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By R. V. Ramani, V. T. Burgos, J. A. McClay

General The underground mining environment has traditionally been hostile and as early mines were developed, coal seams with particularly difficult natural conditions were bypassed in favor of those more easily exploited. Barring the discovery of new and novel sources of energy, the depletion of petroleum and natural gas reserves will eventually force the United States back to the use of coal as its primary energy source. Figure 1 illustrates the trend away from coal which has taken place over the past half century. Today, the demand for coal requires a re-evaluation of all coal seams to meet the needs of the energy market. Difficult mining conditions may result in an increase in the consumption of roof control materials, require greater investment in pumping and ventilation systems, and increase the need for in-depth engineering of far greater safety in production plans. They may also cause delays in mine development and curtail production, all of which combine to drive up the unit production cost. It is reasonable to expect that conditions will continue to deteriorate as current reserves are depleted, thus bringing this factor into greater prominence in the future. For several years now, it has become apparent that in addition to economic objectives, coal companies must set and achieve several concomitant objectives to accomodate society's interest in the conservation of natural resources. Government action to meet this interest has taken the form of two categories of Federal legislation, environmental protection and employee health and safety. The effects of both of these have not been fully evaluated with respect to the total economic picture, although preliminary evidence indicates that an immediate increase in

Jan 1, 1975

By Richard J. Mainiero, Sapko, Marcia L. Harris

Since 1988, there have been thirteen documented incidents in the United States and Canada in which carbon monoxide (CO) is suspected to have migrated through near surface strata into structures or other enclosed spaces as a result of nearby trench blasting or surface mine blasting. From these incidents, there are thirty suspected or medically verified CO poisonings and one fatality associated with these incidents. To better understand the variables contributing to this hazard, the National Institute for Occupational Safety and Health (NIOSH) carried out a small-scale field study to identify key factors that may contribute to the migration of CO through the ground. NIOSH conducted single-hole heavily confined experimental test shots to measure the radial pressure pulse as it propagated through surrounding monitoring holes to determine if a relationship existed between the pressure pulse and resulting CO measurements afterwards. NIOSH also monitored blasts at an airport construction site. Following the detonations, the concentrations of CO, nitric oxide (NO), and nitrogen dioxide (NO2) were monitored for several days in the surrounding satellite holes. The peak CO measurements relative to distances from the shots were compared. Pressure histories and peak particle velocities (PPV) were measured at monitoring boreholes. It was found that the differential pressures recorded within the boreholes give some indication as to the likelihood of CO appearing, whereas the PPV measurements do not seem to be as good an indicator for potential CO migration. In this limited study, changes in barometric pressure had very little influence on removing the trapped detonation products, whereas applying a vacuum to the monitoring holes was effective in reducing the entrapped CO concentration.

By Deno M. Pappas, Christopher Mark, Eric R. Bauer

During 1998-99, groundfall incidents resulted in 27 fatalities and were responsible for over 70% of all deaths in U.S. underground coal mines. To obtain a better understanding of where and why these incidents occurred, a comprehensive analysis of ground fall injuries and fatalities was conducted. The first portion of the study examined various factors associated with roof and rib fall injuries and reportable roof fall noninjuries that occurred during 1995-98. The study found that the room-and-pillar mining method has twice the groundfall incident rate than the longwall method. Mine locations with high groundfall rates seem to correlate to regions where there is a higher concentration of problematic coalbeds. For example, the Illinois Basin has very high groundfall rates, which can be traced back to several key coalbeds-Kentucky No. 13, Herrin/No. 6/Kentucky No. 11, and Springfield No. 5/Kentucky No. 9. High rib fall rates were found in mines located in thick seams. Groundfall rates were found to be 30% to 40% higher during the months of July through September, possibly due to high humidity that may cause the shale mine roof to deteriorate. The second part of the study examined the root causes of failure by reviewing all groundfall fatality reports for 1996-99. Primary and secondary hazard factors were assigned to each groundfall incident. The primaryf actors resulting in these groundfall fatalities were pillar extraction, traveling under unsupported roof, skin failure, construction, longwall faces, intersections, and geologic discontinuities. Defining prominent ground control incident trends and hazards will identify areas where additional study is needed and where innovative solutions need to be developed to reduce these severe occupational hazards.

