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INTRODUCTION TO STATISTICAL INFERENCE The intent of the mineral appraiser in collecting samples from a mineral deposit is to arrive at accurate conclusions concerning the size and value of the deposit. In other words, he wants to derive reliable inferences about the total mineral population from the collected sample data, which (he hopes) is representative of the whole. The discussion of sampling theory in Chapter 2 was oriented toward assuring that our sampling techniques and sampling units would indeed be representative of the total mineral population. Chapter 3 described the most common statistical parameters for defining distribution in various populations. Chapter 4 gave some insight into theoretical distributions of random variables and the probabilities associated with them. The intent of this chapter is to derive inferences from the preceding information about the population mean and the population variance. Knowing something about the normal distribution, and assuming our samples represent a roughly normal population, we can make inferences or logical deductions about the estimated interval or the limits of values which can be assigned to a mineral population. ESTIMATION OF POPULATION PARAMETERS In the application of statistics to mineral deposits it is never possible to know the actual values of the parameters or the theoretical distribution of values within the deposit for which our data are samples. Even after the deposit has been mined out it is questionable if the true value of the parameters can be retrieved accurately, due to dilution, mining, and processing losses. Therefore, our problem is to determine what function of our sample values we should use to estimate the unknown parameters of greatest interest to us-namely, the population mean and the population variance of the deposit. Since we cannot know

Jan 1, 1980

By R. W. Brauchli

During the last few years the compila-tion of formation logs from rotary well cuttings has become common practice among petroleum geologists. This meth-od has undoubtedly furnished a great amount of information valuable for both scientific and commercial purposes. How-ever, in spite of its great usefulness it has certain drawbacks, principally in the contamination of cuttings by cavings. In extreme cases this contamination can reach such proportions that it is next to impossible to draw conclusions with any degree of certainty as to the nature of the formations penetrated by the drill. This difficulty was frequently encoun-tered during the development of the Okla-homa City Field. In many cases where Wilcox sand-the most prolific sand of this field-was drilled, the samples con-sisted almost entirely of shale cavings with only traces of sand. In order to obtain more reliable knowl-edge of the formations encountered while drilling it is therefore necessary to resort to more coring, and above all to improve our present methods of coring. With this in mind a study has been made of the results of coring in the Oklahoma City Field, and the present article is mainly confined to a statistical analysis of the relation between recovery, diameter of cores and drill pipe, length of cores and a few other factors. Most of the coring in the Oklahoma City Field was done during the early part of, the development. A total of around 18,000 feet or 0.3 per cent of the total footage drilled before February, 1932, has been cored, and about 80 per bent of the cores were taken in the Simpson formation at a depth below 6,000 feet.

Jan 1, 1933

By Richard P. Rothwell

THOUGH coal has been mined in this country for more than a century, no systematic effort was ever successfully made to ascertain the total amount produced. The production of the Cumberland Basin, Md., and the shipments from the anthracite fields of Pennsylvania, have been placed upon record, thanks to the intelligence sand foresight of Mr. C. Slack in the former case, and to the late Mr. B. Bannan in the latter. For some of the years between 1822 and 1842, the production of the Richmond Basin was reported by Mr. R. C. Taylor, but since that date till the author undertook this work it was impossible to obtain any statement of the production of this field. A few of the newer fields, such as that of Mt. Diablo, Cal., have been fully reported, and a few of the newer States have also had this service performed by some intelligent private individuals.; but no statistics of coal production have ever been collected either by the State or General Government, if we except the returns for the years 1869-70 of the census report. During the year 1875, by great exertions, I succeeded in obtaining, and July 3d, 1875, gave in the Engineering and Mining Journal what, "though not an accurate statement of our coal production," was " by far the most full and reliable that had ever been published." Though that report showed the production of bituminous coal to be 23,630,094 gross tons, or about six million tons more than had ever before been reported, it was in reality two and a half million tons below the actual output. The more full returns I obtained for 1875 gave many figures for 1874

