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By R. Karl Zipf

The sudden, violent collapse of large areas of room-and-pillar mines poses a special hazard for miners and mine operators. This type of failure, termed a 'cascading pillar failure' (CPF), occurs when one pillar in a mine layout fails, transferring its load to neighbouring pillars, which causes them to fail, and so forth. Recent examples of this kind of failure in coal, metal and nonmetal mines in the U.S.A. are documented. Mining engineers can limit the danger presented by these failures through improved mine design practices. Whether failure occurs in a slow, non-violent manner or in a rapid, violent manner is governed by the local mine stiffness stability criterion. This stability criterion is used as the basis for three design approaches to control cascading pillar failure in room-and-pillar mines-the containment approach, the prevention approach and the full extraction mining approach. These design approaches are illustrated with practical examples for coal mining at shallow depth. Cascading pillar failure {CPF) in room-and-pillar mines can go by many other names, such as `progressive pillar failure', `massive pillar collapse', 'domino-type failure' or 'pillar run'. In this kind of failure when one pillar collapses the load that it carried transfers rapidly to its neighbours, causing them to fail, and so forth. This failure mechanism can lead to the rapid collapse of very large mine areas. In mild cases only a few tens of pillars might fail; in extreme cases, however, hundreds, even thousands, of pillars can fail. CPF can have catastrophic effects on a mine, and sometimes these effects pose a greater risk to health and safety than the underlying ground-control problem. Usually, the CPF induces a devastating air blast as a consequence of the displacement of air from the collapse area. An air blast can disrupt the ventilation system totally by destroying ventilation stoppings, seals and fan housings. Flying debris can seriously injure or kill mining personnel. The CPF might also fracture a large volume of rock in the pillars and immediate roof and floor. In coal mines and certain other mines this can lead to the sudden release of large quantities of methane gas into the mine atmosphere; a methane explosion might result from the CPF. CPF is at the far end of the spectrum of unstable pillar failure. At the other end are slow `squeezes' that develop over days to weeks and, because of their slow progress, do not pose an immediate danger to mining personnel. There is ample warning time for men and machinery to get out of the way of the failure. In a CPF, however, the failure progresses so rapidly that men and equipment cannot be evacuated in time. Significant seismic energy is released as a consequence of the rapid failure and collapse. CPF should not be confused, however, with coal-mine bumps and rockbursts. In some cases the damage can appear similar, but the underlying mechanics are completely different. As will he shown later, the mechanics of CPF depend on the applied vertical stress and the post-failure, i.e. strain-softening, behaviour of the pillars. In a CPF pillars shed their applied load rapidly and have very little residual strength after failure. The collapse itself may release significant seismic energy, but otherwise the mine is seismically quiet. Alter a CPF the openings in the affected mine workings have usually closed completely. In contrast, coal-mine bumps and rockbursts occur in seismically active mines. Research has shown that coal-mine bumps and rockbursts are seismic events induced by mining that damage underground mine workings. Bumps and bursts are thus a subset of a much larger set of mining-induced seismic events.[ Only some of these seismic events damage mine workings; fortunately, most do not. The mechanisms by which a mining-induced seismic event can lead to a damaging coal-mine bump or rockburst is still a significant research area.2 After a bump or rockhursr the affected mine workings may or may not be completely closed. For example, in the coal-mine bump described by Soler and co-workers2 the mine workings remained open even though the pillars were destroyed during the bump event. Because CPF differs from a coal-mine bump or rockburst, the design approaches to control their occurrence also differ. The design recommendations developed here apply to CPF and not to bump- or burst-prone mines. Cascading pillar failure examples Unfortunately, CPF has occurred in room-and-pillar coal, metal and non-metal mines. The most infamous example is the Coalbrooke colliery in South Africa, where 437 miners perished where [si >1 3at1ttsumsus7car kky vArtMixiL7i nesafr tramwsamn ures] on 21 January, 1960.1 Table I summarizes the mining dimensions of 13 examples of rapid pillar collapse in U.S. coal mines. All occurred during the 1980s and 1990s, and all happened suddenly or without significant warning. Most resulted in air blasts and damage to the ventilation system. Table 2 gives the mining dimensions of six room-and-pillar metal and non-metal mines in the U.S.A. where failure occurred in all probability by the CPF mechanism. The collapse areas can be huge. Fortunately, some of these failures gave advance warning. At the lead-zinc mine slabbing from pillars and roof falls began four weeks prior to the main collapse.3 At the copper mine considerable rock noise and smaller failures preceded the main collapse by five days.5 At the copper-silver mine it is not known if nature provided a warning.6 Evidently, the trona mine collapsed without warning.7,8 Rock noise and other failure warnings preceded the silica mine collapse by three weeks. v The presence or absence of warnings at the salt mint is not known. to Most of these collapses induced a substantial air blast; damage to the ventilation systems was limited, however, to bent airdoors and a few downed stoppings, except at the trona mine where extensive damage to the ventilation system resulted.

