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By Peter F. R. Altounyan, Paul B. Cartwright, John W. Cassie

This paper describes measured data on strata behavior obtained in recent years from sites in the United Kingdom and the implications for pillar design. The data include results from overcoring stress measurements adjacent to coal mine roadways and deformation monitoring related to longwall extraction. The stresses adjacent to mine roadways or entries have been measured at a number of coal mine sites in the United Kingdom. The results are analyzed with regard to the information they provide on pillar behavior and strength estimates. A reduction in stress consistent with yielding of the strata adjacent to the roadways is evident. This is consistent with the confined core model for pillar behavior. The pillar strength is dependent on the rate atwhich vertical stress can increase with distance from the pillar edge and hence the confinement provided to the yielded material. The measured data indicate a wide range in pillar strengths. Two groups of results are identified that show significantly different behavior corresponding to differing effective pillar strengths. Estimates of pillar strengths derived from the measured data for these two groups are compared with established equations used for pillar design. The differing behaviors and strengths are attributed to variations in the amount of yielding and deformation in roof and floor strata and hence in the amount of confinement they provide to the coal seam. Numerical modeling is used to provide a comparison with the measured data and to indicate that this provides a feasible mechanism to account for the measured data. As the depth of mining increases, pillars tend to become increasingly wide and squat. In such cases, it is possible for the surrounding roadways to become badly deformed and damaged while the pillars remain stable. The criteria of comparing pillar strengths and loads to establish pillar stability become less applicable in these circumstances; rather, considerations of roadway stability may be the limiting factor in determining suitable pillar dimensions. This is the case for pillar dimensions typically employed around longwall panels in the United Kingdom. Depending on the properties of the site and what are deemed to be satisfactory roadway conditions, this can lead to wide variations in required pillar dimensions. Measured data for deformations in roadways influenced by adjoining longwall workings are presented. These show that in some circumstances the influence of longwall extraction can be transmitted over large distances and confirm the variability in required pillar sizes depending on site properties.

Jan 5, 1999

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

MINE VENTILATION NETWORK ANALYSIS

Jan 1, 1977

Reduce the number of accidents caused by slips and falls from large mining equipment. Approach A powered lift was developed that provides operators with a safer way of getting on and off large machines. How It Works The powered step is designed to lift personnel and materials to working levels on large machines. It eliminates hazardous blind steps and makes it unnecessary to climb on irregular surfaces made slippery by mud, ice, snow, and accumulations of grease. The step is powered by a self-contained electric/hydraulic unit which is connected to a vehicle's auxiliary power supply. When in the "down" position, the step rests about 15 inches above ground level. When the power unit is activated with an electrical switch located on the step, a Single cylinder attached between two lifting arms smoothly lifts the step. In conjunction with the lifting motion, a linkage and bearing arrangement on the mounting end of the lift arms causes the step to rotate towards the machine, so that the step moves in an arc from ground to platform level. When the machine Is operating, the step is automatically locked in the "up" position, protecting it against any damaging contact with obstructions. The step is lowered by activating a pressure release solenoid. An in-line orifice controls downward speed and prevents free fall. On most machines, additional control switches are conveniently located at ground level and in the operator's cab. Visual alarms and machine interlocks are provided where necessary to prevent machine operation when the step is In the "down" position. The powered step can be easily adapted to any type or model of large machinery.

