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By Christopher Mark, Gregory M. Molinda, Timothy M. Barton

The Coal Mine Roof Rating (CMRR) was first presented at this Conference nine years ago. Since its introduction, the CMRR has been incorporated into many aspects of mine planning, including longwall pillar design, roof support selection, feasibility studies, and extended cut evaluation. It has also become truly international, with involvement in mine designs and funded research projects in South Africa, Canada, and Australia. The purpose of this paper is to bring the mining community up to date with recent improvements and applications of the CMRR. The most important new development is a streamlined process for determining the CMRR from exploratory drill core. Just three types of information are now required: •Fracture spacing (or RQD) •Uniaxial compressive strength (or axial Point Load Testing) •Diametral Point Load Testing The moisture sensitivity adjustment has also been changed, and new research has related the immersion test to slake durability. Most recently, the CMRR has been implemented in a computer program, which can be obtained from NIOSH free of charge. The program facilitates calculation of the CMRR from either underground or drill core data. Values from many locations can be saved in a single file, and an interface with Autocad allows CMRR contour plots to be integrated into mine planning.

Numerical models play a significant role in the design of safe underground mining excavations and support systems. Advances in the capabilities of numerical modeling software, together with ever increasing computational speeds, have made it possible to investigate the very nature of the large-scale rock mass and its response to mining excavations. The improved understanding of the rock response obtained from modeling enhances our designs, resulting in greater stability and safety of the mining excavations. To help advance the state of the art in this field, the National Institute for Occupational Safety and Health organized the International Workshop on Numerical Modeling for Underground Mine Excavation Design. The workshop was held in Asheville, NC, on June 28, 2009, in association with the 43rd U.S. Rock Mechanics Symposium. The proceedings include 10 papers from leading rock mechanics and numerical modeling experts in the United States, Canada, Australia, and Germany. The papers address a wide range of issues, including various numerical modeling approaches, rock mass modeling, and applications in coal and metal mines.

Jun 1, 2009

By C. Babcock

When a flat-lying mineral deposit such as a coal seam is mined, some coal is left to separate the roof and floor so that miners and machines can safely mine the seam. The mineral left is in the form of mine pillars. If too much is taken, support problems and unsafe working conditions result. If too little is taken, the mining operation will be unable to compete economically with other mines. Therefore, one must select pillars of the optimal size to maximize mining recovery and minimize risk to miners and equipment. Later, if the pillar support is no longer needed and the surface can be allowed to subside the thickness of the coal seam, then the pillar support can be removed to increase mining recovery, and initial pillar size is not as critical. Only a small part of the information available on pillar design can be presented here. The purpose of this report is to summarize some of the work done by the U.S. Bureau of Mines and others on pillar design, which is reported in the literature from 1833 to the present, and present rock mechanics test results that aid in understanding mine pillar behavior. The variable names used are those of the authors cited. This results in multiple use of some variable names.

Jan 1, 1994

By A. B. Hooker, Iilsley. L. C.

"Flame safety lamps have been used for about one hundred years in coal mines where a dangerous accumulation of explosive mine gas (methane) might occur and thus render the use of ordinary unprotected flame lamps dangerous. Flame safety lamps are not only used for illumination, but also for detecting the presence of dangerous percentages of methane mixed in the air of the mine.The safety of the lamp depends chiefly upon the cooling qualities ofThe safety of the lamp depends chiefly upon the cooling qualities of the wire gauze used to permit free circulation of the air through the lamp. If one enters a part of the mine where methane is present in the air, the methane enters the lamp and coming in contact with the wick flame is ignited and continues to burn within the gauze without igniting the methane surrounding the lamp. If the air within the mine is traveling at a velocity of several hundred feet per minute the burning gases may be driven through the gauze by the air current. If the gauzes are properly designed and of the proper material, these burning gases will be so cooled as they pass through the gauze that they will not cause an ignition of the gas surrounding the lamp. In order to test the effectiveness of a given safety lamp, tests are made in moving explosive mixtures of gas and air arranged to simulate mine conditions.The Bureau of Mines investigated many features relative to the safety of flame lamps and in 1915 established an official schedule known as Schedule 7 whereby flame lamps having certain prescribed qualifications would be approved as permissible for use in gaseous mines."

