Search Documents

By W. E. Miller, G. S. Scott, G. W. Jones

"INTRODUCTION One of the major activities of the Bureau of Mines is the promotion of safety in mining and the mineral industries. Research is undertaken in connection with these problems to determine the explosion and ignition hazards of combustible gases, liquids, and solids and to investigate means of reducing them.Occasionally the Bureau is asked to determine inflammability or ignition temperatures to enhance safety in nonrnineral industries. From time to time it has complied with such requests when no other agency was available to do the work and the investigation could be conducted with a minimum of time and expense. The present investigation is one of this class.Nicotine (C10H14N2), a colorless combustible liquid having a boiling point of 246°C, is usually obtained from tobacco and its products by extraction processes. When heated to its boiling point it decomposes; the purified product is obtained from tobacco extractions by distillation at reduced pressures or is distilled in a current of inert gas.It has an unpleasant odor, a burning taste, and in the undiluted state is highly toxic. Under certain conditions it can be oxidised to nicotinic acid and in the near future may therefore become of considerable economic importance. Nicotinic acid is a component of the vitamin B complex now commonly used to fortify white flour and other foods that normally are deficient in these vitamins."

May 1, 1942

By James R. Boyle

The value of Alabama's nonfuel mineral production in 1985 was $405.9 million, a slight decrease from the record high of 1984. With the exception of clays, output of most nonfuel minerals increased over that of 1984. Alabama was second in the Nation in production of crushed marble and bauxite; third in firre clay; fourth in masonry cement and kaolin; fifth in portland cement and lime; and sixth in ferroalloys and recovered sulfur, Alabama ranked 20th in the Nation in value of nonfuel minerals produced, but ranked 13th in value of industrial minerals. Valuewise, Alabama produced 2.4% of the Nation's industrial minerals.

Jan 1, 1987

By Paul R. Thimas, Edward H. Boyle

"The Bureau of Mines evaluated the long-term cost and availability of primary gold production from 135 mines and deposits worldwide. Collectively, the evaluated countries represent 93 pct of world gold production. Total recoverable gold available (as of January 1984) from a subset of 111 significant producing mines and developing deposits in 13 market economy countries (MEC's) is estimated at 810 million tr oz. The Republic of South Africa is estimated to account for 87 pct of total recoverable gold. The United States and Canada account for 4 and 4.5 pct of the total, respectively. Eighty-three percent of total recoverable gold is available at a constant 1984 break-even price of $400/tr oz, and 70 pct is available at $300/tr oz. South Africa accounts for 90 pct of the gold available at $400/tr oz or less.Major conclusions are that (1) South Africa should remain the largest world producer through the year 2000, (2) annual MEC output in 2000 should not be significantly different than current output given constant 1984 gold prices of more than $300/tr oz, and (3) there may be a significant decline in production after 2010 in the absence of major new discoveries and continued development of new mines to offset the depletion of the South African mines. INTRODUCTIONSince the late 1970's the world gold mining industry has been characterized by dynamic growth in production and volatility in price. World production in 1983 was almost 15 pct greater than in 1980, and the short-term trend continues upward. Annual dollar-based price changes since the early 1970's have been unprecedented in both magnitude and volatility. This commodity, which sold for $35/tr oz3 for over a third of a century, reached an annual average $612/tr oz in 1980. Until 1980, the future price of gold seemed set on an upward trend. Since that year, however, world gold prices have fallen by over 50 pct to slightly over $300/tr oz at the end of 1984.Against this background, this study was undertaken to determine (1) the level of world demonstrated gold resources, (2) total and annual availability of gold mine production, (3) long-run production costs per operation and by national aggregates, (4) the economic and technical factors that impact upon cost and availability, and (5) probable future mine production and cost trends."

Jan 1, 1985

By Charlie Wyche

Principal mineral products in the Dominion of Fiji were gold, silver, pit and quarry construction materials, and cement. In the years 1978-79, the combined total value of these commodities accounted for some $15 million,2 or 85% of the total mineral output. Production of cement, sand and gravel, and quarry products increased substantially, but gold and silver output from Fiji's only operating metal mine continued the down-ward trend of recent years. Mineral exploration by several international mining companies as well as by local prospectors was being carried out over much of Fiji, and a number of interesting prospects were discovered. One of these, a medium-size porphyry-copper prospect in the Namosi area of Viti Levu, W88 at a mining feasibility study stage. At Mount Kasi on Vanua Levu, an extensive program of geological sampling and mapping W88 being conducted, and surface sampling and drilling W88 taking place at some base metal prospects in the south-central parts of Viti Levu. Also, high gold values in surface samples were reported at Vuda in western Viti Levu.