Jan 10, 2000

Provide a full-scale test facility where the effectiveness of all types of subsidence abatement techniques can be evaluated under controlled conditions. Background Subsidence is ground movement resulting from the collapse of overlying strata into a mine void because of failure of the mine roof, mine floor, or support pillars. The failure may propagate to the surface and be expressed as a depression, cracks, or a sinkhole. The surface expression of such features may be delayed until long after mining has been completed. Subsidence has the potential to affect more land area than any other type of abandoned mine land problem. Subsidence also causes direct damage to real property, with significant financial loss and more importantly, presents a danger to public health, safety, and general welfare. Subsidence-related problems are considered to be one of the most important abandoned mine land issues. Backfilling of mine voids is the most common stabilization method used to abate subsidence and protect surface structures. Backfilling or placement of material is performed by hydraulic flushing or pneumatic stowing, using either in-mine or remote methods. The majority of the past subsidence abatement projects has been performed using remote methods from single or multiple boreholes. Other subsidence abatement techniques arc available. For example, various point support methods are used to protect small areas of the land surface and surface structures, without completely filling the mine void. These may be more appropriate under different conditions. Little documented information is available concerning the capability of the various backfilling methods for completely filling a mine void or providing long-term structural strength. Therefore, the Bureau of Mines developed a laboratory for controlled evaluation of backfilling technologies.

Jan 1, 1991

By C. I. Pierce

Knowledge of the water content of oil-bearing formations is important in petroleum-reservoir evaluation work. Electric logging provides a means for making reliable estimates of water content if resistivity-saturation relationships representative of the formations are available. Relationships can be determined in the laboratory by a number of methods. This report describes and presents results of a laboratory investigation conducted at the Bureau of Mines Appalachian Experiment Station, Morgantown, W. Va. (1) to evaluate an evaporation method of attaining water saturations in sandstone samples when determining resistivity-saturation relationships and (2) to compare saturation exponents derived from data obtained, using different methods of achieving water saturations. A series of tests was conducted to determine the effect of evaporation on salinity distribution within the core specimen. Results of these tests show that a zone of high salinity was set up at the surface of a sample during evaporation and that long periods were required for the sample to reach resistance equilibrium after evaporation had ceased. Equilibrium time ranged from several minutes to several days, depending on the sample size and the technique used. The high-salinity zone was removed from the sample by using auxiliary porous material in capillary contact with the sample surface during evaporation. Salinity determinations and resistance measurements indicate that, at saturations greater than the minimum interstitial values, the mechanism of flow during evaporation was one of moisture migration mainly as a liquid from the interior of the test specimens to their exterior surfaces. The concentration of the contained brine remained essentially unchanged, except for a narrow zone near the evaporating surfaces.

Jan 1, 1958

The first phase of our work for PMSRC on this contract was devoted to a comprehensive and in-depth assessment of electromagnetic (EM) noise measurements and data taken by several contractors for use in the design of operational and emergency mine communications. Pertinent measurements and data of other selected investigators were also included in the evaluation. This assessment treated the measurements and instrumentation used, the data analysis and presentation methods, and the utility of the final results. This phase concluded with the identification of the most useful results and methods, the remaining data gaps, the contractor most qualified to fill these data gaps, and the definition (with PMSRC and this contractor - NBS, National Bureau of Standards) of a follow-on noise measurement program, instrumentation system, and data processing methods tailored to obtain the necessary but missing noise data. A partial bibliography of references related to electromagnetic and seismic noise and propagation in the frequency bands of interest was also compiled during this first phase. The body of this Part of the final report presents a summary of the findings of our EM noise assessment, together with detailed recommendations regarding the new noise measurements to be taken and the instrumentation and data processing methods to be used. This work was done during the latter part of 1971 and the early part of 1972. During subsequent phases of the contract ADL was asked to perform on-going evaluations of the continuing program of electromagnetic (EM) noise and propagation measurements made by Bureau contractors, and to utilize pertinent data from these measurements to make performance estimates for