May 1, 1920

Lower workers' dust exposures during bag stacking while ergonomically improving the bag stacking process. Approach Install a new pallet loading dust control system which uses a push-pull ventilation technique along with a hydraulic lift table to control the pallet loading height throughout the entire loading cycle. How It Works A low-volume, high-velocity blower system operating at approximately at 120 cfm blows a stream of air over the top layer of bags on the pallet. The blower system is composed of two 3-inch air jets (approximately 1,200-ft/min velocity) directed toward an exhaust system on the opposite side of the pallet. As these air jets travel across the pallet, they en-train dust generated during bag stacking. The dust laden air is then captured by the exhaust ventilation system which draws approximately 2,500 cfm through an exhaust hood on the opposite side of the pallet.

Jan 1, 1989

By H. B. Hill

Virtually from the date of its discovery in December 1928 the Oklahoma City oil and gas field, Oklahoma County, Okla., has attracted national and international attention. The history of the field has been associated closely with rules and regulations pertaining to production control and proration practices. Early development was rapid, and Oklahoma City soon attained the distinction of being the first major field in which the producing wells were over a mile in depth. Before the structural features of the reservoir had been disclosed every outpost well was considered a "wildcat", so complex appeared the underground geology, The wells not only were deep and the reservoir pressures high, but the production from the early wells was a high A.P.I. gravity oil, accompanied by large volumes of gas. Several "blow-outs" and fired occurred during the early development, and the close proximity of these now unusual events to a large city gave the field much publicity, both local and national. Later, when its production threatened to demoralize the market for oil and its products, the Oklahoma City field again attracted wide publicity. The then little understood geology of the underground reservoir and the diversity of ownership of the land overlying the producing structure made orderly development and production difficult to enforce. Proration was enforced with difficulty., and the, rate of production from the field continued to increase until, on August 4, 1931, martial law was declared in all prorated fields of the State, and most of the wells in the Oklahoma City field wore shut n. On October 9, 1931, permission was granted t o reopen and prod e the wells in the Oklahoma City field. The order permitting production of the wells provided that during the period beginning October 10 and extending to October 20, 1931, all wells in the field that hid not produced more oil than specified under the earlier proration orders and that had been shut in for the required 55-day period were permitted to produce 5 percent of their last potential during that 10-day period. On November 7, 1931, the Corporation Commission of Oklahoma issued an order which divided the Oklahoma City field into the Wilcox, Arbuckle, and Lower Simpson zones for proration purposes. Wells producing from the Wilcox zone were allowed to produce 4 1/2 percent of their potential5/ from November 1, 1931, to January 1, 1932; Arbuckle limestone wells were allowed to produce 250 barrels of oil daily; and Simpson sandstone wells which had a potential of over 2,000 barrels per day or which made 3 percent or more water were allowed to produce 200 barrels of oil per day.

Jan 1, 1937

By H. B. Hill

Virtually from the date of its discovery in December 1928 the Oklahoma City oil and gas field, Oklahoma County, Okla., has attracted national and international attention. The history of the field has been associated closely with rules and regulations pertaining to production control and proration practices. Early development was rapid, and Oklahoma City soon attained the distinction of being the first major field in which the producing wells were over a mile in depth. Before the structural features of the reservoir had been disclosed every outpost well was considered a "wildcat", so complex appeared the underground geology. The wells not only were deep and the reservoir pressures high, but the production from the early wells was a high A.P.I. gravity oil, accompanied by large volumes of gas. Several "blow-outs" and fired occurred during the early development, and the close proximity of these now unusual events to a large city gave the field much publicity, both local and national. Later, when its production threatened to demoralize the market for oil and its products, the Oklahoma. City field again attracted wide publicity. The then little understood geology of the underground reservoir and the diversity of ownership of the land overlying the producing structure made orderly development and production difficult to enforce. Proration was enforced with difficulty, and the rate of production from the field continued to increase until, on August 4, 1931, martial law was declared in all prorated fields of the State, and most of the wells in the Oklahoma City field wore shut in. On October 9, 1931, permission was granted to reopen and produce the wells in the Oklahoma City field. The order permitting production of the wells provided that during the period beginning October 10 and extending to October 20, 1931, all wells in the field that had not produced more oil than specified under the earlier proration orders and that had been shut in for the required 65-day period were permitted to produce 5 percent of their last potential during that 10-day period.

Jan 1, 1936

By C. A. Geffen-Fowler

This report, sponsored by the Bureau of Mines, presents the results of an examination of the safety of the Blind Shaft Borer (BSB) shaft sinking system and an alternative modified BSB design concept in comparison to conventional shaft sinking technology. Detailed study of the two systems was also performed to identify and recommend design changes for optimum safety conditions. A comparison of the BSB systems with conventional shaft sinking was made on the basis of relative risk levels. Risk incorporates both the frequency and the potential consequence of accidents. A safety evaluation of the component operations of the two BSB systems was performed using a Failure Modes and Effects Analysis (FMEA) methodology. The results of this analysis show generally that both BSS systems are safer than conventional shaft sinking. The potential risk of conventional shaft sinking operations could be reduced by over 30%, on the average, with the use of the original BSB system, and by an average of about 10% with the modified BSB. Design change recommendations to further improve the safety of these systems include a better fire suppression system, improved man haulage systems and more compact hydraulics. An operational safety manual was also developed for the modified BSB system.