Jan 1, 1981

Improve surface mine haul-age truck safety and efficiency by providing a means for sensing the weight and distribution of the truck's load. Approach The safety hazards and the economic implications of overloading mine-haulage trucks were analyzed to determine the net effect of that practice on mine operations. The analysis indicated that: Ten to 25 pct overloading is typical; Higher haulage, tire, and maintenance costs occur due to overloading (a 20 pct overload was estimated to increase operating costs 7 pct per ton); Ten to 15 pct of haulage? truck injuries and fatalities are attributable to overload conditions, at a cost over one million dollars per year to the mining industry. Vehicle-weighing technology that conformed to the performance specification for an off-highway haulage truck overload detection system was selected for in-mine testing. How It Works Normally, volumetric estimates are made during the loading sequence which do not account for the varying ore density. Hence, the actual weight of a load is never precisely known. By providing a precise measurement, an overload detection system will not only indicate vehicle overloading, but will also show under-utilization of the truck. One system tested by the Bureau of Mines was the ?Load Analyzer" manufactured by Pactronics Corporation in California. This system consists of a meter-type analog readout for the cab console and three "Electrosensors" (linear variable differential transformers) attached to the main frame. Using conventional welding and brazing techniques, two sensors are attached between the front members of the engine sub-frame and the top of the left and right trailing arms (one sensor per arm). The same techniques are used to attach the third sensor to the rear centerline of the truck. between the main frame cross member and the A-frame. The readout unit on the cab console indicates by color-coding whether each sensor loading is under (green), at (yellow), or over (red) the pre-set rated load. The three-sensor configuration with in-dependent readouts also detects uneven distribution of the load.

Jan 1, 1984

By R. V. Ramani, A. S. C. Owili-eger

System Size N,NX Number of blocks in x-direction M,NY Number of blocks in y-direction NTIMES Number of systems to be simulated LENGTH Length of medium WIDTH Width of medium THICK Thickness of medium NZONE Number of material zones Medium Properties XPERM(I,J) Permeability in x-direction at the point (i,j) YPERM(I,J) Permeability in y-direction at the point (i,j) PHI Medium porosity T Medium temperature Gas Properties PURL, VISCOG Gas viscosity Z Gas deviation factor BETAG Gas compressibility coefficient Initial and Boundary Conditions IBC Initial and boundary conditions NPRESS Number of specified pressures NQUAN Number of specified quantities FACEP Face pressure RESEP Reservoir pressure

Jan 1, 1974

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

A computer model of an existing mine ventilation system can be executed using data developed from ventilation survey results. This model can then be used to analyze and evaluate proposed modifications to the system. The acquisition of field measurements during a ventilation survey and the corresponding development of this information into computer input data have been discussed in detail in the preceding chapters. In this chapter, the data are used in computer-oriented analysis of the mine ventilation system. The PSU/MVS was selected for use because of its advanced capabilities. MINE DESCRIPTION The mine chosen for this application is located in Western Pennsylvania. The Pittsburgh coal seam, having an average height of 5-1/4 to 6-1/2 ft, is mined under approximately 300 to 500 ft of cover. The mine preparation plant and shipping facilities are located at the seam outcrop along a river; mining has progressed from the outcrop to an area about 10 miles from the pit mouth so that there are extensive worked-out areas through which access is maintained to the current mining area. Coal haulage is by conveyor to an underground transfer point, located four miles from the pit mouth, and then by high speed rail haulage to the preparation plant. The rail haulage link is scheduled for replacement by a conveyor in the near future. Mining at the present time is limited to the room and pillar method using continuous miners. Longwall mining had been attempted in the past with only limited success; as a result, several panels originally laid out for longwall mining are currently being extracted by room and pillar work. The

