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By Whitman E. Brown

"As part of a Nation-wide program of the United States Government to develop natural resources, funds were made available to the Bureau of Mines for the investigation of the ""Reduction of Iron Ores by Solid and Gaseous Fuels."" These investigations are concerned with the direct production of iron from its ores without the use of a blast furnace. Many processes have been proposed for the low-temperature reduction of iron oxides, but few have been developed to commercial use. High-quality sponge iron is produced com-mercially only in Sweden.The cost of iron production depends in part on the grade of the ore and increases with decrease in grade. The substitution of cheap natural gas in a sponge-iron process for expensive coke in smelting in the blast fry pace would partly compensate for the use of low-grade ores. If a process can be developed in which inexpensive natural gas can be used as fuel and reducing agent, the large deposits of low-grade iron ore and the natural-gas resources of east Texas may be utilized in the commercial production of sponge iron.Sponge iron may possibly be used to supplement scrap iron, pig iron, or, in special instances, wrought iron. Sponge iron will vary but slightly in composition and will contain little or no nickel, cobalt, manganese, copper, and other allowying metals. It is becoming increasingly difficult to obtain choice scrap iron of nonalloy composition. Pig iron contains 1.5 to 3.0 percent silicon and 3.0 to 4.5 percent carbon. Sponge iron generally contains less carbon than pig iron.The Madaras Steel Corp. in Longview, Tex., built a set commercial-scale sponge-iron plant which was intended to be operated in connection with a steel foundry. The process is based upon the reduction of preheated iron ore, with hot reducing gases under pulsating pressure. Although the Madaras Corp. had previously experimented with the production of sponge iron by reducing the ore with pure hydrogen, several attempts to use a re-formed natural gas as the reducing agent in this pilot plant were unsuccessful. The Bureau of Mines leased this plant and conducted an extensive investigation of the Madaras process on a semicommercial scale.The experiments were not entirely satisfactory, partly because of mechanical difficulties and partly because the reducing gas was not of the best quality. However, much information on the production of reducing gas by re-forming natural gas and on the reduction of iron ore with re-formed natural gas was obtained.The sponge iron produced contained approximately 0.1 percent phosphorus; and, after melting in an electric furnace, the iron contained approximately 0.15 percent phosphorus. The results of attempts to improve the ore by ore-dressing methods were not encouraging."

Aug 1, 1946

By Richard B. Stein

Section 25 has been assembled to give the geological, mining, or metallurgical engineer an overview of some of the important downstream operations that typically follow mining activities. This subject is obviously too broad and complex to be covered in detail within this Handbook. However, the engineer will be interested to learn about the basic fundamentals, and especially how they might affect the economics of the total project from prospecting and mining through to metals recovery and marketing. In this way, it is hoped that the engineer will have a better overall appreciation for the technical and commercial prospects of a mining and metal-producing project.

Jan 1, 2008

Bacteria can play a key role in the processing of 'difficult' ores. Bioleaching opens the way to potentially extract copper from vast amounts of otherwise hard to process refractory low-grade chalcopyrite. In my talk I will outline our research philosophy to develop bioleaching as a Precision Processing unit process step. In our view, Precision Processing is a sophisticated approach to mineral processing where the ultimate goal is to measure and characterise the ore body in-ground and in real time during mining, allowing the down-stream unit processes (bioleaching, in this case) to be continuously tailored and tuned via feedback and feed-forward controls to obtain the highest possible recoveries at the lowest possible cost and environmental impact. I will describe some of the work that we are undertaking to better understand the interfacial phenomena underlying the fundamental bioleaching process with the aim of coming to a Precision Processing approach. We use techniques such as interfacial electrochemistry (scanning electrochemical microscopy, SECM), AFM, zeta potential measurement, and synchrotron science to elucidate the parameters that drive bacterial selectivity and adhesion, bacterial metabolism, and dissolution and precipitation processes for model systems and real chalcopyrite ores. As examples of our research, I will discuss in some detail our method to produce and characterise micro-patterned CuxS - silica thin films as model substrates for electrochemical and bacterial adhesion work and our approach to the interfacial chemical characterisation of extracellular polymeric substances of bio-active bacterial cells. I will also cover some of our recent findings relating to measurement and interpretation of bacterial adhesion on sulfidic substrates and its implications for bacterial adhesion and substrate selectivity. After having identified and discussed crucial leaching parameters, such as pH, Eh, T, [Cu2+], and [O2], the talk will go on addressing some of the early achievements and challenges encountered in our work to design and prepare low-cost, rugged sensing devices that allow the in-situ (in this case, in-dump or in-heap) localised measurement of these parameters. I will conclude my talk by painting the picture of how the work of our group might contribute to realising the dream of transforming bioleaching into genuine high-tech Precision Processing of minerals. This is an ABSTRACT ONLY. A full-length paper was not prepared for this presentation.