Jan 1, 1974

By Almon F. Robertson

"INTRODUCTION AND SUMMARYThis is one of a series of reports describing investigations within the Missouri River Basin in Montana conducted by mining engineers of the Bureau of Mines, Minerals Division, Region II. The primary purpose of these investigations is to provide basic information to agencies of the Department of Interior and others concerned with the planning of power and other water developments in the basin. This report contains only such factual data as have been authorized for public distribution. Special precautions have been taken not to reveal any information or data that are considered confidential.The field investigations for this report were made during the summer of 1949. Virtually all known metallic mineral deposits in the county and same nonmetallic (industrial) mineral deposits were investigated. Most of the mines and prospects have been inactive for many years. The old underground workings generally are only partly accessible; many are entirely inaccessible. Most of the mining claims were located many years ago, and a considerable number were patented. Many claims were abandoned; others were relocated. Nimes and ownerships often have changed. Because of such conditions, much of the information on most of the mines and prospects necessarily has been obtained from available Federal and State publications, private geologists' and engineers' reports, and from owners and local residents.Metal mining in Cascade County, Mont., has been confined mainly to the silver-lead-zinc deposits in the Montana (Neihart) and Barker districts in the southeastern part of the county. The Neihart district has yielded by far the greater part of the county's metal output. The mines generally have been operated intermittently, largely because of fluctuating or low silver and base metal prices."

Feb 1, 1951

By K. E. Stanfield

The oil yields of sections of Green River oil shale in Colorado, Utah, and Wyoming are presented as part of a continuing project to determine oil-shale reserves in the United States. Oil-yield logs, based upon analyses obtained from 1945 through 1952, are presented to show the thickness and richness of 202 sections of Green River oil shale. The logs are based on analyses of approximately 20,500 samples, representing 179,000 feet of shale, which were made by the Bureau of Mines, and upon analyses, representing approximately 26,000 feet of shale, which were made by other agencies. The samples consisted of cores from a Bureau of Mines coring program in U. S. Naval Oil-Shale Reserve 1, Garfield County, Colo., and cores, drill cuttings, and channel samples provided by other agencies, chiefly oil companies. Most of the samples of oil shale from Utah and Wyoming were derived from oil-well drilling operations. As a result, the oil-shale sections were widely scattered and were not extensive or reliable enough to be representative of the significant deposits of Green River oil shale in these States. The oil-shale sections for Colorado, however, were more comprehensive, and a number of the sections were used in a previous report as a basis for estimating oil-shale reserves in Colorado. The present report does not give estimates of oil-shale reserves but is limited to presentation of oil-shale analyses that may be used for future reserve estimates. Other sections of Green River oil shale are being analyzed, and the results will be published in subsequent reports.

Jan 1, 1954

By E. Chin

Under the seventh 5-year plan (1986-90), the Chinese Government continued to implement reform and to open the country further to the outside world in order to accelerate the growth of its national economy. As a result of expanded foreign economic exchanges and domestic achievements in education, science and technology, and cultural and public health undertakings, the national economy was strengthened. In 1988, there was impressive growth in the Chinese economy. The gross national product (GNP) grew by 11.2070 reaching $373.4 billion; 2 the national income grew by 11.4070 to $310.9 billion. The major problem in the Chinese economy was the imbalance between high demand and insufficient supply. Chronic shortages resulted in price increases and high inflation, which averaged 19% for China as a whole and about 30% in urban areas. Macroeconomic stability took precedence over market-oriented reform initiative. Because of rapidly growing inflation, the Government re-imposed price controls and rationing in major cities in the fall of 1988. China continued to be a major world producer of minerals, metals, and fuels. Output of the principal commodities continued to rise. The largest in-crease in production was salt which rose 24% in output in 1988; followed by sulfuric acid, 14%; cement, 12%; soda ash, 9%; caustic soda, 7%; and steel, 6%. For fossil fuels, the increase in output of natural gas was 14% in 1988; followed by coal, 3%; and crude oil, 2%. The output of electricity by thermal-fired powerplants rose by 9% while that for hydroelectric power-plants rose 7%. Although China's overall energy output has increased annually since 1980, the growth in demand continued to outstrip the supply.