By H. E. Perlee

The concentration limits of flammability and autoignition temperatures of trichloroethylene in atmospheres of air, oxygen, and nitrogen tetroxide have been determined in a spherical vessel. The autoignition temperatures of TCE in atmospheres of air, oxygen, and nitrogen tetroxide were found to be 419°, 396°, and 221° C, respectively. The flammability zones of TCE-air, TCE-oxygen and TCE-nitrogen tetroxide mixtures at 100° C were found to be 10.5 to 41, 7.5 to 91, and 13.5 to 69 volume percent TCE, respectively. In addition, maxi-mum combustion pressures of 50 ps and 140 were recorded for constant volume combustion of the lower limit mixtures of trichloroethylene in air and oxygen, respectively.

Jan 1, 1966

By F. Cherpereel, R. Gabillard, J. P. Dubus

We present an electromagnetic method taken from the well known radiogoniometer that allows us to locate at the surface of the ground the vertical axis of a magnetic antenna transmitter buried at a depth h in the earth. The method and the equipment achieved are called R. E. P. E. (Relevé Electromagnétique de Points Enterrés). They are daily used to accurately survey old quarries by using triangulation instruments at the surface of the earth rather than in galeries where the setting difficulties considerably reduce their accuracy and increase the work length. The results of several surveys allow us to give the optimum working conditions of the instruments and show that, when the transmitter is at a 20 meters depth, its position is known at the surface with an error lower than 1 centimeter. The power transmitter is of about 8 watts and we can find its location with an error smaller than 1 meter when buried at a depth of about 100 meters. This equipment may be successfully used for location of subsurface miners. The space surrounding the transmitter must then be free from ferromagnetic bodies.

Jan 1, 1973

By A. T. Iannacchione

Designing coal pillars to provide resistance against overburden and gob loads has long been an aim of rock mechanics engineers. This requirement has become more imperative as greater overburdens are encountered and when mining in stiff coal-bearing strata. Current design procedures rely on theories of coal pillar behavior that take into consideration a common hypothesis. This hypothesis states that the elastic core is surrounded by an inelastic yield zone. The distribution of stress at low-to-moderate pillar loads has been effectively defined by this hypothesis. However, it suffers greatly when applied to large width-to-height (w/h >lo) coal pillars under considerable overburden (>500 m) . In these situations, the hypothesis says the elastic core can achieve unrealistic stress states giving the pillars extremely high calculated strength. A growing body of field studies has shown this is not the case. It has become clear that same other mechanism must be involved. It is the purpose of this paper to discuss the importance of an interface slip mechanism between the coal- bed and the surrounding strata in controlling the extent and pattern of stresses and deformations in a coal pillar.

Develop a user-friendly computer program that permits those interested in mine health and safety to access and analyze on a personal computer (PC) employment, production, and accident data for U.S. coal and metal-nonmetal mines. This software is being designed with a major focus on flexibility and case of use. The Mine Accident Decision Support System (MADSS) will be available for distribution in mid-1994. Currently, the U.S. Bureau of Mines (USBM) is seeking volunteers willing to pilot test a preliminary version of the software and to provide suggestions for its improvement. Background Since 1975, the Mine Safety and Health Administration (MSHA) has compiled large data bases of information about U.S. mines and the reportable accidents, injuries, and illnesses that have occurred in those mines. Employment and production data arc collected on a quarterly basis from each mine and accident information is collected on an incident -by-incident basis. The USBM has compiled estimated costs for each of these accidents using computer models. All of this information is potentially useful to mine health and safety researchers. However, it has been underutilized because it is stored in large mainframe data bases that arc inaccessible to many users and/or are cumbersome and difficult to use.