Jan 1, 1977

By Terry J. Close

In 1985, at the request of the U.S. Bureau of Land Management, the U. S. Bureau of Mines studied part of the 56,623-acre South McCullough Mountains Wilderness Study Area (NV-050-435) in order to evaluate its identified mineral resources. The area studied is located in Clark County, NV, about 30 miles southwest of Boulder City. No mineral resources were identified. The study area contains the eastern part of the unorganized McCullough Mountain (McClanahan) mining district which has had no recorded production. Between 1911 and 1982, 23 lode claims were located in the part of the mining district that is in the study area; four of these claims are currently held by assessment (1986). A total of 11 mineral sites were found and examined during the U.S. Bureau of Mines investigations; 26 mine workings were examined. Of the 11 sites, four are within the study area, and seven are nearby. Of the seven nearby sites, six are adjacent to the west boundary and consist of precious-and base-metals bearing vein occurrences in metamorphic rocks. The seventh site is near the east study area boundary, and consists of a tungsten-bearing vein occurrence that is also in metamorphic rocks. The four sites within the study area consist of vein occurrences in metamorphic rocks that contain silver, gold, arsenic, lead, zinc, and copper. The veins at these four sites are too small and low grade to be classified resources; however, there are indications that three of the sites may have silver and gold resources at depth. Detailed delineation of the veins, and determinations of tonnages and grades are needed. This would entail additional mapping and sampling, trenching and drilling, and opening inaccessible workings.

Jan 1, 1987

By N. S. Dalal, X. Shi, V. Vallyathan

"Electron spin resonance (ESRJ spectrum of the hydroxyl (· OH) radical spin adduct with .the spin trap 5,5-dimethyl-1-pyrrolintt-N-oxide has been obtained in suspensions of freshly ground quartz particles. The concentration of the spin adduct (and hence of the • OH radicals) increases with the amount of grinding. The dust's potential for the generation of the· OH radicals is maximum when fresh (i.e., immediately after grinding) and decreases to 50% in about a day on storage in air. Studies involving metal chelates .indicate that the • OH radical formation involves mainly the silica surface and H20 rather than the Fenton reaction. The results suggest that hydroxyl radical reaction(s) could be important in the lipid peroxidation and fibrogenicity by quartz dust, particularly .in acute silicosis. INTRODUCTIONIn this paper we report on our electron spin resonance (ESR) detection of the formation of hydroxyl (·OH) radicals in aqueous suspensions of freshly crushed quartz particles. This work was undertaken with a view to find possible clues to the role of free radicals in the pathogenesis of quartz-induced fibrogenicity, commonly known as silicosis. We noted that while silicosis is one of the major health hazards in coal and mineral industries, the mechanism by which the quartz particles exert their toxic action on cells and the process(es) by which these actions progress to fibrogenesis are still poorly ·understood (Reiser and Last, 1979; Singh and .Rahman, 1987). It is generally thought, nevertheless, that the action of quartz particles on the biological membranes is the starting point of the silicotic process (Parazzi et - al., 1968). A possible clue to the mechanism of the membrane damage by quartz particles, in terms of the role of oxygenated free radicals, is suggested by the following observations. A suspension of quartz particles in contact with alveolar macrophages has been reported (Gabor et al., 1975; Koike et al., 1982) to initiate an enhancement of lipid peroxidation, defined broadly as the oxidative deterioration of polyunsaturated components of lipids. Hydroxyl (· OH) radicals are known to be capable of peroxidation by abstracting hydrogen atoms from cell-membrane lipids (Halliwell and Gutteridge, 1985) and of initiating lipid peroxidation in lysosomal membranes. (Fong et al., 1973). Arong other lines, it is known that exposure of cell membranes, fatty acids, and unsaturated food oils to ionizing radiation, which generates· OH radicals, causes rapid peroxidation (Halliwell and Gutteridge, 1985). Thus • OH radicals (and also other oxygenated species such as Oi, 10 2, and H20 2) might be expected to play a role in the toxicity of quartz. Earlier studies of the aqueous chemistry of quartz suspensions have reported detection of H2O 2 (Kalbanev et al., 1980), implicating the formation of ·OH radicals as transient species. However, we are not aware of any report of the detection of • OH radicals in quartz reactions, and thus the present study was undertaken. Since it-is known that, because of their high reactivity (hence short lifetime) in aqueous media, the • OH radicals cannot be detected via ESR directly (Finkelstein et al., 1980; Buettner, 1982) we have used .ESR combined with the spin-trap methodology (Finkelstein et al., 1980) for studying the· OH formation. The results show that· OH radicals are indeed formed in aqueous suspensions of freshly ground quartz; thus pointing to ·a possible new clue to the cytotoxicity of freshly formed quartz particles and thereby to silica fibrogenicity."

