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By Kitzinger F

The economic climate of the Canadian mining industry forced an increased interest in rapid, continuous excavation techniques for hard rock formations. The potential applications and advantages of continuous mining over the present drill- blast-muck labour intensive cyclical methods are considerable. Noranda investigated an electrical technique, Plasma Blasting showing considerable promise for mining hard rock. The background of the technology and the theory of blasting rock with electricity is described. The Plasma Blasting process is based on the fast discharge of stored electrical energy into a small amount of electrolyte, suitably located in the rock. The electrical energy converts the electrolyte into high pressure plasma, which expands very quickly, thereby, generating a shock wave. This shock wave produces a stress field inside the rock, resulting in a blast similar to that made by chemical explosives, but without the deleterious fumes. Noranda is currently blasting boulders of 4-5 tonnes and is at present constructing a mobile, autonomous secondary rock breaker for underground and open pit applications. Tests on in situ hard rock formations will lead to the development of a continuous mining machine. Production rates of 500 tonnes per man-shift could be obtained with such a machine.

Jan 1, 1990

By Phillip R. Moyle

A cobalt/manganese occurrence in Clark County, Nevada was the subject of a site-specific mineral investigation by the U.S. Bureau of Mines in 1988-90. The study site is in the northern part of the Million Hills (wilderness) study area which is administered by the Bureau of Land Management. Field work during a period of one week consisted of geological mapping and sampling of workings and outcrops, and geochemical and geophysical surveys conducted on four transects totalling 7,600 ft. Although the concentrations of cobalt (0.1 to 0.5 percent) detected in samples from the fissure zones are within the range of grades associated with world-class economic deposits, the volume of material enriched in cobalt at the study site is insufficient to warrant consideration as a potential resource. Concentrations of manganese, nickel, copper, lead, zinc, barium, and thallium, although anomalous, are too low for economic consideration. At the study site, workings consist of three trenches and nine pits. The exploration history is unknown, and no production is reported.

Jan 1, 1990

By C. W. Chiaretta

Utah Power and Light Company's Deer Creek Mine had been developed to a point where mine ventilation efficiency had declined to an unacceptable level. Problems identified were ventilation of inactive areas, excessive leakage, and restrictions in the return and intake air ways. Mine management implemented an intensive mine ventilation improvement program to alleviate future problems with respirable dust in the working sections and diesel equipment emissions. Program objectives included sealing of inactive areas of the mine, rehabilitation of high resistance areas, and construction of additional intake and return aircourses. Applications of computer modeling techniques are used to predict the effects of ventilation changes and improvements. Improvements are then prioritized to achieve the largest efficiency increases first. Actual real time assessment of the mine environment and ventilation changes are accomplished with a mine wide monitoring computer system. The Deer Creek ventilation improvement program has more than doubled the ventilating efficiency of the mine.

Jan 1, 1990

By Richard J. Mainiero

The U.S. Bureau of Mines in cooperation with Jim Walter Resources, Inc. (JWR), Brookwood, AL, evaluated the use of sheathed explosive charges in breaking up large stones that can jam the feeder¬breaker or pan conveyor on longwalls and halt operations. Use of the sheathed charge reduced the downtime of the longwall panel to 15 to 30 min as compared with the 1 to 2 h required to drill and shoot the stone. Firing the sheathed charge at the face caused no significant damage to Iongwall equipment. Use of the sheathed charge also represented an improvement in safety by eliminating the exposure of miners to the inherent hazards of the face for extended periods of time. Another benefit, which is difficult to quantify, is the elimination of the temptation to shoot mudcaps or adobes, which is illegal in U.S. underground coal mines.

Jan 1, 1990

Develop a method for mapping planar geologic features in deep underground mines where the presence of metal interferes with compass readings. Background A fundamental problem of mapping planar geologic features in deep underground mines is the presence of metal (water and air pipes, track, equipment, etc.), which affects the accuracy and consistency of compasses. Present geologic mapping methods include use of transits or theodolites, both of which are cumbersome and time consuming to use. To complicate the mapping, process each planar feature must be surveyed, and if that feature is not apparent on the opposite wall, it cannot be mapped. Another method of mapping is to stretch a tape measure between two survey spads and place a string along a planar feature on one wall and out into the opening until it intersects the tape measure. This method, in addition to being time consuming, is also inaccurate. Because detailed mapping of planar geologic features deep underground involves many repetitive measurements, a quick, accurate, and reliable method for making such measurements was necessary. The geolaser was developed to make such measurements in deep underground mines where metal interferes with conventionally used compasses.