Jan 1, 1981

By Christopher Mark, Anthony T. Iannacchione

Falls of ground continue to be one of the most serious causes of injury to U.S. miners. Of the 256 fatal injuries that occurred in mining between 1996 and 1998, 59 (23%) were caused by falls of ground (Table 23.1). Falls of ground affect some sectors of the mining industry more severely than others. For instance, nearly 40% of the 98 coal mine fatalities between 1996 and 1998 were caused by falls of ground. Underground miners are at much greater risk than surface miners. Nearly half (45 out of 101) of underground mine fatalities were attributed to roof, rib, and face falls, while only 6% of the 155 surface fatalities were caused by falls of highwalls or slopes. The goal of this chapter is to provide guidance to safety professionals tasked with preventing ground fall injuries. This chapter combines an analysis of the Mine Safety and Health Administration's (MS HA) accident and injury data with a survey of industry "best practices" to safeguard miners from ground falls. Ultimately, this approach can help to form the basis of a sound, proactive ground control program for the mining industry. SOURCES OF DATA All the injury data examined in this study were derived from MSHA's fatal investigation reports and the MSHA accident database. Because falls of ground often result in serious injury, MSHA "Fatalgrams" and fatal investigation reports provide a useful snapshot of ground control issues in the mining industry. These reports are available to the public (on the M FHA Web site at www.msha.gov). Fatalgrams, are one-page summaries that are usually published within a month of an accident. They contain very basic information about the accident with a graphic and a short section on relevant best practices. Fatal investigation reports are the official accident investigation reports filed by MSHA personnel. These reports contain general information about the mine, a, description of the accident, physical factors involved in the accident, a conclusion, and enforcement actions, Enforcement actions typically identify citations and discuss violations to the Federal Mining Law. MSHA also maintains comprehensive statistical data on the mining industry's accident and injury record. The law requires that mines file a report on every reportable accident that occurs, containing information on the accident's location, severity, classification, activity, and nature of injury A short narrative is generally included as well. Accident reports can be searched by many of the above fields.

By M. J. Dailey

This paper is one of a series being prepared by the United States Bureau of Mines on mining practices, methods, and costs in the various mining districts of the United States. The property of the Silver King Coalition Mines Co. is situated in the western past of the Park City mining district, Utah, about 1 ½ miles southwest of the town of Park City, The elevation at the collar of the main shaft is 8,137 feet above sea-level.

Jan 1, 1930

By Oliver Bowles

As the preface states, this bulletin is the fourth of a series of re- ports by the Bureau of Mines on different phases of quarrying in the United States. The first part of the bulletin describes the chief types of cements, the growth of the cement industry in this country, and the character of the raw materials used. The bulk of the report deals with quarrying methods and equipment, and gives especial attention to drilling and blasting; a chapter on rock mining and one on pros- pecting are included. Methods of manufacture are mentioned briefly, as that subject, except as related to quarrying, lies outside the scope of this report; but transportation methods and the effects of the man- ner of mixing the materials at the quarry or crushing plant on quarrying methods are discussed.

Jan 1, 1918

By Thomas P. Mucho, William D. Monaghan, John Wood, Michael A. Trevits

We have tested the ability of ground penetrating radar (GPR) to resolve adjacent mine workings. The work was conducted at two National Institute for Occupational Safety and Health locations – an underground coal mine and an underground limestone mine. The objective of our work was to determine if GPR signals could be received from distant mine workings. The GPR system was calibrated on underground mine pillars of known dimensions using a variety of antennas. The system was then tested at several underground locations in an effort to detect an adjacent drift entry; and an adjacent abandoned coal mine. As a means of verification, an in-seam horizontal hole was drilled from the active coal mine to the abandoned mine to confirm the presence and location of the abandoned mine workings. Our results show that in the case of the limestone mine the maximum depth of penetration where the mine workings could be resolved was 85 ft; and in the case of the coal mine the abandoned mine workings could be resolved at a depth of 205 ft. We conclude that it may be possible to utilize GPR for initial underground mine studies followed by directional drilling to accurately delineate the extent and position of adjacent abandoned mine workings.

By Oliver Bowles

Wire saws have been used for many years in European travertine, marble, and slate quarries. This method of sawing found very limited use in America until 1927 when it was accepted as standard equipment in elate quarries in Pennsylvania where it has been remarkably successful. Details of its operation in slate have been published in a recent bureau report.3 The very limited extent to which the wire saw has been employed in limestone and marble quarries in the United States and the seeming lack of interest even in experimental work to determine its advantages are difficult to explain in vied of its wide use in cutting similar rocks in Europe and its unquestionable advantages in sewing slate in America. In order to encourage improvement in quarry practice the United States Bureau of Mines has endeavored to obtain information as to the extent to which wire saws are used in Europe together with data on the rate and cost of sawing. The information at hand is by no means complete either in territory covered or in details of operation; it nevertheless brings out certain significant features that may be of interest and advantage to quarrymen in the United States.

