximation, the fluid pressures and properties are functions of only areal position in the reservoir and time; and (3) that hydrostatic pressure gradients exist along any line perpendicular to the reservoir's upper surface. The results might be expected after studying several physical considerations. First, no flow is allowed normal to the upper and lower reservoir boundaries, which are relatively close together.

Jan 1, 1969

By G D. Price

Scheelite mineralisation east of the main divide in' the Southern Alps of New Zealand was originally identified by Royden Thompson who is now a geologist with the NZ Geological Survey. This mineralisation was brought to the attention of CRA in 1978. Reconnaissance surveys were carried out in 1979 to delineate the extent of the mineralisation. This was undertaken using ultraviolet light examination of the sediments within the major drainages in the Southern Alps. This defined tentative zones of prospective mineralisation. As a result of this, preliminary reconnaissance, exploration licences were applied for -those areas in which indications of scheelite mineralisation were strongest. A total of 1737 km2 of ground was applied for within four exploration licences. These covered the main Southern Alps mountain chain between the Haast/Wanaka highway and the Mt Cook National Park.

Jan 1, 1983

By Benjamin H. Clark

"For over 50 years, Derrick Corporation has been renowned for its innovative and durable fine screening equipment and screen surface technology. Derrick’s latest innovation, the patented Stack Sizer, offers mineral processors both high tonnage capacity and high separation efficiency on an extremely small footprint.The Stack Sizer is suitable for separations from 6.3 mm down to 75 microns (200 mesh). The Stack Sizer, coupled with Derrick’s patented urethane screen surface technology, offers an extremely economical alternative to hydraulic classifiers, hydrocyclones, and less efficient low volume wet screening systems. Stack Sizers have been used in feed preparation for flotation, spirals, and a variety of jigs. Mineral processors wishing to reduce grinding circuit circulating loads and generation of slimes due to over grinding, thereby enhancing the efficiency of flotation and gravity circuits, now have another technology at their disposal to perform this critical sizing and grade control function.Over 200 Stack Sizers have been installed in numerous mineral processing applications worldwide attesting to the rapid acceptance of this technology. Stack Sizers are currently screening ferrous and non-ferrous metal ores, mineral sands, silica sand, kaolin clay, feldspar, garnet, phosphate, aluminum dross, potash, coal, tantalum, spodumene, niobium, and other rare earth mineral ores.INTRODUCTIONDerrick engineers have long understood and demonstrated the importance of screen width in coupling both high capacity and high separation efficiency for fine wet sizing applications. As opposed to fine dry sizing, where the length of the screening machine is critical for high separation efficiency, introducing slurry feed to screens in a thin and even layer at minimal velocities across wider screen surfaces allows for high capacities and efficiencies, with maximum screen cloth life. This is due primarily to the combination of free liquid and high frequency vibration of the Derrick motors, which allow fine undersize material to pass through the screen apertures. Lacking either of these factors would be extremely detrimental to the screening process. Without the high frequency vibration of the motor, the screen is essentially a low efficiency sieve bend. Without the free liquid to carry fines through the screen openings, the screen is for all intents and purposes a glorified conveyor or dewatering unit, as little or no sizing takes place once the screen is devoid of free liquid. For optimal screening results, Derrick recommends feeding slurry to a screen at approximately 20% solids by volume. Figure 1 shows the Stack Sizer design concept. Note that a single feed point is used to evenly distribute the flow to the five separate feed points."

Jan 1, 2007

By Budiselic C, Hefter G

The uptake of gold by activated carbon from acid chloride solutions involves the reduction of gold(IIl) to metallic gold. Deposition occurs only on the surface of the carbon at localized active sites at first, and subsequently at less active areas. The rate of uptake depends on the surface area of activated carbon, which confirms results from a recently published study (de Siegel and Soto, 1984). Increased rates of uptake were observed at higher temperatures and lower chloride concentrations due to the decreased stability of AuCI4-, the major gold(IIl) species present. Recoveries of gold approached 100 per cent for a contact time of 60 minutes at 20°C in a well stirred solution initially 5 ppm in gold(III) and containing 0.5 per cent w/v coconut-shell carbon. The presence of 0.25 Mnitric acid or 100 ppm iron(IIl) had no detectable effect on either rate or efficiency of gold uptake.

Jan 1, 1985

By M J. Van Der Merwe

The mining industry is facing a serious skills resource shortage, growing commodity demand and cyclical prices. This makes focus and allocation of resources in the early stages of project development very important. To assist with these six key elements in the project prioritization process is proposed, namely: 1) Define the project vision, objectives and business case, 2) Determine the potential show stoppers, 3) Determine the key value drivers, 4) Track changes and provide regular feedback, 5) Evaluate the alternatives and, 6) Ensure proper gate management governance at the decision point. Incorporating these elements in the project development process will assist in resource allocation and focus on the high value aspects of projects and alternatives during the early stages of the project development lifecycle. Keywords: Resource allocation and focus, vision, show stoppers, value drivers, project prioritization, linear programming, business case modelling, management decision.