Jan 1, 1990

By C. C. Johnson

In the fourteen years that Rössing Uranium Limited has been in production, the metallurgical operations and controls on the leaching plant have evolved through four basic stages. Initially, the emphasis was placed on the achievement of consistent plant operation by overcoming severe startup difficulties. The second stage involved the attainment of the design operating targets, and also the commissioning of the ferric-leaching reactors in order to achieve a ferric ion concentration of more than 3,0 g/l. Improvements in control then became the priority, with the emphasis on consistently achieving the target concentrations of ferric ions, total iron, and terminal acidity. The latest phase has concentrated on the optimization of costs by means of adjustments to the historically established operating parameters in order to achieve large savings on consumables while maintaining the leaching efficiencies. Apart from the obvious incentive of reducing costs in an inflationary economy and a depressed uranium market, impetus for this work was given by a change in the type of ore from the open pit, which has the effect of reducing the extraction efficiency while increasing the consumption of consumable materials. These problems and their solutions are discussed in detail, and the importance to cost-effective optimization of an accurate, up-to-date cost-reporting structure is stressed.

Jan 1, 1990

By Robert D. Schmidt

The Cyprus Casa Grande Corporation has provided Bureau of Mines researchers with an opportunity to investigate the hydrology of leaching an in place copper ore deposit. Hydrologic investigations of underground in situ copper leaching are being jointly conducted under a cooperative agreement. The hydrologic concerns of leaching operations at the Casa Grande mine focus on maintaining adequate solution injection and recovery rates, and on distributing the injected leach solution effectively within the ore deposit. Hydrologic considerations underlying these concerns relate to the permeability of the oxide ore zone during leaching, the unsaturated condition of the deposit prior to leaching, and the constraints imposed on in situ hydrologic design by the underground mine setting. The investigation involves monitoring of flow and pressure conditions in 58 injection and recovery wells, estimating permeability conditions using a hydrologic model, and on-site testing of hydrodilation and airlift pumping. Transient, fracture-controlled permeability is determined to be the dominant hydrologic consideration. A statistical modeling procedure has been developed for estimating changes in permeability during leaching. Flexibility in well design and operation is essential for accommodating the changes in fracture permeability that occur during leaching.

Jan 1, 1990

By Kenneth J. Reid, Marian S. Stachowicz

A preliminary evaluation of a new in-stream particle size analyzer has been carried out using materials obtained from a taconite plant in Northern Minnesota. Results are reported for bench scale, pilot scale and full scale tests, the latter being carried out in a taconite plant concentrator. The unit employs a novel scanning laser microscopy principle and details of the equipment configuration and operating principles are presented and discussed. Data acquisition is via an eight channel digital electronic system and particle counts are collected on the basis of reflected light pulse time intervals which are a direct measure of particle size. Output is available as an eight point individual or cumulative size distribution or as computed averages. The practical aspects of sample point location and flow requirements for reproducible results are outlined and discussed.

Jan 1, 1990

The research, development and testing of a Blast Control Plug (U.S. Pat. #4,754,705) funded by the U.S. Department of Energy is described. The plug's function is to improve blasting efficiency through the enhancement of stemming effectiveness and thereby reduce drilling and blasting costs. The plug comprises a solid unit placed in the blast hole within the stemming column above the explosive. It is designed for use with back filled drill cuttings or any other suitable material The research and development program comprised the testing of the plug in small diameter holes in competent rock for both bench and crater blasting configurations and full scale field trials in multiple hole and row blasts using blast holes of from 76 to 387 mm in diameter. Test measurements included stemming displacement and velocity, face movement and extent, peak air over pressure and ground surface peak particle velocity. Data acquisition equipment included a Spin Physics SP2000 high speed video motion analysis system, and acoustic and seismic monitoring units. Substantial reductions in stemming ejection velocity or ejection elimination were achieved whilst reducing stemming length by up to 35% over conventional practice. Peak air blast pressures were also reduced by between 8 and 25 dB. A strong inverse relationship between rock face movement and stemming ejection velocity was found. The implications of the importance of stemming effectiveness in blasting and computer blast simulation is also addressed.