Jan 1, 1988

By Charles L. Kimbell

Bulk carriers, freighters, and tankers are the three classes of seagoing vessels engaged in transporting mineral commodities. However, vessels in these classes are not wholly devoted to mineral commodity transport, as seen in tables 16 through 22. Bulk carriers move considerable tonnages of agricultural products as well as crude minerals, their concentrates, mineral fertilizers, and the like. Freighters, owing to their great variety, can be devoted wholly to hauling mineral products or wholly to non mineral goods, as well as carrying mixed mineral commodities and non mineral commodities. They include general cargo ships, full container ships, partial container ships, roll-on/roll-off ships, and barge carriers. Tankers, although largely engaged in moving crude oil and refinery products, also transport liquid chemicals, molasses, wine, liquefied natural gas, and other fluids. Table 16 shows the distribution of the world's merchant fleet by vessel type in terms of the number of vessels, their gross tonnage, and their deadweight tonnage. The increase of nearly 1.5 % in the number of vessels between 1990 and 1991 compared with a 2.7% growth in gross tonnage and a nearly 2.3 % increase in deadweight tonnage points to an increase in the average size of vessels. Of the four categories of vessels reported, all showed increases in number and in deadweight tonnage between 1990 and 1991 except for "other," and on the gross tonnage basis, all groups registered increases. Although physical characteristics of vessels such as size, draft, crew requirements, type of propulsion system, ratio of gross tonnage to cargo tonnage, and fuel costs have undeniable influences on shipping industry performance, problems of and changes in the quantity and types of materials moved also significantly affect the shipping sector of the world economy, and thus have a bearing on the minerals sector of that aggregate. Unfortunately, comprehensive global data reflecting changes in these critical variables are not published.

Jan 1, 1993

By N. S. Dalal, X. Shi

"The oxidation of NADPH by vanadate(V) in the presence of glutathione reductase showed typical enzymatic kinetics. The oxidation was inhibited by N-ethylmaleimide, a glutathione reductase inhibitor. Superoxide dismutase had no significant effect on the oxidation, indicating non-involvment of the superoxide radical. The vanadate(V) reduction was found to be a one-electron transfer process. These results suggest a new pathway for vanadate(V) metabolism and a new function of glutathione reductase. Compounds of vanadium(V), such as NaV03 , exert potent toxic effects on a wide variety of biological systems (1-3). Despite intense current activity, however, the biochemical mechanism of vanadate(V) toxicity is still not well understood (1- 14). It is believed that one of the important pathways involves the oxidation (by vanadate(V)) of NAD(P)H (15, 16), but, to our knowledge, there has been no report of the identification of any vanadate(V) reductase. With a view to finding if there exists any vanadate(V) reductase, we have investigated the oxidation of NADPH by vanadate(V) in the presence of glutathione reductase. Glutathione reductase (GSSG-R)2 was selected because our previous studies have shown (17) that GSSG-R can act as a reductase for chromate(VI), which is isoelectronic with vanadate(V). We find that GSSG-R does indeed function as a NADPH-dependent vanadate(V) reductase, thus pointing to a new pathway for the metabolism of vanadate(V), as well as to this property for GSSG-R. MATERIALS AND METHODSSodium metavanadate (NaV03 ), henceforth vanadate, was purchased from Aldrich and its solution was always freshly prepared. The GSSG·R used was from bovine intestinal mucosa and was purchased from Sigma. The oxidation of NADPH was followed photometrically as the decrease in absorbance at 340 nm. The spin trap, 5,5-dimethyl- pyrroline-N-oxide (DMPO), was purchased from Aldrich and used without further purification, since very weak or no spin adduct signal was obtained from the purchased sample when used alone.ESR spectra were obtained at X-band (9.7 GHz) using a Bruker ER200 ESR spectrometer. The magnetic field was calibrated with a self-tracking NMR gaussmeter (Bruker, Model ER035A) and the microwave frequency was measured with a digital frequency counter (Hewlett-Packard, Model 5340A). An ASPECT 2000 computer was used for data storage and analysis. The concentrations given in the figure legends are the final concentrations. All experiments were carried out in the phosphate buffer solution (pH 7.2) and at room temperature."

