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By David C. Oyler, Winton J. Gale, Jinsheng Chen, Christopher Mark

A collaborative project between RAG Emerald Mine, NIOSH, and SCT Operations was conducted to investigate ground behaviour, reinforcement performance, and stress redistribution in a coal mine entry subjected to a severe horizontal stress concentration. Field measurements indicated that the stresses applied to the study site nearly doubled during longwall mining, resulting in roof deformations extending to a height of 4.8 m (16 ft) above the entry. This paper focuses on the computer simulation that was undertaken to provide more insight into the roof behaviour and rock bolt interaction during mining. The model’s input rock properties were derived from extensive laboratory testing, and the model itself simulated a broad range of failure mechanisms. The effects of different bolt patterns on roadway behaviour were evaluated. Comparison between the model results and the field measurements indicated that that the model effectively simulated the critical elements of the actual roadway’s behaviour. With the confidence gained, the model was used as a baseline for additional simulations that evaluated the expected performance of alternative roof support systems. The study will also provide a benchmark data set for future applications of numerical modelling to U.S. coal underground mining.

By H. B. Brunot, L. C. IlsLey

The chief object of the Electrical Section of the United States Bureau of Mines is the study of causes and means of preventing accidents resulting from the use of electricity in mines . A large part of this work for the last 20 years has been the inspection and testing of mining equipment under the provisions of schedules which give the minimum requirements considered essential for the safety of equipment intended for use at or near the working faces of dusty or gassy mines . During the first few years of this work , particular attention was paid to the explosionproof features of the various accessories such as motors , controllers , and other parts . The knowledge of the essentials necessary for safe designs of enclosures has since been augmented by field experience and by data obtained in testing a large number and variety of designs . With our present knowledge it would seem that a disproportionate stress was placed on making the various enclosures explosionproof , but not enough thought was given to the danger from wiring and connections outside of explosionproof enclosures . The list of equipment that has met minimum requirements for safety and has been approved as permissible by the Bureau of Mines includes storage - battery locomotives , power trucks , drills , loading machines , conveyors , cutting machines , room hoists , pumps , concrete mixers , and rock-dusting machines . The wiring on some of the machines is comparatively simple and sometimes , except for the trailing cable , may be entirely within the explosionproof enclosures . In general , there is outside wiring between enclosures , and on the larger machines the wiring may be extensive and complicated . In considering the safety of wiring for mining machinery , attention must be given the severe service and unfavorable surroundings imposed by mining conditions . Some of the matters that require consideration are : ground . The lack of care of the exterior wiring to be expected in the average mine . The lack of adequate periodic inspection of the wiring . The absence of adequate facilities for satisfactory inspection and repairs under- The severe conditions of moisture , dirt , mechanical injury , and low voltage encountered in mining service .

Apr 1, 1931

By John R. Bartels

Jan 1, 2009

By Michael S. Miller

The Carson-Iceberg RARE II study area, consisting o; 209,990 acres (134,983 ha), is on the crest of the Sierra Nevada in California, about 35 mi (56 km) south of Lake Tahoe. The area is divided into four parts: C4-986; C5-986; and B5-986, north and south portions. No mineral production has been recorded for the area. However, gold, silver, and tungsten resources and potential for additional resources have been estimated for the area and just north of area C4-986.