Jan 1, 1990

By F. P. A. Robinson, J. W. Fourie

Austenitic stainless steels are welded using low-heat inputs. However, owing to differences in the physical metallurgy of austenitic stainless steels and duplex stainless steels, low-heat inputs should be avoided for duplex stainless steels. This paper highlights the differences in solidification mode and transformation characteristics of these two types of alloys. Recent work on the effect of heat input on the properties of weldments of duplex stainless steels is reviewed.

Jan 1, 1990

By Thomas J. Albin

This U.S. Bureau of Mines report identifies potential causes of slip-and-fall accidents occurring during surface mine equipment maintenance and describes the relative roles of direct worker behavior and machine design. The relative roles of human behavior and machine design in the causation of slip-and-fall accidents were determined through analysis of accident records, observations of maintenance worker behavior, and evaluation of mine machinery. From these data, relative risk ratios were calculated. Behavior had a relative risk ratio of 1.5; machine design, specifically access systems design, had a relative risk ratio of 2.2. Of the access systems, ladders had the highest relative risk ratio, 7.0. This study suggests that accident intervention would be most profitably made in improving the design of systems used to access maintenance worker areas of mining equipment.

Jan 1, 1990

By Lijun Xu, Jan M. Mutmansky

"Mutmansky, J.M. and· Lijun Xu, 1989. Some observations on particulates collected in underground coal mines using diesel and non-diesel equipment. Min. Sci. Technol., 9: 207-218.The results obtained when sampling twenty underground coal mine sections, each in a different mine, are outlined. The sampling effort was oriented toward a detailed characterization of coal mine dusts and thus eight-stage Anderson Model 298 impactors were used as the primary collection instrument. This instrument allowed a fairly detailed size distribution for each of the particulates sampled. Because four of the mines used diesel outby equipment and/or diesel shuttle cars at the face, it is possible to make some comparisons of the particulate distributions in diesel versus non-diesel mines.One of the more interesting results is the pattern that exists in mines lising diesels only for outby utility haulage. Particulates in these mines seem to be consistently heavy in the fine size ranges, perhaps being of significant concern to the industry. While no definite conclusions can be drawn from the limited data, a more detailed study of particulates may provide a better picture of particulate loadings.IntroductionThe subject of particulate emiss1ons from underground diesel equipment is currently a very important topic as health concerns and regulation of diesel particulate emissions have created new environmental problems for mine operators. The amount of particulate matter originating from diesels has not been extensively measured and problems of differentiating coal and mineral dust from diesel particulates make existing data questionable.However, it is necessary to make an assessment of the problem in order to solve it. It is known that particulates from diesel engines are solid aerosols formed in the combustion process. Technically, this places the particles in the category of fumes. It is also known from tests where no mineral dust could be a factor in the measurements that about 90% of diesel particles are less than 1 µm in aerodynamic diameter [3]. To measure the diesel component of a coal/diesel particulate to measure, Johnson et al. [2] have developed procedures for utilizing laser Raman spectroscopy. The determination of diesel content in a coal/diesel mixture is difficult due to the chemical similarity of the two organic materials. However, laser Raman spectroscopy, which is often used for identification of organic materials, has potential if the Raman spectra for the two materials are different and unique. The study concluded that an accuracy of ±~% could be achieved for mixtures containing up to 55% diesel particulate. The method is relatively complex and would need further development for routine application."

Jan 1, 1990

By E. M. Weenink

One of the new direct smelting technologies for the production of lead from sulfide concentrates that has reached the commercial stage is the Outokumpu lead flash/electric furnace ?smelting process. Using data from pilot plant test work, energy and mass balances for a commercial plant were initially calculated by hand. To optimize process conditions, a large number of such balances had to be generated and a computer program using Lotus 123 was developed which provided an excellent opportunity for computer simulation. Operating parameters can be calculated by iteration using input values for feed composition, feed rate, smelting temperature, and lead content of the slag'" The output is presented by means of various views of the appropriate process steps, or in 68 different graphs.

Jan 1, 1990

As an Inspector of Mines in Queensland, my main responsibilities include the enforcement of the Mining Act 1968 - 1986, the Mines Regulation Act 1964 - 1989 and the Metalliferous Mining regulations 1989 to promote the safe and responsible exploitation of the States' mineral wealth.An important adjunct to this task is the offering of an advisory service to the mining industry. However, in the pursuit of my duties to this regard, I have sadly observed in some cases, numerous wrong doings and negative activities by miners which have led to their ultimate demise, not to mention that of others. Despite what I consider corrective advice, I have witnessed, again in some cases, disregard and blind pursuit for the wrong end.This then is a novel approach to get the message home in the form of a light hearted cartoon presentation relating the saga of an average Aussie battler entering the mining game unprepared, making the wrong decisions due to his own ignorance and the cleverness of others, leading finally to his and possibly others' downfall.

