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Develop a simple and practical technique to measure in situ rock mass properties for realistic design and stability evaluation of underground structures. Background The Bureau of Mines has developed basic principles and techniques to determine in situ rock mass properties including Poisson's ratio, deformation modulus, and yield and failure strengths. An instrumentation package consisting of three pressure cells is installed in a single drill hole. Cell pressure response data are acquired and used to calculate and determine the rock mass properties. How It Works A test hole of BX size (approximately 5.7 cm) or larger is drilled to the approximate depth of the measuring point. The last portion of the test hole is drilled with precision bits to EX size (approximately 3.8 cm). The instrumentation package, which consists of one 3.8-cm-diameter cylindrical pressure cell (CPC) and two 5.7-cm-diameter cement-capsulated, flat borehole pressure cells (BPC's), is then installed. A complete history of cell response to changing strata loads is acquired on a continuous basis with a chart-type hydraulic pressure recorder. From these cell pressure data, Poisson's ratios, deformation moduli, and yield and failure strengths are calculated and determined.

Jan 1, 1990

To reduce needless paging of persons by all phones in a mine or mill, while retaining all-location page capability. Approach Standard pager phones of any manufacturer are modified to include the option of selective calling and message holding. How It Works All commercial mine pager phones presently rely upon voice paging via a loud-speaker. When a page is initiated, every phone in the system broadcasts the audible voice page, even phones in locations where the desired person could not possibly be. The advantage of this scheme is that whole-mine paging occurs. The disadvantage is that persons soon begin ignoring pages because they occur all the time, and most are for someone else. Also, it requires considerable battery power from all phones making it necessary to change batteries very frequently, even in phone locations where personnel rarely go. In addition, if a voice page is made and not heard, there Is no way to leave the message. Therefore, persons who at a later time come near a phone, have no way of knowing a page was made and was not acknowledged. This results in situations that often have a direct bearing on safety and productivity.

Jan 1, 1980

By John C. Edwards

To have the capability to predict the development of localized spontaneous heating within a porous coalbed that is subjected to forced air ventilation or in an otherwise quiescent environment in which buoyancy develops, the Bureau of Mines developed three time-dependent mathematical models, which were used to calculate the temperature increase associated with chemisorption of oxygen by the coal. In each model, spontaneous heating is driven by an Arrhenius first-order reaction between the oxygen and coal. Two models are two-dimensional, and one is one-dimensional. In the first two-dimensional model, a constant-velocity forced convection airflow is specified; and in the other, buoyant flow is allowed to develop in the absence of forced convection. The third model evaluates the airflow from Darcy's law and a specification of the pressure at the surface of a one-dimensional porous coalbed. Numerical computations demonstrated how each model could be used to predict the onset of spontaneous heating when the porous coalbed was subjected to constraints of an imposed internal heat source or a high- temperature airflow. The effects of particle size and coalbed compaction upon spontaneous heating were examined with the third model.

Jan 1, 1990

Improve underground long-hole drilling efficiency and safety by developing a lightweight, easily transportable drilling pust that can be adjusted to fit a range of mine opening heights. Background Standard one-piece commercially available steel posts weigh approximately 10 pounds per foot. Transporting these posts underground and carrying them over obstacles and through small mine doors is very difficult. Because the length of a one-piece post cannot be adjusted, variations in mine opening height at the drilling site must be accommodated. This is accomplished by stacking several wooden blocks to form a base for the post, resulting in a dangerously unstable drilling setup. The only alternative to this unstable setup is to obtain a longer post. There problems can be reduced by the use of a two-piece telescoping aluminum post having a 3-foot adjustment range in 6-inch increments. The two-piece extendable post will be easy to transport and carry underground. It will fit any opening height within its adjustment range. One large wooden block is used as a base and one cap block is used at the top to bear against the mine roof. This arrangement results in a stable, rigid setup.

Jan 1, 1990

Decrease dust concentra¬tions of longwall face workers by keeping them up¬wind of the headgate stage loader and crusher. Approach Direct the face airflow from tailgate-to-headgate, the direction of coal transport. How It Works Ventilation is the primary method of dust control on longwall faces, and the most effective ventilation control is to put workers upwind of dust sources. Recent ad¬vances in longwall dust sampling by the Bureau have shown that on some faces, the headgate crusher and transfer points are signifi¬cant sources of dust -some¬times making up more than half of the total dust to which the face workers are exposed. Also, when the air is coursed from head-to-tail, the relative velocity between the air and moving coal on the face conveyor can cause dust entrainment from the conveyor, particularly if the coal is dry. On the faces where these dust sources are a signifi¬cant problem, they may be eliminated by coursing the air from tailgate-to-headgate, provided that the mine roof is stable enough to permit the necessary intake of the tailgate along with an aux¬iliary intake at the headgate.