Jan 1, 1981

By Paul Meadows

The Buckrange reservoir, Stephens field, Ark., is approaching the economic limit of production under present operating conditions. Over 100 million barrels of oil remaining in the reservoir will not be recovered by primary producing methods. The Bureau of Mines, in cooperation with the Arkansas Oil and Gas Com-mission, made the petroleum-engineering study presented in this report to aid operators in evaluating secondary-recovery possibilities in the reservoir and in planning secondary-recovery programs if their initiation is decided. The Stephens field, in Columbia, Nevada, and Ouachita Counties, Ark., is about 12 miles northeast of Magnolia, Ark., and 15 miles west of the Smackover field. Surface elevations in the area average about 240 feet above sea level.

Jan 1, 1956

By J. B. Cheung

The results of a program to demonstrate the technical feasibility of hydraulic borehole coal mining are presented in this report. The hydraulic borehole method of coal mining involves inserting a hydraulic mining device into a borehole that has been drilled from the surface into the underground coal bed. The borehole mining device issues a jet of water under high pressure, which breaks the coal. These pieces of coal, along with the water, form a slurry, which flows to the base of the borehole where it is pumped to the -surface. Phase I of the program encompassed the design, fabrication and factory-testing of a hydraulic borehole mining device. The program was successfully completed with the field tests being conducted at the Wilkeson-Carbonado Coal Field near Wilkeson, Washington. The technical feasibility of hydraulic borehole coal mining was demonstrated by mining 32 tons of coal at a depth of about 75 ft over a period of 4 hours.

Jan 1, 1976

By Graham W. Marks, Betsy M. Jones

"Recently4/ it was shown that the total energy method5/ of spectrochemical analysis is suitable for the quantitative estimation of many of the elements of which ores are composed. It was shown how this method can be applied to the determination of germanium, tin, and lead. Continuing this work, the present report deals with analyses for beryllium, zinc, cadmium, and indium.There are three basic problems in these investigations. The first is to study the influence of those elements that make up the greater part of an ore sample on the spectral-line intensities of the elements for which analyses are being made, the latter generally being the minor constituents. The second is to develop proper methods for the preparation of standard spectrographic curves. Finally, we are concerned with improvement in equipment and procedure, so that greater accuracy can be achieved.As discussed previously, it is better to study as groups those elements that belong to the same group in the periodic table because their spectra are similar. Beryllium, zinc, and cadmium are thus related. Indium was included in this work because it is associated with zinc and cadmium in zinc ores.The authors wish to acknowledge the valuable assistance of the staff of the Bureau of Mines Analytical Laboratory who made the chemical analyses and supplied the ore samples used in this work.A brief description of the procedures followed in making the standard curves and analyses is given below; a detailed discussion will be found in an earlier paper.6/Basically, the procedure for determining a standard curve consists of two parts: (1) Choosing a suitable line in the spectrum of the element to be determined and (2) determining the variation in the intensity of this line with the amount of the element burned in the arc."

Nov 1, 1948

By D. Harrington

"Up to the last 10 or 15 years, responsibility for accidents in mines was generally, though not universally, placed upon the person or persons immediately involved. Present-day thought is rapidly veering toward holding the industry responsible for accidents, with ultimate payment of the bill by the consumer, if financial expenditure should be necessary. While it is undoubtedly correct in principle that responsibility for accidents in and around mines should be shouldered by the employer and while it is probable that as time passes the burden will become even more definitely than now that of the mining companies, on the other hand it is an undeniable fact that large numbers of accidents occur through acts of omission or of commission of some person, very frequently the victim of the accident being the offender.Out of about 3,000 persons killed every rear in our -mines and quarries, nearly half or approximately 1,500 of the fatalities are due to falls of overlying material or of persons, about 500 to haulage, about 350 to fires and explosions, about 125 to explosives, approximately the same number to electricity, and about 300 to various miscellaneous accidents.Generally the accidents from falls involve but one or two persons at a time, and the tendency is now as it always has been to charge the victim or possibly a coworker with the responsibility. Usually this sort of accident occurs at or near a working face (statistics indicate that about 80 per cent of fatalities from falls of roof or rib occur near the face), and as it is Generally agreed that it is the duty of the worker to keep his working place safe, the worker and especially the face worker is given the blame in case of accident."