Sep 13, 2010

By S. D. Botts, F. Cantuarias

"The Antamina project, owned by BHP Billiton Plc, Mitsubishi Corporation, Noranda Inc., and Teck Cominco Ltd., is a $2.3 billion copper/ zinc project, located in the Ancash Department of Peru. The project consists of an open pit mine, a 70 000 ton per day concentrator, a 302 km long concentrate pipeline, port facilities, a new access road, power line, and town site. The project is designed to produce up to 1.5 Mtpy of copper and zinc concentrates over a 23 year project life, and will be the third largest producer of zinc and the seventh largest producer of copper in the world.This mega project is the largest mining investment in the country and, during its construction stage, was the most important construction project worldwide. On May 28, 2001, Antamina commenced testing operations and four months later, it reached commercial production. Antamina was officially inaugurated on November 14, 2001 by Peruvian president Alejandro Toledo.The construction stage of the project generated 8000 direct jobs, with a peak of 10 000 employees, and 30 000 indirect jobs. The permanent workforce consists of approximately 1650 employees, the vast majority of which are Peruvian Nationals, around 30% of whom came from the region where the deposit is located. Approximately 5600 indirect jobs were generated from the project. Independent sources state that Antamina increased the Peruvian mining exports by 30% (mining exports constitute 50% of Peru’s total exports) and Peruvian GDP by 1% in its first year of full operation in 2002.Since winning the privatization bid for the project in 1996, the company has implemented an approach to community development and environmental protection based on sustainable development principals. Throughout the development of the project, a number of initiatives have been undertaken to ensure full involvement of the local populations in community development activities and the company’s environmental program.Due to its size, difficult logistics, cultural considerations and financial aspects, the project has faced a number of unique challenges in the area of environmental protection and management of community interaction. Antamina has been innovative in its approach to these issues and, as a result, has set new standards in Peru for environmental and community management and sustainable development."

Jan 1, 2003

The initial results from the magnetic sludge factorial experiment are summarized in Table 2. For ease in interpretation, the four separate variables are identified with the high and low level of each variable being represented by + and - signs, respectively. Several important relationships are evident from an inspection of the data in Table 2. For example, magnetic sludges were obtained only during the high temperature tests. Secondly, with the exception of the last three tests, there is an apparent correlation between settled sludge volume (or sludge settling rate) and pH. Data on residual dissolved Fee+ indicate that precipitation of iron is not complete at pH 8 and room temperature (Tests l, 3, 5, and 7). Although this should not have any confounding effect on the interpretation of the results, it is an important observation and an aspect of the overall conceptual process that should be considered carefully during any future developmental work. The data in Table 2 were employed more fully in the calculation of main effects and variable interactions for each of the three responses. For this purpose, a codified design and calculation matrix, shown in Table 3, was used. The derivation of this matrix is described by Davies.(9) The positive or negative signs for variable interactions are obtained simply by algebraic multiplication of the signs for each single variable involved in the interaction. Main effects and interactions are calculated by multiplying the response values (Table 2) by the corresponding effect elements (Table 3), summing the results, and dividing by 8. The resulting value for single variables is also sometimes designated as an average effect, since (for tyro levels of the variable only) it is simply the difference between the average response of all trials carried out at the first level of the variable (factor) and that of all trials at the second level. If the effect of one variable changes at different levels of another variable, the two variables are said to interact. The relative importance of the variable or variables in question is reflected by the absolute magnitude of the calculated main effect or interaction. First-order (two variable) interactions are usually easy to interpret in terms of the physical behavior of the system. Second- and higher-order interactions are often less readily understood, and are often of minor significance in any case. The main effects and interactions derived from the present study in the manner described above are listed in Table 4. It should be noted that