Jan 1, 2008

By Kanchan K. Sen

The North Shore Connector (NSC) project will extend the Allegheny County Port Authority?s Light Rail Transit System from downtown Pittsburgh below the Allegheny River to the North Shore via twin bore tunnels. Jet grouting, diaphragm walls, and soil mixing were selected as cost-effective technically viable ground improvement and support of excavation techniques. Jet grouting was specified to provide break-out (egress) and break-in (ingress) block sections at the tunnel boring machine (TBM) launching and receiving pits. Jet grout treatment was also used adjacent to buildings with shallow foundations and below retaining walls along the tunnel alignment. A new method for measuring jet grout column diameter based on electrical resistivity was employed on the project. New equipment was introduced in the U.S for constructing soil mix temporary support of excavation using a soil-mix technique termed Cutter Soil Mixing (CSM) due to the use of two vertical cutting wheels that have evolved from diaphragm wall trench cutter technology. The system allows for continuous water tight soil mix panel construction including steel beams. This paper highlights some applications of jet grouting and various support of excavation systems (e.g. slurry walls, cement bentonite walls and CSM walls), including new innovative techniques (e.g. Cyljet and CSM) used under the constraints of an urban environment.

Jan 1, 2010

By A. Johnson

When are SMART transmitters the smartest choice? To answer this question requires a closer look at SMART transmitter technology. It is necessary to understand this technology in order to recognize how it can best be utilized to give the greatest value for the application. And, once the decision to buy transmitters has been made, it becomes a question of whose SMART transmitter to buy. For, although the under-lying technology is similar, the differences that exist in how the technology has been implemented can make a dramatic difference in the end result. What prudent users of SMART technology do is to analyze their needs by application before making their buying decision.

Jan 1, 1988

By W. J. Spat

Political risk is an integral part of the mining business in Northern Andean countries. Peru, Ecuador, Colombia, and Venezuela all have a higher than average political risk compared with other South American countries. Successful operations in such contexts require: 1. Good political risk information; 2. A thoroughgoing political risk management plan; and 3. A strategy to deal with political risk perception on the part of the investing public. Obtaining quality political risk information, developing a political risk management plan, and addressing political risk perception are the foci of this work.

Jan 1, 1999

By Staff

"In 2014, the estimated value of total mine production of nonfuel minerals in the United States increased. The quantity of production increased for most mineral commodities mined in the United States, as did prices. Notable exceptions were the declines in prices for most precious metals. Minerals remained fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels, including mining, processing and manufacturing finished products. Following the reduction in construction activity associated with the 2008- 2009 recession that continued through 2011, the construction industry continued to expand in 2014, with increased production and consumption of cement, construction sand and gravel, crushed stone and gypsum, mineral commodities that are used almost exclusively in construction. Other segments of the nonfuel minerals industries increased as well. Trends in other sectors of the domestic economy were similar to those for industrial mineral production (Table 1).Discussion of mine production is frequently segmented according to the type of materials produced within the broad categories of metals and industrial minerals. Industrial minerals can be further subdivided as construction aggregates and other industrial minerals. The materials with the highest unit values, usually metals, tend to have very low production rates compared with those of many low-valued materials, such as crushed stone or construction sand and gravel. Therefore, for discussion and analysis of the performance of the minerals industry in general, the value of production is used rather than tonnage produced. Although the value of metals and industrial minerals mined in the United States are similar, if tonnages are compared, construction aggregates dominate, dwarfing the production of all other minerals combined.Mineral industry performanceThe estimated value of nonfuel mineral raw materials, including metals and industrial minerals, produced at mines in the United States in 2014 was $77.6 billion, a 3.5-percent increase from $75 billion in 2013 (Table 2). Net exports of mineral raw materials and old scrap were $15 billion (Fig. 2). Domestic raw materials, along with domestically recycled materials, were used to process mineral materials worth $697 billion. These mineral materials, including aluminum, brick, copper, fertilizers and steel, and net imports of processed materials (worth about $41 billion) were, in turn, consumed by downstream industries with a value added estimated to be $2,530 billion in 2014.In the United States in 2014, mine production of each of 14 mineral commodities was worth more than $1 billion. These were, in decreasing order of value, crushed stone, copper, gold, cement, construction sand and gravel, iron ore (shipped), industrial sand and gravel, molybdenum concentrates, phosphate rock, lime, salt, zinc, soda ash and clays (all types)."