Apr 1, 1930

By L. D. Tracy

"The first study of this subject has been made in Illinois, but as opportunity affords, similar studies will be made in other States. It is hoped that the data obtained will assist the coal—mining industry to standardise the forms of leases, and so avoid some of the abstruse and ambiguous clauses which may be found in many of then and the consequent liability of costly litigation.In some of the publications of the Illinois Mining Investigations prepared under a cooperative agreement with the U. S. Bureau of Mines, the Illinois State Geological Survey and the Engineering Experiment Station of the University of Illinois, the coal areas of the State have been dividedinto eight geological districts, each district being treated separately.report covers District No. VI of that classification, and it is hopedstudies of the other districts will be completed in the near future and similar results published.The report includes a short description of the geological condition the character and quality of the coal and the nature of the surface, data for which have been taken largely from the Illinois Geological Survey publications.Mining methods and percentages of recovery are mentioned, together physisal conditions, market and transportation facilities, because all of these factors have a bearing on royalties and leasing conditions."

Jan 1, 1926

By Mark S. Sanders

This report is a review and synthesis of the published literature dealing with personal equipment items used by low seam coal miners. This report reviews the following items of equipment: headgear, outer garments, respirators, cap lamp, gloves, knee pads, footwear, boots, helmets, ear protection, eye protection. Recommendations for further research and development are included.

Jan 1, 1978

By Wilbert J. Huff

For the past 9 years , the technical studies conducted by the Explosives Division of this Bureau have been summarized in a series of reports issued annually . The following account presents investigations undertaken from July 1 , 1943 , to June 30 , 1944. The work is detailed under a number of main headings corresponding to the organizational structure of the Division , the various activities being under the immediate direction of unit chiefs , who report directly to the author . Specific credit , however , is due to the individual unit leader and his assistants .

Jan 1, 1945

By Bertrand L. Johnson

Before 1914 , Chile , because of her extensive resources of natural nitrates , practically monopolized the world markets for one of the leading fertilizer materials . Since nitrogen also is an important war material , constituting in fact the principal ingredient in many high-powered explosives , the World War and the widespread insistence upon national self- sufficiency for war materials brought about the development of nitrogen fixation plants in all of the larger countries . The production of by- product ammonia from gas and coke plants was likewise stimulated . As a result , Chile , even after the ocean lanes were reopened , was forced to fight for her lost markets . Since the world capacity to produce is still far in excess of annual consumption , the competition between natural and synthetic supplies has been keen and prices have fallen below pre-war levels . Chile has recently succeeded in unifying her industry , utilizing the most efficient process now in operation, and the Government is a partner in the new company that will take over all of the present producing companies . These developments place Chilean nitrate of soda , in a much more favorable position among the markets of the world . More intense competition will undoubtedly follow and , in order that those interested may become familiar with the fields upon which the nitrogen conflicts of the near future may be waged , the following general summary of the nitrogen industry has been prepared .

Jan 1, 1931

By W. E. Wallace, P. S. Mike, C. A. Hill, V. Vallyathan, M. J. Keane

Respirable quartz duet and a kaolin clay dust have been found to be of comparable cytotoxic potential in vitro on a specific surface area basis (Wallace, et a1,1985), despite the distinctly different potentials of quartz and clay for causing pneumoconiosis or pulmonary fibrosis (Sheers, 1984). A respired particle depositing in a respiratory bronchiole or alveolus will contact a pulmonary surfactant hypophase, of which a primary component is diacyl glycerophosphorylcholine, or diacyl lecithin (DPL) (Clements, et al, 1970). Several studies have found that adsorption of such surfactant suppresses in vitro cytotoxic effects of quartz dust (Marks, 1957). Subsequent phagocytosis and digestion by a macrophage may remove the coating, restoring cytotoxic potential and initiating disease processes (Iles, 1979). Adsorption of dipalmitoyl lecithin (DPL) from emulsion in physiologic saline by respirable sized quartz dust and kaolin dusts, and consequent diminution of the dusts' hemolytic and macrophage cytotoxic potential have been reported (Wallace, et al, 1985). This report presents additional data on the cell-free in vitro phospholipase A2 enzymatic digestion of dipalmitoyl lecithin adsorbed on a quartz and a kaolin respirable sized dust (Wallace, et al, 1988) to investigate mineral specific differences in the rates of digestion and of consequent restoration of dust membranolytic potential. Respirable crystalline alpha quarts used was eighty percent smaller than 5 micorometer aerodynamic diameter with a nitrogen adsorption specific surface area of 3.97 m2/g. Respirable kaolin dust was ninety percent smaller than 5 micrometer diameter and had a specific surface area of 13.25 m2/g.