Jan 1, 1877

By Gregory Witte

This paper will explore the technology behind and applications of smart motor control centers (MCCs) being used today in mineral processing facilities. The two technologies to be discussed are solid-state motor controllers that can be installed in MCCs and the complementary digital communication networks that can transmit operational parameters of the solid-state devices to the supervisory system. The toughness and reliability of solid-state technologies have led to a dramatic increase in their usage throughout the mining industry. Products such as solid-state motor protectors, controllers, and variable frequency drives have demonstrated greater flexibility and performance in a variety of applications than their electromechanical and mechanical counterparts. The three key trends apparent in the solid-state devices are: 1. A shift to smaller, smarter, more integrated devices, which allows a single solid-state device to serve the purpose of multiple electromechanical devices but in a much smaller form factor. 2. Distribution of control logic in motor control devices rather than conveyed through a hard wired connection to a central automation system. 3. Embedded network communication that allows supervisory systems to have an expanded view into critical loads and sensors. In applications, the use of smart actuators and sensors with integral local intelligence and communication allow a supervisory controller to send high level commands and let the smart device coordinate its own work The ability of smart field devices to return noncontrolled, nonpoled information opens a whole array of new capabilities for preventive maintenance and diagnostics and forms the basis for an effective motor management program. The smart motor control devices this paper will explore are the smart motor protectors (SMP), smart motor controllers (SMC), and variable frequency drives (VFD).

Jan 1, 2000

By N. J. Gran, W. R. Opie

HYDROGEN in molten aluminum and aluminum alloys, which precipitates during cooling and solidification, is the principal cause of pin hole porosity in ingots and castings. Much attention has been given to determining the effect of temperature and pressure on the solubility of hydrogen in pure aluminum, but little data are available on hydrogen solubility in aluminum alloys. This investigation was undertaken to check results reported for pure aluminum and to show the effect of silicon and copper additions on the amount of hydrogen contained by molten alloys. Previous determinations of the solubility of hy-drogen in molten pure aluminum are plotted in fig. 1. The most reliable data appear to be those of Ransley and Neufeldl and of Baukloh and Oester-len.' The latter authors also report some results on the effect of copper and silicon additions. Up to 6 pct these elements decrease the solubility of hydrogen quite rapidly, with a definite minimum noted at 6 wt pct for both copper and for silicon, although no reason is apparent for these minima. Experimental Procedure The solubility of dry hydrogen in pure aluminum, aluminum-silicon, and aluminum-copper alloys was determined by the method of Sieverts.8 This consists of determining the volume of the gas system above the molten metal at a given temperature and pressure by using an insoluble gas. This volume is referred to as the "hot volume." The system is then evacuated and the soluble gas is introduced at the same temperature and until the same pressure is reached. It is necessary to introduce enough of the soluble gas to fill the space above the metal plus the soluble amount. The difference in the volume of soluble gas and the "hot volume" is the solubility. The accuracy of solubility measurements by the Sieverts' method is primarily depend-

Jan 1, 1951

If an orebody has been drilled to achieve some level of regulatory compliance, then a number of associated geological databases will exist, representing 10 000 to 100 000 m plus of core intervals. The databases usually contain data about assays, lithology, mineralisation and geophysical attributes. They will also include location information such as collar positions and downhole surveys. Obviously this data is collected by geologists for, predominantly, geologists and mining engineers. However, from a process design viewpoint process engineers usually ignore the geology where possible and rely on a small number of metallurgical test samples. Typically these test samples are sourced from convenient and available cores or from a small number of specially drilled metallurgical holes. One of the worst instances known to the author was the design of a SAG mill using only two SAG specific test results (one for each of the major ore types) while, geologically, the orebody was defined by more than 30 000 m of drilling. This paper sets out a philosophy to maximise the use of the geological data, both for process design and in preparation for the commissioning phase of projects. Geological data is used in the identification of preferred locations for metallurgical test samples, for checking the metallurgical validity of the geological ore-type definitions, where necessary developing new ore-type definitions (geometallurgical domains) and developing mathematical relationships for the estimation of important metallurgical factors across the geological database. If the estimation of factors (for example ore competence) is considered reliable enough then there is also the possibility of feeding calculated data back into the block modelling process to allow the generation of metallurgically relevant outputs in the mine plans.

