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By Wilbur I. Duvall

In a review of so 40 papers on damage to residential structures resulting from blasting, only 3 were found that present data on the observed amplitude and frequency of the vibration levels produced by blasting together with an observed degree of damage to a residential structure. The data from these three reports have been analyzed statistically to determine if one of the quantities, displacement, velocity, or acceleration, is more reliable than the others for estimating the degree of damage to a residential structure. From this analysis the conclusion is drawn that a given degree of damage to a structure is most closely related to the magnitude of the particle velocity of the wave motion passing thru the earth at the structure location. On the average, only minor damage it observed for peak particle velocities of 5.4 inches per second, and major damage is observed for peak particle velocities of 7.6 inches per second. When the spread of the data is taken into consideration, the following statement can be made: Wave motions that have a peak particle velocity in excess of 2 inches per second have a fair probability of producing some damage to structures, whereas wave motions that have a peak velocity less than 2 inches per second have a very low probability of causing any damage. Therefore, the recommendation is made that vibration levels in the vicinity of residential structures should be maintained below a peat particle velocity of 2 inches per second. The above criterion for safe blasting is considered to hold over a wide variety of soil and rock conditions because the original data were obtained for a wide range of soil and rock conditions and on various types of residential structures. INTRODUCTION Ever since explosives were discovered and developed for mining purposes, there has existed the problem of what effects the air and ground vibrations resulting from blasting have on structures of various types. This problem is

Jan 1, 1962

Comparing Energy Efficiency of Multi-Pass High Pressure Grinding Roll (HPGR) Circuits With increased emphasis on reducing costs and carbon emissions in mineral processing, it is becoming essential to employ the most efficient comminution devices and to use them to maximum effect. High pressure grinding rolls (HPGR) are considered highly efficient compared with other devices, however their relative efficiency in multi-HPGR circuits is less well understood. A series of comminution tests was carried out to evaluate three multi-pass HPGR circuits and a jaw crusher-ball mill circuit. Combinations of HPGR units (1.0 m and 0.25 m diameter), jaw crushers and Bond ball mills were used to grind a 32 mm top size porphyry copper feed (BBWI = 12.1) to a product P80 size of about 150 ¦m. Up to three passes of HPGR were used in each circuit, with energy measurement and size analysis at each point in the comminution process. The energy efficiencies of individual comminution stages and of the overall circuits were quantified and evaluated using three different approaches. The operating work index method for comparing comminution energy efficiency underestimated HPGR performance due to the large amount of fines generated. The -75 ¦m efficiency factor and F50/P50 reduction ratio interpolation methods both give a fairer measure because they better take into account the amount of fines generated by HPGR. The results show that the relative comminution efficiencies of the three multi-pass HPGR circuits tested differ by as much as 22%, providing insights as how to best employ HPGR in a comminution circuit. The most energy efficient of the circuits tested was a three-pass HPGR circuit with a 1.0 m diameter roll on the first pass in closed circuit with an 8 mm screen followed by a second and third pass in a 0.25 m roll.

Sep 13, 2010

By Haiping Sun, Samir Ganguly, Oleg Ostrovski, M. Yaser Lone

Wettability of graphite by synthetic SiO2-Al2O3-CaO-MnO slags with varied MnO content and by industrial slags was studied at 1350-1600 °C using sessile drop method under argon atmosphere. Initial contact angle was the lowest (110-115o) for the MnO-free slag. For slags with 10-40 wt% MnO, the initial contact angle was in the range 125-135o. The contact angle decreased with the contact time. The change in the contact angle with slag mass was found insignificant. The surface tension of slags obtained from the drop shape analyses was 500-800 mN/m and varied in a narrow range with temperature and MnO concentration. The reduction rate increased with increasing MnO content in the synthetic slag from 20 wt% to 40wt% and temperature. Increasing temperature also increased the rate of reduction. No correlation was observed between the reduction rate and MnO content in the synthetic slags in the range 0-20 wt% and in the industrial slags. The rate of SiO2 reduction from the molten slag was close to the rate of MnO reduction. The MnO-free slag had the largest contact area with graphite substrate. Keywords: reduction, wettability, graphite, slag, manganese, surface tension.