Jan 1, 1988

By T. R. Taubert, D. H. Carlson, J. H. Johnson

"ObjectiveDevelop a portable emissions measurement apparatus to sample and measure tailpipe concentrations of diesel particulate matter (DPM), carbon monoxide (CO), carbon dioxide (COJ, nitric oxide (NO), and nitrogen dioxide (NOJ under steady-state engine load and speed conditions during a 1-minute test.BackgroundThe U.S. Bureau of Mines (USBM) has a comprehensive research program to develop ways to reduce exposure of miners to diesel exhaust pollutants. Engine maintenance has been shown to have important effects on such exposure.Accurate measurements of tailpipe emissions are becoming an essential part of a good maintenance program for underground mines that use diesel-powered vehicles. Past studies of particulates in U.S. underground coal mines have shown that DPM alone may be present at concentrations greater than 1 milligram per cubic meter (mg/m3), half the 2-mg/m3 limit for respirable coal mine dust. A poorly tuned (smoking) diesel engine may be the sole cause for respirable dust concentrations exceeding the limit. Although there is currently no standard specifically for DPM in U.S. mines, regulatory steps are underway, and significant reductions of DPM levels in both coal and metal mines will most likely be required.Tailpipe emission measurements can provide diagnostic information to identify engine malfunctions such as clogged air cleaners, faulty injectors, or incorrect injection timing. In some cases, mine vehicle tailpipe DPM concentrations have been reduced up to 50 percent by engine maintenance and adjustments.An accurate measuring instrument would also be useful for determining the effects of exhaust control devices on tailpipe emissions. Little information is currently available about the overall effectiveness of exhaust controls after long-term use. Raw exhaust concentrations with and without the control device can be measured in underground mines, and from these data a control efficiency can be calculated. Knowledge of the effectiveness of exhaust control devices over time is needed to make intelligent decisions on bow to use and maintain these devices, and when to replace them."

Dec 1, 1995

By C. V. Davis

In the lnvestlg::ìt1on of mAthods for aSS8.7ing platin",. conducted by the Bureau ot MinAs, reoent experiments have d~velopad tha~ with ce..tain orei, especially when thr, quantity Of platinum 1s eonlidarablfl, nit'!le acid w111 not etfßct a iepard-Han of platinum and pa11adium. 'lhe following m;lthod has been found to be accurate and to reiu1 t in a complete S''lun''ation of' th~3:l metals. It is therefo 1" '!eeommei:ed that 1 t ba followed rath::r- than the method of separation with nitrio acid, givèn in Technical Pape'! 270.* At line 22, pagi 14, of that paper, bAglnnlng with ~tarm th,~ metals '.'ith dilute¡ nitrio acid," strikE out the rest of the paragraph, and substttutt~ the pro_t cedure g1 ven below. ?lunder and Thuringer.. have developed mnt¡iods for th"i sflparation of palladium from all the platinum metals exoept platinum bj m ,ans of dlmethy- 19lyoxlme. They state that the~ is no action for several hours if an excess of dimeth¡lglyoxime is added to an aqueous solution of ohloroplatinic acid in the cold, alio that only on boiling is the platinum pTecipi ated ¡~d than only PST't of the platinum i srenoved from the sUut1on. They found that palladium 1s p~ecipi tated quati tat! vely in the oold as (CaH 4N40 Pd) which is insoluble tn water, dilute hydroohlorio acid, dilute acetIc aofd or in 50~ ethyl alcbhol. All of their pT'90ipi tations we~p Carl". ied out ~hile the solutions were being heated. This caused a pal"tia~recipltation of the platinum along wi th the

May 1, 1922

By E. P. Youngman

The law now in effect (January 30, 1931) in the Netherlands with respect to the prospecting for and the developing of minerals is regulated by , or based upon , the French Act of April 21 , 1810 , "Concernant les mines , les minières et les carrières ( Bulletin des Lois No. 285) . " A second edition of a compilation ( by Drs . Ccuvee and Ritter ) of the mining legislation of Holland , including this act with other legal requirements , was published in 1928 under the title of "De Nederlandsche Mijnwetgeving , " by H. T. Tjeenk Willink & Zoon , Haarlem. In this abstract reference is made to the Act of 1810 , the Royal Decree of September 18, 1818 , the Mining Act of 1903 , and the Act of June 20 , 1924 .

Aug 1, 1931