Jan 1, 2007

By Walsh V

The Australian economy has been adversely affected by the hesitation in developing countries to commit to the construction of .new coal-fired power stations. World coal trade which was expected to grow at an appreciable rate has stagnated, world export coal prices have plummetted, and facilities in place in Australia for the production and export of coal are being underutilized. While in some countries this hesitation has been caused by a reduction in electricity load growth, another cause has been the unduly long lead-time imposed on developing countries by the conventional "Banker's Approach" to the planning and initiation of commitments to finance and construct coal-fired power plants. In some countries electricity growth has been met by increased usage of indigenous energy resources, even though this involves costs in excess of imported coal-fired power generation. The avoidance of foreign exchange commitments in these cases can however be desirable. In many other developing countries however, fuel oil continues to be used for power generation at a cost in foreign exchange of up to 50% above the total cost of coal fuel plus capital to construct a new coal-fired power station. The conventional "Bankers Approach" to new power station planning imposes the need for successive feasibility studies to satisfy the normal processes of international development lending agencies. No feasibility study can however, show how keen vendor countries may be to win major power plant contracts; and no feasibility study can determine whether the power station eventually procured will be one of the more reliable, at better than 80% availability, or one of the more unreliable at worse than 60% Availability.

Jan 1, 1987

By Jin Zigang

In China there are more than 30 coal fields menaced by karst-confined water. In the north and east of China there are many collieries which mine coal seams of the Carboniferous and Permian Systems, which are above the Ordovician limestone (general thickness is 500-600 meters). Ordovician limestone is full of karst fissures, contains a lot of water under high pressure (15-65 kg/cm2) near the commercial coal seams (20-80 meters), the water easily infiltrates the thin lime- stone at the point of the structure crevice, so water-irruptions from the floor are the main source of water-related disasters in these coal fields. According to the statistics there were more than 300 accidents of all kinds of water-irruptions from the floor in these fields since the beginning of their development. It is of great significance in developing coal production in the eastern part of China to solve the problem of safe mining of the seams menaced by the karst-confined water of the Ordovician limestone. The research on this subject consists of three parts: (1) investigating the geological structure and hydrogeological conditions of each mine of the mining area; (2) researching the mechanism of water-irruptions from the floor and proposing reliable methods to predict and monitor; (3) improving the mining system and proposing a mining plan with safety precautions against water-caused accidents. The chief task is to research the mechanisms involved and to discover the causes and conditions of the phenomenon. The authors have obtained some findings on this subject in the last five years, making use of the comprehensive observation and research system, which will be discussed under three headings.

Jan 1, 1984

By H. C. Rolseth, J. J. Calaman

6.4-1. Principles of Operation. The jet-piercing process is a patented thermal process which depends upon a characteristic of the rock which is termed spallability. In its simplest terms, spalling is considered as decrepitation resulting from differential expansion of rock crystals due to thermally induced stresses. The number of individual properties influencing the spalling characteristics of rock are so numerous and their interaction so complex that the only truly reliable way to ascertain the spallability of rocks under thermal shock conditions is to expose them to these conditions. However, laboratory and field work have determined the principal thermal, physical, and mechanical properties of rock which affect spallability (10, 18). The approximate relationship between spallability and these characteristics is as follows: [ ] where To is the critical temperature at which, it is believed, a rock becomes elastic or sufficiently plastic to prevent further spalling action. Thermal diffusivity takes into account the amount of heat used in saturating the medium itself during the migration of a heat front. The rate and degree of dimensional changes which influence the spalling tendency of the rock will depend upon the characteristic of the heat gradient in the rock. The greater the spalling tendency, the higher the piercing rate. Those properties most favorable to a high degree of spallability are: 1. Large linear thermal expansion at temperatures below 700°C. 2. High thermal diffusivity at temperatures below 400°C. 3. Equigranular interlocking structure with little or no fine-grained clay or mica alteration products. 4. No significant amounts of soft, low-melting, or elastic mineral or materials which yield after thermal decomposition.

Jan 1, 1968

By Jack L. Woodward

The evolution of surface mining equipment has resulted in larger, faster haulage units, loaders, etc., resulting in increased demands on steering technology. Careful analysis of these systems was warranted to determine if steering-related safety problems have been introduced. The objectives of this program were to: 1. Define the generic types of steering systems being used on mobile mining equipment used in surface mining operations. 2. Gather information on steering-related accidents in mining operations. 3. Assess the need for initiating government-sponsored research into steering system technology. A comprehensive literature survey was conducted concurrent with extensive contacts with mining operations, mining equipment manufacturers, steering system component manufacturers, and government agencies. A Technical Evaluation Group composed of representatives from the above organizations was formed to review the data gathered. It was concluded that the steering systems in use on surface mining equipment are reliable and do not present a safety problem. The Society of Automotive Engineers, Inc. is active in pre-paring voluntary consensus standards to assure that the minimum levels of performance are defined for industry.