Jan 1, 1990

By Lyle Avey

For the purpose of this paper, testwork and general pre-splitting practice will be discussed for the Chimney Creek Mine.

Jan 1, 1990

By Kerr I. D, Kennedy M

Flash X-radiographs were obtained of commercial electric No 6 and No 8* strength aluminium tube detonators in small-diameter cartridges of emulsion explosive at various times after fusehead operation. The trigger system for the radiography was based on the detection of light following fusehead firing via optical fibres inserted into the fusehead cavity during detonator assembly. These experiments were simulated using a finite element hydrocode with realistic treatment of the non-ideal reaction kinetics. Excellent agreement was demonstrated for the shape and position of the shock waves. In both cases, initiation of the emulsion was predominantly forward from the detonator. For the No 8* strength detonator, this initiation resulted from the shockwave delivered through the sides of the detonator, while for the No 6 strength detonator, initiation was the result of a complex interaction between shockwaves originating both from the sides and from the endcap. In the reverse direction (towards the crimped end of the detonators), initiation was only weakly dependent on detonator strength, being controlled mainly by the competing processes of rarefaction from the cartridge boundaries and comer turning of the detonation wave from the forward initiation. The consequences for field performance of small-diameter emulsions will be discussed.

Jan 1, 1990

By R. J. Davidson

The chemistry related to the adsorption of gold, uranium, and transition-metal ions onto algal biomass (activated carbon) is related to the genesis of the Witwatersrand. Detrital gold being washed into the early basin, together with cyanide generated in the atmosphere, would have solubilized as the stable aurocyanide complex, the necessary oxygen being produced from the photosynthesis of carbon dioxide by primitive algae. Pebble-type conglomerates, while providing for the free movement of solutions containing the vital nutrients for prolific algal growth, would have screened of the sunlight, which would otherwise have degraded any free cyanide in solution. With the subsequent decomposition of the algal deposits, it is surmised that carbon-rich layers having adsorptive properties similar to those of activated carbon formed in the conglomerates. Under these conditions, gold (silver) in solution would have been adsorbed selectively as the cyanide complex, together with uranium as the carbonate complex. Any transition-metal ions present would also have been adsorbed onto such a substrate. The subsequent burial and compression of the gold-rich conglomerate with temperatures rising to about 400DC would then have reduced the adsorbed gold to the metal in a single segregated gold-silver metal phase (95 to 99 per cent of the contained gold), while leaving behind a sulphide phase rich in iron, base metals, and arsenic and containing some gold and silver. The recrystalization of this later phase may explain the presence of the rather consistent contents of secondary pyrite in the Witwatersrand conglomerates. Similarly, uranium minerals, some rich in titanium and carbon, may also have formed. An adsorption model would explain the very consistent trends in the gold-to-silver ratios of individual reefs in the Witwatersrand, which suggest an extensive hydrothermal system approaching isothermal equilibrium. Also, as gold grades increase, so silver grades generally decrease, indicating the sequential displacement of silver by gold as classically obtained with activated carbon.

Jan 1, 1990

By Gang Chen

This paper explores the possibility of using short-term time-dependent plate loading tests to estimate the elastic and viscoelastic parameters of the weak floor strata typically associated with coal seams in Illinois. Plate loading tests with incremental loads, similar to incremental creep experiments, were conducted until the floor failure occurred. For each increment, the load was held constant for a period ranging from 1-4 hours until a constant deformation rate was achieved. The deformation-time data were analyzed for viscoelastic parameters of weak floor strata assuming its behavior to be adequately represented by the standard Burgers model. The analysis required development of mathematical equations for the time-dependent deformation of the standard Burgers material under a three- dimensional state of stress. Time-dependent pillar settlement data at one mine were also analyzed for elastic and viscoelastic parameters of the weak floor strata using the developed equations. These parameters were compared with similar parameters estimated from plate loading tests.

