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By D. Harrington

Misuse of explosives and heedless disregard of well-known safety rules covering the use of commercial explosives cause many avoidable accidents resulting in the death or maiming of men who can ill be spared by already undermanned industry at present, and who cannot be spared by their families at any tire. Blasting accidents, when not fatal, are usually serious; the past and present needless loss of life and maiming of men from this cause are appalling and types of waste that can and should be virtually eliminated. Dead, crippled, and maimed men are distinct losses to society as well as to industry, and compensation payments for such accidents represent only a portion of the financial loss, because the value of their lost potential production can only be surmised. By their very nature, explosives are dangerous to handle, otherwise they would not perform the services for which they are used; all men on a blasting crew are subjected to the results of the carelessness of any one member, and in many instances the misuse of explosives by one person has killed scores of fellow workers. Inexperienced men should be assigned to blasting operations only under the close supervision of men well-experienced in the work and familiar with its inherent hazards. Men should be selected for blasting crews that are known to be careful, willing to follow instructions, cool-headed, and unlikely to become excited in an emergency; they should be instructed in the safe handling of explosives in accordance with the safety rules established by the explosives -manufacturing companies or the safety codes of the various industrial organizations. Unfortunately, American industry has never adopted a uniform code for the safe handling of explosives; however, many mining companies have made rules that will eliminate most unsafe practices if established safe procedure is followed carefully. The Bureau of Mines has issued numerous pamphlets giving information on the causes of accidents due to explosives in the mining industry and indicating the ways in which a good proportion of those accidents can be avoided.

Jan 1, 1943

By H. R. Hardy Jr., E. J. Kimble Jr., H. W. Shen

"The primary objective of this research project is to study the character of the bit-coal interaction during coal cutting and its influence on the size and shape distributions of the generated dust. Secondary objectives include the investigation of the acoustic emission technique as an indirect method for coal dust characterization and remote bit wear monitoring. The results of the project will be useful in developing efficient coal cutting techniques which significantly reduce the harmful coal dust components, and in providing methods for remote monitoring of bit condition and associated coal dust character. This paper will outline recent experiments carried out on coal under uniaxial compression, linear single-bit cutting, and cutting using a laboratory-scale, single-bit shearer. During the experiments acoustic emission and a variety of other mechanical parameters were monitored. · A commercially available artificial intelligence computer package, namely: JCEPAK (Intelligent Classifier Engineering Package), has been utilized to provide a powerful and objective means for AE waveform analysis. This program is able to evaluate a number of features of each AE event and to make objective comparisons between AE signals associated with different loading or cutting parameters. Finally, the paper will discuss the results obtained from a variety of coal breakage tests.INTRODUCTIONStudies to date clearly indicate that the reduction of the severity, and eventual elimination, of Coal Workers' Pneumoconiosis (CWP) depends on gaining fundamental understanding in a number of major areas. These include dust generation and entrainment, transportation, suppression, medical effects of dust and possible treatment. At present a project is underway by the authors to investigate the character of the bit-coal interaction during coal cutting and its influence on the size and shape distributions of the generated dust. An important aspect of this on-going project is the development of acoustic emission (AE) criteria which will make it possible to carry out remote monitoring of coal cutting operations. Suitable on-line analysis of monitored AE data would allow engineers to evaluate factors such as shearer bit condition and cutting efficiency, and to quantify the particle size and shape distribution of the generated dust. The on-going AE studies are fundamental in form and were undertaken to evaluate the general feasibility of AE monitoring techniques using simplified coal cutting procedures. This paper will outline recent experiments on coal under uniaxial compression, linear single-bit cutting, and cutting using a laboratory-scale, single-bit shearer. Additional information on these studies are presented elsewhere [4]."