Jan 1, 1979

By Anshumali Gangwar

This paper outlines the chance constrained binary integer program developed by the author in his doctoral dissertation at Columbia University, New York, 1973. The optimum planning of a mining program involves the determination of a production schedule which maximizes the net present value of the mining property. The actual mining process has an inherent stochastic and discrete nature. In particular, the demand for the mined product and the grade of the mineralized material in the ore are the two most important stochastic mining variables. The decision to mine or not to mine any block of a mining property is a binary integer variable. This paper outlines the formulation of pit production scheduling problem as a chance constrained binary integer program. The deterministic equivalents of these chance constraints are nonlinear in binary variables which have subsequently been linearized. The planned objective is to meet with a stipulated high degree of reliability, all the random demands as they materialize with a random supply of the commodity being marketed as determined by the eventuating random grade values of the exposed ore blocks and the mining system's production constraints such that the discounted total production costs over the entire planning horizon are minimized or the profits maximized. The emerging surface of the mine in each scheduling period is determined by the values taken by the binary decision variable associated with each block of material in each scheduling period.

Jan 1, 1982

Provide the mining industry with a wireless surveying system for increasing efficiency in the drilling of methane drainage or exploration boreholes. Approach The Bureau of Mines has pioneered the technique of methane control by drilling long, horizontal drainage holes from within the mine complex. It was recognized during the early drainage projects that a major portion of the drilling operation was dedicated to hole surveying. In some cases more time was actually being spent on the surveying operation than on drilling. The large amount of time required for hole surveying was the result of having to pump an instrument to the bottom of the hole, then retrieve it with an attached wire line. Naturally as hole depth increased, so did the amount of time needed to perform the survey operation. If the survey operation could be improved it was obvious that overall efficiency in drilling of long, horizontal methane drainage holes would be greatly increased. The Bureau of Mines, therefore, developed, fabricated and tested in an operating coal mine a permissible wireless survey system specifically designed for small diameter methane drainage drilling. The prototype survey system was completed in 1982 and was given the IR-100 Award by Industrial Research and Development Magazine. A second generation survey system is currently being constructed using updated state-of-the-art electronic technology. The second generation system will be more portable, more reliable, easier to maintain, and less costly.

Jan 1, 1984

This paper presents a review of heat illness in mining, including reference to several recent investigations by the author. Heat illness is a collective term, covering the conditions of heat stroke, heat exhaustion, heat cramps and miliaria rubra. Heat stroke is life-threatening and is by far the most serious condition. It is rare in mining, if appropriate control measures are instituted. Heat exhaustion is primarily due to hypohydration, following prolonged sweating in hot conditions. Symptoms include fatigue, headaches, dizziness, anorexia, nausea, vomiting, shortness of breath, or brief syncope. Confusion, ataxia, prolonged unconsciousness or convulsions are strongly suggestive of heat stroke. Heat cramps are painful involuntary contractions of skeletal muscle associated with work in hot conditions. The limbs are usually involved and the spasms typically last a few minutes, during which the affected part of the body is incapacitated. Heat cramps tend to occur in heat exhaustion, when hypohydration becomes marked. Miliaria rubra is a skin rash caused by extravasation of sweat into the skin, as a result of obstruction of the sweat glands. It occurs after prolonged and profuse sweating in hot environments. It can take three to four weeks of sedentary duties, in an air-conditioned surface environment, for the condition to resolve. Heat illness would be unlikely in underground mining, if the thermal environment was sufficiently well controlled by ventilation and refrigeration. This is however, often not practicable. Where engineering controls alone cannot provide sufficient control of risk, the residual risk can be assessed using an appropriate heat stress index. While procedural controls may further reduce the residual risk, it is important to remember that these are less reliable than engineering controls and cases of heat illness may still occur. Procedural controls include the application of heat stress limits, education, hydration, self-pacing, early symptom reporting, medical advice, acclimatisation procedures, air conditioned accommodation, support to achieve a healthy body mass index, and an effective emergency response capacity.