Jan 1, 1971

Fluorspar was not mined in the United States during 2004, although a small amount of usable synthetic fluorspar (CaF2) was produced from industrial waste streams. The majority of fluorspar consumed in the United States came from imports or stockpiled material purchased from the National Defense Stockpile (NDS). In addition, consumption is supplemented by use of by-product fluorosilicic acid produced at phosphoric acid plants. In 2004, annual production of fluorosilicic acid was 50kt (55,000 st) or about 88 kt (97,000 st) of 92 percent fluorspar equivalent. In 2004, annual production of fluorosilicic acid was 50kt (55,000 st) or about 88 kt (97,000 st) of 92 percent fluorspar equivalent.

Jan 1, 2005

Flotation testing has been done at laboratory scale on hematite mineral and ore samples using stage additions of various hydroxamates. Chemisorption of hydroxamate species onto the hematite surface was inferred from the results, possibly involving both the undissociated hydroxamic acid and hydroxamate ion as maximum recovery occurred close to the pKa of the hydroxamic acid. Flotation testing on a specular hematite ore containing 40 per cent Fe and 42.5 per cent silica gave highest iron grades in concentrate at pH 6, in contrast to published data which suggested pH 9 as the optimum value for ore processing. Using octyl hydroxamate, a rougher concentrate assaying 67 per cent Fe at 51 per cent recovery was obtained using four stage additions of 50 g/t at pH 6. For lower grade concentrates still meeting the chemical analysis for pigment grade micaceous hematite (minimum Fe assay 60 per cent) iron recoveries of 80 per cent were possible for stage additions of 50 g/t octyl hydroxamate in the pH range 6-8.

Jan 1, 1999

By N. E. Idenyi

The effects of compositions and firing temperatures on the physico-mechanical properties of blended Nsu fireclay and Nkalaha redbrick clay have been investigated. The clay samples were compounded according to the following ratios: 10:90, 20:80, 30:70, 40:60 50:50, 60:40, 70:30, 80:20 and 90:10 in the order Nsu: Nkalaha respectively, and test samples made and fired at 9000C, 10000C 11000C and 12000C. The properties tested for were the modulus of rupture, porosity, shrinkage, apparent density, water absorption and bulk density. From the results obtained, it is inferred that the blends have a maximum service temperature of 11000C, with the 30: 70 blend presenting the best characteristics. A conclusion is drawn to the effect that the blend could be adapted for the production of ceramic earthenware, electrical porcelain pin insulators, cement manufacture and for refractory linings where temperature requirements are less severe.

Jan 1, 2006

Computation is believed to be a powerful tool in scaling-up chemical processes and in designing materials, however, is being challenged by low predictability and limited scalability. This presentation will discuss the promising future of multi-scale computation in solving these two problems to realise the real-time simulation of industrial processes. Multi-scale structures are a common nature of most chemical systems and the meso-scale phenomena are believed to be the road blocks not only in improving the predictability of physical modeling but also in extending the scalability of computation. Focusing on the meso-scale phenomena, a series of research has been carried out at the Institute of Process Engineering, Chinese Academy of Sciences, for the past three decades. Starting with a simple idea of modeling the meso-scale clusters in gas-solid two phase flows, the so-called EMMS (Energy-Minimisation Multi-Scale) model was established. In verifying the stability condition of the model, the pseudo-particle approach was proposed to explore the micro-mechanisms in particle-fluid systems, and the strategy of the EMMS model was extended to other six different multi-phase systems, resulting in a unified conceptual formulation of multi-phase complex systems expressed by a multi-objective variational problem. In applying this model to different multi-phase systems and to industrial problems, it was recognised that the EMMS model defined a new paradigm of multi-scale computation by realising the structural similarity between software, hardware and the problems to be computed. This paradigm of computation was implemented on a multi-scale supercomputer with a capacity of 1.0 petaflops by integrating CPUs and GPUs (Graphic Processing Units), showing high efficiency and low cost. Running the EMMS model on this computer, the simulation of hydrodynamics of multi-phase systems can be speeded up very much, indicating a promising future of virtual reality of process engineering. The presentation will review this series of work, introduce successful applications in industries, and will be concluded by emphasising the critical importance of the meso-scale phenomena as the bridge between macro-dominants and micro-mechanisms. This is an ABSTRACT ONLY. No full paper was prepared for this presentation.