Jan 1, 1993

By H. P. Rue

For the proper control of gasoline treating plants there is need of a quick test for corrosion. In "sweetening" gasoline that is, in treating it to remove evil smelling mercaptans or to convert them to disulphides or sulphides the sodium plumbite ("doctor") method is generally used. This method involves agitation of the gasoline with "doctor solution's (sodium plumbite made by dissolving litharge in a solution of caustic soda) in the presence of free sulphur3. One of the common mistakes in the technique of this process is the addition of too much free sulphur, which will dissolve in the gasoline and cause it to be corrosive. In the operation of a continuous sweetening; or treating plant, a check on the corrosiveness of they product is imperative at all times. The copper-strip test commonly used in specifications take, so long to perform that the plant may fail to function properly for some time before the operator discovers it. The writer has investigated a rapid corrosion test method involving the use of metallic mercury, recently developed by Messrs. G. T. Granger, refinery superintendent, and A. B. Comstock, chief chemist, of the Barnsdall Refineries, Inc., Okmulgee, Okla. They have used this test successfully for several months in controlling the operation of their continuous treaters any have come to the conclusion that it has several advantages over the copper-strip test. Chief among these is the time caved, as the copper-strip test takes at least one-half hour, while the mercury test can be wade in about five minutes. It is very evident that this is an important item in controlling a continuous treater.

Jan 1, 1928

By R. T. Johansen

The wettability of petroleum reservoir materials by water and crude oil has been recognized as an important factor in determining waterflood behavior. The problem of simulating and studying reservoir conditions and characteristics, to produce laboratory results congruous with field experience, has been examined by many methods. (1, 2, 3, 4).4/ The most generally accepted approach to this problem is determining wettability of the porous medium by imbibition methods; or, after solvent extraction, predetermining the wettability of the samples by coating the surface of the medium to render it preferentially oil-or water-wet (3, 5). The emphasis of wettability studies has been placed on the characteristics of the reservoir materials with little consideration being given to the fluids themselves. Therefore, the wetting tendencies of crude oils have been investigated by a recently developed method (6). Imbibition and the more general phenomena of capillary pressure are the most direct ways to measure wettability. The simplest type of capillary pressure observations involves the use of an interfacial-tension capillarimeter, which does not produce as separate values either interfacial tension or contact angle. Actually, these quantities do not have independent significance in reservoir engineering, and the property of wettability they are intended to evaluate is given, immediately by capillarimetric measurements.

Jan 1, 1961

By Elton L. Litchfield

The techniques for direct initiation of detonation, developed by the Bureau of Mines, have been applied to gaseous mixtures of oxygen with methane, 'thane, propane, butane, or hexane. An exploding wire was used as the initiation source to determine minimum stored electrical energies required to effect detonation of mixtures between one-half and two times the stoichiometric fuel ratios. Detonations were obtained in the most easily initiated mixtures of ethane, propane, butane, and hexane for initiation energies between 24 and 33 joules at 1 atm and 28-43 joules at 0.5 atm initial pressure. Methane mixtures, at 1 atm, were not observed to detonate when initiated with up to 484 joules.