Jan 1, 2005

By H. C. Fowler

No exact demarcation can be made between producfion engineering and engineering research projects which interest production engineers because the results of today's engineering research make possible many of the applied production engineering methods of tomorrow. A corollary of the development of fundamental research is that so-called practical research becomes necessary. Assuming engineering research to include all subjects related to oil and gas production on which knowledge is being increased through experimentation and through analyses of data obtained from both the laboratory and the field, a review of the work of 1932 shows that the fundamental concepts of at least three major problems have become better understood—bottom-hole pressures, solubility of gas in oil, and fluid movement—and that the established data on the relationships of oil and gas have been applied to obtain more efficient and more economic production of both. Engineers no longer are concerned primarily with the initial development of devices for obtaining the pressures at the bottom of wells. Advancement in the technique of obtaining reliable pressure readings in wells has been rapid. One of the first public suggestions regarding apparatus for obtaining precise information at the bottom of oil wells was made before the Petroleum Division of the A.I.M.E. in 1928. Even during the early development stages in East Texas, reservoir pressures were estimated from well-head observations. Soon, however, a number of proved devices and methods were available, and today bottom-hole pressures in many fields are being recorded and studied as an essential part of the production programs. The research now turns to interpretations of data, obtained with these devices, in terms of reservoir energy and to the development of methods whereby the oil and gas will be withdrawn in accordance with rational and equitable programs based on oil-gas-energy relationships. The term ((bottom-hole pressures" should not be interpreted as indicating the full scope of all research on this problem. By using pressure (and temperature) data obtained in related vertical-flow studies,

Jan 1, 1933

Provide coal mine shafts/slopes with an optimum coal mine shaft fire and smoke protection system composed of reasonably-priced, reliable hardware. Approach Accident and injury data indicate that a relatively low percentage (5%) of underground coal mine fires occur in shafts or slopes. Nevertheless, shaft or slope fires are extremely serious because they block critical escape routes for miners. That also can happen when combustion products resulting from fires in other mine areas contaminate shahs and slopes. Seeking the optimum configuration for a shaft/slope fire and smoke protection systems, the Bureau of Mines gathered data on the performance of existing fire detection devices and signal telemetry systems In several mines, and analyzed the generic protection needs of the U.S. underground coal mining industry. The optimum system developed by the Bureau provided an adequate number of detectors, a wide area of coverage, and an extensive data acquisition, analysis, display, and storage capability. This system. recommended for fabrication and in-mine testing, consisted of a microcomputer-controlled master panel located in the test mine's slope hoist room, and four remote units. Two of the remote units were placed on the surface atop upcast ventilation shafts, a third was situated underground near the slope bottom, and a fourth was installed at the slope top in intake air.

Jan 1, 1986

Caving is the lowest cost underground mining method, provided that drawpoint spacing, drawpoint size and ore handling facilities are designed to suit the caved material and that the drawpoint horizon can be maintained for the draw life. In the near future several open pit mines that produce in excess of 50 000 tons per day will have to examine the feasibility of converting to low cost, large scale underground operations. Several other large scale, low grade underground operations will experience major changes in their mining environments as large dropdowns are implemented. These changes demand a more realistic approach to mine planning than has occurred in the past, where existing operations have been projected to increased depths with little consideration of the change in mining environment that will occur. As economics force the consideration of underground mining of large, competent orebodies by low cost methods, the role of cave mining will have to be defined. In the past caving has generally been considered for rock masses that cave and fragment readily. The ability to define cavability and fragmentation, the availability of large, robust LHDs, a better understanding of draw control requirements, improved drilling equipment for secondary blasting and reliable cost data have shown that competent orebodies with coarse fragmentation can be exploited by cave mining at a much lower cost than with drill and blast Methods.

