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By Dale Berner, Michael O’Sullivan

"This article focuses on lessons learned from innovative designs including in-the-wet construction methodology and modified foundation conditions, for two United States Army Corps of Engineers (USACE) megaprojects. Olmsted Dam FoundationThe over $2 billion Olmsted Dam on the Ohio River is currently under construction 16 mi (29.6 km) upstream from the confluence with the Mississippi River. The project is under the jurisdiction of the Louisville District of the USACE. It will consist of an 800 ft (244 m) long tainter gate section, a 1,400 ft (427 m) navigable pass, two boat abutment sections, a fixed weir section, and upstream and downstream scour protection. The Olmsted Dam and its two 1,200 ft (366 m) locks, which were built in 2002, will eventually replace both Locks and Dam #52 and #53, both built in 1929, and thereby bring significant benefits to the Ohio River navigation system.In 2002, the Jacobs/COWI JV completed the design of the dam; which was an engineering challenge for several reasons. A significant consideration was its proximity to the New Madrid Fault, which could impose an 8.4 Richter scale seismic event on the structure, which is located in an area of potentially liquefiable alluvium. The extensive seismic analysis performed by the designer included a response spectra analyses, lateral pushover analyses of pile foundations, hydrodynamic added masses, pile group effects, and the development of kinematic motions as a result of the soil-pilestructure interaction."

Jan 1, 2016

By R. A. Wattenbarger, H. J. Ramey

A systematic study has been made of the application of the real gas pseudo-pressure m(p) to short-time gas well testing. The m(p) function can be used in real gas flow problems to account for the variation of viscosity and z-factor with pressure. A mathematical model was solved numerically to generate solutions of various real gas flow problems. The effects of turbulence, formation damage and wellbore storage were included in the model. The analysis of simulated well tests showed that the interpretation methods normally used for liquid flow are generally accurate when the m(p) is used. For practical rates without turbulence, the solutions are not rate-sensifive, and the flow capacity.. kh and skin effect can be determined accurately from either a buildup or a drawdown test. However, the kh calculated from a drawdown test can be significantly low when turbulence is present. A case was simulated in which this error wa.s 36 percent. Turbulence does not affect the determination of kh from buildup tests. The proper determination of kh from p and pa buildup and drawdown plots is developed by analyzing their relationship to the m(p) method. A simple equation is given that can be used for long-range gas well performance forecasting. This expression is compared with a method pre-sended by Russell et al." Introduction The formation flow capacity and wellbore damage condition can be determined for liquid-producing tests by means of buildup and drawdown tests. These tests make use of short-time pressure transient data rather than stabilized flow tests that are often used for gas well testing. Tracy' presented a method of gas well testing that was based on ideal gas equations and utilized p2 buildup plots. This method was shown to be good for low pressure wells. MatthewsZ suggested plotting p and using an average slope and average gas properties. This method was more successful on high pressure wells. Al-Hussainy, Ramey and Crawfordh howed that variation in gas properties could be simplified by using the real gas pseu do-pressure m(p). Some cases showed that the use of the m(p) function Original manuscript received in Society of Petroleum Engineers office Aug. 8. 1967. Revised manuscript received June 11, 1968. Paper (SPE 1835) was presented at SPE 42nd Annual Fall Meeting held in Houston Tex., Oct. 1-4. 1967, and at SPE 4th Annual Eastern Regional ~eetin$ held in Pittsburgh. Pa., Nov. 2-3. 1967. 0 Copyright 1968 American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. 'References given at end of paper. provided an accurate method of interpreting buildup and drawdown tests. Because the work of Al-Hussainy et al. included only a few actual cases, there was a need to explore the use of the m(p) method for a greater variety of flow conditions. The occurrence of turbulent flow around the wellbore often is an important factor in gas well testing. Swift and Kiel,' and Carter et a1.' treated turbulence in gas well testing, but did not consider the variation of viscosity and z-factor with pressure. This paper presents the results of an investigation of the application of the m(p) method to buildup and drawdown testing. Vhe investigation included the effects of turbulence, formation damage and wellbore storage. Gas Flow Equations To formulate the mathematical model, many of the assumptions usually used in well testing theory are applied. The system has radial geometry with a closed outer boundary and is composed of a horizontal porous formation that has uniform and isotropic rock properties and uniform thickness. Allowance is made, however, for a radial region of reduced permeability near the wellbore. This region represents formation damage. The geometry of the system is shown in Fig. 1. Darcy's law does not always apply to gas flow. A more general expression is needed for non-Darcy, or "turbulent" REGION OF DAMAGED PERMEABILITY SEALED BOUNDARIES ClRCULAR WELL BORE Fig. 1—Radial flow model. AUGUST, BT7