Jan 1, 1966

By Nick Derick

The continued growth of steel production in the Western States is contingent upon the development of new iron ore sources. Recent development of economical techniques for concentrating and agglomerating taconites has focused attention on the low-grade magnetite deposits near Atlantic City, Wyo., as potentially important sources of iron ore for blast furnace smelting. Therefore, the Federal Bureau of Mines has made comparative evaluations of blast furnace burdens that incorporate pellets produced from Atlantic City concentrates. The Bureau also has evaluated the relative effect of Utah coke on blast furnace performance, using a high-quality Eastern coke as a basis for comparison. This work was done in the Bureau's experimental blast furnace at Bruceton, Pa. Tests determined the maximum wind rate that could be used while a continuous stock movement was maintained in the furnace. The furnace was operated at wind rates ranging from 800 to 1,400 std. c.f.m., them maximum limit of the blowers for the 1.75 in.-diameter tuyeres used. Using a normal Utah ore burden and Utah coke, the furnace went into a tight hanging condition with a wind rate above 950 std, c.f.m. Using the experimental pellet burden again with Utah coke, the wind rate could be increased to 1,000 std, c.f.m. and probably to 1,050 std. c.f.m, before tight hanging occurs. This represents an increase of 5 to 10 pct. in the wind rate. The experimental results indicate an accompanying increase of iron production, as much as 8 pct.

Jan 1, 1961

By N. Grosland, G. Kopp, L. Frey-Law, D. Wilder, M. Contratto, S. Rahmatalla, T. Xia

Heavy equipment manufacturers have made a long-term commitment to minimize operator vibration exposure for comfort, performance, and health reasons. Domestic and international guidelines/standards and EC laws dictate exposure limits based on measurement of vibration at the interface between the seat and the operator’s buttocks using seat-pad accelerometry.1-4 This is historically based on the assumption that the only major source of vibration is transmitted through the seat pan. However, vibration may also be imparted to the head and neck via the steering wheel and/or arm-rest controls and a relatively rigid upper body.5 Unfortunately, little is known regarding the influence of arm position on head and neck motion. The purpose of this study was to investigate relative head and trunk motions during riding simulations of large construction equipment, using three different arm control options. Methods Five typical heavy equipment ride files were “played back” through a man-rated Servo Test 6-degree-of-freedom vibration system. An 8-camera Vicon motion capture system operating at 200 frames per second, recorded the motion of reflective surface markers on 5th, 50th, and 95th percentile right-handed male subjects, using 3 seat and control configurations (steering wheel (SW), floor mounted armrest controls (FM), seat-mounted armrest controls (SM)). Two trials were performed for each ride and seat control combination (each trial: 60 sec of 6-dof and 60 sec of vertical vibration). The relative motions (change in distances) from the marker over the xiphoid process (caudal end of sternum) to markers over each shoulder, each mid-clavicle, the presternal notch, and to each of four markers on a tight band around the head were calculated (12,001 frames, 6-dof motion only). As a rigid body control, distances between markers on the head band were also monitored. The standard deviation (SD) of the 12,001 distances between pairs of markers was normalized by the mean (L) of the associated distances producing: SD/L which was used as a measure of motion. Error assessments were also performed by analyzing the motion between relatively fixed markers (on the headband). A repeated measures analysis of variance was used to evaluate the results. While five ride files were used, only one ride file containing significant lateral acceleration components was analyzed for comparing the effects of two armrest controls versus use of a steering wheel for this part of our study. Results Values of SD/L between the points on the relatively rigid head band were consistently small and similar to each other for all conditions with one exception due to treatment (SM v SW, p=0.0145). SD/L between the markers over the xiphoid process and the presternal notch, another region that should be relatively rigid, were also similar to each other for all conditions. Use of floor-mounted, arm rest controls versus a steering wheel produced a significant increase in the value of SD/L between the xiphoid process and: the right shoulder marker (92%, p=0.0316), the right mid-clavicle marker (47%, p=0.0478), and the right-front marker on the head band (28%, p=0.0182). Use of floor-mounted, arm rest controls versus seat-mounted, arm rest controls