Jan 1, 1931

By Wilbur I. Duvall

Surface vibrations of ground, rock, and structures resulting from blasting or other sources are often measured with portable seismographs. These instruments are usually supported by a three-point mount or tripod which is simply placed on a horizontal surface on which vibration levels are to be measured. The rigid-body motion of a tripod-supported seismograph is considered from the point of view that there should be no slippage of the feet with respect to the surface and none of the feet should leave the surface as a result of imparted motion. From these studies the following design criteria are deduced which assure that the seismograph will respond accurately to vibration levels as large as 1/2 g.:3/ First, the coefficient of friction between the feet and the surface on which the instrument rests should be as large as possible, preferably approaching unity; second, the center of gravity of the instrument should be vertically above the centroid of the three-point mount; and third, the vertical distance between the center of gravity of the instrument and the centroid of the three points of contact with the surface should be less than the perpendicular distance between the centroid point and anyone of the three sides of the triangle formed by the three points of contact. Portable seismographs that do not satisfy these conditions should be clamped to the surface if vibration levels above 0.1 g. are to be recorded.

Jan 1, 1961

By Thomas E. Popplewell

This paper is one of a series being prepared for and published by the United States Bureau of Mines describing the mining and treatment methods and costs obtained in sand and gravel plants throughout the United States. These papers are designed to disseminate technical information regarding the methods used. The cost tabulations represent operating expenditures only and not total costs. It is recognized that publication of total costs might in many instances cause embarrassment to individual operators as well as to the industry as a whole. On the other hand operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations shall ensue.

Jan 1, 1932

By D. Harrington

An explosive may be defined as a substance (usually a mixture) that has the property of yielding, readily to combustion or oxidation upon application of flame or shock, the combustion or oxidation process being rapid and accompanied by formation of such relatively large quantities of gases that much violence and pressure are produced; these, in turn, react against their surroundings and cause what is termed an explosion. By their very nature their action is destructive and disruptive of adjunct materials; hence, all explosives axe potentially hazardous and every type of explosive, irrespective of its relative safety, should be handled, .stored, and used with utmost care at all times and under all conditions. It should always be remembered that any explosive can be rude safe only in certain of its features and under certain conditions and circumstance. If these facts (and they certainly are facts) are always kept in mind, most of the modern types of explosives can be utilized advantageously in our industrial life and with a considerable degree of safety. That commercial explosives can be handled. safely is borne out in part by the fact that in the past 15 years at least 3,000,000,000 pounds of the commercial explosive dynamite have been transported by railroads in the United State, without injury to any person, insofar as available records indicate.

Jan 1, 1939

By H. Robert Ensminger

As a result of the new mining law implemented in August 1985 and the programs conducted by the Institute Ecustoriano de Mineria (INEMIN), which was created by this legislation, there was considerably greater activity in the nonfuels mineral sector during 1986. Over the next 2 years, INEMIN will be developing a national mining plan that will guide Ecuadorean mineral development for the balance of this century. As stage one of INEMIN's mineral study, historical records were reviewed and 300 abandoned mines and 1,200 unexplored mineral deposits were available for further investigation. In 1986, INEMIN established 5 branch offices and negotiated 250 new mining contracts with foreign companies valued at $16 million. Despite all this activity, INEMIN officials estimate that 100,000 square kilometers remain available for claim staking. Technical assistance contracts were signed with Belgium, the Federal Republic of Germany, Italy, Spain, and the United Kingdom, to assist in a variety of assignments ranging from helping prepare the national minion plan to the development of industrial mineral deposits.