Jan 1, 1969

By Whiten WJ

Although cone classifiers have received little attention in the modelling of mineral processing units they are one of the oldest non-mechanical classifiers. Their use has enjoyed a revival in recent years because of their low cost of installation and operation. In this paper the development of models for cone classifiers is reviewed and a new model is proposed. The experimental work, data collection and analysis are briefly described, and the new model is presented and discussed. The data used in the model development are made up from three distinct experiments using different units in each case. There are 21 data sets from a 3 m cone treating the tailings in a copper concentrator, 24 data sets from a 0.3 m pilot-scale cone, and 29 data sets from a laboratory glass funnel (0.(Y73 m diameter) used as a cone classifier, giving a total of 74 data sets. The model structure was developed from an analysis of particle settling in classifiers, using specialised model building software. The size of a particle settling in a separator and the forced flow through the apex of the cone were related via hydrodynamic dimensionless groups to the operating conditions of the unit. The model predicts the separation efficiency using the following four parameters: efficiency curve shape factor, cut-point, underflow density (per cent solids) or underflow pulp velocity. The model covers a range of feed flowrates from 1.2 to 5000 1/min.

Jan 1, 1993

By Steve H. Carpenter, Henry E. Otto

The explosive welding of metals is dependent upon the production of a jetting action caused by the collapsing of one metal plate against another. Successful welds are generally accomplished if the yield strength of the metals is in the range of 10,000 to 90,000 psi and the sonic velocity of the metal is greater than the detonation velocity of the explosive if direct contact explosive is being used.' Should the detonation velocity exceed the velocity of sound in the metal it may still be possible to obtain the jetting action and a good weld. However, in most cases where a high detonation velocity is used complications arise because of reflected shock waves which tear the bond apart as fast as it is put together.' Explosive welding of lead presents several problems since its yield strength and sound velocity are very low. Various values have been published3-5 for the velocity of sound in lead ranging from 2000~ to 23004 m per sec. Most of the high-order explosives have detonation velocities on the order of 6000 to 8000 m per sec, which precludes their use. The dynamites have a lower detonation velocity of around 2800 m per sec which is still somewhat too high. Lower-order explosives such as ammonium nitrate (1070 m per sec) must be used to weld lead in the as-received condition if the explosives are used in direct contact. Rather than use low-order explo'sives it was decided to alter the sonic velocity of the lead. The sonic velocity is directly related to the modulus of the material according to the following expression: Fig 1—Interface of explosive weld of lead to steel. Lead is on top As-polished Magnification 75 times as well as the yield strength. Bolling et al. 6 show that the shear modulus of lead single crystals increases from about 0.72 X1011 dynes per sq cm at 300°K to about 0.98 X1011 dynes per sq cm at 0°K, an increase of approximately 3 5 pct. This gives an increase in the sonic velocity of around 700 m per sec. Hence, the sonic velocity of lead at cryogenic temperatures is approximately equivalent to the detonation velocity of the low-order dynamites. We have obtained high-quality lead to steel explosive welds using a 40 pct dynamite in direct contact with the lead. Prior to detonation the lead was chilled with liquid nitrogen (78°K) to increase the strength and sonic velocity. Welds were made while the lead was cold. Specimen sizes were 3 by 6 in. A preset angle of 5 deg with a 0.10-in. standoff at the base was the geometrical setup used. The amount of explosive used for optimum welding of an 1/8 -in. -thick lead sheet to a steel plate was found to be 7 g per sq in. A PETN sheet explosive line wave generator was used to insure a linear detonation front through the dynamite. A photomicrograph of a lead-steel weld is shown in Fig. 1. The typical wave effect that constitutes a good explosive weld is present. When tested in shear, the weld failed in the lead, indicating that the bond is stronger than the lead base metal. Higher-order explosives were also tried without success. We believe this indicates the importance of matching the detonation velocity and the sonic velocity for successful explosive welding. Note Added in Proof. High quality explosive welds of lead to steel have recently been obtained at ambient temperature using a low velocity (1000 M per sec) free running dynamite. The weld interface obtained is comparable to Fig. 1. 'S. H. Carpenter, R. H. Wittman, and R. J. Carlson: Proceedings of the First International Conference of the Center for High Energy Forming, Syracuse University Press, syracu.se, N. Y., in press. 'A. HI Holtzman and G. R. Cowan: Welding Risearch. Council Bull., No. 104, April, 1965. 'Metals Handbook, 8 ed., p. 1062, Metals Park, Ohlo. 'J. M. Walsh, M. H. Rice, R. G. McQueen, and F. L. Yarger: Phys. Rev., 1957, vol. 108, pp. 196-216; 'L. V. Al'tshuler, K. K. Krupnikov, B. N. Ledener, V. I. Zuchikhin,