Dec 1, 1996

By A. Wahab Khair, Nagendra P. Reddy

"This paper presents an analysis of preliminary tests on the effect of in-situ and operating parameters on fragmentation of coal using a specially designed unique automated rotary coal cutting simulator (ARCCS). In these tests coal blocks with an approximate dimension of 18 in. x 15 in. x 6 in. (45.7 cm x 38.l cm x 15.2 cm) were first. subjected to confining pressures, equivalent to in-situ conditions. Such. blocks were then cut by the cutting head of the ARCCS, thus simulating the action of the continuous miner in underground coal mining. During the tests under a particular set of in-situ and operating parameters a number of other parameters such as 1) penetration of bit into coal, 2) penetration resistance (thrust and cutting pressures), 3) rotating velocity of cutting head, and 4) acoustic emission activity in the coal block were monitored. After each cutting cycle the fractured surfaces were photographed and a velocity survey was conducted by using a sonic technique. At the end of each experiment the cutting paths of the bits in coal were photographed using an optical microscope with a camera attached to it. Furthermore, the coal fragments were collected in bags using a vacuum cleaner. These fragments were then sieved for size distribution analysis. The results of the preliminary tests indicated that underground coal cutting can be simulated in the laboratory and the effects of the important parameters, i.e. operating and in-situ parameters, can be studied successfully. INTRODUCTIONThe continuous-mining machines which were introduced in the 1950's now account for more than half the production of coal from underground mines. Unfortunately, these continuous miners, which were designed for increased productivity, have also increased the concentration of respirable dust in mines. As a result, the Federal Coal Mine Health and Safety Act of 1969 was enacted to enforce on the coal operators that the airborne respirable dust not exceed 2 mg/m3, and was intended to reduce the incidence of coal workers pneumoconiosis. This plus the other aspects of the legislation and the subsequent monitoring and enforcement by MSHA made it very imperative that the coal operators provide a relatively healthier and safer working environment for the coal miners. Since 1970, the Federal government has paid over 11.7 billion dollars to more than 470,000 miners with coal workers pneumoconiosis and their survivors (1). These regulations, coupled with the assessment of the continuing burden on miners, the mining industry and taxpayers appear to have provided an impetus for the mining .community towards comprehending the different parameters that influence dust generation and entrainment."

Jun 1, 1988

By M. M. Barr

Rapid expansion of the titanium-metal industry focused attention upon ilmenite as a possible substitute for the more expensive and less abundant rutile in producing titanium tetrachloride. Most of the rutile available for this use is imported. Preliminary studies were undertaken to determine the chlorination characteristics of high-titanium slags produced by electric-arc furnace smelting of alluvial Idaho ilmenite at the Federal Bureau of Mines Northwest Electrodevelopment Experiment Station, Albany, Oreg. Low silicon, calcium, and aluminum contents of the slags enhanced their potential value for chlorination.

Jan 1, 1958

By Stanton L. Tainter

"As an adjunct to its minerals-investigation program, the Bureau of Mines has developed a number of operating devices and techniques worthy of note. This paper, prepared under the supervision of J. H. Hedges, chief, Tucson Branch Mining Division, and under the general supervision of Lowell B. Moon, chief, Mining Division, reports upon certain methods devised to overcome difficulties encountered in cementing of diamond-drill holes at a Bureau of Mines project at Christmas, Gila County, Ariz.Pressure grouting was employed to recondition a caved hole it was desired to reopen and deepen. The hole, which had boon stopped 7 months previously at a depth of 488 feet, was caved below 449 feet in a contact zone of claylike, altered diorite and crumbly metamorphosed limestone. As other means of obtaining moderate pressure were not available, carbon dioxide gas, drawn from tank of liquid carbon dioxide through a pressure reducing and regulating valve, was used. The hole was reopened successfully with 12 grouting jobs.Another hole, where cawing from several water-bearing fractures between 202 and 232 feet gave trouble, was successfully cemented by the use of a grouting plug. An attempt to cement through the rods had failed, owing probably to agitation caused by water currents. Pressure grouting through the caning set above the cave could not be need, because water was forced up outside the casing when pressure was applied. The problem was solved by using a wooden plug 1-13/16 inches in diameter, which, when soaked in water, expanded to a tight fit in an AX hole. A hole was drilled through the plug, and a rubber flap valve was nailed to the lower end. In the upper end of the plug the hole was enlarged to fit loosely over an EX rod coupling finished smooth. The plug was lowered on the end of the drill rods to a point about 10 feet above the cave, where it was allowed to expand tightly to the hole. Cement grout was then pumped through the rods, and the rods were removed from the hole. After allowing time for the cement to set, the wooden plug was chopped out and drilling van resumed.Over 300 tests were made to determine the type of cement most suitable for use on the Christmas job, and the effect of cement-water ratio, temperature, and various admixtures on workability, setting time, and strength. The results of these tests, described in detail in the body of this report, indicate the desirability of thoroughly testing available cements when it is necessary to drill holes under difficult conditions that may cause failure.When it became desirable to reopen and deepen a caved drill hole, it was considered easiest to recondition the hole by pressure grouting, As other mans for obtaining moderate pressure were not available, a method utilizing carbon dioxide gas was employed. The hole was reconditioned successfully with 12 grouting jobs."