Jan 1, 1990

By Nicholas Kyriazi

It is of interest to know how to obtain as high an absorption efficiency as possible from a CO2-absorption canister used in closed-circuit breathing apparatus. In this study the Bureau of Mines found that varying the bed depth and the cross-sectional area of a canister changes its absorption characteristics. In tests using four ,1 rectangular, variable-depth canisters with different cross-sectional areas, the Bureau found that, given a constant weight of the chemical absorbent, LiOH, and a constant COa input, the canisters with a greater cross-sectional area reached C02 levels of 0.5 volume-percent in the effluent gas sooner than did the canisters with a greater bed depth. However, resistance to flow through the canister increases with bed depth, and a trade-off is inevitable. It was anticipated that the efficiency of a canister would increase with increasing intergranular air space approaching the tidal volume of the breathing waveform and then level off at some point under 100 percent. This postulation was partially substantiated. Cylindrical and radial canisters were also tested and compared. It appears that shape is not as important a factor in absorption efficiency as bed depth, since neither canister differed significantly from the rectangular canisters with regard to absorption efficiency values.

Jan 1, 1980

By A. C. Fieldner

"Purpose and Nature of Tests:The rapidly increasing use of motor vehicles and trucks in the United States is creating an entirely new problem in the proper ventilation of tunnels, subways and other confined spaces through which such machines must pass. This problem has become of immediate importance because a tunnel 3,000 ft. long is being designed to pass under the Hudson River between New York City and New Jersey. Another tunnel at Pittsburgh 5,700 ft. long through the South Hills, is already under construction, and a third tunnel, 6,000 ft. between Boston and Past Boston is proposed. It is probably that other tunnels will be started in various parts of the United States in the near future.The ventilation of such tunnels is a serious matter, on account of the poisonous nature of automobile exhaust gases. It not uncommon to read about finding a man dead in his garage. Generally this happens on a cold, winter morning, after he has been running the engine with the doors and windows closed."

Mar 1, 1920

Remotely monitor overburden response to longwall mining using time domain reflectometry (TDR) and a combination of hardware and software, as part of the U.S. Bureau of Mines (USBM) program to characterize subsidence. Background TDR was developed in the 1960's as a method to locate, discontinuities in coaxial transmission cables. In this method, voltage pulses sent along a cable are reflected by cable defects. The pulse reflections are used to determine the type and magnitude of the defects. The TDR concept was extended to material property measurement by embedding cables into particular materials and evaluating the cable's dielectric behavior as material properties were modified. This technique was adapted by the USBM in 1978 for use in monitoring rock movement during underground mining. The same concept is utilized today. A coaxial cable is grouted into a rock mass that is expected to deform. Progressive rock movement causes the cable to deform, as shown in figure 1, and changes to occur in the cable's electrical properties, which then produce changes in TDR reflection signatures. The technology has advanced to the point where it is now possible to distinguish shear deformation from tensile deformation and to quantify rock mass displacements by analyzing the TDR signatures.