Jan 1, 1990

By Clarence Hall, S. P. Howell, W. O. SNELLING

The explosives used in coal mines not only occasion accidents such as occur in the use of explosives elsewhere, but they frequently cause widespread disasters by igniting explosive mixtures of mine gas and air and of coal dust and air, or both. In addition, the firing of ex- plosives so shakes the walls and roofs of the mines as to cause falls, with their attendant casualities. Considering the large number of explosives and their wide range in composition and properties, it is obvious that certain of them should prove more suitable for use in coal mines than others. The problem is to determine which explosives are the most suitable for this purpose and the precise conditions under which they may be used with the greatest safety. Of course this problem could be worked out in actual mining, but experimental investigations when accompanying commercial opera- tions are hazardous and slow. To obtain the information sought, in the speediest and most economical manner, laboratory methods must be resorted to. The adoption of such methods began about 30 years ago with experiments in an iron gallery mounted on wheels, at Zwickau, Germany. This laboratory method of attacking the prob- lem has so commended itself that it has not only been repeated else- where in Germany but has at intervals been officially adopted, with many modifications and additions, by the Governments of Belgium, Austria, France, and Great Britain. Such was the status of coal-mine investigations in Europe when in 1904, an organization in the Geological Survey, which in 1907 be- came the technologic branch, was created to investigate the mineral- fuel resources of this country. At that time no division of the Na- tional Government had official cognizance of conditions existing in our mines, but through its system of collecting fuels for tests the technologic branch was forced to recognize that coal-mine accidents are a factor that must be reckoned with in determining the extent and availability of our mineral-fuel resources. This became so apparent, and it was so obviously a function of this branch to make a systematic research as to the cause and prevention of such acci- dents, that in July, 1907, experts were appointed especially to deal with this problem. As a result, not only was Bulletin 333, on Coal- Mine Accidents: Their Causes and Prevention, prepared and pub- lished, but through personal inspection of foreign testing stations, and a study of their reports and the critiques of their methods and operations, definite plans for the establishment of such a testing station in this country were formulated. In the latter part of 1907, four grave disasters occurred in close succession consequent on explosions in the Monongah mines in West Virginia, where 368 men were killed, the Darr mine in Pennsyl- vania, where 160 were killed, the Naomi mine in Pennsylvania, where 34 were killed, and the Yolande mine in Alabama, where 61 were killed. These frightful disasters so quickened the public con- science, and so plainly demonstrated that both humanitarian and economic needs demanded that steps be taken to prevent the re- currence of such accidents, that in 1908 Congress made a special appropriation for an investigation as to the "causes of mine ex- plosions." A similar appropriation was made in the following year. By act of May 16, 1910, the Bureau of Mines was created "to make diligent investigation of the methods of mining, especially in relation to the safety of miners, the use of explosives, the prevention of accidents," and other matters relating to mining. Therefore, these investigations are at present conducted in obedience to an organic act instead of being dependent solely upon special appropriations. The first appropriation became available July 1, 1908. Through the courtesy of the War Department a portion of the grounds and buildings of the arsenal at Pittsburgh was granted for the use of the technologic branch of the United States Geological Survey. Work was immediately begun in procuring and erecting the necessary instru- ments and appliances for carrying out the desired tests and inves- tigations and in adapting the existing buildings or in erecting new structures to contain the apparatus. The Pittsburgh testing station was officially opened and regular work was commenced on December 3, 1908, the apparatus and appliances having been tested, the force drilled in their use, and the equipment and methods inspected and passed upon by foreign experts.