Nov 1, 1949

By W. E. Anable

The Bureau of Mines studied the purification of commercially available yttrium by melting it in a 100-kw electron-beam furnace. Button-scale melts were made to determine the ultimate purification that could be attained by melting yttrium at 1,733° to 1,770° C at low pressure (0.05 to 0.1 micron) for 1 to 120 minutes. In addition, numerous melts were made to study the effect of doping yttrium with carbon, 17 selected metallic additions, and 3 compounds. Except for nickel and zirconium, the metallic impurities in yttrium were lowered significantly on extended treatment; silicon was lowered only slightly. The nonmetallic impurities} oxygen, nitrogen, and carbon, were not lowered except on short exposures. In isolated instances, the oxygen content was lowered from 5,860 ppm to about 5,000 ppm. In most instances the carbon con-tent was lowered from 545 to about 220 ppm in 20 minutes and then increased again. It was concluded that yttrium cannot be purified by direct heating or by the doping technique employed.

Jan 1, 1965

By T. T. Read, T. L. Joseph, F. H. Royster

In a preliminary study of the beneficiation of iron ores conducted by the Bureau of Mines, one of the authors (T. T. Read) found it necessary to ascertain, if possible, how much effect a decrease in the silica content of an iron ore has upon the cost of making pig iron from the ore. In the beneficiation of iron ores the most important impurity to be removed is usually silica, and the amount that can be expended on a beneficiation process to reduce the silica content of the ore is obviously determined by the amount of increase in the value of the ore after beneficiation. The price that can actually be obtained for a beneficiated ore is, of course, a matter of negotiation between the seller and the buyer, but since the relative value of different grades of iron ore must be chiefly based upon the cost of making pig iron from them, an approximation as to the effect which decrease in the silica content of ore has upon the cost of snaking pig iron is an important guide in estimating what probable average gain will result from subjecting an ore to a beneficiation process. A search of the literature failed to reveal any detailed statement on this important topic, but fortunately the data are at hand to permit making an approximate calculation of the probable effect. For the purpose of the calculation assume three iron ores with the following composition (natural):

Jan 1, 1924

By Changwoo Lee, Jan M. Mutmansky

"This paper results from the research at The Pennsylvania State University into establishment of standard procedures for characterization of respirable coal dust performed by the Generic Mineral Technology Center for Respirable Dust and supported by the U.S. Bureau of Mines and the Mining and Mineral Resources Research Institute at The Pennsylvania State University. The research performed within this particular project is oriented primarily toward standard methods of sampling and characterizing respirable coal mine dust underground so that the chemical, physical, and morphological characteristics are known and can be related to the incidence of coal workers' pneumoconiosis (CWP) in Pennsylvania.The research was initiated by con¬ducting a search of the literature to determine what coal and geologic variables may be related to CWP. The effects of coal rank, free silica content, the mass of respirable dust, and the level of trace elements were the major variables studied. It seems to be evident that the free silica content, the rank of coal, and the mass of respirable dust are the major concerns in defining the causes of CWP. However, based on the literature survey, the authors have concluded that verification of the causes of CWP is a multivariate problem and must be analyzed in an appropriate statistical manner.The results of a multivariate analysis of ten trace elements recorded on Pennsylvania coals are presented. Five of these trace elements were found to be of use in differentiating one coalfield from the others. Of these five elements, chromium and zirconium showed a strong positive correlation with the rank of coal while strontium showed a negative correlation.The design of the field sampling work and its application in future research is the final topic discussed. The sampling plan is oriented toward continuous miner sections with eight-stage impactors as the collection equipment. All of the field work will be conducted in the coal measures of the Allegheny Formation and above with both dust and channel samples being collected in the same mines.Coal workers' pneumoconiosis has been an important topic of concern to miners, mining engineers, and epidemiologists for decades. The general cause of the dis¬ease, the inhalation of coal mine dust, is well known, but the specific coal and geologic variables that affect the incidence and severity of the disease are still subject to debate and study. The primary objective of this study is to identify those variables of Pennsylvania coals that contribute to the CWP problem. To accomplish this task, a field sampling program is to be conducted to relate the characteristics of the coal dust, the coal seam properties, and the geologic variables to the occurrence of CWP.The first year of this study has been involved with both a literature review and experimental work oriented toward identification of causal variables related to CWP. The results of this work are presented here along with plans for implementation of the findings in future research.The previous studies of CWP causal variables have been conducted by scientists, engineers, and medical personnel. Many different types of studies have been performed with emphasis on interpreting the effects of dust mass concentration, mineralogy of the coal, the rank of the coal, and trace element concentrations upon the incidence of CWP in various coalfields. Most of the research has been conducted during the last two decades, with the British Isles, West Germany, and the United States being the primary countries involved.The review of the literature was conducted to determine which variables are likely to warrant further study in Pennsylvania. Previous research studies have related CWP to free silica and other mineral content, the rank of coal, the mass of dust in the working place, and the trace elements in the coal and lung dust. In the following sections, each of these topics will be discussed and analyzed."