Jan 1, 1982

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the composition as shown by proximate analyses. To these, when required, are added the ash-softening temperature, the free-swelling index, and the Hardgrove, grindability index. Under most of these specification contracts the bidders guarantee the quality of the coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instructions 2 issued by the Bureau of Mines; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the contractor; if it is not, a price adjustment is made. Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) provide valuable data for use in evaluating future bids. In addition, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal.

Jan 1, 1970

By G. W. Murrie, W. P. Diamond, S. W. Lambert

A geologic study of the Mary Lee Group of coalbeds in the Black Warrior coal basin was undertaken to examine coal stratigraphy and determine regional trends and extent of the coalbeds. The area investigated encompasses 835 square miles in Jefferson, Walker, and Tuscaloosa Counties, Ala. More than 700 core logs were used to construct a structure map, coal, interval, and overburden isopachs, and cross sections. There is evidence that structure affected sedimentation. Coalbed isopachs indicate the Mary Lee Group was deposited in fluvial-deltaic and low-lying coastal plain environments. The Mary Lee coalbed is the only coalbed which is continuous throughout the area, commonly with two benches which have a combined thickness of 2 to 12 feet. The Mary Lee coalbed changes rank in the basin from high- through medium- to low-volatile coal. The methane gas potential of the Mary Lee Group coals is estimated to be greater than 1 trillion cubic feet. There is an excellent correlation between the orientation of surface cleats with those measured underground in the Mary Lee coalbed. The face cleats roughly parallel the axes of the area's folds and trend northeast-southwest.

Jan 1, 1976

By Oliver Bowles

"The introduction into mines, quarries and manufacturing plants of machines and tools operated by compressed air has revolutionized methods of operation to an extent comparable only with that occasioned by the invention of explosives and the utilization of electricity. The use of compressed air in pneumatic tools, in rock drills, and for the operation of pumps and other machinery is well known to most miners and quarrymen, but its application as a substitute for explosives for breaking rock in a few granite quarries has received little publicity.In the region of Lithonia, a few miles from Atlanta, Georgia, is a dome of massive granite used widely for building stone and for paving blocks. The most remarkable structural feature of the granite is the absence of joints and sheeting planes. The term ""joints"" is applied to open fractures that commonly occur in rocks, usually vertical in direction or nearly so, and spaced from a few inches to several feet apart. On the Lithonia granite outcrop, however, one may walk over the bare rock surface for hundreds of feet without finding any indications of a joint, ""Sheeting planes"" are open fractures at various levels, approximately parallel with the rock surface. The presence of such planes when spaced several feet apart greatly facilitates quarrying, and where absent, as at Lithonia, the necessary fractures must be made artificially.The forcing of artificial sheeting planes is accomplished as follows: Two holes of about 3-inch diameter arc drilled close together and to a depth of about 8 feet. Two men work at these holes all summer, and sometimes part of a second summer. A very small charge of black blasting powder, not more than a spoonful, is placed in each hole, tamped with clay, and the charges are fired simultaneously with an electric battery. This starts a small fracture running outward from the bottoms of the holes. There is in most granites one direction of easy splitting known among quarrymen as the ""rift"", and as the rift direction in the Lithonia granite is horizontal the fracture follows a horizontal plane,"

Aug 1, 1920

Bag stackers who use semi-automated palletizing machines and air slides may be exposed to high concentrations of dust. To reduce dust exposure, use an exhaust ventilation system in conjunction with an envelope of clean air over the bagstacker provided by an overhead air supply. Description of Hazard Mineral processing plants in the United States and throughout the world process material that is finely ground and placed into bags for shipping to the consumer. These bags normally range from 50 to 100 pounds in weight. Once the material is placed in these bags, a bag stacker loads the bags onto pallets. A bag stacker is exposed to a lot of dust that is mainly released by the force from loading the bag onto the pallet. The two main sources are the dust on the outside of the bag and the dust that escapes from inside the bag as it is loaded. The Mine Safety and Health Administration's (MSHA) records indicate the bag stacker's dust exposure is one of the highest of all workers at mineral processing operations. Ways to reduce the dust exposure and strain to the bag stacker are in constant development. Recently, automated systems have been built. These systems range from fully automated, which totally remove the worker from the bag-stacking process, to semiautomated systems, in which the bag stacker still performs some of the functions. This Hazard Control deals with controlling the bag stacker's dust exposure during use of a semi-automated palletizing machine. The worker slides the bags into position on the palletizing machine. Once an entire layer of bags is positioned, the bag stacker operates the controls on the palletizing machine to lower the layer of bags onto the pallet. An air slide is built into the semi-automated palletizing machine so the bags are easier to move. This slide uses a metal table with air jets that exit through small holes at high velocities, similar to an air hockey game. The dust problem occurs because the air slide causes dust to blow up onto the bag stacker, significantly increasing the dust exposure.