Jan 1, 1968

By M. Suzuki, T. Shiomi, M. Nakada, K. Tsutsumi

Mold powder plays an important role in the continuous casting process for high quality steel production. It is well known that mold powder entrapment causes surface defects in steel sheet and the high viscosity of mold powder prevents the entrapment of mold powder in molten steel in ultra low carbon steel. This paper deals with the entrapment of mold powder caused by suction by Karman?s vortex in a laboratory experiment. At first the effect of the viscosity of oil and interfacial tension between water and oil was investigated in a water model experiment. Then hot model experiments were carried out by mold powder and molten steel. The amount of mold powder entrapment was affected by the viscosity and the interfacial tension between molten steel and mold powder. As a result, the following equation of the mold powder entrapment was obtained. m=1.06*107?-0.255?m-s-2.18 The amount of mold powder entrapment decreased when the viscosity and interfacial tension increased. But the effect of viscosity was larger than that of interfacial tension in the case of the industrial mold powder when the viscosity was under 0.5 Pa.s, interfacial tension was from 1200to 1300 mN/m.

Jan 1, 2004

By Kah Lert

"The Red Mountain porphyry molybdenum deposit is situated in the Big Salmon Range, approximately 80 km east-northeast of Whitehorse, Yukon.Red Mountain is underlain by Paleozoic, argillaceous sedimentary rocks of the Yukon Cataclastic Complex, which have been intruded by a multi-phase mid-Cretaceous stock.Mineraliwtion, quartz stockwork, metal zonation, and an alteration assemblage characteristic of a porphyry molybdenum system have been superimposed on quartz monzonite porphyry and adjacent homfelsed sedimentary rocks. A later, barren and pyritic quartzeye diorite porphyry body and related dikes have dissected the quartz monzonite porphyry, homfelsed sedimentary rocks and associated molybdenite mineralization.Drill-indicated geological reserves of molybdenum mineralization outlined consist of 187 270 000 tonnes grading 0.167% MoS2.IntroductionLocationThe Red Mountain porphyry molybdenum deposit is located at 60°59'N, 133°44'W (NTS 105 C), approximately 80 km east-northeast of Whitehorse, Yukon. The property is situated within the rugged Big Salmon Range, 15 km east of the north-northwest-trending Teslin River. Red Mountain, at an elevation of 1702 m, consists of relatively steep, talus covered slopes with prominent gossanous bluffs marking the southeast flank. Relief on the property is 700 m, with tree-line at an elevation of 1450 m to 1500 m (Fig. 1)."