Jan 6, 2006

By Eric G. Zahl, John P. Dunford, Hamid Maleki

Coal bumps are influenced by geologic conditions, the geometric design of coal mine excavations, and the sequence and rate of extraction. Researchers from private industry and government agencies around the world have studied mechanisms of violent failure and have identified individual factors that contribute to coal bumps. To develop predictive tools for assessing coal bump potential, the authors initiated a comprehensive study using information from 25 case studies undertaken in U.S. mines. Multiple linear regression and numerical modeling analyses of geological and mining conditions were used to identify the most significant factors contributing to stress bumps in coal mines. Twenty-five factors were considered initially, including mechanical properties of strata, stress fields, face and pillar factors of safety, joint spacings, mining methods, and stress gradients. In situ strength was estimated in 12 coal seams where uniaxial compressive strength exceeded 2,000 psi. Allowances were made for favorable local yielding characteristics of mine roof and floor in reducing damage severity. Pillar and face factors of safety were calculated using displacement-discontinuity methods for specific geometries. This work identified the most important variables contributing to coal bumps. These are (1) mechanical properties of strata, including local yield characteristics of a mine roof and floor, (2) gate pillar factors of safety, (3) roof beam thickness, joint spacing, and stiffness characteristics, which influence released energy,(4) stress gradients associated with the approach of mining to areas of higher stress concentrations, and (5) the mining method. By combining the strength of both analytical and statistical methods, new capabilities were developed for predicting coal bump potential and for building confidence intervals on expected damage.

Jan 5, 1999

The results of a Feasibility and Design Study of Surface Impregnation Equipment to be used for Chemical Stabilization of Coal Mine Structures are described in this report. The study was sponsored by the United States Department of the Interior, Bureau of Mines, under Contract H0210055. This program was undertaken as an essential part of the Bureau of Mines Chemical Ground Stabilization Program. The responsible prime contractor was The Eimco Tunneling and Mining Machinery Division of the Envirotech Corporation. The Rocketdyne Division of the North American Rockwell Corporation performed part of the feasibility study and design and testing of the metering and feed system as a subcontractor to Eimco.

Jan 1, 1972

By H. Billmayer

This report covers the period from June 17, 1974 to February 20, 1975, and describes the work performed in compliance with the requirements of Contract No. H0346102 and Modification No. 1 thereto. The purpose of the contract was to design protective canopies for an Elkhorn Scoop, a Lee Norse Miner, a Wilcox Miner and a Wilcox Bolter; to construct mockups of the canopies; and to obtain machine operator evaluations of the canopy designs by assessing the mockups while installed on their machines in the mines. The overall program objective was to achieve protective canopy designs for the four machines which would be acceptable to the operators.

Jan 1, 1975

By Jacqueline A. McClaskey

The U.S. Bureau of Mines (USBM) Information and Analysis Directorate collects worldwide data on virtually every commercially important non fuel mineral commodity. These data form the base for tracking and assessing the health of the minerals sector of the U. S. economy. The USBM's data collection activity was instituted by the 47th Congress in an appropriations act of August 7, 1882 (22 Stat. 329), which placed the collection of mineral statistics on an annual basis. The most recent authority for the USBM survey activity is the National Materials and Minerals Policy, Research and Development Act of 1980 (Public Law 96-479, 96th Congress). This act strengthens protection for proprietary data provided to the U.S. Department of the Interior by persons or firms engaged in any phase of mineral or mineral-material production or consumption.

Jan 1, 1992

By Arthur L. Murray

"While serving as surgeon with rescue car No 11 of the U. S. Bureau of Mines, the writer visited the principal metal-mining camps of Utah during the latter part of 1919. In visiting the mines, meeting and conversing with miners, and talking over the medical situation with physicians in the various camps, the number of cases of lead poisoning encountered was great enough to attract attention.With a view to procuring more definite information as to the number and distribution of cases of lead poisoning throughout the State, a study of the records of the State Board of Health was undertaken. Utah had no ordinance re¬quiring the reporting of occupational diseases, so it was not possible to secure data an cases A study of the mortality records by years gave the following results.:Year Deaths from lead poisoning.1910,11911,01912,21913,11914,61915,41916,11917,31918,11919,2These few deaths would seem to indicate a fairly low case rate, but when it is realized that lead poisoning is rarely an immediate cause of death and that the train of sequelae in this disease frequently leads to chronic involvemeets of the digestive, nervous, circulatory or genito-urinary systems, it is apparent that the number of deaths showing lead poisoning as the cause can not be taken as an index of the cases prevalent. The time elapsing between the presence of the active signs of lead poisoning and the terminal illness from pathologic conditions excited by lead absorption may be years, and the initial cause, lead poisoning, is frequently lost sight if entirely, hence the death certificate shows no evidence of the primary cause."