Jan 7, 2001

By George C. Branner

This Bureau of Mines report presents information on the origin, collection, movement, and consumption of iron and steel scrap in California and Nevada. As far as practicable, information is presented on a grade basis. The iron and steel scrap industry in California is important from the standpoint of employment, economic essentiality, and dollar value. About 16,000 persons are either directly or indirectly employed on a full- or part- time basis in the collection, preparation, and sale of iron and steel scrap in California; in 1957 about 70 percent of the tonnage of products of California steel mills, valued at $271 million, was derived from scrap; the value of scrap in 1957 ($117 million) is about $10 million greater than the value of portland cement produced in California that year. The iron and steel scrap industry in Nevada is small.

Jan 1, 1960

By George S. Koch

The distribution of gold in part of the Getchell mine, Humboldt County, Nev., is presented through the statistical analysis of 956 assays of rock cuttings from wagon-drill holes. Two methods to predict grade in undeveloped parts of the ore body are evaluated, and the possibility of sampling bias is tested. The distribution of gold is compared with that in three other Nevada gold deposits of the same type characterized by gold particles mostly of submicron size associated with carbonaceous rocks, and also with that in deposits with coarse-grained gold. Usually, fewer samples of a given type are required to make a satisfactory grade estimate for submicron deposits than for coarse-grained deposits. The economic consequence is that submicron gold deposits are likely to be less expensive to sample and evaluate than coarse-grained deposits.

Jan 1, 1970

By George M. Lucich

This report describes a sensitive, proportional temperature controller developed by the Bureau of Mines that is useful in the temperature range from 40 to 400° C with an accuracy of ±0.10 C. A temperature controller of this kind is potentially useful for regulating temperatures in air chambers, liquid baths, furnaces, and reaction vessels, and for other applications. This instrument was developed to control the duration and temperature of the heating cycle of a charcoal-filled adsorber that is part of a special helium analyzer used by the Bureau. The controller was made from commercially available parts, and can be easily modified to provide continuous temperature control. The circuit is solid state and employs no electromechanical devices. Over a 2-year period of use as a component of the special helium analyzer, this temperature controller performed successfully and required no maintenance.

Jan 1, 1979

By I. N. Beall

The present survey indicates 'that the average volatility of motor gasoline now being marketed throughout the country falls well within the limits of Federal Specifications. As would be expected, there is a slight decrease in volatility as compared with the gasoline marketed last wine:., but on the average the gasoline sold today is about the same as that sold last summer. During the past five years the Bureau of Mines has made semi-annual surveys of the gasoline marketed in the United States. To obtain a sample of each gasoline sold is obviously impracticable, but the cities in which samples have been collected have been so chosen as to be representative of the more important marketing territories. It is believed, therefore, that the samples obtained are indicative of the quality of gasoline marketed throughout the country.

Jan 1, 1925

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

APPENDIX C SCALING RELATIONSHIPS 1. Scaling Law for Fly Ash Crater Formation The scaling law derived for predicting crater diameters at different scales is developed below by considering the equation of motion of individual fly ash particles. It is assumed that the air drag on each particle is characterized by Stokes flow, and at the borehole - passage intersection the air velocity and the fly ash particle velocity are the same. The equations of motion for a fly ash particle are the following, (see Figure C-1).

Jan 1, 1973

By Irven A. Jacobson

The thermal reactions of l-methylindole were studied in the temperature range of 525° to 627° C in a flow reactor. The major products consisted of 2-methylindole, 3-methylindole, indole, quinoline, hydrogen, and methane. 2-Methylindole is formed from 1-methylindole by an irreversible isomerization reaction. The 2-methylindole isomerizes in a reversible manner to 3-methyl-indole, the equilibrium favoring the 3-methyl isomer. Indole is formed directly from 1-methylindole. Quinoline is formed from l-methylindole, 2-methylindole, and 3-methylindole.

Jan 1, 1971

By Alan H. Goode

The advancement of high-temperature drilling fluid technology for application in geothermal environments is part of the Bureau of Mines program for more efficient development of our Nation's energy resources. The bentonite constituent of water-base drilling fluids is sensitive to destabilization by high-temperature and salinity. A substitute material for bentonite, phosphate slime, which is reported to be saline resistant, was considered. These studies show that spray-dried slime suspensions have more favorable rheological behavior, but poorer filtration properties, as compared with bentonite suspensions.