Sep 13, 2010

Jan 1, 1969

By R. Mensah-Biney

The aqueous biphase separation process (ABS) has been used to separate ultrafine industrial minerals. The partition behavior ofTiO2, Al2O3, Fe2O3 and kaolin was not pH dependent. The partition behavior of SiO2 was, however, pH dependent. The partition coefficient of kaolin in PEG 3400/ Na2CO3 biphase system was 150 and that of the silica in the same system was 0.02, resulting in a separation factor of 8500 between kaolin and silica. The aqueous biphase separation system was used to separate free silica from kaolin in a raw clay sample from Mexico. The partition behavior of mica, feldspar and clay from North Carolina was also evaluated.

Jan 1, 1999

By Sabina Brady

Nearly a decade and a half after the US and China established formal diplomatic relations, and two decades after the two countries signed the Shanghai Communique and established commercial ties, the world, and perhaps China itself, has discovered that a wealth of natural mineral and energy resources lie beneath China's soil and directly off its coast. The country's coal reserves and oil and gas potential are well known. Its ferrous and nonferrous metal reserves are respectable and in a number of instances pre-eminent. According to 1981 Minerals Yearbook estimates - more often than not below those now being claimed by China - the country's aluminous metal reserves are about 907 Mt (1 billion st); iron ore reserves are 40 Gt (44 billion st); and copper reserves are about 46 Mt (54.4 million st) of contained metal. In addition, the country has about 10.7 Gt (11.8 billion st) of phosphate reserves, the fourth largest in the world, and 3 Gt (3.3 billion st) of pyrite. China's national Sixth Five Year Plan promulgated in late 1982 ended a stringent three-year retrenchment or readjustment period in which a number of major development projects involving foreign participation initiated in the late 1970s were shelved. The new Five Year Plan is a signal both within and outside of China that things are now moving again, and that major industrial and service sectors are receiving the kind of funding and flexibility they need for expansion, construction and modernization. The new plan's strategy for growth is measured and much less grandiose and frenetic than it was five years ago when China flung open its doors to foreign companies and invited participation in large-scale development projects. Now, the country's reticence to spend foreign exchange to purchase key equipment, technology, and services -a reaction to these projects and the spending they entailed - is clearly on the wane. In China's effort to quadruple its GNP by the year 2000, there is a new willingness to use some of its substantial foreign reserves. In fact, it is projected that 1983 will witness a $1.9 billion deficit, with a $2-3 billion deficit in 1984 and 1985. The following article discusses implications the Sixth Five-Year Plan has for nonferrous metal development in China. It is the first in a series of three articles on Chinese mineral resource development to be published in Mining Engineering over the next few months. The second article will identify specific nonferrous projects underway, while the third in the series will focus on trade and development opportunities for phosphate and potash producers in China. China's Ambitious Plans In the last few months, the exploitation of China's nonferrous resources and development of its industrial processing capabilities have begun to receive increasing attention on both provincial and central levels. Unlike the earlier modernization drive of 1978 when China's ferrous sector - best typified in the Baoshan iron and steel project - got the lion's share of the Ministry of Metallurgical Industry's (MMI) energy and resources, it now appears that in some respects the nonferrous and industrial sectors are finally moving out from beneath the dominating shadow of ferrous and getting their own day in the sun. Separation of Nonferrous from Ferrous One clear demonstration of this is the establishment in April 1983 of the China Nonferrous Metals Industry Corporation (CNFMIC). The corporation is composed of 819 enterprises with over a million workers, and also includes 12 nonferrous metal construction companies, eight design institutes, and three prospecting companies. Of ministerial rank, CNFMIC is responsible for the development of both the country's nonferrous resources and its processing facilities. Although closely tied to the parent ministry from which it sprang (i.e. MMI), CNFMIC, at least theoretically, is separate and independent from it. One strong indication that this independence is, or soon will become a reality, can be seen from the fact that the new corporation is not headed by the former MMI officials, not even those who made up the ministry's now defunct nonferrous bureau. Instead, its president Qiu Chunfu is formerly of the State Economic Commission and the China International Trust and Investment Corp. Its general manager Fei Ziwen, an engineer in his early 50s, is from the Jiangxi Province Copper Corp. The new nonferrous corporation appears to be powerful