Jan 1, 2007

By B B. Du, Y N. Lu, L X. Wang, S L. Wu

The cohesive zone in the blast furnace is largely affected by the softening and melting behaviour of ferrous burden because of its vital role in the blast furnace process. The Visual High Temperature Methodology (VHTM) has been given to study the softening and melting behaviour of sinter, two kinds of lump ores and acid pellet intuitively. Before softening, both two kinds of lump ore swelled and more serious for lump ore B because of its denser structure than lump ore A. The softening and melting temperature intervals are different from one another and this phenomenon contributed to the gas permeability of ore layer in the cohesive zone since the ‘ore window’ has formed. Besides, the softening and melting behaviour of mixed burdens have been studied, where it has been found that the softening and melting characteristics of mixed burden A (consisting of sinter and lump ore A) is better than mixed burden B (consisting of sinter and lump ore B) and mixed burden C (consisting of sinter and acid pellet) despite the poorest characteristics of lump ore A. The reason is that the high temperature interactivity between lump ore A and sinter is much better than lump ore B and acid pellet. The high temperature interactivity is mainly influenced by the chemical compositions, porosity and contact condition. This paper provides a new research method for the softening and melting behaviour of iron ore and an important technical basis for the optimisation of blast furnace burden.CITATION:Wang, L X, Wu, S L, Lu, Y N and Du, B B, 2017. The softening and melting behaviour of single and mixed iron ore burdens, in Proceedings Iron Ore 2017, pp 605–610 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By O. J. C. Runnalls

"Canada became the world's largest uranium producer in 1984. That leadership position is likely to be maintained for many years into the future because of a firm production base, many undeveloped known deposits with commercial promise, and a large geologicalpotential for new discoveries.There are some uncertainties on the horizon, principally because of restrictive actions in process within the U.S.A., which are aimed at preserving a deteriorating domestic uranium industry. Should such actions result in import restrictions, for example, there would be a negative effect on foreign producers at least in the short term. Canada may avoid such difficulties under a tentative U.S.-Canada free-trade agreement where restrictions on the import of Canadian uranium into the United States would be eliminated. Over the longer term, demand for Canada's uranium resources will grow because of the foreseen growth in the world's installed nuclear power capacity. IntroductionSince the phenomenon of nuclear fission was discovered in 1938, the utilization of uranium has grown substantially. Initially, the principal use for uranium was in the production of nuclear weapons. However, once civilian nuclear power reactors began to be built in the 1950s, an increasing fraction of uranium output was directed to the production of fuel elements for use in electricity generating stations.The cumulative uranium production by those countries in the World Outside Centrally-Planned-Economies Areas, WOCA, during the period 1938 to 1985 exceeded 800 000 tonnes of uranium. Some 60% of that was mined in the United States and Canada, as indicated in Figure 1. In 1986, nearly 80% of WOCA output came from five countries, Canada, United States, South Africa, Australia, and Namibia, as indicated in Table 1 and illustrated in Figure 2.During the past decade the world annual consumption of nuclear energy has more than tripled (Fig. 3). As of December 31, 1986, the world total of nuclear power reactors had reached 394 with a total net capacity of 270 GWe. The thermal output from nuclear power plants in 1985 exceeded 60% of the energy contained in all of the oil produced that year in the Middle East. Thus, nuclear power has already become an important component in the world energy supply picture."

Jan 1, 1988

Role of Bubbles in the Action of Flotation Agents

Sep 13, 2010

By B. Genc

After the explosion at Middelbult Colliery, South Africa in May1993, which claimed 53 lives, the South African Coal Mining Industry and the Safety In Mines Research Advisory Committee (SIMRAC) united forces to establish a surface facility to develop and test on-board flame suppression systems for continuous miners and roadheaders. The first test that was conducted in this newly constructed test tunnel at the Kloppersbos Research Facility, CSIR was in July 1995.Since then 70 tests have been conducted using the facility and have focused on on-board active ignition suppression systems for continuous miners (CM) and road heading (RH) machines to enhance the safety of South African mine workers in collieries. These suppression systems are mounted on the CM or RH machine and detect the occurrence of an ignition by means of light-sensitive sensors. The electronic signal from the sensor triggers the suppression system, creating a flame-suppression curtain, containing and extinguishing the flame in the immediate vicinity of the ignition. Forty-three tests have been conducted with an active on-board suppression system present inside the test tunnel. Since flame propagation speed is an extremely important parameter, the CSIR-Miningtek made the results of the test programme available for re-analysis. Flame speed depended on whether a machine was present in the heading or not, the geometry of the heading and the volume and composition of the explosive mixture of gas. Flame speeds of up to 190 m/s were recorded. However, the active suppression systems were almost always successful in containing flame propagation.