Jan 1, 2014

By R. V. Ramani

This volume is the second of a four-volume final report on research carried out under a contract from the U.S. Bureau of Mines on the development of a computer simulation model for surface mine reclamation planning. The other volumes are titled as follows: Volume I: Ore Reserve Estimation, Volume III: Mine Coordinate Generator System, and Volume IV: User's Manual for OPMHS/2. The dragline model described in this report simulates the movement of the dragline bucket across the digging face, the swing load, the dump, and swing back. It is programmed to handle chopdown, key cut, main cut, and rehandling operations. Provisions have been made for simulating equipment and mining delays. Any mining method can be specified in terms of numbered blocks, the dragline positions for the mining block and the dumping location for the block. Accounting procedures permit the calculation of production rates, rehandle volume, dig and delay times. The model can be used to study the effects of varying mining conditions, cut width, and spoiling sequence with special reference to toxic spoil, overburden and bench removal procedures. The basic input data for the model include machine parameters, the geology and material characteristics, the mining parameter, and the delay characteristics of the equipment.

Jan 1, 1985

By S. D. Hill

To help insure the continued viability of the minerals and materials sector of the U.S. economy, the Bureau of Mines is conducting research and disseminating technology that will result in more efficient minerals extraction. As part of this effort, a process is being investigated that involves an aqueous chlorine-oxygen leaching procedure to treat complex sulfide concentrates to produce ZnCl2. Subsequent fused-salt electrolysis of the ZnCI2 produces high-purity zinc metal. Previous reports described preliminary, small-scale research on the chlorine-oxygen leaching system and fused-salt electrolysis of ZnCl2. This report discusses the details of design, construction, and longterm, continuous operation of both monopolar and bipolar fused-salt cells. The effects of temperature, electrode gap, current density, electrolyte composition, and electrode configuration on current efficiency and energy consumption were determined for a ZnCl2-KC1-NaCl electrolyte system. Zinc metal was produced at the rate of about 50 lb/day in a monopolar cell which was operated continuously for 60 days with current efficiencies from 85.8 to 98.6 pct and an average power consumption of 2.1 kwhr/lb. Bipolar cells with several different electrode configurations were operated for 90 days. A current efficiency of about 70 pct and power consumption of about 1.7 kwhr/lb of zinc were achieved using a three-electrode-pair, bipolar assembly with a chlorine gas lift pump to circulate electrolyte.

Jan 1, 1981

By R. G. Burn

"A brief outline will be given of the concept of risk and its implications with regard to investment in exploration. The relationship between risk and decisions under uncertainty will be examined as a prelude to identifying those factors which contribute to exploration risks:consideration of the effects of corporate objectives (e.g. survival, expansion, diversification) on exploration strategy and ultimately on success or failure, exploration and mining as an investment (the relationship between risk and reward) and the desired return on investment; exploration odds, funding levels, staying power, financial exposure and the concept of gambler's ruin;origins of uncertainty in exploration decision-making-man-made risks and natural hazards; the nature of introduced constraints at each exploration decision stage and their effect on the rate of success;improving the chances of success and the invest reduction of risk through sound exploration strategy, effective project generation and efficient target detection capabilities."

Jan 1, 1984

By S. Al-Thyabat

Conditioning of flotation feed is an important prerequisite for efficient flotation. This process depends on parameters such as conditioning time, slurry concentration and slurry pH. The objective of this paper is to optimize the conditioning process for the flotation feed. This was achieved by first conducting preliminary experiments at constant slurry pH to determine the significant ranges of slurry concentration and conditioning time. Then, factorial experimental design (32 experiments) was used to investigate the significance of the above parameters and their interactions on flotation recovery and grade. Statistical analyses using ANOVA approach showed that flotation recovery (R) and concentrate grade (g) were affected by feed conditioning. It was found that concentrate grade was linearly proportional to the slurry concentration and conditioning time, while flotation recovery was exponentially proportional to the conditioning parameters. A contour plot of the flotation response (recovery and grade) against conditioning parameters showed that the optimum operating parameters for flotation feed conditioning was a conditioning time of 1.5 to 2 minutes and a slurry conentration of 55% to 60%.

Jan 1, 2008

By Peter Moser, G. Reihholf

Holcim, one of the world's leading suppliers of cement, aggregates and concrete, has set up a few years ago a working group “Quarry” in order to optimize the performance of its central European quarry operations in terms of work safety, environmental standards and economic performance. One of the activities of this working group "Quarry" addresses the subject of blast fragmentation in the quarries. A benchmark study of the blast work in all quarries has shown substantial differences for the various operations in terms of drill& blast costs. Especially big differences were found with respect to the drilling patterns as a function of the borehole diameters and with respect to the utilization of the borehole volume for charging the explosives.