Jan 1, 1995

By J. M. Singer

The objective of this investigation was to determine minimum air velocities and entrainment rates for coal and rock dust dispersion in wind tunnel experiments under conditions that simulate dispersion from surfaces in coal mines where airflows are induced by weak gas explosions. Dust deposits were bed-or ridge-shaped; particle sizes were 6 to 80 microns (cohesive deposits) or 100 to 150 microns (free-flowing deposits); and wind tunnels were 7.62 cm wide by 5.08 cm high by 300 cm long, and 2.4 m wide by 1.5 m high by 215 m long. The investigation showed that minimum air velocities (directed at mid-height) of separate, layered, or mixed piles of coal dust and rock dust were within the range 5 to 30 m/sec, independent of size of wind tunnel. This finding considerably facilitates scaling of data to mine-size passageways. Free-flowing deposits dispersed relatively slowly by single-particle detachment; cohesive dusts dispersed faster by the breaking and lifting of large clumps along weak failure flames; particle dispersion occurred in flight. Layered or mixed deposits of coal and rock dust did not disperse selectively. Semiempirical expressions were derived relating minimum air velocities and dispersion rates to dust-pile geometry, cohesion, porosity, and bulk density.

Jan 1, 1972

By Cemal Can Maslak, Vijaya Bhushan Rao, Vidyaranya Bandi, Karsten Beckhaus

A Large Earth Cum Rock Fill, ECRF Dam is under construction at Polavaram in the state of Andhra Pradesh in India as part of an irrigation project. The Embankment crest width of the dam is 12.5m and base width is of approximately 136.75m with a stepped sloping height of 27m on both upstream/downstream sides. Once the 1.2m Thick Plastic concrete cut-off wall is constructed below the dam along the longitudinal central axis to avoid seepage, this magnificent structure will be supported on a series of Deep Mixing Columns and Stone Columns that are evenly arranged under the footprint of ECRF Dam forming a smooth transition of gradually reducing stiffness moduli of treated ground from the center of the embankment, where the foundation stresses are high, towards the edges in order to be able to progressively limit the settlements under the dam to a specified allowable limit. As such the required post treatment stiffness in case of stone columns is 2 times of the in-situ stiffness of foundation soil, whereas it is expected to be 5 times improvement for Deep Mixing as per project specifications. Laboratory testing and Field Trials undertaken successfully to verify the design.

Sep 1, 2022

By Jaime Fernández Conca

"El siguiente estudio señala la ubicación, fisiografia, depósito, importancia y cubicación del fierro producido en la mina del cerro Casca, situada en el distrito de Mollendo, provincia de Islay, departamento de Arequipa. Según el estudio microscópico del mineral, los depósitos de fierro del cerro Tarpuy y del cerro Miramar se dividen en dos partes: la primera se inicia en la parte baja y mediana de cerro Tarpuy, donde la mena está constituída solamente por hematita, y la segunda, se encuentra en la parte alta del cerro, formando la magnetita y hematita. Asimismo, la cubicación aproximada del fierro, señala que la zona mineralizada tiene una forma piramidal y la base, una longitud aproximada de 120 m, con un ancho medio de 80 m.; la altura de la mineralización será aproximadamente de 60 m. Estas dimensiones darían 288,000 m3 y aproximadamente 1,000,000 de toneladas de mineral. En el aspecto económico, dado que su ley en sílice es muy alta y no permite una fundición en alto horno, el yacimiento minero no tiene por el momento valor comercial como mineral de exportación. Por ello, sería conveniente la aplicación de un tratamiento de concentración por gravedad o por el campo magnético."

Jul 20, 1956

By K C. Corin, N Ndamase, M Tadie

Mining operations in arid regions are compelled to reduce their consumption of fresh water. Closed water circuits are an attractive solution and, in addition to reducing freshwater consumption, have the added benefit of reducing reagent consumption as well as the environmental impact by eliminating effluent discharge. Accumulating ionic species have been shown to hinder collector adsorption which reduces the recovery of valuable minerals. Numerous studies have investigated the effect of degrading water quality on collector adsorption however there is very limited understanding as to how this takes place from an electrochemical perspective. This study therefore aims to investigate how the presence of accumulating ionic species at varying concentrations affects the electrochemical adsorption of sodium ethyl xanthate onto galena. The synthetic plant water used in this study comprised of single salt solutions to isolate the effects of the ionic species of interest. The ionic strengths were varied between 0.0242 M, 0.0727 M, 0.1212 M and 0.2426 M which correspond to University of Cape Town (UCT) Centre for Minerals Research (CMR) synthetic plant waters of 1, 3, 5 and 10SPW, respectively. Mineral rest potentials indicated how changing water quality affected xanthate-mineral interactions. Microflotation observed the impact of changing water quality on mineral floatability.