Jan 1, 1981

By W. M. Myers

[Utilization of small stone is recognized as one of the important problems of the lime industry. The term ?small stone' is used to designate material that is too small for calcination in tie shaft kilo. The maximum dimension A such stone rosy be placed at four inches. The introduction of any considerable quantity of stone having demensions lee: than this into the charge of a kiln impedes the draft and readers successful operation of the kiln difficult on impossible. Attempts design a shaft kiln which would calcine stall stone satisfactorily have not been successful to date. Thousands of tons of this small stone arc produced daily, and while part of it finds a market, for it has many uses, the profit is usually small an competition is teen and prices are low. Production of the material is, however, so greatly in excess of market that surplus of hundreds or possibly thousands of Jose axe place daily in stock piles and classified as waste. in a few instances a fortunate combination of circumstances, such as a program of or other work requiring large quantities of concrete aggregate, may mate it possible some quarries to market this stone later at a profit, teat in general the chances A profitable utilization are slight, and the quarry operator has the expense of handling this waste stone and providing a storage site for it. The brittle nature of limestone makes it impossible to quarry the stone and crush, it to size suitable for the shaft kilns without producing an excess of undesirable fines. Elimination of fines by changes in quarrying or crushing practices cannot lee expected. On the contrary, the adoption of more modern methods of quarrying in recent years has increased the proportion of small material. The tendency is to blast the roan with large charges of explosives and crush it with mechanical crushers, which produces more fines than the older methods of careful blasting with small char yes and sledging the rock by hand.. We increasing use of underground mining of limestone has also increased the production of small stone, as blasting in the confined space of an underground stope shatters the rocs more completely than quarrying in the open. The use of the very friable limestones, such as the limestone of Florida for the manufacture of lime adds a new factor to the calcination of small stone. These friable lime limestones have a low tensile strength and crumble in the kiln, causing trouble. Successful calcination of these stones is accomplished in specially]

Jan 1, 1926

By P. G. Clites

This study was undertaken to determine the effect of consumable-electrode vacuum arc melting on the properties of copper and to determine the applicability of the process to the production of cast shapes of copper. Ingots and castings were produced from electrolytic tough pitch copper (ASTM designation ETP), from electrolytic cathode copper (ASTM designation CATH), and from oxygen-free copper (ASTM designation OF). The products of this study were evaluated to determine the effect of the melting process on the removal of impurities from the copper and on the physical properties of the copper. The results indicate that consumable-electrode arc melting can be satisfactorily applied to the melting and casting of copper. Ingots prepared directly from electrolytic cathode copper contained slightly higher levels of impurities than are found in commercial oxygen-free copper, Excellent results were obtained with centrifugal castings of unalloyed copper, and reasonably successful static castings can be produced if proper mold and gating systems are employed.

Jan 1, 1963

By John F. Wiggert

The first signal system used in the Homestake mine between the cagemen and hoisting engineers was a mechanical one. It consisted of small cables or jointed steel rods hung in the cage compartments and counterbalanced with weights or springs. These cables or rod strings were connected to the mechanically operated gongs at the engineers' positions by means of bell cranks and steel wires. At the various stations the bell lines were also fitted with bell cranks and connected levers, so that the cagemen could operate the bells from the stations when they were handling rock or other material and not riding on the cages. Such a system was inherited from the days before extensive electrical development. It served quite well for shallow shafts, but for depths of a thousand feet or more it was very slow and cumbersome. It required consider-able muscular effort to operate it quickly, because of the inertis of its great weight and also because of frictional resistance. The maintenance cost was quite high because of the many wearing parts.

Jan 1, 1937

By G. H. Hopkins

Like most industries, the refining industry has in recent years been confronted with the problem of a decreased martin of profit, due both to a general lowering of prices and to rising costs. This has resulted in accelerating a program of increased efficiency an evidenced by improved methods and the installation of equipment designed to affect a number of economies hitherto regarded as unimportant. Perhaps the most important of these has been that of fuel economy for, as is not often realized, a refinery consumes about one-tenth as much fuel as it produces. A recently completed canvas., made by the Bureau of Mines for the purpose of determining the trend of fuel consumption at refineries in the United States, showed the following outstanding points, (1) a decrease in the use of oil for fuel in 1926 of approximately 4,000,000 barrels as compared with 1925; (2) a small decrease in the use of coal; (3) a material increase in the use of gas, both natural gas and refinery gas; and (4) a considerable increase in the use of petroleum coke.