Jan 1, 1988

By G. L. Hundley

An anhydrous chlorination process has been developed by the Bureau of Mines for the production of copper, ferric oxide, and sulfur from chalcopyrite. The first part of the process is a chlorination step in which elemental sulfur and a mixture of iron-copper chlorides are produced. This paper describes the second step of the process in which the copper and iron chlorides are reacted with oxygen to selectively convert the iron chloride to ferric oxide and chlorine leaving the copper in the chloride form. The chlorides are pulverized and dropped countercurrent to a flow of oxygen in a vertical 20-cm-diam. reactor at 800° C. By leaching with brine, the copper chloride may be separated from the insoluble iron oxide and reduced to copper powder by electrowinning. It has been demonstrated that 70 to 80 pct of the iron can be converted to oxide in a single-stage operation with a chlorine content in the offgas of 80 pct. After removal of the oxygen, this chlorine could be recycled to the chlorination step. A two-stage operation will convert 98 to 99 pct of the iron in the mixture to insoluble oxides. The offgas from the second stage contains 70 pct chlorine.

Jan 1, 1974

By F. S. Crawford

During the course of a study of the safety organizations of the various iron mining companies in the Lake Superior district considerable in¬ formation regarding the methods of safety inspection in use was obtained which may be of value to other companies beginning safety work or contemplat¬ ing changes in their methods. A short description of the safety-inspection methods of eleven of these companies is given in this paper, and in the appendix are illustrated a number of forms used for safety inspections by several of the companies. Most of the companies whose methods are described use few forms for formal inspection. The one long form (10) attached which is used for a general in¬ spection by the safety inspector appears to present a good method for enabling the inspector to check all branches of his inspection and to assure himself that everything has been covered. All names of companies have been deleted from this paper and from the forms because the object is to disseminate information of constructive value rather than to point out the methods of particular companies by name.

Aug 1, 1931

By S. L. Windes

For a number of years, the Bureau of Mines conducted tests on various types of structures to determine the effect of seismic vibrations emanating from quarry blasting in an effort to determine an index of damage . Associated with these tests , occasional records were made of the characteristics of. the air blast or concussion from the explosions . Although the importance of the air - blast problem was recognized , the equipment was not designed for air -blast measurements , nor was the early research program concerned with the problem . After the ground - vibration tests had been completed , attention was turned to study of the air blast and its effect . The air - blast problem in reference to quarry and mine blasting may be divided conveniently into three phases : (1 ) Determination of the fundamental characteristics of the air blast , such as the pressure - time relationship , speed of propagation, attenuation , and the like ; ( 2) effect of blasting conditions on these air -blast characteristics ; and ( 3) determination of the conditions necessary for damage to structures . The initial step was the development of microphones suitable for recording the anticipated blast pressures. Such microphones were designed and built during 1940 , and described in technical detail for publication ( 2)3/. Briefly, the microphone adopted was a small, plate - diaphragm condenser type . The recording was through special transducer amplifiers with low -frequency response to zero cycles per second and a Duddell - type oscillograph of special design .

Feb 1, 1942

By Kenneth L. Cashdollar

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRL Lake Lynn Experimental Mine and after laboratory explosions in the PRL 20-L chamber and the Fike 1-m3 chamber. The dusts studied included both high and low volatile bituminous coals. Low temperature ashing for 24 hr at 515°C was used to measure the incombustible content of the dust before and after the explosions. The data showed that the post-explosion incombustible content was always as high as or higher than the initial incombustible content. The MSHA alcohol coking test-was used to determine the amount of coked dust in the post-explosion samples. The results showed that almost all coal dust that was suspended within the explosion flame produced significant amounts of coke. Measurements of floor dust concentrations after LLEM explosions were compared to the initial dust loadings to determine the transport distance of dust during an explosion. All of these data will be useful in future forensic investigations of accidental dust explosions in coal mines or elsewhere. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health or the Mine Safety and Health Administration.