Aug 24, 2022

By G. H. Faye

The prospect of obtaining high-grade concentrates from Canadian pyrochlore ores is rather unlikely, and experimental beneficiation pro-cesses ?appear to have yielded products in the range of 3 to 20 per cent N'b205? A possible solution of the problem is to find an economical chemical method for recovering high-purity Nb2?05 from such concentrates. A technically feasible but economically unproved process is outlined in this paper, in which the concentrate is decomposed by an acid attack and the oxides of niobium and tantalum are isolated and then separated by liquid-liquid extraction. The solution of the ore is adjusted to 7 M HF-5 M HNO3 and the niobium and tantalum are extracted from this solution with methyl isobutyl ketone. The mixed oxides of niobium and tantalum are recovered from the oxdanic phase and dissolved in 0.5 M HF-1.0 M HNO3. Tantalum is extracted preferentially from this solution with methyl isobutyl ketone, leaving niobium in the aqueous phase. By the use of this process it is possible to produce niobium pentoxide and tantalum pentoxi.de in 99.5 per cent purity with a recovery of approximately 95 'per cent, under lab-oratory conditions.

Jan 1, 1957

By Ernst Langer

INTRODUCTION Morro do Niquel is located near the small town of Pratdáolis in the southwest part of the State of Minas Gerais, Brazil, about 300 km in a straight line north of São Paulo and 300 krn west of Belo Horizonte. The deposit is known since 1935. Systematic exploration started, however, only in 1957 and production with one furnace in 1962. Since 1969, after the installation of a second furnace, the mine produces about 2 500 tons of nickel, contained in ferronickel, per year. This production is now consumed totally by the Brazilian steel industry. The "Morro do Niquel" is a serpentinite stock of 900 by 400 m which rises 200 m high above the surrounding metamorphic rocks of Algokian age (see Figure 1). On top of the hill there is a leached barren zone of about 200 by 400 m, generally 20-30 m deep, which consists practically only of a boxwork of quartz colored brown by limonite. Surrounding this zone on the sides of the hill is weathered, decomposed serpentinite which contains about 213 of the economic nickel mineralization. Roughly 113 of the ore reserves lie below the leached overburden representing ore of a different type. The geological map and cross-section, Figure 2, give a clear picture of the occurrence.

Jan 1, 1979

By Hermann Irresberger

SUMMARY In the German hard coal industry, relevant parameters influencing strata control have been identified in many years of intensive research work. The research results allow the formulation of the technical requirements on the design of shield supports as a function of the geological and operational conditions the face machinery is subject to. Keys to strata control are support resistance adjusted to the individual conditions of application and the tip-to-face interval. The technology to implement these requirements in actual operation is available. The automation of the shield-advance work cycle, currently setting in, can further contribute to improve strata control. In doing so, however, we must not forget the demand for an unsophisticated and low-cost design of shield supports with high operational safety. INTRODUCTION The German hard coal mining Industry produces coal from flat and inclined seams in depths between 400 and 1,300 m. The coal is exclusively won by longwall working involving face lengths up to 280 m. The thickness of the seams being worked is between 0.7 m and 4.5 m. Coal winning is fully mechanized with drum shearers or coal ploughs; two, three, or four leg shields are predominantly used as supports.

Jan 1, 1984

By C. J. Pritchard, A. B. Cecala

An evaluation was performed on a district recirculation system at a trona mine in Granger, WY. A 1.52 m-diam (5 ft-diam), 37.3-kW (50-hp) vane axial fan was installed in a crosscut between the intake and return airways and recirculated about 31.4 m3/s (66,578 cfm) of air back into the intake. This amounted to a recirculation factor of about 20% of the return air. This air was part of the primary ventilation to three different continuous miner sections at operating distances of between 610 m (2000 ft) and 1829,m (6000 ft) from the recirculation fan. The mine environment was constantly monitored for respirable dust, methane and carbon monoxide in the operating sections and in the main intake and return entries. In addition, air samples were taken with and without the recirculation system during the evaluation and analyzed using gas chromatography. The results of this study showed only small increases in dust, while all other mine contaminants remained at such low levels that it was impossible to determine any relative changes from the recirculation system. Because of this, a brief SF6 tracer gas analysis study was subsequently performed to more precisely determine an increase in a mine contaminant with the recirculation system.