Jan 1, 2006

The reduction of zinc from slags by a molten, carbon-saturated bath was examined in a laboratory study under conditions of continuous slag feeding. The results show that it is possible to reduce the bulk of the zinc from the slag before there is a net reduction of iron. However, the recovery of zinc was not as high as in batch tests performed in an earlier study. Lead in the slag was reduced simultaneously with the zinc to very low levels and was volatilised. Copper in the slag was reduced and dissolved in the alloy. An attempt was made to identify potentially commercial ways of treating zinc slags using an iron bath. The approaches that appear to have the greatest potential are reduction in a batch process using electrical heating and reduction in a continuous process with co- or countercurrent flow of the slag and alloy. In the latter the alloy would be prepared in a separate furnace before being contacted with the slag. The purpose of this would be to superheat and carburise the alloy so that no additional heat or reductant would have to be supplied in the slag-alloy reactor

Jul 1, 1991

By Lawrence W. Sott

This Bureau of Mines report presents several factors that currently enter into the design, manufacture, and testing of windows and lenses used in explosion-proof enclosures. Emphasis is also given to the sealing concepts for lenses. Criteria for adhesives and sealants are suggested based on the survivability of an explosion-proof enclosure as a structure, rather than upon the minimum material properties of its constituents. Procedures for surface preparation of adherends are also discussed.

Jan 1, 1982

By O. Kangal

Flame retardant materials can be incorporated or applied to products, including plastics and textiles, to increase their resistance to fire. Incorporating a flame retardant in combustible materials and plastics is a common procedure to reduce the risk of fires. Flame retardant applications include interior and exterior woods, structural steel columns, fabrics, open and closed cell foam, pressure treated wood, Formica and all types of fabrics for use in commercial applications as well as residential applications where their fire protection products can save lives and valuables. Huntite and hydromagnesite are amongst the most important flame retardant additives materials. Although various areas of the world have potential huntite and hydromagnesite deposits, their place in industry is not well known, and a detailed field search for their deposits has not yet been conducted. They are active during the starting phase of a fire, in that they prevent the spread of an inner or exterior source of ignition to the flame-retarded material, thereby, preventing, delaying or inhibiting the spread of a fire. Flame-retardants are, therefore, just one element among many in a concept for preventive fire safety. To obtain huntite and hydromagnesite concentrates that are more than 95% pure, which are used in flame retardant industry, flotation tests were conducted on low-quality huntite and hydromagnesite ores.

Jan 1, 2009

By E. Pizarro, A. Videla, G. Compan

One of the main problems related to mining investment decisions is the use of accurate prediction models. Metallurgical recovery is a major source of variability, and in this regard, the Chuquicamata processing plant recovery was modelled as a function of geomining-metallurgical data and ore characteristics obtained from a historical database. In particular, the dataset gathered contains information related to feed grades, ore hardness, particle size, mineralogy, pH, and flotation reagents. A systemic approach was applied to fit a multivariate regression model representing the copper recovery in the plant. The systemic approach consists of an initial projection of the characteristic grinding product size (P80), based upon energy consumption at the particle size reduction step, followed by a flotation recovery model. The model allows for an improvement in the investment decision process by predicting performance and risk. The final geometallurgical model uses eight operational variables and is a significant improvement over conventional prediction models. A validation was performed using a recent data-set, and this showed a high correlation coefficient with a low mean absolute error, which reveals that the geometallurgical model is able to predict, with acceptable accuracy, the actual copper recovery in the plant.

Jan 1, 2015

"In mechanized mining, poor equipment efficiency (availability, utilization, productivity, and quality) can endanger the success of the operation. This case study will show how an initiative to improve equipment performance developed into a comprehensive turnaround plan for the mine that placed it in the forefront of performance achievement.As part of a company-wide review process, poor overall equipment effectiveness (OEE) was identified as a major reason for the mine not achieving its targets. A project to improve the OEE identified eight improvement areas (elements) that contributed significantly to the poor performances. Measurement metrics were determined for these elements, followed by determination of baseline and target (improved) key performance indicators (KPIs). Cost savings associated with the improved efficiencies were calculated and tracked throughout the project. The mine team determined the specific actions required to achieve the target KPI in each element. These were individually developed and managed like mini-projectswith allocated responsibilities for delivery. The paper will indicate how this OEE improvement initiative triggered an improvement in almost all sections of the mine. Soon after launch, the initiative gathered momentum as the KPIs starting to improve. A visible tracking system exists at the mine and each employee can see the improvements and feel the success. The original eight elements were extended by five more, and the mini-projects grew as participants saw the success of the initiative.This paper concludes that through management and worker involvement, visible measurement and controls, and carefully chosen improvement elements, the mine was turned around. It is now achieving and exceeding its targets, and employee relations and motivation as well as safety have improved considerably. All of these achievements are reflected in the bottom line."

Jan 1, 2016