Jan 7, 1983

By Joseph J. Diehl, Brian B. Khalighi

This paper discusses the Queens Water Tunnel, No. 3, Stage 2, being driven by a new Robbins High Performance (HP) Tunnel Boring Machine (TBM).The paper is divided into four sections. In the INTRODUCTION section, a short overview of the scope of the project is presented. In the GEOLOGY section, the geological condition along the tunnel drive is briefly introduced. The TBM DESIGN section discusses the various design criteria and the resulting machine specifications. The paper concludes, in the TBM OPERATION section, with a case history describing the tunneling operation from start-up to the time of the writing of this paper.

Jan 1, 1997

By L. F. Ruppert, R. C. Milici

Coalbed methane (CBM) is currently being produced from a relatively small area in the Dunkard and Pocahontas basins, in the northern and central parts of the Appalachian Basin, respectively. In general, much of the production occurs where the coal beds are beneath 500 feet or more of overburden, where the rank of the coal is high-volatile B or greater (%Ro >0.8), and where the natural fracture system is enhanced by structural deformation. It is anticipated that near-term CBM development will continue within these areas and will expand in the Appalachian basin as technology improves and as the price of gas rises.

Jan 1, 2003

By C. A. Rowland

The use of the Bond Work Index to size industrial grinding equipment is well known. Its use to measure grinding efficiency was presented by C.A. Rowland, Jr. at an AIME meeting in 1976. However, due to a bureaucratic error, the paper was never submitted for publication. This metric has nevertheless been adopted by industry as a widely used standard. The purpose of this paper is to re-present and update the application of this tool as a standard for measuring grinding circuit efficiency. Definition ?standard, n. something established for use as a rule or basis of comparison in measuring or judging capacity, content, extent, value, quality, etc.; as standards of weight and measure? (Webster, 1958).