Jan 1, 1990

Blasting, particularly bench blasting, uses finite length cylinders of explosive close to two free faces. The rock to be blasted is usually intersected by a complex 3-D system of joints. To fully simulate a blast, a 3-D dynamic model is required. It is shown that the static stress distribution around a long cylinder can be reproduced by superposing the static stress distribution of a suitable chain of spheres. Thus, the dynamic results for individual spheres given by Favreau (1969) can now be substituted for the static results to give a dynamic model of the stress distribution around a long cylinder. Comparison of measured and computed waveforms show that the measured waveforms are much more attenuated and dispersed than expected. The consequences for explosive evaluation and design are Discussed.

Jan 1, 1990

By N. S. Dalal, Xianglin Shi

"Electron spin resonance (ESR) measurements provide direct evidence for the involvement of Cr(V) in the reduction of Cr(VI)· by NAD(P)H. Addition of hydrogen peroxide (H2 O 2) to NAD(P)H-Cr(VI) reaction mixtures suppresses the Cr(V) signal and generates hydroxyl (·OH) radicals (as detected via spin trapping), suggesting that Cr(V) reacts with H2O 2 to generate the ·OH radicals. Reaction between H2O 2 and a Cr(V)·glutathione complex, and between H2O 2 and several Cr(V)-carboxylato complexes also produces ·OH radicals. These results suggest that Cr(V) complexes catalyze the generation of ·OH radicals from H2O 2, and that ·OH radicals might play a significant role in the mechanism of Cr(VI) cytotoxicity. KEY WORDS: ESR. spin trapping, Cr(VI) reduction, Cr(V), hydrogen peroxide, free radicals.INTRODUCTIONThis communication reports an ESR spin trapping detection of hydroxyl ( OH) radicals.in reactions between some Cr(V) complexes containing biologically important ligands and hydrogen peroxide (H2O 2 ). This work was undertaken because while the reduction of Cr(VI) to lower oxidation states has been suggested as a key step in the mechanism of Cr(VI) toxicity, the reaction· mechanism is not yet clear. 1 Mutagencity has been well documented for Cr(VI) via various bacterial assays, while Cr(III) has been shown not to be mutagenic.2 • 3 Since it has been reported that compounds containing Cr(VI) do not react with isolated DNA,4 the reduction of Cr(VI) by other cellular constituents has been thought to be important in the mechanism of Cr(VI) induced DNA alteration.1·4 • 5 For cellular systems earlier studies include those on the reduction of C~(VI) by microsomes,6-8 rat liver DT-diaphorase,9 and aldehyde oxidase. 10 Regarding the reduction mechanism, Jennette used ESR spectroscopy to show that a long-lived Cr(V) complex is formed as an intermediate in the microsomal reduction of Cr(VI) in the presence of NADPH.8 She postulated that Cr(V) is the ""ultimate"" carcinogenic form of chromium compounds. This conclusion has led to many further investigations of the formation of Cr(V) in the reduction of Cr(VI) under biologically relevant conditions.11 - 19 More recently, however, it has been suggested that oxygen-derived radicals generated during the Cr(VI) reduction are the species responsible for the DNA alteration.20.2• To the best of our knowledge, however, no information is available on the generation of such radicals in the reduction of Cr(VI) under biologically relevant conditions, except some preliminary results on the glutathionyl (GS·) radical formation in the reduction of Cr(VI) by glutathione (GSH). 11 - 19 We, therefore, undertook a systematic investigation of the reaction of Cr(VI) with NAD(P)H, GSH, ix-hydroxycarboxylic acids, and H2O 2 • NADPH was chosen as a model reductant because of its ubiquitous existence inside the cells, its critical role in the enzymatic Cr(VI) reduction,1·6-9 its representation of important cellular Cr(VI) reductants, and its ability to reduce other metal ions.22 GSH was chosen as another model Cr(VI) reductant because GSH also exists inside cells, it represents another important category of cellular Cr(VI) reductants, the thiols, and it also plays an important role in the Cr(VI) toxicity .1• 1 ""- 19.i3.i4 For further clarification, we also studied the reaction of Cr(VI) with several '1'.-hydroxycarboxylic acids in the presence of H2O 2 since these acids are definitively known to reduce Cr(VJ) to form stable, isolable Cr(V).25 .2 6 The results obtained indicate that Cr(V) complexes, produced in the reduction of Cr(VJ) by cellular reductants, react with H2 O 2 to generate ·OH radicals, which might be the initiators of primary events in Cr(VI) carcinogenicity."

Jan 1, 1990