Jan 1, 1988

By D. A. Hill

Introduction The fields of an infinite line source in the presence of a conducting half-space have been examined by Wait and Spies (1971). In any real communication link using a current-carrying cable for the transmitting antenna, the cable is of finite length. Here we examine the fields of a finite length cable carrying a constant current in the presence of a homogeneous conducting half-space. The constant current assumption is valid at sufficiently low frequencies when an insulated cable is grounded at the end points (Wait, 1952; Sunde, 1968). Here we examine both surface and buried cables since both downlink and uplink communication links are of interest. Also, we examine both frequency and time solutions since either CW or pulsed communications may be used. Finally, it is necessary to include both magnetic and electric field solutions since reception could be with either loops or dipoles. Since the finite cable solution is more complicated than both the infinite line source and the short dipole solutions, we explore under what conditions a cable appears to be either infinitely long or very short. Some special cases, such as- the low frequency limit, permit analytical solutions which exhibit the dependence on various parameters, such as cable length, quite clearly. Frequency Domain Subsurface Fields The geometry of a line source of length 2[l] located on a conducting half-space with the observer in the half-space is shown in Figure 1. The fields

Jan 1, 1973

By R. Hogg

"Particles play an important role in our environment and in many aspects of human activity. Much of the Earth's surface - sand, soil, rocks - consists of particles, as do clouds in the atmosphere, smoke from fires, and dust in our homes. Many of the foods we eat - cereals, flour, instant coffee - and everyday items such as pharmaceuticals, cosmetics, detergents and other cleaning products are encountered in the form of particles. Inks and paints consist of very fine particles dispersed in liquids. Modem agriculture uses huge quantities of fertilizers and pesticides, largely in particulate form. The list could be extended almost indefinitely; particle systems are obviously an important part of our daily lives. But what do we know about them? For most people, the answer is probably: not much.We are all familiar with the three common states of matter: gas, liquid and solid. In many respects, particle systems should be regarded as a distinct class of their own. The particles themselves may be solid but we all know that a heap of sand is quite different from a solid rock. A cloud of liquid droplets - fog - has much more in common with a cloud of solid particles - smoke - than it does with a bucket of water. There are certain characteristics and properties which are unique to the particulate state. The behavior of any particle system is determined not only by the material from which the particles are made, but also by interactions among the particles and with their environment. These interactions become increasingly important as the size of the particles decreases, and for exceedingly fine particles, smaller than about one micrometer (0.000001 meters or 0.00004 inches), these interactions dominate and we enter the realm of colloidal systems.Particle SystemsA system in which discrete entities - particles -are dispersed in a continuous medium can be regarded as a particulate system. The particles and the medium can consist of a solid, liquid or gas. The various combinations and some common examples are listed in Table 1. The properties and behavior of these systems depend on the characteristics of the particles, the nature of the medium, and the relative abundance of the two phases. In general, it is the latter which determines the kind of behavior exhibited by the system.As a general rule, the behavior of particle systems follows that of the dispersed phase (the particles) at high concentration, and that of the continuous phase (the medium) at low concentration. For example, both powders and smokes consist of solid particles in a gaseous medium. However, in a powder the solids typically occupy over one half of the total volume; in many respects powders behave like solids. In a smoke, on the other hand, the particles may take up only a few parts per million of volume, so that these systems generally behave like gases."

Jan 1, 1989

By Lewis C. Karrick

This paper is based on data obtained in the course of the oil - shale investigations of the U. S. Bureau of Mines , conducted in cooperation with the State of Utah . The amount and quality of oil that can be produced from any shale may be made to vary to an important degree by changing the temperature relations existing in the shale charge during destructive distillation . The rate at which the oil is formed from the shale is affected by the rate of heat supply , and therefore by the temperature of the shale during its thermal de composition . The quality of the oil formed may be controlled by altering the temperature of the shale , and therefore , the rate of formation of the oil . Variations in the yield and quality of shale oils may be caused by inherent properties of the retort used , but in any event the properties of the crude oil and yield are very largely the result of the extent to which the thermal de composition has progressed . Recognition of these principles will aid in explaining to a large degree the reasons for the wide variations in oils produced from the same shales by different " processes " . These principles also may be applied in the operation of different types of retorts in order that crude oils of a type most profitable to the operator may be produced . The Bureau of Mines has conducted an extended series of tests in the dee structive distillation of oil shales , in order to determine the wide variations that may be effected in the quality and yield of shale oil by changing the rate and temperature at which the oil is formed . These tests furnished interesting information on the four related points : yield of oil , quality of oil , temperatures required to distill shales , and time required for distillation .