Jan 1, 1992

By King D

Recent field experiments in the United Kingdom (Buchanan, 1979) have shown that the in-seam technique is capable of detecting a 1m fault in a 3m seam, at a range of 280m and with a resolution of ¦40m. Comparable tests in Australian collieries are proceeding. Although the practicality of an implementation of the technique on a routine basis remains to be demonstrated, the potential of the technique for the prediction of outbursts clearly warrants detailed examination. This potential will,depend, inter alia, on the level and scale of variations in elastic (and anelastic) properties of bodies of coal undergoing stresses associated with mining. Available data, mainly from studies of the seismic properties of gas saturated reservoir rocks, confirm the intuitive view that stress increases give rise to increases in seismic wave velocity and decreases in wave attenuation, markedly at low stresses (as pore spaces close with little resistance) but less so as stress increases. Such increases are of the same order as aniso- tropic effects, but should provide impedance contrast sufficient for detection by in-seam seismic methods. At higher stresses, cracks form within the rock mass. Results from research on earthquake prediction provide some clues to the behaviour of sedimentary rocks sub- jected to large stresses. In particular, the

Jan 1, 1980

By Virgil J. Stachura, Calvin L. Cumerlato

The U. S. Bureau of Mines is conducting research on blasting methods that reduce highwall overbreak and the associated rockfall hazards. This paper presents the results of tests using a low-density water gel to improve the quality of air-decked presplit blasts at a surface coal mine in New Mexico. The explosive's specific gravity averaged 0.50 and was bulk loaded using a modified truck which injected the gassing agent. Reductions in overbreak and resulting rockfall were achieved in comparison to a highwall presplit with ANFO. The test sections used 15° angled blast holes and resulted in 1,119 m (3,672 ft) of air deck presplit highwall using a low-density water gel which was then compared to 894 m (2,934 ft) of highwall shot with an ANFO air decked presplit design. The total quantity of explosives per hole ranged from 68 to 113 kg (150 to 250 lbs) and the 27 cm (10-5/8in) holes were 19- to 33-m (62- to 108-ft) deep on 5.5 m (18-ft) centers. Periodic visual examination and photographic surveys of the highwall test areas were used to document the amount of rockfall. In addition, laser profiles of selected sections were conducted to further delineate the damage and highwall contour differences.

Jan 1, 1995

By Abhilash, S. Sarkar, T. Venugopalan, P. Meshram

"To explore blast furnace slag as a secondary resource for rare earth elements (REEs), blast furnace slag containing lanthanum (La), cerium (Ce), erbium (Er) and neodymium (Nd) in concentrations of 17, 16, 4 and 44 ppm, respectively, was processed with sulfuric acid while optimizing the parameters of acid concentration, temperature and pulp density. The experiments showed that recovery rates of 92, 36, 35 and 52 percent for La, Ce, Nd and Er, respectively, were achieved at 1 to 5 weight/volume (w/v) percent pulp density using particles smaller than 250 µm and treating with 1 M sulfuric acid for one hour at room temperature. Raising the temperature to 95 °C promoted the dissolutions of Ce and Nd to 89 and 84 percent, respectively, for the same 1 M acid concentration and one-hour duration at 5 w/v percent pulp density. Cyanex 923 was preferred over Cyanex 301 for the purification of REEs from leach liquor. In another route, the leach liquor was subjected to precipitation with 0.5 to 1 M oxalic acid, resulting in a product with 4 to 5 percent concentration of REEs.IntroductionRare earth elements (REEs) are important materials in numerous high-technology applications, but they have high supply risk, giving rise to the study of new sources. The recycling of REEs has been well researched, especially on a small scale, but has not been widely implemented. Less than 1 percent of REEs were recycled in 2011 (Binnemans et al., 2013). REEs occur in a large number of minerals in oxidic compounds, such as oxides, carbonates, phosphates and silicates, and are present as mixtures at 10 to 300 mg/kg concentrations in many rock formations, such as basalts, granites, gneisses, shales and silicate rocks. The most abundant REE in the Earth’s crust is cerium (Ce), at a concentration of 20 to 70 mg/kg, followed by neodymium (Nd) and lanthanum (La), with heavier REEs being less abundant (Binnemans et al., 2013). REEs occur in nature in their oxidized forms in salts and minerals due to their electropositive nature and high affinity for oxygen. The possibility of recovering REEs"