Aug 1, 1921

By Oliver Bowles

Wire saws have been used for many years in European travertine, marble, and slate quarries. This method of sawing found very limited use in America until 1927 when it was accepted as standard equipment in elate quarries in Pennsylvania where it has been remarkably successful. Details of its operation in slate have been published in a recent bureau report.3 The very limited extent to which the wire saw has been employed in limestone and marble quarries in the United States and the seeming lack of interest even in experimental work to determine its advantages are difficult to explain in vied of its wide use in cutting similar rocks in Europe and its unquestionable advantages in sewing slate in America. In order to encourage improvement in quarry practice the United States Bureau of Mines has endeavored to obtain information as to the extent to which wire saws are used in Europe together with data on the rate and cost of sawing. The information at hand is by no means complete either in territory covered or in details of operation; it nevertheless brings out certain significant features that may be of interest and advantage to quarrymen in the United States.

Jan 1, 1931

By Ivan L. Nichols

Tailings dumps at Mercur, Utah, contain about $7 million worth of gold in 3.5 million tons of mill tailings assaying about 0.07 ounce of gold per ton. Commercial mining and milling at Mercur ceased in 1942. To determine whether improved technology was now available that might permit economic reprocessing of the Mercur dumps, the Bureau of Mines probed for a low-cost method that would be applicable to these tailings. A composite sample prepared for laboratory studies assayed 0.062 ounce gold per ton. About 10 percent of the gold occurred as a water-soluble cyanide. Conventional cyanide leaching dissolved 32 percent of the gold, and hot, strong cyanide solution dissolved 42 percent. Results were not improved by pretreatment with acids, bases, or oxidants. After expensive preroasting, gold recovery by cyanidation was increased to 65 percent. The simple procedures were ineffective, and more effective procedures were too costly for economical processing of Mercur tailings.

Jan 1, 1970

By M. W. Von Bernewitz, E. H. Denny

The use of oxygen breathing apparatus during rescue and recovery operations at both coal and metal mines has become so commonplace that there is a tendency for the industry not to give such apparetus the full measure of credit that it deserves in any particular disaster , therefore , the data presented herein should give some idea of what has been done in this regard during the past 15 years that is , up to 1910 by the Technologic Branch of the U. S. Geological Survey , and thence ( to the end of 1922) by the U. S. Bureau of Mines .

Feb 1, 1923

By H. C. Ko

Heats of solution of calcium carbon-ate (calcite) and calcium oxide in hydrochloric acid were determined by solution calorimetry. Combination of these two heats yields a value of 42.643±0.024 kcal/mole for the enthalpy of calcination of calcite at 298.15 K. Literature data on ?H°298.15 of calcination of calcite were reviewed and compared. Thermodynamic properties for the calcination process were calculated from 298.15 to 1,500 K using Gibbs energy functions. This research was undertaken by the Bureau of Mines as an effort to provide thermodynamic data for the advancement of minerals technology, energy conservation, and environmental preservation.

Jan 1, 1982

By H. O. McDonald

Solutions containing Cr6+ and sulfuric acid are used in a number of surface-finishing operations. Substantial quantities of chromium and copper are lost and pollution problems are created when the spent solutions are discarded. To minimize the undesirable environmental effects while improving secondary resource recovery technology, the Bureau of Mines is conducting research to detoxify and recover metals from these solutions. Spent etchants are treated to remove copper and reduce Cr6+ to Cr 3+ in an electrolytic cell. The anodes and cathodes are granulated coke. The spent solution is continuously pumped through the electrodes. Hexavalent chromium is reduced to trivalent chromium, and copper is recovered at the cathode. Reoxidation of Cr3+ at the anode was not observed. The removal and recovery of copper reduction of Cr6+ lessen chemical demand and increase efficiency in waste in treatment operations associated with the use of these solutions.

Jan 1, 1980