Jan 1, 1995

This Technical Memorandum Report is a collection of three working memoranda, prepared during the course of our work for the Bureau of Mines and bound together for convenient reference. These working memoranda present preliminary performance estimates, for baseband voice and narrow- band through-the-earth electromagnetic communications systems of principal interest to the Bureau, for operational/emergency mine communications. The calculations were prepared to obtain early indications of the feasibility and governing parameters of such communications systems. They are based on limited, but pertinent, coal mine electromagnetic noise data acquired to-date by Bureau of Mines contractors; and of theoretical signal-attenuation characteristics for two transmitter antenna types of present interest to the Bureau. The memoranda examine the cases of baseband voice and narrowband communications for uplink and downlink transmissions, for frequencies up to 3kHz. Downlink transmissions are via a horizontal wire antenna, up- link transmissions via a vertical-axis loop antenna, for typical mine depths of 300, 600, and 1000 feet. Representative coal-mine overburden conductivities of 10-2 mhos/meter (moderate and common) and 10-1 mhos/meter (high) were used; for voice and narrowband, 10-1 for narrowband only. Examples of high, moderate, and low; surface and subsurface; harmonic and broadband-impulsive noise conditions were taken from NBS and Westinghouse (WGL) mine noise data, together with examples of high- and low levels of ELF atmospheric noise taken from M.I.T. Lincoln Laboratory data. These feasibility calculations are not intended to serve as definitive and complete treatments, but as a starting point: to establish first-order estimates of the magnitude and variability of transmitter power requirements under different noise, overburden conductivity, and mine depth conditions; to identify relationships, conditions, or frequencies that are likely to limit or enhance system performance; to reveal items requiring further investigation and data still required; and to suggest practical methods for optimizing system performance. These objectives were met by the calculations. Simple experiments to support these calculations can and should be carried out; together with more detailed investigations of specific modulation, coding, noise-suppression, voice-compression and signal-conditioning techniques, aimed at producing through-the-earth operational/emergency mine-communication systems that are not only effective, but practical and economically sound.

Jan 3, 1972

By Takashi Ohya, George V. Keller, Richard G. Geyer

One aspect of a program to improve the chances of survival following coal mine disasters is the development of a communications system which will allow surviving miners to make their circumstances known to rescue teams. At present, it appears that an electromagnetic system may be most practical. The development and design of an effective electromagnetic communications link for signalling between mine workings and the surface requires knowledge of pertinent physical properties of the rocks overlying the mine workings and the characteristics of the ambient noise against which a communications signal must be recognized. Knowledge of the overburden electrical transmission properties is useful not only for determining a practical operating transmitter frequency at a given mine, but also for ensuring the best possible electromagnetic coupling for routine or emergency communication purposes. Field studies of the electrical transmission properties of the overburden of coal mines in Colorado, Illinois, and Pennsylvania generally show that a rela- tively uniform and unimodal electrical conductivity distribution exists provided that the region has not been subject to considerable structural or metamorphic deformation such as that observed in the Gary District of West Virginia. Measurements of ambient surface electromagnetic noise levels at several mines in Colorado, Illinois, and West Virginia were taken and analyzed and are presented in the form of amplitude histogram plots both as a function of frequency and time of day. These amplitude histograms may be used in conjunction with overburden resistivity data in implementing an uplink communications beacon system which will yield a specified signal-to-noise ratio at the surface. Numerous C.W. field transmission tests were made in various coal mining environments with use made of either a buried vertical-axis transmitting loop or a short insulated grounded current line. These transmission tests were made from 20 Hz to 20,000 Hz in frequency and at several geographic surface receiving sites. The results of these field measurements show, in general, good agreement with theoretically calculated results. Since the produced surface magnetic field from a buried vertical-axis loop source or the produced surface horizontal electric field from a buried horizontal current line show better agreement with theoretical results, they could be used for beacon location system. One criterion would be in detecting the equatorial and polar null lines of the horizontal electric field component which is normal to the direction of emplacement of a buried transmitting line current source. A second criterion would be in the surface mapping of the maximum in the vertical magnetic field directly over a vertical-axis loop transmitter and the associated null in the vertical magnetic field at a horizontal offset distance which is about 1.4 times the depth of burial of the transmitter. Finally, a third criterion would lie in the surface mapping of the null in the horizontal magnetic field directly over the vertical-axis beacon and the associated maximum in the horizontal magnetic field at an offset distance from the transmitter axis of half the depth of burial of the loop transmitter. In mapping the vertical magnetic field over a buried vertical-axis loop transmitter, the size effect of the transmitter loop must be taken into account when the separation distances between the transmitter and receiving sensor are less than ten times the effective radius of the source loop; increasing the size of the transmitting source relative to the source-receiver separation distance shifts the null in the vertical magnetic field to greater offsets. In mapping either the vertical or horizontal magnetic field over a buried vertical-axis loop transmitter, care should be exercised in ascertaining that measured nulls and maxima are along radials through the axis of the buried source loop. For the main part, coupling experiments show that ambient electromagnetic noise in coal mining districts is less of a problem above 1000 Hertz. But secondary and perhaps undesirable maxima and null phenomena (as well as penetration problems) would occur in many coal mine provinces in the behavior of the surface horizontal magnetic field (over a buried vertical-axis loop transmitter) if transmission frequencies as high as 10 kHertz were used.