Jan 1, 2017

By Norman E. Breslow, John A. Montgomery, Sanford W. Horstman

Reconstruction of historical exposures to silica dust is required in an ongoing cohort mortality study of workers in the diatomaceous earth (DE) industry. However, historical data were collected using three different sampling methods. This study was conducted to derive empirical quantitative relationships from linear regression equations between the three methods: standard impinger, total mass, and respirable mass. Dust from one diatomaceous earth processing plant was sampled simultaneously by all three methods. Results from 61 clusters of the three sampling devices indicate that the phcle size distribution of the dust varies with the two parent products sampled. baghouse product and main product. The relationships between particle counts and respirable mass are: Respirable mass (mg/m3) = 0.064 (mppd) impinger count for baghouse product dust, and respirable mass (mg/m3) = 0.018 (mppcf) impinger count for main product dust. The relationships between particle counts and total mass are: Total mass (mg/m3) = 0.837 (mppcf) impinger count for baghouse product, and total mass (mg/m3) = 1.21 (mppcf) for main product dust. In all four euuations, the intercept did not differ significantly from zero, and the correlation coefficients ranged from 0.90 to 0.95. Results are compared with data from four previously published studies.

Jan 1, 1991

By Christopher J. Pritchard

Federal mine safety regulations prohibit the recirculation of face air In a gassy Class III metal-non metal mine. Tg Soda Ash, Inc, operates a 2.0M ton/yr (2.2 million st/yr) underground gassy Class III trona mine In southwest Wyoming, currently liberating approximately 5,700 m3/day (200,000 ft3/day) of methane. Because of the low methane emissions and the incombustibllity of trona, it was decided that Tg would be an excellent environment to test recirculation at a U. S. gassy mine, for possible future use by Industry. A research program was begun with the cooperation of MSHA, the U.S. Bureau of Mines, the University of Utah, and Tg. Initial testing centered around re-using shop air under¬ground. Next, conduct a continuous miner section recirculation test to see how the face contamination was affected by 305m (1,000 ft) and 610m (2,000 ft) recirculation distances. A district test followed to examine the effects of the critical parameter - respirable dust. Finally, a long-term program to study respirable trona dust transportation and deposition in mine airways to plan for district fan siting and effects on face air dust levels.

Jan 1, 1995

By Robert A. Jankowski, J. Drew Potts

The Bureau has identified several ventilation techniques and a water spray application for reducing auger mining dust levels. The dust control methods all work by improving air quantity or flow patterns at the face. Section airflow is maximized by reducing air leakage between entries. Sealing stoppings with brushed- on mortar, containing fiberglass additives, reduces leakage. Heading airflow is maximized by properly installing the brattice curtain and keeping the area between the curtain and rib free from obstructions. The brattice curtains should be hung at least 1.7 m (5.5 ft) from the ribs in 7.9 m (26 ft) wide entries and kept less than 4.6 m (15 ft) from the face. A tight curtain seal is created by using the mine air pressure to force the curtain against the timbers, roof and floor of the mine. Using both a blowing curtain and an exhausting curtain will isolate some face workers from dusty air. The Bureau designed, auger clearer spray system, can be used to force heading air across the active face. Laboratory tests indicate that the auger clearer spray system can increase face velocities by more than 0.5 m/sec (100 ft/min), while using less than 0.13 l/sec (2.0 gal/min) of water.

Jan 1, 1989