Jan 1, 1912

By Frank S. Wartman

"The experimental flotation work described in this paper was undertaken to test the conclusions derived from a previous microscopic and chemical study of several samples of converter slag. That study3 resulted in the conclusion that approximately 90 per cent of the copper content of a converter slag wad in either the sulphide or metallic form, and that if the slag were cooled slowly the copper-bearing material would be in particles of such size that they would be freed from silicate and magnetite grains by grinding the slag to pass a 150-mesh sieve. If this were true, it should be possible to separate the copper-bearing grains from slowly cooled, converter slag by the flotation process.Many attempts, of which the author has seen no published account, have been made to treat slags, especially converter slags, by flotation. In every case these trials have been made with chilled slags, in which, as shown in the preceding report, the copper-bearing material is top finely disseminated, to be freed by any reasonable degree of grinding.The flotation tests described in this paper have shown that it is possible to recover by flotation about 30 per cent of the copper content of a converter slag containing 3 per cent copper and to obtain flotation concentrates which have a copper content of 35 per cent.Acknowledgment is made to G. L. Oldright, supervising engineer of the section of nonferrous metallurgy, U. S. Bureau of Mines, for valuable assistance and direction; to W. A. Sloan for chemical analyses; and to Alfred P. Towne for assistance in experimental manipulation."

Apr 1, 1931

By E. K. Stanek

This report contains results of two major efforts related to electrical transients on mine electrical power systems. The first area concerns the use of digital computers to model mine electrical power systems and predict transients or duplicate field recordings of transients. Two existing general purpose circuit analysis programs were used. The first was the TRW Engineering System Simulator or TESS. The second was Electronic Circuit Analysis Program or ECAP. TESS proved to be superior to ECAP in several important characteristics, including system size limitations and modeling nonlinear elements. The second major topic covered in this report is the evaluation of commercially available surge suppression devices. These devices were found to be quite acceptable and guidelines for the selection and placement of surge suppressors were included. The final important item is a listing of the worst-case transients, from a design point of view, for ac and de utilization systems and ac distribution systems.

Jan 1, 1979

By Jeffrey Shawn Peterson

The testing procedures of the u.s. Mine Safety and Health Administration specify that intrinsic safety acceptance tests be conducted using a standard tungsten-cadmium electrode configuration in the break-flash apparatus. However, in realistic mining environments, other materials may be more likely sources of sparking. Information defining the probability of spark ignition between common materials such as aluminum, brass, copper, lead, tin, cold-rolled steel, and stainless steel is of more practical value in determining ignition hazards. The U.S. Bureau of Mines has completed an investigation of the influence of material on the ignition probability using the breakflash apparatus. By comparing ignition currents or ignition voltages corresponding to a probability of one ignition per thousand sparks to those found previously for cadmium, a margin of safety may be estimated for each material. This report presents the results of an investigation into the influence of disk electrode material on the probability of ignition.

Jan 1, 2010

The Determination of Sound Exposures (DOSES) software was developed by the National Institute for Occupational Safety and Health (NIOSH) specifically for use by mine management and safety personnel. DOSES simplifies the record-keeping and analysis associated with time-motion studies and worker noise exposures, making it easier to identify and solve noise problems. The software relies on a time-motion study that profiles the worker?s daily activities. At the same time, noise measurements are collected with a dosimeter or sound level meter (SLM). Observations about the worker?s location and tasks or other activities are recorded along with times and durations so they can later be matched up with the noise data. After the completion of a time-motion study of the worker?s daily tasks and locations (possible noise sources), which measures the worker?s noise exposures during the recorded events, the information is entered into DOSES. The program then displays information about the worker?s accumulated noise dose over time.

Jan 1, 2009

By Michael R. Yenchek

The U.S. Bureau of Mines investigated the performance of portable power cables under transient conditions. This research had a twofold purpose: (1) to define the thermal characteristics of electrically overloaded trailing cables, and (2) to conceptualize electrical protection for cables that allows maximum cable efficiency without diminishing electrical safety in underground mines. Several tasks were undertaken in support of these goals during the 3-year research effort. Overload tests ranging from 2 to 12 times rated ampacity were conducted in the Bureau's Mine Electrical Laboratory. Two thermal models of energized type G-GC trailing cables were constructed, one based on thermodynamic theory and the other using empirical data from previous Bureau load tests. The empirical model was then incorporated into an interactive computer program that can assist designers and approvers of mining machines in selecting the appropriate size trailing cable. This program can be the basis for a cable protection system that ensures that cables are not the source of fires, ignitions, burns, or explosions underground.