Jan 1, 1927

By Dean H. Ambrose

This Bureau of Mines publication summarizes the status of mine electrical equipment reliability research. Failure rate data were estimated from theoretical, laboratory, and field studies. Tables are presented listing reliability characteristics of molded-case circuit breakers, undervoltage relays, ground check monitors, cables, motors, and control circuitry. Application of failure rate data is shown in tables listing maintenance scheduling intervals of components and components that are most sensitive to the probability of hazardous voltages on power distribution systems in the mines. Complete, accurate, and appropriate failure rates on mine equipment are of the utmost importance for reliability evaluations.

Jan 1, 1985

By H. Polat, Q. Hu, M. Polat, S. Chander

"The electrostatic charge on spray droplets of ionic surfactant solutions and coal particles was measured and the results were correlated with the dust collection efficiency. When various surfactant were added, the magnitude of the droplet charge increased significantly and it was observed to be a function of surfactant type and concentration. The concentration of maximum droplet charge coincided with surfactant concentration where maximum collection efficiency was observed for these surfactants. Particles of coal also carried substantial amount of charge magnitude of which seemed to be a function of coal rank.Based on the results presented in this paper, it was concluded that ionic surfactant primarily act as a strong electrostatic charge inducer for droplets. Due to interactions between these highly charged droplets and naturally charged particles, the efficiency of droplet-particle collisions play a primary role when compared to the wetting and engulfment phenomenon which could only follow a successful collision. INTRODUCTIONWater spray are widely used to suppress airborne dust in mine atmospheres (Walton and Woolcock, 1960; Kobrick, 1970; Hamilton, 1974; Jayaraman et al., 1986). Several investigators have considered the use of surfactants to enhance the effectiveness of water sprays especially for difficult to wet particles such as those of coal (Glanville and Wightman, 1979). The capture of dust particles by water droplets involves droplet-particle collisions, adhesion of particles to droplets, and engulfment of particles into droplets. Surfactants affect these sub processes through their influence on droplet charge, surface tension, and wetting. The last two mechanism have been thoroughly studied in recent years (Walker et al., 1952; Cohen and Rosen, 1981; Glenville and Haley, 1982; Chander et al., 1988; 1991). However, little attention has been paid to the role of electrical charge on particles and droplets on the collision and adhesion of spray droplets and dust particles."

Nov 1, 1995

By A. W. Kbair, L. D. Gehl

"INTRODUCTION The rock-bit interaction during the cutting process in underground mines has been a matter of great concern to mining operators, researchers and manufacturers, particularly after the passage of strict environmental laws. Coal cutting bears directly on airborne coal dust generation and rock cutting generates frictional sparks which may cause face ignitions, jeopardizing the productivity, safety and economy of the industry. It is imperative to investigate into the factors which have influence on bit we.ar. Hurt and Evans (1981) concluded that the point attack bits have greater ignition potential than the conventional wedge shaped bits, and also worn bits were more responsible for ignition than the new bits. The results of a study (Khair et al., 1992) suggested that after 7% weight loss, the bit should be replaced. The polycrystalline compact diamond (PDC) tipped bits are reported to be cost effective in a study done by USBM (Twin Cities Research Center), and it was stated that the PDC tipped drill bits had 80 to 100 times longer life than the ordinary tungsten carbide (WC) tipped bits.This paper presents the results of the experiments which were conducted utilizing a coal cutting simulator at the laboratory of the Department of Mining Engineering, West Virginia University, USA. The description of the machine and the experimental set-up have been described elsewhere (Khair et al., 1989; Gehi & Khair, 1994), and therefore, will not be discussed here. The rock types which were used in experimen~ are Tennessee sandstone, Berea sandstone and Indiana limestone. The operating parameters include (1) drum speed, (2) water spray pressure and (3) bit type. Besides studying the wear characteristics influenced by the above mentioned variables, the effect of these parameters on the required cutting force, specific energy consumption, acoustic emissions rate and rise in temperature of the bit were also studied. A preliminary study was also done to compare we.ar characteristics of the WC bits with those of the poly-crystalline compact diamond tipped bits."