Jan 1, 2008

By J. D. Miller, R. J. Smith

Earl C. Herkenhoff Publication of the article "The Flotation Behavior of Digested Asphalt Ridge Tar Sands" by R.J. Smith and J.D. Miller has confirmed and again spotlighted a most significant and important development in the field of tar sand and heavy oil mining. This is the ability to recover 95 % of the bitumen in dry tar sands by a hot water process. The initial investigation by Miller and Sepulveda in early 1978, "Separation of Bitumen from Dry Tar Sands," was the first blockbuter. It is disappointing that there has been so little scientific and industry ackowledgement that the authors laid to rest the long entrenched belief that the sand grains had to be "water wetted" for a hot water process to be applicable. Dr. Miller and his researchers at the University of Utah used slightly different mineral dressing terminology in describing their process but it is essentially the old, established technique of high solids attrition scrubbing at elevated temperatures with a conditioner or modifier, followed by dilution and froth flotation. Similar techniques were described in detail for other nonmetallic minerals in the mid-1940s by Stuart Falconer of American Cyanamid Co. The authors used a 15-minute "scrub" period (or in their terminology "digester step") at 73% solids and 95°C (203°F) in a 0.3 m solution of sodium carbonate -about 4 kg/t (8 lb per st) of tar sand. Flotation was at 10% solids. Obviously, the scrub is an expensive step with respect to energy input but the high recovery of bitumen appears to justify it. Two basic questions then arise: • What are the effects of shorter scrubbing time, lower temperature, and less sodium carbonate? • Would a two-stage approach be advantageous? That is, could you get the major proportion of the bitumen with a mild scrub and apply the high power and temperature only to the refractory portion? These variables should be evaluated. Apparently, all results were only for rougher flotation. What would the grade and recovery of bitumen be if multiple cleaner flotation steps were employed? We must concede that a 60-62% grade of bitumen leaves considerable room for upgrading. Finally, it should be noted by all executives who approve funds for heavy oil recovery schemes, most of which are variations of in-situ methods, that mining can yield a 95% recovery of bitumen. That is correct, 95%. Imagine what that does to the total barrels recovered from a heavy oil resource compared with the scrawny 30-35% maximum recovery we are getting now. The conclusion-let's mine heavy oil and tar sands. Reply by R.J. Smith and J.D. Miller We, too, share Mr. Herkenhoff s enthusiasm for the mining of tar sands-heavy oil and continue the development of related processing technology. Specifically, it will be noted that by appropriate control of bitumen viscosity in the feed (probably the most important variable for successful separation) the recovery can be accomplished at low digestion temperature and low addition of alkali. A 91 t/d (100 stpd) pilot plant based on our technology is now being operated by Enercor in Salt Lake City (Hatfield, Oblad, and Miller, 1982). In these same pilot facilities, rougher concentrates containing more than 80% bitumen on a dry basis are being produced from Asphalt Ridge Feed. However, the processing of certain other tar sands results in incomplete digestion of bitumen/sand aggregates as discussed elsewhere (Miller and Misra, 1982). Such undigested aggregates are shown in Fig. 1. In this regard, it is intended that a recycle stream will be installed in the pilot plant to provide for redigestion of middling products. Further details regarding surface chemistry aspects of this tar sand technology have recently been published (Misra, Aguilar, and Miller, 1981). References Hatfield, K.E., Oblad, A.G., and Miller, J.D., 1982, "Pilot Plant Recovery of Bitumen from Oil Wet Tar Sands," Processing, Second International Conference on Heavy Crude and Tar Sands, Caracas, Venezuela, Feb. 7-17. Hatfield, K.E., Oblad, A.G., and Miller, J.D., 1982, "Pilot Plant Processing of Oil-Wet Tar Sands," Symposium, Rocky Mountain Fuel Society, Salt Lake City, Utah, Feb. 18-19. Miller, J.D. and Misra, M. 1982, "Hot Water Process Development for Utah Tar Sands," Fuel Processing Technology, Vol. 6, No. 1, April, pp. 27-49. Misra, M., Aguilar, R., and Miller, J.D., 1981, "Surface Chemistry Features in the Hot Water Processing of Utah Tar Sand, Proceedings, "Symposium of Separation Science and Technology for Energy Applications," Gatlinburg, Tennessee, May 5-8.

Jan 11, 1982

By John Organiscak

A majority of continuous mining machines employ a water spray system and a machine mounted flooded-bed scrubber to suppress and capture dust during coal mining. These machine mounted dust control systems must be designed to function within the localized face ventilation system at the mining section to control both dust and methane. Spray systems can impede or improve the scrubber effectiveness in controlling dust or methane at the mining face. Laboratory experiments were conducted to examine the effect of spray type, spray pressure, machine body blocking sprays, and scrubber airflow on dust and gas levels while using a 12.2 m (40 ft) exhaust ventilation curtain setback from the face. These experiments were conducted with the mining machine positioned at the end of a simulated 6.1 m (20 ft) sump and slab cut. Results indicate that the hollow cone nozzles with blocking sprays best complemented the flooded-bed scrubber performance in an exhaust ventilation system. This external spray system notably reduced dust and gas levels on the off-curtain side of the mining machine for both the sump and slab cut as compared to the flat spray nozzles. Higher scrubber airflows reduced dust and gas levels on the curtain side and in the return of the continuous mining machine. The remote operator position, located on the off curtain side and parallel to the inlet end of the exhaust curtain, sustained the most stable and lowest dust levels around the mining machine.