Jan 1, 1995

Provide an accurate, reliable means for determining when a sealed mine or mine section can be safely reopened after a fire. Approach The Bureau of Mines performed a research investigation that resulted in the development of a mathematical formula for deriving a quantity, called RATIO, which can be used to define when a sealed mine or mine section has returned to safe recovery conditions after a fire. Research Results There were two major results from this Bureau research. Over a period of several years, the Bureau of Mines conducted six experiments at its Bruceton Experimental Mine in Pennsylvania. The experiments involved sealing the mine after several tons of piled coal had been allowed to burn continuously for 2 to 3 days. Although gas data obtained during the experiments revealed nothing significant, measured smoke particle levels were found to correlate with the stages of combustion and temperatures of the smoldering coal pile. Moreover, it was found that no smoke particles are produced when high-temperature smoldering exists deep within the mass of the coal pile since the smoke particles are filtered by the coal surrounding the hot region. Smoke is emitted into the mine atmosphere only if combustion is occurring near exposed surfaces. As suggested by these findings, any decision to recover a sealed mine area based primarily upon the absence of smoke particles is not a wise derision.

Jan 1, 1988

By Harry J. Olson

Geothermal Energy has a great potential for meeting the electrical and thermal energy requirements of many countries and territories lying along tectonically active zones within and surrounding the Pacific Basin. Energy requirements for many of these small, scattered volcanic island nations preclude development of conventional generating facilities large enough to incorporate any economies of scale. However, by attempting to discover and develop shallow, relatively low temperature, geothermal reservoirs associated with recent vulcanism on many of the volcanic islands, exploration expenditures and risks, and problems associated with the development of high temperature resources can be reduced. Exploration and development drilling for these resources can be accomplished with truck mounted rotary drilling rigs that are less costly and more suitable for operations within the island infrastructures than the conventional rigs normally used in the drilling of deep, high temperature geothermal resources. Experience over the past decade with small, modular, binary (Rankine) cycle generating units indicates that geothermal energy can provide a reliable source of baseload electricity in the amounts required and at a cost that is competitive with other alternative and conventional energy sources. Development of shall, moderate temperature, geothermal resources with small, modular binary cycle generating units can provide ideal additions to the energy sources of many of the Pacific volcanic island nations within the framework of their island economies.

Jan 1, 1991

By A. Roy, T. LeBel, P. Coursol, P. Lind

At the early stage of a mining project, small amounts of concentrates are available for testwork. For gold concentrate or ores containing significant arsenic levels, batch bench scale roasting is often unreliable, leading to highly variable gold recoveries to be used in the project’s financial justifications. With an appropriate bench scale unit using continuous feeding and residence time control for solid and gas phases, reliable numbers can be obtained at small scale with only a few hundred grams per test condition. This paper describes the development of a pilot fluid bed roasting unit by Kingston Process Metallurgy Inc. (KPM) to perform representative trials on gold concentrates containing arsenopyrite, arsenian pyrite and carbonaceous components. Calcines produced under different conditions were characterised by chemical analysis and electron microprobe; the calcine microstructure obtained is described. The most important parameter affecting gold recovery is oxygen content in the roasting atmosphere, with the lowest controlled oxygen level giving the highest gold recoveries. Higher local temperatures in the bed may cause the formation of molten glassy phases which can also reduce the gold recoveries significantly. The impact of roasting conditions in the two inch fluid bed is compared with commercial results obtained in full scale operation.

Jan 1, 2014

By Poplawski R. F

A 32-channel PSS seismic monitoring system was commissioned at Mt Charlotte mine in 1994, and at the time it was the first such system in Australian mines. The system continuously observes the occurrence of seismic events and locates them accurately in space and time. Mt Charlotte has a history of seismicity, with the largest event in recent years of Richter magnitude 4.3. The decision to 'go seismic' was made despite some uncertainty regarding its potential usefulness. However after the first year of operation, benefits have been realised in terms of less production downtime, improved mine safety and mine planning, and better understanding of the nature of Mt Charlotte seismicity. The seismic network has performed well, recording 550 events in its first year of operation to a location accuracy averaging ¦ 12 metres. System reliability is excellent, with very little downtime, and acceptable operation and maintenance times and costs. Observations show major distinct changes in the rate of mining induced seismicity over time periods of weeks and months. Events have tended to cluster in specific mine areas and on particular faults and structures. Case examples of pillar preconditioning, breakout around an orepass, and a major stope rockburst, illustrate the role of seismic data and the benefits it brings to safety, productivity and planning.

Jan 1, 1995