The twelve latexes listed in Table XI penetrated A horizon soil as shown by elution through a laboratory soil column and gave good sealing efficiency. See details in Table XII. High elution through laboratory soil columns of 4 to 6 inches depth is desirable because it predicts penetration of latex to a greater depth in the field. No definite correlation was evident between penetrating ability and particle size, surface tension, or pH. Most of the materials, however, were characterized by low surface tensions in the 36 to 53 dynes/cm range while particle sizes were usually in the intermediate range of about 1500 to 2500 Å. Naugatex J-3471 (a highly crosslinked styrene-butadiene copolymer) was the most promising of this group for stability, penetrating ability; and sealant efficiency. It also showed utility with [B] profile soil. Many of the other latexes tested in this investigation showed good sealing efficiency but were judged unsatisfactory because they gave low penetration or formed surface films with & horizon top soil. In general, latexes containing cationic surfactants were not satisfactory because they formed a heavy surface film. This is due to neutralization of the positive latex charge by the negatively charged soil particles.

Jan 1, 1972

By X. Shi, V. Vallyathan, N. S. Dalai

"Electron spin resonance (ESR) measurements show that grinding of quartz particles in air produces silicon-based (Si- and SiO-) radicals which decay with aging in air. ESR spin trapping measurements provide evidence for the generation of hydroxyl and possibly superoxide radicals from a suspension of fresh quartz particles. The hydroxyl radical generation potential of the fresh quartz particles decreases on storing in ambient air and on the addition of catalase, superoxide dismutase, desferoxamine, or DMSO. Silica-induced lipid peroxidation also decreases on storing the fresh particles in ambient air. These findings suggest that oxygenated radicals play a role in the biochemical mechanism of pneumoconiosis in general and acute silicosis in particular.INTRODUCTIONThis communication summarizes our electron spin resonance (ESR) investigation of the formation of oxygenated radicals by freshly crushed quartz particles in a cell-free aqueous medium, and its potential role in the biochemical mechanism of acute silicosis. This study was undertaken because the mechanisms by which the quartz particles exert their toxic action on cells and the process(es) by which these actions progress to fibrogenesis are still not well understood. 1-3 It is generally believed, however, that the action of quartz particles on the cell membrane is the starting point of the silicotic process. 1,4 Since the first step must involve surface reactions, characterization of the chemical structure of the surface of quartz particles has been the subject of several recent studies!-' For example, we reported that mechanical crushing of quartz under normal atmosphere generates silicon-based (Si• and SiO•) radicals which decay with time, and that these radicals are associated with a higher cytotoxicity of fresh quartz dust as compared to that of an aged dust from the same stock. 6,8 Independently Fubini and coworkers' have also reported on the formation of Si• and SiO• -type of radicals from quartz particles crushed under atmospheric conditions. Gulumian and van Wyk9 have reported that quartz particles react with hydrogen peroxide (H202) to generate hydroxyl (•OH) radicals. These authors9 suggested that this process might contribute to quartz's pathogenicity but the mechanism of the -OH radical formation was not clarified. Earlier, Gabor and Anca10 had suggested that the cytotoxicity of quartz particles might be associated with the generation of some factor or factors possessing the properties of a free radical and hence capable of promoting the peroxidative chain cleavage of polyunsaturated fatty acid moieties of the phospholipids in the cell membrane. More recently, Weitzman and Graceffa 11 reported that asbestos is able to catalyze the generation of -OH radicals from H2O2. Their later work12 indicated that lipid peroxidation might be one of the mechanisms of tissue injury by asbestos."