Dec 1, 1995

By P. M. Gruzensky

In view of some of the outstanding properties of chromium, considerable effort has been made in recent years to prepare the high-purity metal in ductile form. The object of this investigation was to obtain such metal by electrolysis of chromic acid solutions and to determine the conditions that yield optimum results. The apparatus is described, as well as the parameters that received consideration. Ion-exchange resins were employed to remove cation impurities from the electrolyte. Tensile specimens prepared from the electrodeposits by arc melting, press forging, swaging, and drawing, were ductile at room temperature. INTRODUCTION Metallic chromium displays an exceptionally high resistance to corrosion, oxidation, and wear at elevated temperatures. Although these properties are utilized to some extent when chromium is alloyed with other metals, such as in stainless steels, high-chromium alloys and pure chromium are not employed as engineering materials because of a serious lack of ductility and impact resistance at room temperature. Because high-chromium alloys appear promising as refractory metals for applications such as in gas turbines, much interest has been shown recently in the preparation of uniformly ductile chromium and in determining which factors contribute to its brittleness.

Jan 1, 1957

By William H. Pomroy

Fires in underground metal and nonmetal mines pose a threat to the safety of underground miners and to the productive capacity of this Nation's mines. Contaminated air (smoke, carbon monoxide, and other products of combustion) is the primary life safety hazard created by a mine fire. The most reliable defense against the hazard posed by the rapid spread of contaminated air underground is early warning fire detection and rapid evacuation. This Bureau of Mines report describes the design and operation of four prototype early warning fire detection systems, for underground noncoal mines, presently undergoing prolonged in-mine testing by the Bureau. The systems are described within the context of the underground mine environment.

Jan 1, 1985

By W. J. Fene

It is often desired to obtain samples of air in places where collection by ordinary methods is not feasible, as in shafts amore means of descent or ascent are not provided, in sewer manholes, in gas or water wells, in empty oil tanks, and in sealed areas in mines. Heretofore, when such sampling was required, it was necessary to utilize the aspirating method, which was not always satisfactory; and to obtain samples of air in deep shafts, it was necessary to use long sections of rubber tubing, which was not always available. DESCRIPTION OF NEW DEVICE A new method or "device" employs a common snap-type mousetrap to break the neck of a vacuum tube at the place where it is desired to collect the sample (see fig. 1). A mousetrap is mounted on one end of a block of wood 11-3/4 by 3 by 3/4 inches in such camper that a lead weight attached to the trigger hall spring the trap when the device is given a sharp jerk. A vacuum tube is placed on the other end of the block and held in place by a strong rubber band. A strip of corrugated rubber is placed on each side of the grooved block to prevent the tube from clipping when the sample is taken. An adjustable shoulder, provided with a rubber cap, is pieced se that the neck of the vacuum tube will rest on it. The shoulder is made adjustable to accommodate various sizes of tubas and to keep the neck of the tube from breaking tee far back from the point. A metal handle is fastened to one end of the block, with a hole in the end through which the brass wire used for lowering the device is tied. The device is enclosed by a strong wire-gauge covering, hinged on one side and so arranged that it can be locked shut on the other side. This covering prevent: breaking of the tube while it is being lowered or raised in a shaft or other place. Brass wire of not less than 22 gage should be used for lowering the device. A detailed drawing of the device is shown in figure 2.

Jan 1, 1940

By Maria I. De Rosa

This report analyzes mine fires for all U.S. underground and surface coal mining categories by state and2-year time periods during 1990–1999. Risk rate values are derived, and ignition source, methods of fire detection and suppression, and other variables are examined. The data were derived from Mine Safety and Health Administration (MSHA) mine fire accident publications and verbal communications with mine personnel. The analysis will provide the National Institute for Occupational Safety and Health, MSHA, and the mining industry with a better understanding of the causes and hazards associated with mine fires and will form a basis for future fire research programs.