Jan 1, 2006

By Welby G. Courtney

The Bureau of Mines conducted an exploratory field survey to determine the amount of airborne coal dust, the size distribution of the dust, and the rate of dust deposition in coal mine airways. The survey was taken at eight underground locations in operating coal mines. The rate of dust deposition in the airways depended upon the concentration of air-borne dust and decreased exponentially with distance from the dust source. The rate was seemingly independent of the size of the airborne dust particles. The rate of deposition, along a return, for the coal dust from a fade being mined with a continuous mining machine closely matched the rate for the rock dust from a trickle duster. A sample rock-dusting schedule for that return is presented; that is, the trickle duster should be operated for 3-112 hours after every five shifts to protect the average deposit of new float coal dust in the return, but operation after every three shifts is preferred, to protect an occasional heavier deposit.

Jan 1, 1982

By E. D. Eastman

"The factors that determine the efficiency of reduction of iron oxides by gaseous reducing agents may be considered in two classes; those which effect the equilibrium between the reacting substances end their products, and those which affect the rete of reaction. Both sets are of prectical importance, the former as influencing the maximum possible efficiency and the latter as determining what fraction of the maximum yield may be readily or profitably obtained. In addition, the thermal changes attending the reduction greatly affect the chance of successful industrial application of any such process, and knowledge of them is necessary for the intelligent design of apparatus and control of the reaction. Some aspects of each of these three divisions of the problem are discussed below.I. The Maximum Reducing Power of Fuel Gases on the Oxides of IronsThe gases that heve been considered specifically in this work are coal gas, water gas and producer gas, typical analyses” of which are given in Table 1 Of the various hydrocarbons represented in Table 1, (several being grouped or averaged as C2R4), methane is the only gas assumed to be capable of existence at appreciable pressures under the conditions of interest here. The equilibria in the several systems which may ensue when one of the above gases is allowed to react with the iron oxides, may therefore be represented in the most general case by equations of the type of the following arbitrarily chosen ones:"

Jun 1, 1923

By L. Kaufman

Fifteen boride composites were synthesized by hot pressing and evaluated by physical and incendivity testing as non-sparking tool materials. The incendivity tests, conducted at the U. S. Bureau of Mines, Albany Research Center, compared the boride compo-sites with standard cobalt-bonded tungsten carbide material used for coal cutter bits. Two titanium diboride composites and two zirconium diboride composites out-performed cobalt-bonded tungsten carbide in wear resistance and reduced tendency to cause ignitions. However, three of these candidates exhibited undesirable chipping. The remaining candidate, a TiB2-(Ni, Cu) composite, did not chip, nor did it cause ignitions at levels where cobalt-bonded tungsten carbide tools caused ignitions in the incendivity tests. Thus, this material appears to be a logical candidate for further development.

Jan 1, 1973

By Robert E. Barieau

General expressions for evaluating practically all the thermodynamic properties of a fluid from a single equation of state are derived. Most of the formulas are expressed in terms of the compressibility factor, with this factor being an explicit function of the temperature and the molal density. Similar expressions are given using reduced variables.

Jan 1, 1967

By Hillary W. St. Clair

This report gives the results of an experimental study of the progressive changes that occur in particle size and size distribution when a homogeneous and isotropic mineral is subjected to crushing by impact. The mineral used in the study was uniformly sized quartz, which was crushed in a simple drop¬-weight machine that applied impact energy up to about 100 kg-cm per g. Screen analyses of the crushed products were analyzed by the method of moments to determine the mean size, variance, skewness, and kurtosis. Analysis of the data from these experiments shows that the mean size of the crushed product is a function of the energy input and the initial size. The size distribution is functionally related to the degree of size reduction. As the mean particle size is decreased, at first there is a corresponding increase in the variance and decrease in the skewness, But, as size reduction is carried further, each tends eventually to approach a steady value, and the form of the size distribution becomes stable.