Jan 1, 2002

By Miguel Gutiérrez

This paper will seek to provide an awareness of the challenges the permitting process presents to the engineering design for open pit mining projects in Perú. This awareness will create a better understanding of the permitting process within the several groups in mining companies that are responsible for getting the mine project started or continue its operations.

Sep 21, 2013

By D. E. Kirby

In line with the Bureau of Mines' goal of providing technology to maintain a supply of minerals adequate to meet national economic and strategic needs, a method for recovering chromite from lateritic materials was investigated. Laterites are a large resource of Ni, Co, and Cr, critical metals of which the United States has insufficient domestic sources. A roast-leach method was developed by the Bureau to extract nickel and cobalt from domestic laterites. A concurrent effort was made to recover chromium from either unprocessed laterites or the leach residues. This report characterizes laterites and laterite leach residues. It describes a chromite recovery procedure using conventional industrial beneficiation equipment for sizing, low-intensity magnetic separation, and gravity concentration. Concentrates containing 20.0 to 22.4 pct Cr (29.0 to 32.7 pct Cr203) and with a 1.6:1 to 1.9:1 Cr-Fe ratio were recovered from laterites and residues containing 1.3 to 2.5 pct Cr with recoveries exceeding 50 pct. Because of their low grade and fine size, these concentrates would be suitable for preparing chromium chemicals. The direct beneficiation of laterites for chromite recovery resulted in the minerals containing nickel and cobalt concentrating in slime products. No iron oxide coproducts of acceptable grade were recovered from either laterites or residues.

Jan 1, 1982

By Zhigan Deng

Cooling crystallization was used to separate iron (III) and nickel (II) from acidic sulfate solution produced by leaching of molybdenum-nickel black shale. The effect of K2SO4 concentration, crystallization temperature, solution pH and crystallization time on recovery of nickel (II) and precipitation of iron (III) was investigated, in order to obtain effective separation of nickel and iron. The optimum parameters determined were as follows: 200 g/L K2SO4, 10 °C crystallization temperature, solution pH of 0.5 and 24 h crystallization. Under these conditions, 97.6% nickel (II) was recovered as K2Ni(SO4)2, 6H2O crystals and only 2.0% of the total iron (III) was precipitated. Recrystallization yielded K2Ni(SO4)2, 6H2O crystals with a purity of 98.4%.

By R. B. Schluter

Magnetite pellets were simultaneously reduced and indurated on a laboratory scale in order to determine the effects of temperature, induration time, degree of metallization, and sulfur content upon the physical and chemical properties of prereduced pellets. The reductants were commercially-pure tank gases. Among the findings were these: 1,100° C is the minimum temperature that will produce acceptably hard pellets using carbon monoxide as the reduc-ing gas. Prolonged treatment time improves the pellets' crushing strength, but the rate of improvement falls off sharply after 2 hours' induration. At 1,120° C, 75-percent metallization produces the maximum crushing strength; there was no corresponding peak at 900° or 1,050° C. Sulfur in the furnace atmosphere lowers the required induration temperature. A few tenths of 1 percent sulfur in the pellet increases the sintering rate of metallic iron in pellets by forming a liquid FeS phase that facilitates iron transfer.

Jan 1, 1968

By P. Roy

Smelting or converting of sulphide concentrates and mattes in a batch operation presents a challenge when directing the off- gas to a conventional acid plant. The Hindustan Zinc Ltd. (a division of the Vedanta Group of companies) Chanderia Lead Zinc smelter was presented with such a challenge that was met with the adoption of the Cansolv® SO2 Scrubbing System. The Ausmelt top submerged lance technology used at Hindustan Zinc generates a furnace gas stream that containsbetween 0.1 vol% and 12 vol% SO2 during the three stages of batch smelting. Cansolv® SO2 Scrubbing Technology captures the SO2 to ensure that treated flue gas exits the facility at a concentration below 100 ppmv SO2 and it releases SO2 in a controlled fashion, to more closely match the needs of the existing acid plant. The application of a regenerable scrubbing system to capture SO2 from a batch-operated furnace and convert it to acid in a conventional acid plant was a first of its kind in the world. This paper provides an update on the design and operation of the Hindustan Zinc SO2 recovery system and suggests two improvements to the basic flow sheet that optimize the cost of SO2 scrubbing further.