Jan 1, 2010

By G. T. Krempasky

In an attempt to develop a suitable precast concrete support for underground use, two different models (1955 and 1958) of a five-piece concrete set were designed, fabricated, and tested under adverse loading conditions. Model 1955 was designed to withstand an ultimate, uniformly distributed, vertical load equivalent to what a three-piece, 12- by 12-inch wood set of intermediate-grade Douglas fir would withstand. A design figure of 138,000 pounds for the vertical load was used on both the 1955 and 1958 models. In addition, the 1958 model was designed to withstand a uniform horizontal load of 7,000 pounds per foot and additional concentrated-point loading. The step- by-step design of each model is presented in the appendixes. A series of five destruction tests was conducted underground on the 1955 model, and results of the tests showed that the type and method of blocking were of major significance.

Jan 1, 1963

By Lloyd Williams

A vertical air shaft in the Birmingham, Ala., iron district was sunk with a circular cross section and lined with concrete at a relatively low cost to provide needed ventilation for an iron-ore mine. The method of sinking the shaft is described, and the costs are stated in mar-hours with a descriptive list of equipment and a statement on the size and use of temporary buildings. Preparation began May 2, 1955, and the shaft was completed at a depth of [680] feet by September 22, 1956. By October 1956, all temporary building and [aft]-sinking equipment had been removed. The total direct-labor cost for the operation, including preparation and dismantling, was 50,700 man-hours, or 30.2 man-hours per foot. Total rock and dirt removed amounted to 17,523 cubic yards (in place), and the shaft lining required 4,635 cubic yards of concrete to form a circular air shaft with an inside diameter of 16 feet.

Jan 1, 1960

By Jack I. Paige

In this Bureau of Mines study, two fluidized-bed reactors were designed, built, and operated, one as a sorber for S02 and the other as a contactor for the regeneration of the sulfur-laden alkalized alumina. The target of 90 percent removal of S02 from a flue gas stream containing 0.3 percent S02 was attained by using a sorbent feed of 10-15 grams per minute into a 5-inch bed depth of alkalized alumina. The sorption unit was operated at about 330° C. Complete regeneration of the laden alkalized alumina containing 5 to 10 percent sulfur was accomplished in approximately 1/2 hour. An excess of reformed propane at about 730° C was the regenerating gas. Attrition losses, a major problem with this sorbent, ranged from 0.9 to 7.9 percent of the inventory. Data from these tests demonstrate, within experimental error, the validity of equations developed from short-term, thin-bed tests related to sorption and regeneration rates.

Jan 1, 1970

By Joseph M. Pugliese

The Bureau of Mines through its contract research program recently analyzed the mining and environmental requirements in the premining stage for copper mining in the northern highland of Wisconsin. The Critical-Path-Method (CPM) was used in this research. However, a step-by-step derivation of the CPM Diagram was beyond the scope of this effort. The Bureau of Mines objective now is to show, step by step, how the original hand-computed CPM Diagram was constructed. The streamlining (restructuring) of this diagram from the original effort is also summarized. The critical path time (longest time) through the original CPM Diagram was 25.12 yr, excluding public liaison effort. This diagram showed the involvement of the regulatory agency, mining applicant and public in the premining stage. Analysis of this diagram produced a streamlined version which reduced the critical path time by nearly 7 yr. The CPM construction methodology offered here may be applied to mine planning for any mining operation.

Jan 1, 1983

By Thomas M. Barczak

This Bureau of Mines report describes research on developing technology to utilize shields as roof load monitors. Three-dimensional equations of static quilibrium are presented for a generic two-legged long-wall shield. The equations are presented in the most general form, assuming a force and moment vector at each reaction by rigid-body analysis of the shield mechanics. The resulting system of equations was found to be indeterminate to a very high degree. A three-dimensional solution to measurement of the resultant reaction on the canopy by the strata activity and shield response required the elimination of several forces or moments that were thought to be nonparticipating or to not significantly affect overall shield mechanics. Required measurements for solution of the equilibrium equations were leg, canopy capsule, and lemniscate link forces. Two-dimensional analysis, which considered forces acting only in the roof-to-floor and face-to-waste plane, was also provided by reduction of the three-dimensional equations~

Jan 1, 1987