Mar 1, 1923

By L. O. Bacon

This Bureau of Mines report summarizes the results of laboratory work in the design of instrumentation for obtaining the dynamic tensile strength of rock at minimum loading. Minimum loading is defined as the lowest tensile loading by pulse reflection to cause fracturing. The instrumentation for obtaining dynamic tensile strengths of rock cores evolved into the use of a compressed-air pellet gun to impact one end of a rock core, suspended by wires, at increasing increments of air pressure. Maximum strain was measured on most or all of the impacts, and the strain at fracture of the core was obtained by extrapolating the pellet velocity-strain curve to the pellet velocity at fracture. Stress at tensile fracture was obtained from the maximum s train, and the dynamic Young's modulus was calculated from the rod velocity by using simple rod theory.

Jan 1, 1962

By B. E. Davis

As part of its program to increase the domestic availability of critical minerals, the Bureau of Mines conducted characterization and beneficiation studies on a St. Johns County, Fla., phosphate ore that was mined by borehole mining. Results revealed that the ore from this test mine was mostly sand-size carbonate-fluorapatite and quartz and contained 24.6 percent P205. Concentration by various flotation techniques produced phosphate concentrates that ranged, in percent, from 30.0 to 31.4 P205, 0.73 to 0.80 MgO, and 2.8 to 7.2 acid insoluble. Recovery of the phosphate from the ore ranged from 89.4 to 96.3 percent.

Jan 1, 1982

By L. D. Tracy

"This paper represents work conducted by the Bureau of Mines in cooperation with the Illinois Geological Survey and the Engineering Experiment Station of the University of Illinois.IntroductionThe present report covers conditions and mining royalties in District VIII of the coal fields of Illinois, as designated by the Illinois Geological Survey. The various districts have been described in the reports on the Illinois coal-mining investigations, carried on cooperatively by the Illinois Geological Survey, the engineering experiment station of the University of Illinois, and the U. S. Bureau of Mines. This district includes Vermilion and Edgar Counties, but as the coal-mining operations in Edgar County amounted to only 827 tons in 1923, the data here given have been confined to Vermilion County.A similar report on District VI (Williamson and Franklin Counties) has been issued as Serial 2722 of the Bureau of Minos.A description of geological and mining conditions, and a discussion of market and transportation facilities, have been included because these have an important bearing on the royalties specified and the general conditions of the lease.Mining ConditionsDistrict VIII is better known as the Danville district and in 1923 produced 4,177,000 tons of coal, or approximately L per cent of the total output for the entire State for that year, which was 79,300,000 tons."

Apr 1, 1926

By 1980, the U.S. mining community had reached a broad consensus regarding coal pillar design. The pillar load could be estimated from tributary area theory, and the pillar strength from empirical formulas and laboratory coal strength testing. Then the growth of longwall mining required new thinking. Recently, powerful design methods have emerged from analysis of large data bases of real-world pillar successes and failures. These include the Analysis of Retreat Mining Pillar Stability (ARMPS), the Analysis of Longwall Pillar Stability (ALPS), the Mark- Bieniawski rectangular pillar strength formula, and guidelines for preventing massive pillar collapses. Sophisticated numerical models have also helped transform the pillar design landscape. In the process, our understanding of pillar mechanics has been greatly enriched. A new paradigm divides pillar failure into three categories:

By Motohisa Kanda

The time and amplitude statistics necessary to adequately describe electromagnetic (EM) noise in mines are illustrated through computer software techniques. They are 1) Allan Variance Analyses (AVA), 2) Interpulse Spacing Distributions (ISD), 3) Pulse Duration Distributions (PDD), 4) Average Crossing Rates (ACR) , and 5) Amplitude Probability Distributions (APD) . These statistics are illustrated using data taken from a rather large store of raw analog data recorded in operational mines. The curves generated for the illustrations characterize the noise environment in the mines from which the corresponding data were taken, and should aid in the design of reliable communication systems for such mines.