Jan 1, 2007

By K. O. Bennington

Enthalpies of formation of three sodium titanates were determined by hydrofluoric acid solution calorimetry, The values obtained for formation from the elements at 298.15° K are -370.9±0.5 kcal/mole for Na2TiO3, -832.1±0.9 kcal/mole for Na2Ti307, and -1,510.9±1.7 kcal/mole for Na2Ti6013. Tables of enthalpies of formation and Gibbs energies of formation are given as a function of temperature both from the elements and from the component oxides for Na2Ti03 and Na2Ti307.

Jan 1, 1973

By Warren L. J

The effectiveness of shear-flocculation as a method for upgrading simple mixtures of ultrafine (1-11 \lm) scheelite and garnet was evaluated. Statistical methods were used in the design and analysis of the main test program.The stirrer speed, stirring time, and initial weight ratio were all found to have significant effects on both the recovery and grade of the floes produced. The particle sizes also had an effect on the final grade. There were several important interactions between factors which also affected the results. Optimum conditions for shear-flocculation were established, and under these conditions about 80 per cent of the scheelite could be recovered at a grade which depended on the composition of the starting mixture. Starting with mixtures containing 10 and 50 per cent scheelite, the best final grades were between 20 and 50 per cent and between 70 and 90 per cent respectively, the actual value depending on the particular combination of particle sizes.

Jan 1, 1977

By A. Cichowicz

In this study, techniques used to design earthquake-resistant structures are applied to the deep-level mining environment. Earthquake engineers seek to identify the cause of potentially damaging resonance, and design or reinforce structures to reduce these effects. Similar techniques have been used to analyse the dynamic behaviour of the rock mass surrounding a stope in a deep South African gold mine. A three-dimensional seismic array installed in a stope at TauTona Mine (previously Western Deep Levels, East Mine) provided an opportunity to examine the evolution of the wave field close to an underground opening. A set of three-component geophones installed in a borehole above the panel revealed the development of surface waves as wave fronts reached the excavation, and an array of vertical component geophones fixed to the hangingwall provided a two-dimensional map of site effects. While the collected data do not include damaging seismic events, quantitative analysis enabled phenomena which could lead to damage, to be recognized. In the vicinity of the excavation, the energy of the seismic signal is generally transformed from high frequency to low frequency. It was found that seismic events with relatively high corner frequency (150 Hz?200 Hz) usually excite several modes of vibration (30 Hz to 110 Hz), while events with low corner frequency (30 Hz?50 Hz) do not always excite higher modes of vibration in the structure. This implies that the rock mass around the excavation is a complex medium, and should be studied using the multi-degree-of-freedom model. A strong structural effect (due to the excavation shape) was revealed as a low frequency coda wave (at 40 Hz and 60?70 Hz), well developed on the skin of the hangingwall. A strong site effect was revealed by changes in signal properties between hangingwall geophones, exhibiting strong resonances around 160 Hz and in the range 200 Hz to 300 Hz.

Jan 1, 2000

By C. Lemmer

The resolution with which the different categories of resources are forecast for Witwatersrand gold reefs should ideally tie in with block sizes that are optimal in terms of the variability structures of the reefs. A tool, called the ?variancegram?, is proposed as a basis for block size choice. A variancegram is intrinsic to the particular reef and mine concerned. A further requirement is the ability to attach global confidence limits to weighted average estimates built up from combinations of local kriged estimates. Approximations to derive global kriging variances based on variables derived from local kriging deliver hugely inflated results if ordinary kriging is used, and markedly better, but not accurate, values if simple kriging is used. These approximations improve as the number of samples used in kriging each block is increased. It is shown that the behaviour of the different components of the global kriging variance with increasing number of samples, all differs, but they all link to the variancegram for the particular reef. The variancegram can thus be used to correct the different components to the values they would have had if all samples were used in kriging each block, and so deliver the ?correct? global kriging variance, even though only a limited number of samples were used in kriging each block. The desirability of having very stable solutions implemented in production systems is taken into account in the proposals. It is anticipated that the same variancegram findings will also hold for other densely sampled deposits, but this remains to be investigated.