Jan 1, 2010

By O. T. Berge

Development and production from open cut mines continued its vigorous growth trend during the year 1968. Material handling and transportation were again exposed to the use of larger equipment with shovels, trucks and front end loaders leading the way. Highlights of World Mining Activities Africa: The Anglo American Corp. opened a new high-grade copper mine in Zambia during the year. In Angola, the Companhia Minera do Lobita planned a 3 million ton iron ore production for 1968 from new mines which will ultimately produce 5 million tons per year. A feasibility study of Bethlehem Steel Co., for the development of large high- grade iron ore reserves in Gabon, was in final stages of completion this year and Pickands Mather and Co. continued its investigation of iron ore deposits along the Ivory Coast.

Jan 2, 1969

The original work statement of this contract was entitles: 'A Accident Analysis Model for Use in Underground Coal Mines.' The contract was scheduled for a duration of 26 months and was to be in three phases: Phase I - Model Development, Phase II - Application of the Model, and Phase III - Installation, Monitoring and Evaluation of the Model. Alter three months in Phase I, it became apparent that much of the needed data for the model was nut available and could not be made available within the original study schedule. Proceeding as plumed would have resulted in a model of limited utility. Personnel from Theodore Barry and Associates and the Bureau discussed the problem in detail and mutually decided to utilize the majority of remaining funds to assist the Bureau in solving these data problems and develop a stronger ongoing capability for safety analysis within the Bureau. Both tie contractor and the bureau officials involved believed that this decision greatly enhanced the Bureau's ability to develop future accident prediction models, whose rigor would greatly exceed what was currently possible.

Jan 1, 1972

By S. D. Thompson

An AIME transaction by P.L. Allsman (1960), "Analysis of Explosive Action in Breaking Rock," contains many useful concepts applicable to blast design. Of special interest was the derivation of a heave blasting burden formula, which is important in establishing the maximum burden. Unfortunately, its derivation contains a fundamental error and then a compensating one. This formula was: [ ] The derivation used the impulse-momentum principle, with a 0.3 m thick (1 ft thick) radius of rock mass being acted on by an explosive impulse. However, the rock weight was not converted to mass by dividing by the gravitational constant. This mistake can be verified by checking the units in the formula, which resolve into m%-sec instead of meters. Adding the gravitational constant corrects this: [ ] If the minimum velocity is now taken as 0.3 m/sec (1 ft per sec), as was recommended, excessively large burdens result. Any appropriate rock velocity should be capable of throwing the rock mass a minimum distance so that the swell needed for breakage can occur. Unless the burden is extremely small and the bench height is very high, it is unlikely that a velocity of only 0.3 m/sec (1 ft per sec) will be sufficient. A review of the literature indicates that average rock velocities observed by camera studies typically range from 15 to 30 m/sec (50 to 100 ft per sec) (duPont deNemours and Co., 1977; Tansey, 1979). On this basis, a minimum rock velocity of about 15 m/sec (49 ft per sec) would be expected and not 0.3 m/sec (1 ft per sec). When a velocity of 15 m/sec (49 ft per sec) is inserted into the corrected formula, the results approximate those of the original formula with a velocity of 0.3 m/sec (1 ft per sec). The errors were approximately self-compensating [ ] References Allsman, P.L., 1960, "Analysis of Explosive Action in Breaking Rock," Transactions, AIME, Vol. 217, pp. 475-476. E. I. duPont deNemours and Co., 1977, Blasters' Handbook, 175th Anniversary Edition, Dupont, Wilmington, DE, pp. 233. Tansey, D.O., 1979, "The DuPont Sequential Blasting System," CIM Bulletin, Vol. 72, July, p. 80. Thompson, S.D., 1981, "Critical Review and Revision of Surface Blasting Practice," MS thesis, West Virginia University, pp. 308-316.

Jan 3, 1985