Jan 1, 1989

By W. J. Fene

It is often desired to obtain samples of air in places where collection by ordinary methods is not feasible, as in shafts amore means of descent or ascent are not provided, in sewer manholes, in gas or water wells, in empty oil tanks, and in sealed areas in mines. Heretofore, when such sampling was required, it was necessary to utilize the aspirating method, which was not always satisfactory; and to obtain samples of air in deep shafts, it was necessary to use long sections of rubber tubing, which was not always available. DESCRIPTION OF NEW DEVICE A new method or "device" employs a common snap-type mousetrap to break the neck of a vacuum tube at the place where it is desired to collect the sample (see fig. 1). A mousetrap is mounted on one end of a block of wood 11-3/4 by 3 by 3/4 inches in such camper that a lead weight attached to the trigger hall spring the trap when the device is given a sharp jerk. A vacuum tube is placed on the other end of the block and held in place by a strong rubber band. A strip of corrugated rubber is placed on each side of the grooved block to prevent the tube from clipping when the sample is taken. An adjustable shoulder, provided with a rubber cap, is pieced se that the neck of the vacuum tube will rest on it. The shoulder is made adjustable to accommodate various sizes of tubas and to keep the neck of the tube from breaking tee far back from the point. A metal handle is fastened to one end of the block, with a hole in the end through which the brass wire used for lowering the device is tied. The device is enclosed by a strong wire-gauge covering, hinged on one side and so arranged that it can be locked shut on the other side. This covering prevent: breaking of the tube while it is being lowered or raised in a shaft or other place. Brass wire of not less than 22 gage should be used for lowering the device. A detailed drawing of the device is shown in figure 2.

Jan 1, 1940

Multiple-seam interactions are a major ground control hazard in many U.S. underground coal mines. In some U.S. coalfields, particularly in central Appalachia and the West, the majority of today’s mines are operating above and/or beneath previously mined seams. The effects of multiple-seam interactions can include roof falls, rib spalling, and floor heave. These can seriously disrupt mining operations and threaten the safety of miners. In early 2006, a West Virginia coal miner was killed by rib roll that occurred in a high-stress zone beneath a remnant structure in an overlying mine. Fortunately, not every multiple-seam situation results in hazardous conditions. Indeed, the vast majority do not. For the past several years, the National Institute for Occupational Safety and Health has been conducting research to develop better techniques for predicting the location and severity of multiple-seam interactions. During this investigation, more than 50 mines were visited across the U.S. coalfields. Nearly 300 case histories were collected and analyzed using multivariate statistical techniques. The study also employed the numerical model LaM2D to estimate the multiple-seam stress, the Analysis of Longwall Pillar Stability (ALPS) and the Analysis of Retreat Mining Pillar Stability (ARMPS) programs to determine pillar stability factors (SFs), and the Coal Mine Roof Rating to measure roof quality. The study focused on the two most common types of multiple-seam interactions: • Undermining, where stress concentrations caused by previous full extraction in an overlying seam is the main concern; and • Overmining, where previous full extraction in an underlying seam can result in stress concentrations and rock damage from subsidence. The study confirmed that overmining is much more difficult than undermining, and isolated remnant pillars cause more problems than gob-solid boundaries. For the first time, however, it was possible to quantify these effects in terms of the equivalent thickness of interburden needed to compensate for them. The study also found that pillar design is a critical component of multiple-seam mine planning. Many of the failed cases involved pillars whose SF seemed inadequate once the multiple-seam stresses were accounted for. Weaker roof was also found to significantly increase the risk of multiple-seam interactions. The most important result of the study is an equation that predicts the critical thickness of the interburden required to minimize the likelihood of a multiple-seam interaction. This equation was incorporated into a step-by-step methodology that allows mine planners to evaluate each potential interaction and take steps to reduce the risk of ground control failure. Such measures could include installing cable bolts or other supplemental support, increasing the pillar size, or changing the mine layout to avoid the remnant structure entirely. These Proceedings also contain several previously published papers that cover other facets of multiple-seam mining research. Two papers describe the LaModel family of software developed by Professor Keith A. Heasley of West Virginia University. The LaModel programs were designed for calculating the stresses and displacements in coal mines or other thin, tabular seams in layered media. The original three-dimensional version of LaModel is essential for detailed analyses of complex multiple-seam scenarios. LaM2D, by contrast, implements a simplified two-dimensional model that is suitable for quick approximations of the multiple-seam stresses and strains. Three additional papers in these Proceedings describe the extensive multiple-seam experience of the Harris Mine, examples of extreme multiple-seam mining from the central Appalachian coalfields, and longwall mine experiences in Pennsylvania, West Virginia, and Utah. The final paper reports on a numerical modeling study that provided some insight into the mechanics of multiple-seam mining.

Jan 5, 2007