Jan 1, 1975

By R. V. Ramani, C. B. Manula, A. Owili-Eger

ANALYTICAL PRESSURE - VOLUME COMPUTATIONS FOR THE MINE PROTOTYPE A new coal mine is projected, with entrance by slope 1,500 feet long. Nine main entries will be standard for development, five as intake and four as return. One return shaft is planned near the slope bottom, and an intake shaft and portal are planned 5,000 feet north of the slope bottom. The slope will have an area of 150 square feet and a perimeter of 55 feet. A belt and supply track will be within the slope. The return shaft will be circular with a diameter of 18 feet and will be 500 feet deep with an escapeway. Two hundred feet of the shaft and 500 feet of the slope will be concrete lined. Select the fan to operate five units per shift and drive the 5,000 feet to a proposed new portal, using the slope for an intake. Two main splits are planned with the maximum of three units on any split. The amount of air desired at each unit is 25,000 c.f.m; a shop at the slope bottom will require 10,000 c.f.m. In the solution of this or any similar problem, the first step is to determine the resistance factors. CALCULATION OF R FACTORS Slope area = 150 sq. ft.; Perimeter = 55 feet; Length = 1,500 feet. The friction factor K must be established. Five hundred feet of the slope is smooth lined, moderately obstructed by belt; K = 35. The remaining 1000 feet is in sedimentary rock and moderately obstructed; K = 85.

Jan 1, 1975

Provide a more efficient method of cooling hot working environments in deep mines than is possible with single stage spray coolers or cooling coil heat exchangers. Approach Pass warm mine air through several stages of horizontally oriented water sprays fed by the chilled water supply of the mine. How It Works This concept extends the capabilities and potential applications of the coolers described in Technology News nos. 71 and 93. In this multi-stage design, hot ventilation air is cooled while passing through horizontal water sprays. Air enters the cooler through a diffuser section which slows the airflow and distributes it evenly across the cooler with a minimum of pressure drop. This ensures uniform exposure of the warm air to the cool water and consequent high thermal efficiencies. In the three-stage cooler shown, cold mine service water is sprayed from the first water stage manifold on the downwind end of the cooler. Slightly warmed water from this spray stage is collected in a sump, pumped and then resprayed through the second stage manifold. The process is repeated again for the third-stage. An overall counterflow heat exchange effect is thus achieved by exposing the hottest incoming air to the warmer, third-stage water spray first and to the coldest, first-stage water spray last. Wave plate eliminators can be employed between stages of water sprays to increase thermal efficiency or at the outlet to minimize the water discharged into the mine ventilation air. Cooled air can then be ducted to hot work spaces or simply released

Jan 1, 1985

By Thomas V. Falkie, R. Venkataramani

Underground coal winning operations can broadly be classified as conventional, continuous, and longwall mining. In conventional mining, the operations of cutting, drilling, blasting, loading and hauling, and roof support are performed in that sequence in each working face in a work area. The major difference between continuous and conventional mining is that the coal is cut and loaded by a continuous miner in the former, thereby combining the unit operations of cutting, drilling, shooting, and loading into one. Longwall applications have been viewed with great interest in recent years, and although at the end of 1970 there were only 37 longwall installations in the U. S. with combined production of less than 4 percent of underground total, there is no question about the growth potential of longwall in the United States. Increased capacity, versatility, and power characterize continuous miners today. Although continuous miners have outsold conventional gathering-arm type loading machines for some years, the latter, in the new extra-high capacity types, are continuing to find wide use. Whether the mining system is continuous or conventional, the haulage units may include six-wheel articulated shuttle cars, tractor-trailer units, or extensible belt and bridge-conveyor systems, all tending to increase the productivity of the face units. The decision as to which to choose - continuous or conventional mining - is complicated, and both systems are capable of high production rates. Most continuous miners in use today have a revolving pick-mounted drum to cut the coal and a gathering arm loading unit. Functionally, there is little difference between the loading unit in a

Sep 1, 1972

To cool hot working environments in deep mines more efficiently, while substantially reducing the maintenance required by presently used cooling coil heat exchangers. Approach A mine's chilled water supply cools fresh air enroute to hot working areas, in an improved, direct-mixing heat exchanger. How It Works Warm, fresh ventilation air traveling through the mine's ventilation tubing enters the lower portion of the cooler heat exchanger through a large round opening designed to accept the ventilation duct. This air flow is turned upward and evenly distributed by egg-crate lattice and pair guide vans at the bottom of the cooler. On the diagram, warm air enters at the bottom left. As the air moves upward through the cooler, it passes through a plastic or wire mesh pad which is arranged so that it offers the most resistance to upward airflow immediately above the cooler inlet: this more or less equalizes the upward air flow along the length of the cooler. The air next moves through the cold water sprays, and then through a wire-mesh demister pad before exiting from the cooler at the top right. Cooling of the air is accomplished in several stages. As the incoming air passes through the lower plastic or wire mesh pad, it is exposed to water flowing downward through the pad to the water sump. This is water that has fallen from the sprays or dripped from the upper wire-mesh mist eliminator. This water is slightly warmer than the spray water since it has already done some cooling,

Jan 1, 1981