Jan 9, 2004

Hang ventilating air curtains so that they can be installed, moved, opened and closed more easily than curtains that are spadded or nailed in place. Approach Low-leakage plastic curtains fitted with grommets along the top were threaded onto a steel cable which is suspended from roof bolt plates. The system was tested in two mines. How It Works The curtains are threaded onto a steel cable which is suspended from roof bolt plates by S-shaped hooks. See Figure 1. The outby end of the cable is reeled off a hand operated winch; the inby end of the cable is anchored to a roof bolt plate by means of a cable grip and an S-shaped hook. To install the curtains the following procedure is used. First, the winch is located at least 5 feet outby the last open cross-cut. The base of the winch can be secured to the mine roof with short roof bolts, only about a foot long.

Jan 1, 1978

By J. B. Janus

This report, the 25th in a series, lists analytical data of coal samples collected by the Bureau of Mines in connection with the purchase of several million tons of coal for various Government agencies during fiscal year 1975. Tipple samples were collected by Bureau of Mines engineers at tipples as coal was being loaded into railroad cars or trucks. Ultimate analyses are given for these coalbeds only. The delivered coal was sampled at destination in accordance with instructions furnished by the Bureau of Mines, and all samples were analyzed in the Bureau laboratory at Pittsburgh.

Jan 1, 1976

By John R. Bartels

In laboratory testing, the Bureau of Mines established criteria by which common resin-grouted roof bolting systems can be evaluated and compared. Ultimate strength and stiffness were determined for nonten-sioned full-column, point-anchor, tensioned full-column, and debondable resin-grouted bolts, and for variations on full-column boltsn Bolt per-formances were compared using the performance of the 3/4-in full-column resin-grouted bolt as the standard. New and innovative systems can also be qualitatively compared against this standard. Since the medium into which a resin-grouted bolt is installed is one of the most important parameters affecting bolt performance, various host mediums were used in the testing: sandstone, concrete, simulated coal, simulated shale, and plaster. Bolt performances expected in other mediums can be inferred from the response patterns obtained in these mediums. Results indicate several functional differences among bolt types. Where resistance to shear is important, point-anchor bolts may outperform nontensioned full-column bolts at a lower cost. In medium-to soft-strength rock, tensioned full-column bolts perform best. Also, varying the resin-steel ratio seems to have little effect on the properties of a full-column bolt, when proper resin mixing is ensured.

Jan 1, 1985

By Ani Chitaley

A new method has been developed for handling supplies in underground bituminous coal mines. A survey indicates industry wide implementation potential for the proposed method. Reduction of supply handling accidents' by as much as 73% and improvements in the productivity of face operations by at least 3% are anticipated benefits. The new method is based on the palletization of daily supplies and the use of a forklift for carrying out the handling tasks at the underground section. A prototype of the forklift has been delivered to the U.S. Bureau of Mines. The forklift has demonstrated several important features necessary for underground supply handling such as compactness, maneuverability, visibility, ease of control and auxiliary attachments for hoisting, carrying timber and pulling. Design improvements are recommended for future generation underground forklifts. These relate to higher speed, increased battery duty cycle, higher payload and modified traction/steering to eliminate plowing of soft mine floors.

Jan 1, 1983

By Jack E. Fraley

Poor lubrication reduces the life of wire hoist ropes when they are used in corrosive environments. Although lubricants are added to ropes during the manufacturing process, these lubricants can deteriorate during use, and it is often necessary to add more lubricant to both the interior and exterior of the rope while it is in service. The U.S. Bureau of Mines evaluated the effectiveness of synthetic lubricants, using electromagnetic nondestructive testing (NDT) to measure deterioration in ropes while they were in service. For nonpressurized lubricant applications, synthetic lubricants appear superior to petroleum-based lubricants in their ability to penetrate to the interior of a rope. Therefore, the synthetics offer better wear and corrosion protection.

Jan 1, 1990