Jan 1, 1972

By Kevin Ashley

Because toxicities may differ for Cr(VI) compounds of varying solubility, some countries and organizations have promulgated different occupational exposure limits (OELs) for soluble and insoluble hexavalent chromium (Cr(VI)) compounds, and analytical methods are needed to determine these species in workplace air samples. To address this need, international standard methods ASTM D6832 and ISO 16740 have been published that describe sequential extraction techniques for soluble and insoluble Cr(VI) in samples collected from occupational settings. However, no published performance data were previously available for these Cr(VI) sequential extraction procedures. In this work, the sequential extraction methods outlined in the relevant international standards were investigated. The procedures tested involved the use of either deionized water or an ammonium sulfate/ ammonium hydroxide buffer solution to target soluble Cr(VI) species. This was followed by extraction in a sodium carbonate/sodium hydroxide buffer solution to dissolve insoluble Cr(VI) compounds. Three-step sequential extraction with (1) water, (2) sulfate buffer and (3) carbonate buffer was also investigated. Sequential extractions were carried out on spiked samples of soluble, sparingly soluble and insoluble Cr(VI) compounds, and analyses were then generally carried out by using the diphenylcarbazide method. Similar experiments were performed on paint pigment samples and on airborne particulate ?lter samples collected from stainless steel welding. Potential interferences from soluble and insoluble Cr(III) compounds, as well as from Fe(II), were investigated. Interferences from Cr(III) species were generally absent, while the presence of Fe(II) resulted in low Cr(VI) recoveries. Two-step sequential extraction of spiked samples with (?rst) either water or sulfate buffer, and then carbonate buffer, yielded quantitative recoveries of soluble Cr(VI) and insoluble Cr(VI), respectively. Three-step sequential extraction gave excessively high recoveries of soluble Cr(VI), low recoveries of sparingly soluble Cr(VI), and quantitative recoveries of insoluble Cr(VI). Experiments on paint pigment samples using two-step extraction with water and carbonate buffer yielded varying percentages of relative fractions of soluble and insoluble Cr(VI). Sequential extractions of stainless steel welding fume air ?lter samples demonstrated the predominance of soluble Cr(VI) compounds in such samples. The performance data obtained in this work support the Cr(VI) sequential extraction procedures described in the international standards.

Jan 1, 2009

By R. L. Grayson, S. S. Peng

"Abstract. Sampling of respirable dust and analyses of samples have been partially completed for a longwall panel. Physical and compositional properties which have been characterized include:l. Respirable mass concentration, 2. Mineral composition,3. Particle size distribution by mineral,4. Particle shape distribution by mineral,5. Particle angularity distribution by mineral, and6. Respirable size distribution.Analytical techniques used in the characterization of samples are described, and results are reported with emphasis placed on relationships between the various characteristics and worker locations. Details of existing mining conditions, equipment arrangements, dust control methods and operating system parameters are presented.INTRODUCTIONThrough the work of many researchers worldwide, the health of coal miners in modern societies is now protected from dangerous exposure to respirable coal mine dust. A vast amount of research culminated in the exposure-response model of Jacobsen, et al. (1971) whi3h has been used to establish the 2mg/m exposure limit in the United States. According to the model, exposure to respirable dust for 35 years at this level or less would prevent the occurrence of a clinically significant case of coal workers' pneumoconiosis (CWP). The exposure limit, of course, must be adjusted whenever greater than five percent free silica exists in the respirable dust.The Jacobsen model was built around a mass concentration exposure, which showed the highest correlation with incidence and progression of CWP. As Morgan; et al. (1973) noted, howev.er, the quantity of respirable dust inhaled is not the only significant factor. It is noted that although mass of respirable dust correlates highest with the incidence of CWP, it is not a causal factor. Indeed, the insidious processes causing the disease occur on the cell-particle scale, requiring microscopic investigation."

Mar 1, 1989

By William C. McLaughlin

In the deep vein mines of the Coeur d'Alene mining district, rock bursts are a potential hazard to the mine structure and underground personnel. Damage repair costs are estimated by one company to exceed $1 per ton of ore mined. The Bureau of Mines, in cooperation with the mining companies, has conducted research intermittently over the past 10 years to help reduce bursts. Onsite inspections of major rock bursts were conducted, and reports were submitted to mine management; these included the geology and geometry of the affected area. The paper discusses the development and improvement of microseismic and surface monitoring equipment. The underground microseismic network, when operated on a regular basis and the results plotted daily, is capable of detecting stress concentration in certain areas. The surface seismographs record rock bursts, blasts, earthquakes, etc., throughout the district and show approximate location, time, and relative intensity of the event.

Jan 1, 1976