Jan 1, 2014

By Belcher C. B

The Groote Eylandt manganese ore deposits contain mainly pyrolusite and cryptomelane with lesser amounts of the manganese minerals lithiophorite, todorokite, psilomelane, and nsutite. The major non-manganese minerals which occur are quartz, kaolinite, and goethite.Determination of the mineralogy relies mainly on x-ray diffraction analysis. Quantitative methods for the determination of pymlusite and cryptomelane in Groote Eylandt manganese ores have been developed, A large amount of isomorphous substitution may occur in the manganese minerals and a number of minor and trace element associations have been noted. A correlation has been established between the potassium and cryptomelane contents for a wide range of ore types. Anomalous calcium, magnesium, and sodium values occur in samples containing todorokite, and barium is associated with psilomelane. Groote Eylandt lithiophorite appears to contain negligible amounts of lithium (<O· 05 per cent).A relationship between the H20+ and the Al203, K20, and Fe203 contents has been estahlished indicating that much of the combined water content is due to the presence of kaolinite and goethite, and cap be removed by beneficiation of the ore.

Jan 1, 1975

By Jack J. Ayotte, Michael R. Nadon

"Today's demand for better and more efficient methods inspires new approaches to construction and mine development.A project at Asarco's Aquarius Mine provided a challenge that resulted in the adaptation of a civil construction technique to a mining application.This paper describes the construction of an escapeway shaft to surface from the mine's 150m level. The prime consideration was to provide the most cost-effective method of establishing a shaft collar in the 145 ft (44 m) of water-bearing overburden. This problem was resolved with the employment of the drilled in-caisson method.The remainder of the 500ft (152m) deep shaft was raise bored and portable hoisting equipment was used to install a permanentmanway and shaft liner.IntroductionHaving completed the first phase of exploration development in 1982, J.S. Redpath Limited was engaged to carry out an engineering and cost study to investigate the feasibility of re-opening Asarco's Aquarius Mine near Timmins, Ontario. The scheme was to develop the proven ore reserves and proceed with shrinkage stoping while carrying out further exploration development and diamond drilling.One significant and costly component of the project was the provision of an escapeway shaft to supply additional ventilation as well as a second means of egress from the mine. The major complication to this task was the presence of 145 ft (44 m) of water-bearing overburden at the site. The first and obvious approach was to use conventional ground-freezing methods as had been employed previously on .this property for the initial development shaft. This being the only ""sure"" method available at the time of the budget estimate, it was used as a basis for the study but its considerable projected cost and time demand inspired further investigation into other possible solutions.After considerable research and several brainstorming sessions, a Redpath team came up with an approach whose basic procedures had been used extensively in the civil construction field, although they were novel to the mining industry."

Jan 1, 1987

By E. F. Divers

This Bureau of Mines report describes the results of a program to develop small, rugged mechanical dust collectors (scrubbers) with high dust collection efficiency and low energy comsumption for controlling dust in coal mining operations. All of the scrubbers described are similar in configuration and are powered by 6-hp, 2,000-ft3/min vane axial fans. Air pressure differential is less than 6 inches water column. Height of the scrubbers? including fan is less than 14 inches, width is less than 16 inches, and length is less than 45 inches. The flooded fibrous-bed scrubber achieved respirable (less than approximatey 7 µm) dust collection efficiencies of 95 percent. The small-diameter-cyclone scrubbers showed about 92 percent efficiency and can be best where excess water is a problem. The wetted brush scrubber showed 88 percent efficiency at low cost, and the wetted fan scrubber showed a slightly lower efficiency (87 percent) but offered the smallest size and cost. A suitable water droplet eliminator is described.

Jan 1, 1978

By Pasi Korkeakoski

There are about 400 multi-storey buildings founded on wooden piles in the city centre of Turku in Finland. Soil conditions are variable from hard rock to very soft clay. Due to the soil conditions and ground water lowering there are basically four different types of underpinning projects. Under dimensioned cohesion piles in a deep clay layer, decaying cohesion piles, a combination of these two reasons and decaying end bearing piles in a thin clay layer area. Many different execution methods have been used such as impact driving, jacking and drilling and combinations of these.

Jan 1, 2000